Saturday, December 29, 2012

dinner aura

(this and the previous post were written as dated, but are posted today, 1-5-13; the times are today's time).

last night, just as we were starting our saturday night banquet, i noticed that everything i was looking at seemed distorted, and then realized that a scotoma was developing, just below and right of fixation. i wasn't able to pay much attention to this one, since i had to eat dinner without looking like a lunatic, but it seemed normal; straightish out to the right of fixation, then arcing downward. there was a period early on where the scotoma was very difficult to find, but i think it was just distributed, or at least not exactly the same in both eyes, but was still there. whereas usually the headache would have started about halfway in, this time there was nothing; maybe a slight sense of headache-like pressure behind the forehead, but no pain. i am guessing this was maybe due to the constant alcohol ingestion? by the time the 10-15 minute mark came around, i had probably had at least 2 shots of baijiu.

absence of a headache was good, since following this i went with jp's father, uncle huang, and uncle wang to get my 'feet washed', which really turned out to mean a full-body massage. a full-body massage while fully dressed in winter getup, sweaters and pants and long underwear. it was nice, though! and lucky no headache, since there was a stage of head-beating.

also, i didn't detect any sort of prodrome. in the morning, i had felt it inordinately difficult to form sentences, and made some strange mistakes in chinese, producing strangely wrong words, which i noticed at the time as out of the ordinary. otherwise, nothing obviously in prediction..

Thursday, December 27, 2012

random observations:

(rambling chinese vacation edition):

1. due to jet lag, woke up at about 5:30am yesterday, lay in bed for ~1.5hrs. of course a thousand random thoughts ran through my head, but for a while a lay there watching the augenlicht. long, long ago i noticed how it cycles: against the dark, reddish-black background, a brighter cloud coalesces around the fovea, then fades, then coalesces again. the cycle is somewhere between 5-10 seconds, the cloud is a very low-frequency modulation (maybe ~5degrees across) of the high-frequency noise grain.

what i noticed yesterday was that as the cloud fades, some parts of it seem to 'stick'; this is hard to describe. imagine that the cloud was displayed on a screen, and that its brightest parts, around the peak, were 'clipped'; then, as the could fades, the clipped parts persist, then brighten noticeably, then dissipate as the cycle continues. the impression is similar to a very bright afterimage floating in front of a fixated object, except that my eyes were closed, and i was certainly dark adapted. the clipped portions are sharp-edged, small (half or a quarter degree across), with the spatial appearance of little interconnected droplets of a liquid. i wasn't able to tell if they had the same structure on each cycle, but it seemed that they did.

i cannot guess meaningfully what this is. some sort of pattern formation machinery being stimulated by the structure of the cloud cycle, which has a slower decay constant? it seems familiar, so i might have noticed it at some other time in the past when i found myself lying in bed, unable to go to sleep. when i was in college, that happened a lot, because i would have classes in the morning and force myself to bed, despite wanting to stay up until 2 or 3, and so i'd lay in bed for hours sometimes, waiting to sleep.

i also noticed that i could very clearly see the 'eye crank lines', especially when looking down, whereas usually i can't see them when my eyes are closed.

2. when we finally got out of bed yesterday morning, discovered it was snowing. it eventually stopped snowing and started raining, so the weather yesterday was miserable. still, we drove down south to visit family. we went to visit j*'s father's older sister, who i'd never met before, in a village in another corner of fanchang; her home was like something out of a fairy tale, not so surrounded by garbage and chaos like some of the other villages (which are still nice to visit, don't get me wrong). i had jingping take some pictures. there was a mountain running up directly on the side of the village, with a bamboo forest; spread out away from the mountain and the village was a large expanse of vegetable gardens. we had lunch cooked on a wood stove (and with some electricity). i hope that china is able to keep from totally losing this world as it moves on into the future.. all they really need is to find a way to deal with the garbage.

on the way down there, we drove on a new highway which took us through several tunnels beneath the mountains. at some point, to the right, in the distance, maybe a mile or so distant (in the south of wuhu, there are mountains and there are flat plains, and stark, sudden transitionsn between them), through the snowy, rainy, smoggy haze, i saw a massive building, seemingly in the middle of nowhere. it looked like something in DC; the size of the pentagon, ten or twenty stories wide, sixty stories wide. then, a little further south, a gigantic factory or processing plant, like a refinery or the biggest concrete plant you've ever seen. then, a mountain. i didn't bring the GPS to track where we went this time, but i can probably figure it out from memory. this reminds me of last year, something i never wrote down; on the bus back to shanghai, in the distance i could see a glowing tower, probably a hotel, surrounded by nothing else. it was probably fifty stories high, and surrounded by what looked like a 4th or 5th-tier town. maybe we'll see it again this time, since we're probably taking the same bus back.

also on the wuhu note, i've noticed lots of songbirds here in the subdivision, first time in four winters. maybe whatever drove them away is getting better?

3. dinner at uncle's restaurant. dog meat tastes weird. it was worth a try.

4. still on the roman history kick, been reading Tacitus' history of the 'year of four emperors', on the civil war that commenced with the death of Nero. it really is great reading. in the section on Otho's last stand and suicide, i paused for a while and thought about how all this had happened. i still don't know much about roman history, but i've read livy, so i know something about the beginnings of the republic and how it came to be; and i've read plutarch's lives of marius, sulla, crassus, pompey, and caesar, so i kind of understand how the republic cascaded into the empire.

i thought, the romans had all these lawful institutions for separating power, trading offices more-or-less peacefully and agreeably, avoiding autocracy and civil wars. they kept this up for hundreds of years, but only because to have faltered would have probably meant the end of rome, because there were still so many other powerful players in the vicinity. only after those players - the etruscans, the gauls, carthage - were subjugated, only then could the internal struggles really commence. the rise of the emperors, through the disruptions of marius to caesar, put an end to those struggles by ending all the power sharing. but that meant that once an emperor had failed, the struggles would flare again, and there would be civil war. the situation described - and witnessed first-hand - by Tacitus was the first of several times that this would happen, and it would eventually bring the end of the empire.

so i thought all of that, putting together the pieces that so many others have put together so many times, and then i turned the page, and Tacitus himself begins a digression where he outlines the same reflections on the same reasoning, and again i was impressed at the immediacy of reading the thoughts of a person who lived and died more than 1800 years ago.

5. despite the preceding item on how great Tacitus is, i switched yesterday (at the beginning of the next book of Tacitus, on Vespasian's rebellion) to reading Darwin's 'on expressions of man and animals', or whatever the title is. i've wanted to read this for years, never got around to it until there it was, Free on Ibooks. reading Darwin is great because of the way he makes his thinking so transparent; he explains everything iteratively, first in broad terms, then more and more specific, each time tacking on anecdotes or examples with more and more density. origin of species and the descent of man were written similarly, spiraling down from general statements to specific demonstrations, with examples at every level, but there was less anecdote; here, Darwin is on every page noting a story from some friend or acquaintance, or describing the behavior of his own dogs or farm animals. so, the story is solidy anecdotal, but still convincing, because you can see how he is being led at each stage to a question; if such-and-such is true, we should observe this, and here is an example that we all know, or an anecdote that i'm sure you'll recognize (e.g. how a dog acts when in anticipation of something he likes).

i also like all the talk about "nerve-force". the idea that this nerve-force overflows from the channels of immediate use, into channels of frequent or necessarily convenient use, and only later into less frequently used channels, is important in a lot of his examples. also, his 'principle of antithesis' in explaining some expressions is, i think, an interesting example of something more general than an adaptation aftereffect. for example, the excited dog, when it finds that it will not get what it expects, will look dejected - the 'hot-house face' - with this expression explained as, essentially, the aftereffect of adaptation to an excited manner. i think i will look more into this idea of antithesis in behavior..

Saturday, December 22, 2012


trying, trying, to get to a black belt in tkd. it's hard, because i am not good at tkd. i have no athletic talent whatsoever, but i try anyways. sometimes it goes well.

so i keep hurting my back over the years, and for the most part it's been less frequent in the past 3, what with the regular exercise. however, i hurt it badly, permanently, last year, after *resting* for a month. not resting actually, but working on a grant proposal, doing nothing but sitting/slouching and reading/writing.

so then, lately, i decided to start doing the sunday afternoon core training class, which is basically variations on sit-ups that you do in rounds, over and over again. it's good. i did it this sunday. the day before, i went to the grocery store, and forgot that we were almost out of rice, so i didn't buy any.

monday night we ate the last of the rice, so tuesday night, on the way home, i went by the grocery and bought two bags, because if you buy two you get a discount. then i went home. this was all on foot or by train. with two 15 pound bags of rice. i didn't perceive a problem.

wednesday night i reached out to lift up the toilet seat, and something in my upper back exploded. so no more tkd for the rest of the week, and it hurt a lot. it's mostly better now, hurts, but i'm not partially immobilized anymore. thursday and friday, along with the back pain, my right arm hurt and my hand was numb. so i'm suspicious that the damage wasn't just to a muscle, but to some part of the spinal machinery, although if so maybe it shouldn't be improving so fast.

i wrote a facebook poem about it:

people who stand
on escalators
cervical spinal nerve eight
the north wind
on cambridge street

in other news, i'm like most americans, preoccupied with guns lately. i don't think anybody has a right to have one, that sums up my opinion. oh well.

going to china tomorrow morning! that will be nice, except i have work to do that i'm not interested in doing but have to do anyways. should be alright.

also, this came out a few days ago, didn't know where to put it, it's pretty ordinary:

undirected urges
to assemble words
vaguely resembling
the task at hand

sitting quietly
struggling silently
ignoring tomorrow
avoiding time

congealing thoughts
pooling together
into my hands
out of my mouth

watch and wait
the page to complete
vaguely resembling
the task at hand

Wednesday, December 12, 2012

red boots

m* is visiting the lab, sitting behind me at the desk where p* used to sit. he's leaving friday. i've had several talks with him about methods relating to the blur adaptation studies, and he's really helpful in clarifying certain issues. he's always solidly skeptical.

he has a whole foods paper bag under his desk, i think it's filled with bottles of beer. when you come in the door to the office, if he's sitting there at the desk, you see his back, and the red and brown paper bag sitting on the floor right next to his feet. yesterday, several times, i came in the door and thought immediately i saw him sitting there wearing red cowboy boots, only to realize what i was really seeing. deja trompé!

Monday, December 10, 2012

bo xilai rides my train

Bo Xilai rides my train. He's usually there when I get on at Reservoir on the 9:45. He always has a seat in the rear car, where I ride in the morning. He sits facing the rear, which I figure he does so that fewer people have a chance to recognize him. A lot of Chinese people ride the D train, but I've never noticed anyone seeming to recognize him. Maybe they do and just ignore him.

He wears Nikes and blue jeans. He doesn't look wealthy or powerful. Sometimes I see him reading a Chinese newspaper, but usually he's just sitting there looking around kind of nervously, or napping with his eyes closed. He rides to the Chinatown stop and gets off. His son went to graduate school at Harvard, so he must have some connections to some Chinese people in town.

But still, why is Bo Xilai riding the train in Boston? Isn't he afraid of being recognized, especially in Chinatown? He's supposed to be under house arrest in China, not riding around on public transit in America. He can't assume that everyone will be friendly and understanding. You'd think it would be excellent tabloid material: "Bo Xilai Escapes to Boston". And what's he doing in Chinatown? Maybe he has a job in a store or a restaurant to pass the time, trying to start a new life, or maybe he's going to some kind of a meeting of exiles.

He always looks a little confused and uncomfortable. I feel like everything isn't right with him. Maybe he's homesick? I saw the pictures of his wife in the docket. Does he think she really did what they say she did? I wonder if she's here too, in Boston. I haven't seen her. Maybe he's just lonely. Maybe he doesn't know anyone here, and he goes to Chinatown to remind himself of China.

I wonder what will happen when it's time for Bo Xilai's trial. Will they use a look-alike? Maybe they'll cancel it, or hold it in secret. Maybe they'll announce that he's died. I can't believe that they'll announce that he's escaped. We'll see what happens - it will all be in the news. I won't tell anyone what I know, though, whatever happens. If Bo Xilai wants to stay in Boston and ride the D-Train, it's really none of my business.

Monday, December 03, 2012

train headache

slightly excruciating headache. developed on the train. may or may not be migraine, it's a fuzzy cloud of pain centered between behind my eyes and my palate. maybe a sinus thing instead, or maybe there's an interaction with the winter air and the train heating. nauseated and photophobic. i keep holding my breath.

Sunday, December 02, 2012

visual phenomena at the two edges of sleep

1. going to sleep last night, and saw that high t.f. flicker, though i didn't have a headache at the time. actually, haven't had one in almost 2 months, i think. woke up this morning feeling like i had a hangover, but no headache per se, so maybe i had a migraine in my sleep? or, it was an overdose on thai food. there were definitely abdominal repercussions.

2. been meaning to write this down: jingping usually gets up before me what with the school and all, and usually when she gets up to leave it's still dark. if she turns on the bedroom light and i'm sufficiently conscious but still with eyes closed (and maybe also if my face is pointing in the right direction), i will see a quick red flash. nothing interesting, right? but the flash has a geometric structure, a hexagonal lattice, like an M-scaled honeycomb. a typical sort of visual field hallucination, but i only started noticing it in recent months.

that is all.

Monday, November 26, 2012

blur or no blur?

Some notes on the aftereffects of a paper revision I just submitted (not coincidentally linked to the rambling at the end of the previous entry):

The big problem I have left over after the last revision of the blur adapt paper is this: does it mean anything? I've wound up half convinced that while I have a good explanation for a complex and strange phenomenon, it may be seen as boiling down just to a measurement, by visual system proxy, of the stimuli themselves. That is, all the stuff about selectivity, slope changing, symmetry of adaptation, etc., might all just be a figment of the wholly unnatural way of blurring/sharpening images that we've used.

What's left? The method is good. There are also questions about the spatial selectivity of the phenomenon, and, most importantly I think, about its timecourse. If blur adaptation is something real and not just a spandrel interaction between contrast adaptation and strange stimuli, it doesn't make a lot of sense that it would manifest in everyone in the same way unless it did have some sort of perceptual utility. The utility that exists is a good question. Let's make a list:

1. Changes in fixation across depths. Most of the people who do these experiments are young and have good accommodation. Blur is one of the things that helps to drive accommodation, to the point where if everything is working correctly, within a few hundred (less?) milliseconds of changing fixation in depth, the image should be focused. So, blur adaptation would not be useful in this situation. Maybe it's useful when you're older, and for this reason it sits there, functional and in wait, for the lens to freeze up? Seems unlikely and implausible, but possible. When you get old, and look at different depths, the sharpness of the image will change, and it would be nice to have some dynamic means of clawing back whatever high s.f. contrasts might still be recoverable in a blurred image.

2. This begs the question of how much can be recovered from an image blurred locally. That is, the slope-change method is basically using an image-sized psf, which is what makes it so weird. Blur doesn't usually occur this way, instead it occurs by a spatially local psf applied to the image, like a gaussian filter. If an image is gaussian blurred, how much can it be sharpened?

3. Viewing through diffusive media, like gooey corneas or fog or rain, or muddy water. The latter phenomena, if I'm not mistaken, affect contrast at all frequencies, while stuff-in-the-eyes effects optical blur, i.e. more attenuation at high than at low frequencies. It would be nice to know, in detail, what types of blur or contrast reduction (it might be nice to reserve 'blur' for the familiar sense of high s.f. reduction) occur ecologically. We also have dark adaptation, where the image is sampled at a lower rate but is also noisier. The noise is effectively a physical part of the retinal image (photon, photochemical, neural), meaning that it's local like an optical defect and not diffusive like fog. Maybe blur adaptation is mostly good for night vision?

4. Television. CRTs. Maybe we're all adapted, long-term and dynamically, to blurred media. All captured and reproduced media are blurred. CRTs were worse than current technology, resulting in displayed images that were considerably blurrier than the transmitted images, which themselves were blurred on collection and analog transmission. Digital images are blurred on collection, although light field cameras seem to be getting around this, and digital displays are physically much less blurred. Maybe those of us who grew up watching CRT images, and accepting them as a special sort of normal, adapt more than the young people who are growing up with high-resolution LCD images?

5. Texture adaptation, i.e. adaptation to the local slope of the amplitude spectrum, i.e. exactly what is being manipulated in the experiments. This would be fine. Testing it would be a bit different; subjects would need to identify the grain or scale of a texture, something like that. I think that the materials perception people have done things like this. Anyways, this sort of adaptation makes sense. You might look at an object at a distance and barely be able to tell that its surface has a fine-grain texture, so a bit of local adaptation would allow you, after a few seconds, to see those small details. On the other hand, if you get in really close to the object so that the texture is loud and clear, and you can even see the texture of the elements of the larger texture, especially if there's a lot of light and the texture elements are opaque, this is effectively a much sharper texture than what you were seeing before, even within the same visual angle. The 1/f property of natural images is an average characteristic. Locally, images are lumpy in that objects represent discontinuities; textures on surfaces usually have a dominant scale, e.g. print on a page has a scale measured in points, and that will show up as a peak in the amplitude spectrum. So, texture adaptation, where the system wants to represent detail, seems like a plausible function for what we're calling blur adaptation. Maybe the system should work better somehow if images are classed in this way?

6. Parafoveal or 'off-attention' defocus. We almost always fixate things that are sharp, but if the fixated object is small, whatever is behind it will be blurred optically. Similar situation if the fixated object is viewed through an aperture, the aperture will be blurred. Whatever adaptation occurs in this situation must be passive, just contrast adaptation, as I can't imagine that there's much utility to the small gain in detail with adaptation to a gaussian blur.

For all of these situations, spatial selectivity makes sense but is not necessary. Even if you're viewing a scene through fog, nearby objects will be less fogged than faraway objects, but it all depends on where you're fixating; other object at different depths will be more or less fogged. At any rate, foveal or parafoveal adaptation is most important, as peripherally viewed details are, as far as I can understand, subordinate. If the process is spatially localized, as it should be if it is what it seems to be, then global adaptation is just a subset of all possible adaptation configurations. Temporal selectivity is more questionable. If the process is genuine, and not just broadband contrast adaptation (though this begs the question of what should the timecourse be for contrast adaptation), how fast should we expect it to be? If it's mostly used for long-term (minutes) activities (fixating muddy water, looking for fish; other veiling glare situations; gooey eyeball; accommodation failure), maybe it could stand to be slower, with a time constant measured in seconds, or tens of seconds. If it's mostly used for moment-to-moment changes in fixated structure, i.e. texture adaptation or depth (off-attention), it should be fast, with a time constant measured in hundreds of milliseconds.

Actually measuring the temporal properties of the adaptation might therefore help to some degree in understanding what the process is used for.

Sunday, November 25, 2012

reading about history

An idle essay on history, for the holiday!

In the past couple of years, a good portion of my recreational reading has been history, and some of that has been by ancient historians: Plutarch, Sima Qian, Livy. For the past few weeks, I've been alternating between two books, a collection of abridged Livy (from the Ad Urbe Condita) and Wittgenstein's Tractatus Logico-Philosophicus, which is a study of how language is connected, or can potentially be connected, to reality. I'm not claiming to fully understand the Wittgenstein, but there has been an interaction.

There are lots of reasons why reading history is enjoyable. The main reason, for me, is that it is so edifying: you are learning how the world came to be the way that it is, and you're also learning about certain constancies of the human condition, mistakes and actions and etc that have been repeated over and over again for thousands of years. Another reason is that it is entertaining in the same way that reading fiction is entertaining: there are heroes and villains, victories and tragedies, and all of it is ambiguous and complex, at least in hindsight.

What the TLP made me think about was this (although not in the confusing terms of propositions, pictures, facts, etc): the page one reads is a surface into which has been pressed different shapes. When one reads, one is feeling these shapes, and mentally reconstructing whatever it was that impressed them. When one reads fiction, the impressor is, supposedly, always secondhand, in that it is the mind of the author that has been impressed, and the author has reconstructed ideas based on those impression, recombined them into mental realities, and then created new impressions based on those mental realities in the page. One then uses those impressions to reconstruct the author's mental realities. Since these reconstructions are not based on physical reality, they constitute in the language of the TLP false facts (although, strictly, many of the components of these false facts must be true; a falsehood cannot be sensible if it is not seemingly possible, its possibility being dictated by the local truth of its parts).

When one reads history, then the intention is that physical reality is impressed into the page, and that when one reads history and reconstructs his own mental realities, these should be (or be close to being) true facts. This is the intention of the honest historian, but he must inevitably fail, because he cannot base all, or even most, of his impressions on physical realities. Historians gain their knowledge by reading what was written by others before them, and then they compile what they have read into narratives that can be understood holistically by others. The historian must judge what are true and false facts, and impress only the true facts. Since other writers may not have thought of themselves as historians, and may not have been intent on impressing true facts, these judgments will be difficult, and the historian will sometimes fail.

So, when reading history as a naive consumer of text like myself, one is in the interesting situation of feeling out these impressions and forming mental reconstructions of the impressors, which are actually impressions of reconstructions of impressors that are actually reconstructions themselves and et cetera. Some of the impressions are mostly true (with local falsehoods), and some must be mostly false (with local truths). It's like Indiana Jones and the Holy Grail, except there's no reward or punishment for deciding that one or another fact is true or false. In reading fiction, the decision is implicit in the definition, but in reading history, you get the sense of walking along the true side of a very fuzzy edge, a transition into the false side. This transition gets broader and broader the further back in time one goes.

This then gets back to another issue which I'd like to write about sometime: the ubiquity of blur. All systems for transmitting information lose local details before they lose fundamentals. High spatial frequencies are lost in image formation; high temporal frequencies are lost as sound travels through a medium; sharp edges on an object are worn down by friction over time; genetic mutations effect molecular changes in the phenotype; and the details of history - names, dates, the precise unfolding of events - are misremembered or, mostly, forgotten. These are details in the literary sense, but they seem exactly analogous to physical details: what happened in Caesar's final days? Did he go to the forum in spite of warnings? Was Brutus really his son? These sorts of details, the answers to these sorts of questions, are permanently forgotten, but we know the larger, deeper, important events: Caesar was murdered by a conspiracy of Senators.

Interestingly, in the same way that a knife might be sharpened, or faded images might be retouched, old stories about the past might be sharpened up with added details; doped with false facts, to bring them into narrative focus. Caesar was warned about the Ides of March; he saw Brutus and said, "You too, my son?" The doping could also be with irrelevant facts: this is what you could buy from a street vendor in those days, this is what the men and women of this station wore on their feet. This sharpening, false or irrelevant, is enjoyable in a special way when it comes from someone who was writing more than 2000 years ago, because it is more immediate: nothing (except for the translator) has touched these impressions since they were formed. It's like holding something very, very old in your hands.

Sunday, November 18, 2012

finally a post about those eye crank lines

has anyone ever tested basic visual psychophysics as a function of gaze direction? i don't think so. would it be interesting or important to do so? i think so.

1. when i crank my eyes out as far as i can, i see weird phosphene patterns around my foveae (below). nobody has given me a good explanation for what these phosphenes are, except that they are probably produced by some sort of tension or torsion on the optic nerve. this isn't much of an explanation, because the phosphenes are so local and fine that if it was torsion i would expect them to be everywhere. it could be the correct explanation, but then i need an explanation for why they aren't everywhere, or what is special about foveal optic nerve fibers etc etc in their placement in the optic nerve. the sort of thing i guess i could figure out from reading.
whatever the cause of this effect, it means that in the extreme, direction of gaze has an effect on low-level perception, i.e. i am seeing spatial phosphenes - which, really, look like band-pass patterns - and not hallucinating faces or whatever. so, it stands to reason that less extreme directions might also have effects that are more subtle.

anyways, i hope i am not tearing apart my optic nerves by doing this experiment. i try not to do it too often, but it's like thinking about reciting pi. when you think about reciting pi, you have to recite as many digits as you can remember. you can't stop. give me a second.

2. if e.g. contrast sensitivity is entirely determined by retinotopically coordinated visual mechanisms - i.e. retina, LGN, V1, striate cortex - direction of gaze shouldn't make any difference, because these areas don't know anything about direction of gaze. but visual areas in the parietal cortex do know about direction of gaze - areas like LIP and VIP combine input from the visual system, of such quality that it is used to plan eye movements, with proprioceptive, vestibular, motor, and other inputs.

it's implicit in the theory of psychophysics - the theory that physical stimuli are translatable into perceptual states, which are then behaviorally accessible - that the last stage of vision is motor, since no psychophysics can be done without motor responses. this is one reason why neuroimaging is not psychophysics.

so, if vision interacts with non-visual inputs, and if these same inputs mediate behavioral measurement of visual ability - i.e. psychophysics - then is it reasonable to suppose that direction of gaze should affect basic visual abilities? a good hypothetical mechanism for producing an effect would be the internal noise source. no one should suppose that the noise limiting performance is entirely visual, because this assumes that the rest of the system is deterministic, which it is not. since the rest of the system is not deterministic, the portion of the random variation that is contributed by the parietal cortex might well vary with the tonic motor state of the system; the part of the brain that is guiding or maintaining the motor aspects of the system, and mediating the responses of the system according to the experiment design, might be better adapted or learned in one gaze state than in others.

3. visual neglect. i guess this is a higher-level thing, but from what i've heard, it's independent of basic sensitivity; how could this have been confirmed? how can basic testing be carried out with the same quality in the neglect region as in the unaffected region? this sounds like something that's been tried over and over, and that i could go read about. a quick survey of some titles, abstracts, and a couple of the most relevant-sounding papers suggests that when such sensitivity has been measured, its in the non-neglect areas, but that the researchers are nonetheless looking for a connection. there's a paper where they suggest there's no difference in contrast sensitivity or s.f. discrimination between two groups of stroke patients, some with neglect symptoms, some without; that could mean that even a stroke big enough to cause neglect, while sparing early visual cortex, won't bother basic sensitivity, or that any serious enough stroke will impair sensitivity on basic tasks. hm...

Thursday, November 15, 2012

stack puzzle

Okay, I’ve been wondering for a while whether or not something is a valid question – a good question or a bad question. It is related to a few entries I’ve written here in the past year (esp. this and this), and to a paper that I’m about to get ready for submission.

The question: are the percepts contributed by different layers or modules of visual processing perceived as embedded within one another, or as layered in front of or behind one another?

Such percepts could include brightness, location and sharpness of an edge, its color, its boundary association; color and shape and texture of a face, its identity, its emotional valence, its association with concurrent speech sounds; scale of a texture, its orientation, its angle relative to the frontal plane, its stereoscopic properties.

All of these, and more, are separately computed properties of images as they are perceived, separate in that they are computed by different bits of neural machinery at different parts of the visual system hierarchy. Yet, they are all seen together, simultaneously, and the presence of one implies another. That is, to see an edge implies that it must have some contrast, some color, some orientation, some blur; but this implication is not trivial. That is, a mechanism that senses an edge does not need to signal contrast or color or orientation or scale; the decoder could simply interpret the responses of the mechanism as saying ‘there is an edge here’. To decode the orientation of an edge requires that many such mechanisms exist, each preferring different orientations, and that some subsequent mechanism exists which can discriminate the responses of one from another, i.e. the fact that the two properties are both discriminable (edge or no; orientation) means that there must be a hierarchy, or that there must be different mechanisms.

So, whenever something is seen, the seeing of the thing is the encoding of the thing by many, many different mechanisms, each of which has a special place in the visual system, a devoted job – discriminate orientation, discriminate luminance gradients, discriminate direction of motion, or color, etc.

So, although we know empirically and logically that there must be different mechanisms encoding these different properties, there is no direct perceptual evidence for such differences: the experience is simultaneous and whole. In other words, the different properties are bound together; this is the famous binding problem, and it is the fundamental problem of the study of perception, and of all study of subjective psychology or conscious experience.

This brings us to the question, reworded: how is the simultaneity arranged? From here, it is necessary to adopt a frame of reference to continue discussion, so I will adopt a spatial frame of reference, which I am sure is a severe error, and which is at the root of my attempts so far to understand this problem; it will be necessary to rework what comes below from different points of view, using different framing metaphors.

Say that the arrangement of the simultaneous elements of visual experience is analogous to a spatial arrangement. This is natural if we think of the visual system as a branching series of layers. As far as subjective experience goes, are ‘higher’ layers in front of or behind the ‘lower’ layers? Are they above or below? Do they interlock like... it is hard to think of a metaphor here. When do layers, as such, interlock so that they form a single variegated layer? D* suggested color printing as something similar, though this doesn’t quite satisfy me. I imagine a jigsaw puzzle where the solution is a solid block, and where every layer has the same extent as the solution but is mostly empty space. D* also mentioned layers of transparencies where on each layer a portion of the final image – which perhaps occludes lower parts – is printed; like the pages in the encyclopedia entry on the human body, where the skin, muscles, organs, bones, were printed on separate sheets.

But after some thought, I don't think these can work. An image as a metaphor for the perceptual image? A useful metaphor would have some explanatory degrees of freedom; one set of things that can be understood in one way, used to understand something different in a similar way. Where do we get by trying to understand one type of image as another type of image? Not very far, I think. The visual field is a sort of tensor: at every point in the field, multiple things are true at the same time, they are combined according to deterministic rules, and a unitary percept results. Trying to understand this problem in terms of a simpler type of image seems doomed to fail.

So, whether or not there is a convenient metaphor, I think that the idea of the question should be clear: how are the different components of the percept simultaneously present? A prominent part of psychophysics studies how different components interact: color and luminance contrast, or motion and orientation, but my understanding is that for the most part different components are independently encoded; i.e. nothing really affects the perceived orientation of an edge, except perhaps the orientations of other proximal (in space or time) edges.

Masking, i.e. making one thing harder to see by laying another thing in proximity to it, is also usually within-layer, i.e. motion-to-motion, or contrast-to-contrast. Here, I am revealing that my thinking is still stuck in the lowest levels: color, motion, contrast, orientation, are all encoded together, in overlapping ensembles. So, it may well be that a single mechanism can encode a feature with multiple perceptual elements.

Anyways, the reason why I wonder about these things is, lately, because of this study where I had subjects judge the contrast of photographic images and related these judgments to the contrasts of individual scales within the images. This is related to the bigger question because there is no obvious reason why the percept contrast of a complex, broadband image should correspond to the same percept contrast of a simple spatial pattern like a narrowband wavelet of one type or another. This is where we converge with what I have written a few months ago: the idea of doing psychophysics with simple stimuli is that a subject’s judgments can be correlated with the physical properties of the stimuli, which can be completely described because they are simple. When the stimuli are complex and natural, there is a hierarchy of physical properties for which the visual system is specifically designed, with its own hierarchy, to analyze. Simple stimuli target components of this system; complex stimuli activate the entire thing.

It is possible that when I ask you to identify the contrast – the luminance amplitude – of a Gabor patch, you are able to do so by looking, from your behavioral perch, at the response amplitude of a small number of neural mechanisms which are themselves stimulated directly by luminance gradients, which are exactly what I am controlling by controlling the contrast of the Gabor. It is not only possible, but this is the standard assumption in most contrast psychophysics (though I am suspicious that the Perceptual Template people have fuzzier ideas than this, I am not yet clear on their thinking – is the noisiness of a response also part of apparent magnitude?).

It is also possible that when I ask you to identify the contrast of a complex image, like a typical sort of image you look at every day (outside of spatial vision experiments), you are able to respond by doing the same thing: you pool together the responses of lots of neural mechanisms whose responses are determined by the amplitude of luminance gradients of matched shape. This is the assumption I set out to test in my experiment, that contrast is more or less the same, perceptually, whatever the stimulus is.

But, this does not need to be so. This assumption means that in judging the contrast of the complex image, you are able to ignore the responses of all the other mechanisms that are being stimulated by the image: mechanisms that respond to edges, texture gradients, trees, buildings, depth, occlusions, etc. Why should you be able to do this? Do these other responses not get in the way of ‘seeing’ those more basic responses? We know that responses later in the visual hierarchy are not so sensitive to the strength of a stimulus, rather they are sensitive to the spatial configuration of the stimulus; if you vary how much the configuration fits, you will vary the response of the neuron, but if you vary its contrast you will, across some threshold, turn the neuron on and off.

I don’t have a solution; the question is not answered by my experiment. I don’t doubt that you can see the luminance contrast of the elements in a complex scene, but I am not convinced that what you think is the contrast is entirely the contrast. In fact, we know for certain that it is not, because we have a plethora of lightness/brightness illusions.

No progress here, and I'm still not sure of the quality of the question. But, maybe this way of thinking can make for an interesting pitch at the outset of the introduction of the paper.

Thursday, November 08, 2012


I keep noticing, lately, near- and far-peripheral flashes, phosphenes. There was one a few minutes ago, maybe 10deg below fovea, very obvious and yet hard to localize (it was almost as though it extended close to the fovea); I checked for a blindspot, found none. So, based on all these recent sparky things, I predict something happening in the next few days (especially since the BA paper is just about done, so I'm about to go through another relax-contract phase).

Monday, November 05, 2012


probability of an event occurring
likelihood of a condition existing

how often have i misused these words? unknown.

if i search this blog, i find one clear misuse of 'likelihood', in "a specific instantiation..." ("likelihood of a pass"); i use the term two other times, in the first post ever and in a later one that refers to that one. in those instances (likelihood that you are alive at age x) i think it's ambiguous, but i'll count those as accurate.

amazingly, there is only one post where i use the word 'probability' in the relevant context. and i can't tell if i'm using it right or not. i'm kind of disappointed in myself.

seems i've fallen off the HAZ-PJ wagon. writing is going well, though, which is good.

Friday, October 26, 2012

government as a design problem

trying to work on a paper revision due sooner and sooner, but i keep thinking about politics. of course, it is The Time to think about politics, but i wish i could escape it.

anyways, here's what i've been thinking, a tiny idea:

from the institution of a new state or government, for a time, it is reasonable to expect the government to grow and acquire new features. this is just because upon its institution, the government must be incomplete or flawed. virtually nothing complex can approach perfection, especially in its first design.

however, at some point, we might consider the institution - or, and here's the real idea, a given version of the institution - to be complete. that is, we have this complex structure, with many parts and many layers and many functions, and it is intended to accomplish many things under particular constraints. presumably, changes made to this structure over time are intended to fulfill these intentions. we could think of this as efficiency, i.e., how much of what the system is meant to do is it actually doing? this is a funny idea, since it implies that if the system exceeds its mandate, it is being overly efficient. i will get back to this in a moment.

the idea is that a version of the institution can be considered complete, in that a time will come when it's clear to everyone that no changes, or only basic maintenance changes, are necessary to meet the objectives of the system; or, it might be decided that the objectives are outdated, and that new objectives have arisen, and that a new system needs to be designed to replace the old one. have we ever reached that point with the american federal government? i think maybe we have, and it was a long time ago: pre-civil war, really. in the 1850s, the federal government wasn't really creating many new responsibilities for itself, and was instead preoccupied with its intended functions of maintaining relations between the states, applying tariffs in international trade, occupying new territories that would eventually become states, etc. i think this is the tail end of what historians refer to as the "second party system": FED2.0. FED2.0 was rolled out in the 1830s, had some successes early on, and then crashed and burned.

it was around the time of the civil war that the government basically went through a big redesign, acquiring new responsibilities which then required new features to be fulfilled. this was the "third party system" that lasted until the 1890s, when it was replaced with FED4.0, which lasted until the great depression. versions 3 and 4, i think, are not really considered to be very good versions (and probably could be collapsed into subversions of FED3), while a lot of people are clearly very nostalgic for versions 1.0 and maybe 2.0 (and might see those as subversions of FED1).

in the 1930s, the government went through a huge redesign: FED5.0; the end of the 1960s saw a big advance on this (FED5.1), and now we're probably at version 5.3 or 5.4. version 5 is the longest-lived political system that the US has had (or similar with FED3/4). clearly, i think, it's time for a redesign. at this point, the two parties are just concerned with adding, subtracting, or modifying features, with a strong tendency towards addition (the 'ratchet effect' or 'featuritis'). i think that a lot of people thought that with o* and the d*s, after the 2008 election, we would be moving on to a new version 6; a lot of people thought that in 2004 with b* and the r*s. neither succeeded; i don't think that either really succeeded in moving a new subversion, either: we're stuck in beta, at 5.3.2 or something like that.

so, back to 'excess efficiency'. what is that? it's not what it sounds like. when a system isn't quite fulfilling its promised aims, if it wants to preserve itself (consider that institutions don't want to die), it might throw up new proxy aims. it can them give the illusion of accomplishment or fulfillment by moving to meet those new aims, thus obscuring the fact that the old aims aren't exactly complete; or, that they're no longer valid, and that the system thus is working to fulfill aims that no longer exist. i.e., excess efficiency is a sign that a system is desperate and needs to be replaced.

Monday, October 22, 2012

taxes and politics

a friend posted this link on facebook, along with a quote to the effect of, "raising taxes to pay for investments in the middle class creates jobs". i resisted posting a response there because i don't like to argue about these things and would rather keep my opinions to myself, and because (relatedly) i am afraid to affect others' opinions of me in ways that i don't have close control over. so i thought i'd post a response here, where no one can read it:


while i agree generally with sentiment that says the rich should be taxed relatively more, the idea that this is then turned around by the federal government into "investment in the middle class" is not obvious to me. i think that very little of taxation, at least in a developed country like the US, translates directly into economic growth. in fact i think it tends to be the opposite, and i agree more with the idea that raising taxes tends to suppress growth.

a large portion of government spending put in place by the democratic party (which is presumably the favorable political dimension for the approving audience of this talk) is in the form of political favors to constituencies that have an insignificant impact on the economy (poor, elderly); institution of new bureaucracies which have to be funded at the same time that their mandate is usually to impose some form of *restriction* on certain types of economic activity; increased funding of dysfunctional programs without improving function ("education"); and, you can be sure that the more the US government collects in taxes, the more it will spend on the military, or on foreign aid, etc.

interesting case in point relevant to our livelihoods: significant government spending goes into biomedical research, which winds up making people live longer at the same time that it makes all forms of healthcare more expensive (MRI for everybody! one-of-a-kind cancer drug for my grampa! YOU CAN LIVE FOREVER NOW). i guess this creates jobs in the hospital/rest home industries.

*not that any of these things are wrong per se*, but it's not clear how any of this works as investment in the consumer class that generates net jobs. i think the government of a developed country actually has very little capacity to "create jobs", except in managing trade policy and maintaining transportation infrastructure. i.e. i think this guy's argument is pretty arguable.

Sunday, October 14, 2012


finally working on that blur adaptation paper. not much else to think about or report.


last saturday (the 6th) woke up with a headache, fairly painful: i'd rate the usual ones at 2/10, and this was a 4/10. today, i wake up with one even worse: i'd put this at 6/10 (assuming it can get much worse). this is awful - it's as bad as that night tukrong punched me in the head 10 times. what is going on with my brain?

Friday, October 05, 2012

task done

we made it: the proposal is submitted. transitioning to revising papers. woo hoo?

Wednesday, October 03, 2012

inevitable negativity

i am now (technically) a faculty member at harvard medical school ("instructor": about as junior junior junior as possible)! wow! and, (technically), no longer a postdoctoral fellow: i am now a "senior scientific associate". all so i can apply for a grant with a less than a 1% chance of getting funded (optimistic i am). so, something there. beautiful appearance of progress.

also, couple of papers accepted; probably will have a paper in PLoS-one, which is nice, but i'm third of four authors, so..


came up with this on the train, coming home last friday night (9-28-12)

on Cambridge Street
put away
your umbrellas
or they'll wind up
cast aside
in tattered heaps

on Cambridge Street
thrust your head
into the wind
and bear the rain
it's autumn
it's not cold yet
be thankful

Sunday, September 30, 2012


quick notes for the end of september:

week 1 of bring-your-laptop-to-work was a success; worked steadily in the lab every day, and came home each night to do particular jobs by hand, with pen and paper. extremely effective. laptop came back home friday night; going to continue this for the foreseeable future. should make the next MS revision and the following MS submission much easier.

headache last night, gradual onset; eventually focused pain above right eye socket; photophobia; went to bed, closed eyes, weird eigenlicht flicker, maybe 40-50Hz; what is that? slight headache remnant now, indistinct.

recent weirdness with reading text, usually notice in the morning; right now, left of fixation feels scotoma-like, but i can see there..


also, a story: when i sit at the kitchen table, in the chair by the window, i have a view of the pantry area, with the fridge and the back door. my leather sandals are wedged between the fridge and the wall, by the door, so i can wear them outside when i go to throw trash out.

i regularly mistake the sandals, peripherally, for Olive the Cat, sitting by the back door, wanting to go out. then i foveate them, and see that they are my sandals. this has happened repeatedly, maybe dozens of times: deja trompé!

Tuesday, September 25, 2012

why do i keep writing poems

Batten down the hatches!
In this electric squall
Or else we'll be sent to the deep -
The web will drown us all.

So home I'll go! To printed word,
With pen and paper work.
No opportunity to drift
Through forums or to lurk

In hiding from my calling,
I'll forge ideas by thought
And stare down syntax, words reform
To make all logic-wrought.

So batten down the hatches!
And keep the ship afloat
For though I'll try to steer us,
The net may wreck this boat.

Friday, September 21, 2012

grant, presentation, paper, model

Been trying to skip between several jobs: grant proposal with a looming deadline, modeling experiments for a paper revision with a looming deadline, looming conference presentation... well, the conference is over, and the grant is coming along, though I still do not believe I will make it.

The paper..  okay, another paper: poked an editor yesterday, and he came back with a 'minor revision' request, which I fulfilled by late afternoon today. So, finally, we have a journal article - in a 1.0 impact factor journal - to show for a 3 year postdoc. Sigh. Another in revision, in a better journal, but that's the big problem: I'm doing all these model tests, but I can't get any real momentum because I keep flipping back to the grant. Sigh. I keep complaining about the same thing. Need to set a deadline - 3 more years? - after which if I'm still making the same complaint, something needs to change.

Let's talk about the model stuff. I've talked about it already in the past few posts: in the original paper, I proposed a modification to an existing model, a minor modification, which was able to closely fit our data, but which was a bit complexified, and difficult to explain exactly why it worked as well as it did, and also unable to show how varying its parameters explained the variance in our data, etc. So, it "worked", but that's about all it did. It didn't explain much.

The existing model we call the "simple model". The simple model is indeed simple. It's so simple that it's almost meaningless, which is what frustrates me. Of course it's not that simple; you can interpret its components in very simplified, but real, visual system terms. And, it basically can describe our data, even when I complexify it just a bit to handle the extra complexity of our stimuli. And this complexification is fine, because it works best if I remove an odd hand-waving component that the original author had found it necessary to include to explain his data. Only... it doesn't quite work. The matching functions that make up the main set of data have slopes that are different in a pattern that is replicated by the simple model, but overall the model slopes are too shallow. I spent last week trying to find a dimension of the model that I could vary in order to shift the slopes up and down without destroying other aspects of its performance..  no dice.. fail fail fail.

So, I'm thinking that I can present a 'near miss': the model gets a lot of things right, and it fails to get everything right for reasons that I haven't thought hard enough about just yet. I really need to sit some afternoon and really think it out. Why, for the normal adaptor, is the matching function slope steeper than the identity line, but never steep enough? What is missing? Is it really the curvature of the CSF? How do I prove it?

Now, out of some horrible masochistic urge, I'm running the big image-based version of the "simple model". This version doesn't collapse the input and adaptation terms into single vectors until the 'blur decoding' stage. It seems like, really, some version of this has to work, but it hasn't come close yet. Looking at it now, though, I see that I did some strange things that are kind of hard to explain... Gonna give it another chance overnight.

Sunday, September 16, 2012

too far, too far

one hundred words
in haiku form
while waiting for
my flight on a
sunday evening
in september:

Rochester airport
September Sunday evening
me and three women

80s pop radio
electric piano solo
fluorescent lighting

now another man
sneakers, backwards baseball cap
the sun is setting

PA announcement
the guy's voice croaks like Stallone
a fine disco beat

two smartphones, a book
two pair boots, one pair flip flops
not a conjunction

what will our plane be?
CRJ, Boeing, Airbus?
another man comes

three women, three men
the humans are trickling in
going to Boston

the sun sets slowly
slower than it usually does
suspicious liquids

dinner of junk food
reflection of ceiling lights
in my laptop screen

Saturday, September 15, 2012

morning aura

in rochester for the OSA vision meeting.

woke up this morning about 6:30ish, with terry yelling at me to wake up. went to take a shower, and while there, realized i couldn't see my fingertips as i was washing, grabbing soap, etc. got out of the shower, got dressed, left the room and went to the lobby. got there a little after seven, and the scotoma was well into the periphery, flickering etc. it was just like the last three: left field, straight right-left through the upper field and arcing downward into the lower field.

the last one i managed to record, back in june, had a time gap between the foveal scotoma and the peripheral arcs, which i had post hoc explained as me needing to recalibrate some part of the perimeter or something. but during the last two, i noticed that the scotoma actually does seem to disappear between the foveal appearance and the peripheral arcs. wonder what is going on with that...

didn't notice any peripheral rough spot this time, but it was so early that i might just have been too dazed.. these morning scotomas that i've experienced - the last one a few weeks ago, and the one last year in the winter - they seem to have started just as i awoke. may be coincidental, since it's just a sample size of three, but i haven't had one start a half hour after waking, and i haven't woken up halfway through one (though the first time, i think i lay there with my eyes closed for the first 10 minutes or so). might be interesting to look up what sort of neurochemical changes occur in cortex, esp. visual cortex, during waking.

headache was ok, took some tylenol this time. nauseated all day long.


yesterday (or maybe thursday night, not sure), i remember feeling suspicious that something might be about to happen: i had the thought, i should keep track of these suspicions, to see if they're actually correlated. it is possible that i am suspicious very frequently, and just notice the coincidences..

Thursday, September 13, 2012

Deja Trompé

When I was in graduate school, I lived in Old Louisville, and walked, most days, down 3rd street to campus. Whenever I crossed the big road separating the neighborhood from campus, Cardinal Avenue, at a certain spot, I would see something up in my right peripheral visual field, and think, "Starlings!"

It was never starlings. It was always the tattered insulation hanging off a bunch of power lines strung over Cardinal. I remember this because even though I learned, pretty quickly, that I wasn't seeing starlings in that instant whenever it occurred, the fastest part of me - whatever part just automatically identifies salient stuff in the vast periphery - always thought that I was.


It not that I was hallucinating starlings. A bunch of speckly black stuff fluttering against the sky kind of looks like birds, even when you know it isn't. You can't blame me. I don't blame my visual system. It's an honest mistake. The interesting thing is that I kept making it, over and over again, with apparently no control over it. An inconsequential and incessant perceptual mistake.

I've noticed similar situations over the years, but right now I can't remember the others. I should start making a list. I bring this up because recently someone cleaned out the shared kitchen on this side of the institute, and because I always turn the lights out in the same kitchen.

I think that, because I always turn out the light when I leave the little kitchen, other people have started following my example, and now, often, when I go to the kitchen to get hot water for my tea, the light is already out. This makes me happy. It's happened very gradually. Change is slow, usually.

Usually. Recently, the development office got a new temp who is apparently a complete OCD clean freak. It's great. She cleaned this kitchen and the other one. She put up little signs everywhere telling people not to be such pigs. I love her.

Anyways, now, when I go into the little kitchen to get my water, I stand at the dispenser, watching it to make sure my hand doesn't stray and I don't get scalded, and the microwave with its little sign sits down in my lower left field. Often, lately, the light is out when I get there. I leave it that way, because there's enough light trickling in from the hallway. Every time I am in this configuration, with the light out, it looks for all the world that there is light coming out of the microwave window.

This happens over and over again. It's very robust; I can stand there and look straight at the microwave and its little paper sign, and that's what I see; then I look away, and the sign becomes an emission of lamp light from within the microwave. I can turn the mistake on and off by moving my eyes back and forth.

Again, I don't blame my visual system. It's doing the best it can. I've seen so many microwaves, and when they're cooking, they usually have little lamps inside, so you can see your whatever rotating on the little turntable. If the room is dark, the image is basically of a luminous rectangle in the front door of a microwave. Not many microwaves that I have known have worn little paper signs on their doors. To their disgusting, disgusting peril.

There must be a name for this, but I can't find it. So for now I'm going to invent a term: deja trompé‎, "fooled again". Deja as in deja vu, "again seen"; trompé‎ as in trompé l'oeil, "deceives the eye". Seems like the right flavor for this sort of thing. I'll start keeping track of these, however rare they are. I'll inaugurate the list with a new entry label.


Wednesday, September 12, 2012


Trying to figure out how to proceed with this adaptation paper, and I retreat here.

Minor problem is the rewrite: this will get done, not too worried about it. May be the last thing that gets done, since the major problem needs to be solved materially first.

Major problem is the modeling. The original paper details a complexified version of the model proposed by the authors of a paper that our paper basically replicates, accidentally. We were scooped, and so I thought that to novelify our paper, I would take their model and try to push it a little further, and do some extra analysis of it.

What I didn't do was what I should have done, which was to also test the simple model and show that it is somehow inadequate, and that complexification is therefore justified or necessary. I am actually ambivalent about this. My main idea was that we should take a model which has generalizable features and use it to explain the data; but, it's true that the more sophisticated version can't really be credited with achieving anything unless the simple one can also be shown to fail.

So the problem is that I have to do a lot of testing of the simple model. So, I decided that I would scrap the section that was already in the paper and replace it with an evaluation of the simple model, but make up for the lack of 'advance' by employing the simple model in a more realistic simulation of the actual experiments. This is what I've been trying to do, and basically failing at, for several weeks now.

The first idea was to use the simplest form of the model, but the most complete form of the stimuli: videos, played frame by frame and decomposed into the relevant stimulus bands, adaptation developing according to a simple differential equation with the same dimensions as the stimulus. This didn't work. Or, it almost worked. The problem is that adaptation just won't build up in the high frequency channels, unless it's way overpowered, which is against any bit of evidence I can think about. If high frequency adaptation were so strong, everything would be blurry all the time. I think it should be the weakest, or the slipperiest.

Soon after that, I gave up and retreated to the 'global sum' model, where instead of using 2d inputs, I use 0d inputs - i.e. the stimulus is treated as a scalar. I get the scalars from the real stimuli, and the same dynamic simulation is run. It's tons faster, of course, which makes it easier to play around with. I figured I would have found a solution by now.

See, it's so close. It's easy to get a solution, by adjusting the time constants, how they vary with frequency, and the masking strength, and get a set of simulated matching functions that look a lot like the human data. But I figure this is uninteresting. I have a set of data for 10 subjects, and they seem to vary in particular ways - but I can't get the simulated data to vary in the same way. If I can't do that, what is the point of the variability data?

Also, last night I spent some time looking closely at the statistics of the original test videos. There's something suspicious about them. Not wrong - I don't doubt that the slope change that was imposed was imposed correctly. But the way contrast changes with frequency and slope is not linear - it flattens out, at different frequencies, at the extreme slope changes. In the middle range, around zero, all contrasts change. Suspiciously like the gain peak, which I'm wondering isn't somehow an artifact of this sort of image manipulation.

I don't expect to figure that last bit out before the revision is done. But, I'm thinking it might be a good idea to play down the gain peak business, since I might wind up figuring out that e.g. adaptation is much more linear than it appears, and that the apparent flattening out is really an artifact of the procedure. I don't think I'll find that, but - did I mention I'm going to write a model-only paper after this one? - seems a good idea not to go too far out on a limb when there are doubts.

I have a nagging feeling that I gave up too soon on the image-based model...

Friday, September 07, 2012

talk: 97%

did a dry run today for my FVM talk. i think it went well, but there was a good amount of feedback. (incidentally, earlier this week i came to the lab, and passed my preceptor e* talking with a familiar old guy in the hall; a few minutes later, e* brings the guy to my office and asks me to show him my work. the old guy was l.s., one of the elder statesmen of european psychophysics. turns out he had been a postdoc at the instutute more than 40 years ago, and was in town, and had just dropped in to see old friends.. i took him through my presentation at quarter speed, and he was very enthusiastic. made some suggestions about controlling for the 'knowledge' aspect of my stimuli and experiment design. took notes. had a good talk with him, he seems to know my grad school mentor well, knows all his students. so i didn't go to ECVP this week, but i got to spend a morning with one of its founders...)

anyways, the dry run: p* was the only one, as i guess i expected, to make real comments on the substance of the talk. he had two points/questions:

1. what happens if the two images are different, i.e. if they have different phase spectra? i have not tried to do this experiment, or to predict the result. i guess that technically, the model that i am evaluating would make clear predictions in such an experiment, and the perceptual process i am claiming to occur would be equally applicable. but, really, i am tacitly assuming that the similarity of the two images is tamping down noise that would otherwise be there, somehow in the spatial summation, that isn't actually reflected in the model but that would be there for the humans. but, it might work just fine. i should really try it out, just to see what happens... (*edit: i tested it in the afternoon, and the result is exactly the same. experiment is harder, and the normalization is wacky, but seems clear it works...)

2. don't the weighting functions look just like CSFs? isn't this what would happen if perceived contrasts were just CSF-weighted image contrasts? yeah, sure, but there's no reason to believe that this is how perceived contrast is computed. the flat-GC model is close to this. i wonder if i shouldn't just show a family of flat-GC models instead of a single one, with one of them having 0-weighted GC...

the other main criticism was of the slide with all the equations. this is the main thing i think i need to address. i need to remake that slide so it more naturally presents the system of processes that the equations represent. some sort of flow or wiring diagram, showing how the equations are nested...

also need to modify the explanation of the contrast randomization; not add information, but make clearer that the two contrast weighting vectors are indeed random and (basically) independent.

Monday, September 03, 2012

two out of three ain't enough

okay, so, really, i spent the labor day weekend watching youtube videos, looking at funny gifs, reading the news, and other random things, while running half-baked model simulations for the blur adaptation revision.

first thing i did was to run the video-based model through the experiment on the same three adaptation levels used in the original experiment. it worked at an operational level, i.e. it matched sharper things with sharper things and blurrier things with blurrier things, and the effects of the adaptors were correctly ordered - it didn't do anything crazy. on an empirical level, though, it was wrong.

for the original subjects, and most of the replication subjects, the perceived normal after blank adaptation should be matched to a slightly sharpened normal-video-adapted test; the simulation did the opposite. not a huge problem, but like i said, against the trend.

bigger problem is that the simulation failed to get the 'gain' peak for the normal adaptation condition; instead, gain just increased with sharpness of the adaptor. now i'm rerunning the simulation with some basic changes (adding white noise to the spatial inputs, which i don't think will work - might make it worse by increasing the effective sharpness of all inputs - but might have something of a CSF effect; and windowing the edges, which i should have done from the start).

one funny thing: even though the gain for the sharp adaptor is too high (being higher than for the normal adaptor), the gains for the normal and blurred adaptors are *exactly* the same as the means for the original three subjects: enough to make me think i was doing something horribly weirdly wrong in the spreadsheet, but there it is:

weird, but too good to be true. undoubtedly, every change to the model will change all of the simulation measurements, and the sim is definitely as noisy as the humans - even the same one run again would not get the same values.

Sunday, September 02, 2012


I seem to have gotten into treating this thing as a migraine journal, so here: headache last night (Saturday). Strange one, came on slowly, from mid-afternoon, increased gradually until 10 or so, when it was actually pretty irritating. May be something else. It's kind of still here, vaguely. Front of the head, above-behind the eyes, but something about it is different. Dunno.

As for work, I should have done more this weekend. I have 3 current main foci: FVM presentation, blur adaptation revision, and R01 application.

The presentation is >90% done. I'm leaving it for a few days.

The blur adapt revision is 0% done. I'm trying to figure out what "simple" model to replace the section in the paper with. If I can't get it to work by the end of the week, I think I'll have to stick with the original "complicated" model, and *add* material (thus making it *more* complicated) to explain why the simple version can't be easily adapted to work. What this entails is about an hour of programming and 24 hours of running the simulations/measurements so I can see the results and decide on what isn't working and make changes and repeat the process. In the meantime, I do nothing productive. So:

R01 application is... well... I don't want to do it. It's futile, but it's my job. Will start soon. Should have started this weekend.

Wednesday, August 29, 2012

dream science?

Too many entries - let this be the last one for August.

Fantastically, incredibly, unbelievably, implausibly, Monday night I had a dream that directly relates to Monday's entry. I'll leave out irrelevant details: I dreamed that I was experiencing a migraine aura.

In the dream, I noticed the phosphene-like foveal scotoma, and at first had the "is it an afterimage? what bright light did I look at?" reaction, and then realized what it really was. It was upsetting, actually, because the last one was just 1 week previous, and I felt like once a week is a bit too frequent.

I then set about trying to record the aura with my perimetry program, except that my computer was now a large, flat panel lying on the floor, like a giant i-pad. The layout was of course different - not a blank gray screen, but a thin-line black grid, like a Go board, on a wood-brown background. Jingping was there, and kept trying to move the grid around, and I kept telling her to stop.

Once I was trying to record it, the scotoma was no longer foveal, but extended 10-20 degrees out, straight to the left and then arcing downward towards the inferior vertical meridian. This makes me think that I wasn't actually experiencing an aura in my sleep - to get from the foveal scotoma to 10-20 degrees should take 15-20 minutes, and I don't think that much time actually passed in the dream - it seemed like less than a minute. Of course, time and space are both funny in dreams, so who knows. There was no headache on Tuesday, anyways.

It was very frustrating trying to set the fixation point in the dream perimetry program. I just couldn't fixate - I would set it in one place, and then felt that it should be somewhere else. I think I finally gave up and started sticking my hand in the scotoma to probe its size.

So, whether or not I was really experiencing an aura, or just dreaming that I was experiencing one, is an interesting question. It seemed like a real one, and I noted lots of spatial details: the tiny phosphenic bead of the foveal scotoma, the fuzzy noisiness of the peripheral scotoma arc (though the periphery seemed clearer somehow in than true peripheral vision), the thin black lines of the perimetry grid, the unfixable fixation spot.. If visual experience includes V1 activity, and if the visual aura occurs in V1, and if V1 is quiet or suppressed during dreaming, how could I have seen what I did, unless spatial vision includes a good deal of higher-level inference?

It seems that I proposed an experiment on Monday afternoon, and then did the experiment in my sleep that night. I have never been so efficient!

Monday, August 27, 2012

summation or conclusion?

So, I'm realizing now that this note from a few days ago is touching on this entry from several months back (if only I could keep everything in my head at once...). In the latter, I was talking about the idea that visual experience is a stack of phenomena, extending all the way down to the optical image, even to the light field, and all the way up to cognition and emotion. In the former, I realized that my standing, computational interpretation of the classification image experiment involves an assumption that estimates of a particular psychological construct - perceived contrast - are mediated by the same processes whether the stimulus is simple or complex.

This stance doesn't conflict with the 'stack' idea, but when you think of both together it seems dubious. With simple stimuli, there isn't much else elicited by the visual pattern, so estimates of its properties can be localized to a small set of possible mechanisms, which is the point of using simple stimuli in the first place. So, there are multiple layers to the stack, but most of them are relatively empty or inactive. When the stimulus is complex, all those other stacks are now active, and filled with activity which is ostensibly more important and interesting to the observer. Is it reasonable to continue to assume that the observer can make use of the same information in that 'spatial vision' layer that he could when there was nothing to distract him elsewhere?

I realized this connection because I was thinking of the implications of one alternative (complex visual qualia are the result of highly nonlinear summation of simple visual qualia) or the other (complex qualia may be inferences drawn from 'basis' qualia, that could possibly exist - as perhaps in a dream - independently of those bases). How do you tell the difference? Take away the spatial vision level, and see what is left. How to do this? Lesions maybe, but the first thing that comes to mind is to compare what imagery looks like when you're seeing it versus when you're dreaming it.

Friday, August 24, 2012

punched in the head

title says it all. punched a few times in the head, and now i have a headache. feels migrainish. it is possible that getting punched in the head in just the right way can trigger a migraine. or maybe i have a concussion? i do have a big red bruise on my forehead, so maybe the pain is on the outside, muscular, and i just can't tell the difference since it's all just front-of-the-head.


**edit, 0:23, 8/27/12
the bruise is still there, fading, and the flesh is a bit tender - worse yesterday - but the headache was gone when i woke up saturday morning.

Thursday, August 23, 2012

vacation report

Spent the last 5 days (Sat-Wed) down in Tennessee/Alabama, visiting family. Monday morning, Jingping woke up about 8 and went looking around and came back saying that my parents were still home, when she thought they should be out taking a walk somewhere. I was barely awake, still hadn't opened my eyes. When I finally did a few minutes later, I found that I was halfway through a scintillating scotoma, maybe around the 15-20 minute point. It looked a lot like last time, left field, relatively straight scotoma from above fixation leftward, arcing downward and below. I got out of bed and went to sit in the sunroom to watch the rest of it. The scintillation was rather weak, but still noticeable - I knew what was happening within a second or two of opening my eyes. The headache started soon after I got out of bed, and was kind of a bad one. Above-behind my eyes, focused on the right side. Nauseated and dizzy for a day, which sucked because I had to drive down to Huntsville Monday afternoon (in my parents' Prius with an expired Kentucky driver's license, don't tell my mother). Still hurt a bit Tuesday night.

I think that maybe the slight headache I described on the 16th might have been part of the prodrome for this one, otherwise I didn't notice any signs.


Last night on the way home I had an insight into how to explain the low-pass gain control that I'm proposing. A basic Barlow-Foldiak type anti-Hebbian learning rule should develop low-pass weights if a set of scaled filters is repeatedly exposed to low-pass input, or maybe even if it's just exposed to white noise. Gonna try this later today!

Friday, August 17, 2012

contrast or inference?

Norma Graham makes an interesting point, which I've seen quoted many times, in her book on spatial vision. She notes that it is as if the brain is transparent to what is happening in the early levels of visual processing, and that this is curious. It's curious, but it's a typical stance for someone who studies spatial vision; we assume that discrimination or identification or detection of signal strength is mediated almost entirely by the filters that are transducing the signal, not those that understand it, or respond (overtly) to it.

Whether or not this transparency holds when complex images are viewed is, I think, totally unknown. It may be that the percept elicited by a complex scene really is the sum of its parts, and that it simply provokes additional sensations of meaning, identity, extension, etc., which are tied to spatial locations within the scene. So, the visible scene that we are conscious of is indeed an object of spatial vision. This is the point of view I generally adopt, and I think it is common.

Another view is that the percept is entirely inference. Boundaries, surfaces, colors, textures, etc., are qualities in themselves, inferred from particular organization of spatial structure, and these then are organized in such a way that objects and identities and meanings can be inferred in successive stages. These inferences are what is seen consciously; perhaps inferences, and the evidence for them (the matter of spatial vision), are experienced simultaneously, but the substantive inferences, being the important elements of experience, are what dominate consciousness. So, only a small part of the phenomenal scene is actually constituted by e.g. luminance contrasts, and much more of it is constituted by higher level inferences. I think this point of view is also common, maybe especially in the current generation of visual neuroscientists.

The latter view is not exclusive of Graham's observation. If the patterns that are viewed are simple enough, they will not form objects, and will not have meaning. Or, they will be interpreted only as what they are, which doesn't require much inference, or only circular inference (which isn't a bad thing necessarily, when you really do want to conclude that a thing is itself, e.g. a gaussian blob of light, on the basis of its being a blob of light; usually, you want to infer that there is a letter on a page on the basis of a particular arrangement of blobs of light).

So, in the experiment that I'm currently analyzing to death, I am clearly taking the first view, in which case I think my conclusions are solid. If the second view is more accurate, what does the result mean? It could mean that inferences about image strength are based on higher frequencies just because they are the more susceptible to loss in a weak signal. If I'm asking subjects to judge image contrast, they could easily interpret this as judging image strength, and then their judgments would be biased towards the most delicate parts of the image, but they would still take everything into account.

This latter interpretation is still interesting, but it doesn't require "suppression". It is worth mentioning and I should at least include it in the manuscript, although the FVM talk probably will not have space... already there's barely space for the default story.

Thursday, August 16, 2012

nausea, photophobia, headache

woke up slightly late today, started to feel sick on the train; slightly nauseated all day long (mainly manifesting as excessive salivation, gross), a bit of photophobia. might be eyestrain or due to my crooked (broken, $10) glasses. briefly on tuesday night inverted the contrast on firefox, but then switched it back. at the time it was because my glasses seemed smudgy and i just couldn't get them clear, thought, "ah, it's a sign!", but decided no, it's the glasses. right now definitely a slight headache. as usual in my forehead, just above my eyes, maybe a bit left of center.

quick note

Something I've been meaning to write a note on for a while. Even as I write this, I don't have the idea quite in my head.

What is it about apparent contrast that is interesting, as opposed to sensitivity? By most measures, they're the same thing. If I ask someone to do an experiment where they have to discriminate between one contrast and another, I'm assuming that they are doing some mental comparison between two apparent contrasts, or memories of two apparent contrasts. By varying the physical difference between the two contrasts, I can then quantify the person's performance on this task, e.g. the difference at which they can no longer measurably discriminate. These are the sorts of measurements that are usually made in psychophysics.

These performance measures are understood to reflect the subjective, phenomenal properties of interest. But they involve a nearly unsolvable confound: we can't tell what part of the discrimination is due to relative internal response strength and what part is due to internal noise.

So to me, measuring apparent contrast is a way at getting around this problem. You get to measure, directly, the internal response to the stimulus. The new problem, then, is in quantifying what you've measured. The reverse correlation experiment that I did, I realize now, was cognizant of all this, but it was subliminal for me. The experiment is not measuring performance, but it is very similar to an experiment that would be measuring discrimination performance. In this experiment, the stimuli are always easily discriminable, so there are no limits to measure. The subject is asked to discriminate between the strengths of the two stimuli, but I measure no interval or reliability of this discrimination. This is because there is no objective stimulus strength.

The purpose of the experiment is to find out what constitutes stimulus strength when strength is defined, to an observer, as luminance contrast. What I get back is (no matter how I measure it) a description of what components count more or less than other components in making decisions about stimulus strength. I then test a bunch of plausible models to see whether they might also count components in similar ways. Lucky for me, only a particular type of model works, so I can make a sort of conclusion from the study.

So, apparent contrast is the way things look, and then behaviors can be carried out on the basis of how things look. Most visual psychophysics directly analyzes the behaviors that are based on appearances. I've tried to directly analyze the appearances themselves. Did I succeed?

Monday, August 13, 2012

unifications of china 1

Random idea from this weekend: create a set of spatiotemporal maps illustrating the unifying conquests of China. For fun. Let's make a list:

1. Qin: Ying Zheng and Guanzhong
Qin was one of many Warring States in the centuries leading up to the first true unification of China in 9780HE. Qin was based in the area around and to the west of Xi'an, which is protected by mountain ranges and accessible only through narrow passes (I traveled through the Hangu pass to visit Xi'an in 12010HE): hence the region's name of Guanzhong, "within the passes". The conquest has an ill-defined starting point, since the different states had been in contention for centuries. However, it was with Ying Zheng's rule that most of the work was done: between 9771 and 9780, China proper went from seven states to one. This period, the Qin Unification War, could be taken as the first.

2. Han: Liu Bang and Guanzhong
Qin didn't long outlive Ying Zheng, who died in 9791. Soon after his death, Qin was overthrown and broken up into a number of kingdoms, united in theory by the Emperor of Chu, who was in fact a puppet of the warlord Xiang Yu. Xiang Yu's confederation quickly disintegrated into civil war between Xiang's Chu state and Liu Bang's Han state, which lasted from 9795 to 9799, when Chu was finally defeated and absorbed into Han. Han, by the way, based its power in the mountain-protected cities of Hanzhong and Chang'an, as Qin had done. Xiang Yu had placed his capital in Pengcheng, in eastern China. This war, and its result, was messy: at any given point in time, even for a decade after the war ended, it was unclear just who was in charge of particular regions, and a lot rested on the proclaimed allegiances of one or another warlord. However, there are standard interpretations of who was with who and when, that could be used to clarify an illustration.

3. Wei/Jin: Cao Cao and Guandong (east of the passes)
Han lasted for 400 years. When it finally collapsed around 10190, there were more than 20 years of war, followed by a half-century period of fracture into the Three Kingdoms of Wei, Wu, and Shu. The Wei state, based in the western edges of the central plains, just east of the mountain strongholds favored by Qin and early Han, eventually conquered Shu in 10263, was replaced in a coup by Jin in 10265, and finally conquered Wu in 10280. After this, Jin slowly fell apart, and China wouldn't be put together under one government again for another four centuries. The Wei/Jin unification was so slow, taking more than 80 years, that it can't really be considered a 'conquest'; it was a slow succession of local wars, with long spaces of quiet in between. I don't think this one would count.

I don't know much about the establishment of Sui - we'll wait until I've read a bit more on it before I continue.

Wednesday, August 08, 2012


Yes, so my glasses broke about 2 weeks ago. I explained it already in the July 24 post.

I still don't have my new pair. Should be here any day now. I'm wearing a 10-year old pair, over-negative in both eyes, but only at night to watch the Olympics and "work" on my laptop. Otherwise I need to be within 12 inches or so to see clearly.

At distance, my acuity is no better than 20/200. I can tell just by looking into the distance and sticking a finger out: no detail that I can see is much smaller than maybe a quarter of the thickness of a fingernail (a little bigger than a degree). So, my acuity limit is probably not much more than 4cpd.

If this was the best I could do, I would be on the bad end of low vision. But it gets better the closer you get to my face (come on, get closer to my face) - like I said, everything is sharp and clear within a foot or so. But, at distance - which is how I spend a lot of my commuting time, at least, and a lot of time at taekwondo - I'm 20/200. How bad is that?

For one thing, 4cpd is about the acuity limit of a cat (or of some jumping spiders). So it's not bad on a basic vision standard, because cats and jumping spiders are very visual creatures. 4cpd is good enough to get by on vision. But for a human, in the world of humans, it's not too good. At distance I can't recognize faces, at all. Ten days' practice, and I just can't do it if I don't have some other information, and then I don't think it counts. I can't read signage - I can't tell what trains are coming into the station at Government Center. None of that is debilitating, but it makes sense to call it a handicap. High frequencies aren't just details, they're content.

20/200 is resolvable detail of 10 minutes of arc. At 35cm, about where my laptop screen is right now, 10ma is about 1mm, which sounds small. But the dot pitch (vertical/horizontal pixel separation) on my screen is about .227mm. With my corrected acuity being around 20/15, I should be able to see details at least as small as 1ma, about .1mm apart, so I can discriminate individual pixels with my normal acuity. At 20/200, I wouldn't be able to discriminate details smaller than 4 or 5 pixels across; I would definitely not be able to read this text (whose lines are 1 pixel thick, and which tend to about 10x5 pixels HxW).

Printed text, which I like to hold pretty close to my face, at least 20cm, would still be unreadable. I'd have to hold it much closer, where the shadow of my head would start to get in the way. I'd need large print. I wouldn't be able to read music. I'm wondering how much acuity you need to do the classic threading of a needle (I haven't even started to wonder about depth perception - I noticed that it was off for the first few days, but I seem to have adapted pretty well, and I'm not afraid to cross the street as I was at the start), or to slice meat and vegetables without slicing yourself - it's not the same as reading, since you're looking for centroids for those things, but I wouldn't really want to try...

Not that I'm going to try, but I could: visual acuity at about 20 degrees eccentricity is close to 20/200. There you have to contend with crowding, though, so you're effectively worse off.

So 20/200 isn't disabling, but it does prevent you from accessing all sorts of primate-relevant stuff. Faces, reading, music, fine finger-based activities. It's been interesting, but I'm just about ready for my new pair of ($10!!) glasses to arrive.