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very slight headache lately. nothing obvious beforehand - maybe some occasional false-alarm-foveal-scotoma feelings, but nothing ever showed up.

those false alarms: when reading, i get a feeling that the text is smudged or jumbled, but when i try to see what's wrong, even one eye at a time, i can't actually find any defects. at other times, it's less clear, because the non-text world is more complicated, but i still haven't actually caught and analyzed any of these defects. so, i still don't know if they're false starts, like a CSD bubble that stops soon after is starts, or just high-level false alarms, i.e. paranoia.

anyways, that's it. working on text for a talk next month. tiny bit of writing lately. somehow i have three people reviewing the classification image manuscript. need to get back to the blur adaptation revision sooner rather than later. not looking forward to it, but once i'm into it i think it should be okay.

scintillating scotoma 3.b

I just can't let this go. Maybe this is as far as I can get with it for the time being. I wasn't satisfied with the straight-line model of the CSD wave that I had been playing with, because there was just no straightforward way of figuring out direction, origin, speed, etc. But I had a great idea: say the wave is like a surface wave, with a point origin, spreading out in every direction at a the same speed. Maybe this isn't true; it may be that the phenomenon is limited to V1; it may be that the origin is, e.g., the interface between cortical areas; it may be that the speed or direction varies. The first isn't a problem, but if we assume the second two (point origin, constant velocity) are true, or close to true, then we can come up with the simple model you see in the gif above: according to my June 24 data (fit with a lazy grid search), the CSD is a surface wave, traveling at (exactly!) 3mm/min, arising within about 3mm of the V1/V2 border, near the foveal confluence.

I'm not going to go into detail here about the spatial properties of the wave. It's simple, that's enough for you.

Anyways, nothing crazy here; this is all consistent so far with what I understand of the published research so far. It's a lot of fun figuring out how to create and convert all these maps, and it's amazing just how solid those parameter estimates are given the data. Sometime soon I'll look deeper into it, hopefully I can put it off for a while.

scintillating scotoma 3.a

I went ahead and figured out how to do the cortex transform. there are many papers describing the equations; some good recent ones (like this one) which are basically reviews at the same time that they are tweaking one or another aspect of the basic model. It's not really that complicated; the log-polar transform is very similar, except that the angles are calculated outside the logarithm. The space-V1 transform is the logarithm of a complex number representing the spatial coordinates plus the limit of the foveal confluence. The paper I linked above describes what further steps can be taken to get the transform more precise, accounting for meridional anisotropies. they go further, but I stopped there. The basic model was proposed by E.L. Schwartz in 1977, and hasn't changed much since then; I'm using Schira et al's version with their shear equation, and some parameters they cite in another paper.

This is similar to the second plot from the last post, but you will notice the geometry is different, as it gets narrower towards the fovea (lower part). Colors indicate time in minutes as shown by the colorbar. The grid drawn in the background isn't labeled, but it's easy to understand if you've seen these before. The lines going up and down are, from left to right, the superior vertical meridian, the left superior 45 degree meridian, the left horizontal meridian, and so on. From bottom to top, the left-right lines are spaced 5 degrees of visual angle apart. You don't see the first one until about 30mm up. The origin in this plot, (0,0), is where the foveal representation converges with V2 and V3, the foveal confluence.

This is interesting, the foveal confluence. I probably had heard of this before and forgotten it. I actually stated to E* yesterday that I didn't know what was on the other side of the foveal edge of V1, though I knew that the edges are flanked all the way around by V2. In fact, V1, V2, and V3 foveae all meet in the same place. This is apparently a relatively poorly understood region of visual cortex; imaging and physiology studies have focused on the more peripheral regions. The reason is that it can't be certain of what is being studied if one looks closely at the confluence, since the three areas are mixed together in a fashion that is still not well understood. I'm going to read more about this (the main writing on it is by the same group as the paper I cited at top; this one explains things up front).

Okay, so that map. What can I do with it, now that I have the coordinates right (or as close to right as I can)? Yes: I can measure the rate of progression of the wave in cortical distance over time. Awesome. I don't have the best method worked out just yet, but here's my approximation, summarized in the last figure below:

On the left, we have the same coordinates as in the figure above. The plotted line is the mean, over time, of the recorded scotoma regions. This is not a great measure of position of the waves, since as they got further out and larger, I couldn't trace them completely, and because it took time to trace them, so at a given epoch a trace might be in one place, or another, and that shows up here as a back-and-forth wave, on top of whatever sort of limiting bias is imposed by the screen size, etc. Still, it's okay. We know this because of the next plot: On the right, we have the distance of that waggly trace (from its starting point near the bottom of the left plot) as a function of time. A straight line. That's not why we know it's okay; it's because of the slope of this line: 2.76 mm/min. This is extremely slow, but exactly in the realm of cortical spreading depression. Not going to give references on that (need to save some work for an actual paper on this business), but they're there. Pretty sure I'm doing this right.

scintillating scotoma 3

another event is now shimmering its way out into my far left periphery. i used the dynamic perimetry program i had written; seems to work. some improvements can be made; need to include warnings or preventions for the cursor going out of screen. should implement cursor size info/adjustment. maybe cursor color or shape.

i mention the last two because definitely, there is a general sort of aftereffect. it's scotoma-like, but with no clear location of the scotoma; i.e., it feels like things are missing, e.g. if i put my hand out about 15-20 degrees left, stuff just feels kind of scrambled. actually, there is definitely a blind spot about 30 degrees left, i just found it. this is too far to measure with this screen; perimetry stops at ~20 degrees, i guess.

again, i don't know what the precursors were. been depressed all weekend (see previous post); saw some funny spots yesterday, and got preoccupied with some really visible floaters yesterday afternoon at tkd, which is probably unrelated. seems like the main indicator is just a superstitious feeling that "i wonder if it's going to happen again". maybe that's the CSD running through my frontal lobe somewhere.

note that i'm basically having a monthly period: the first of these (that i recorded here) was April 24, then May 28, and now it's June 25 (24).

i've been meaning for a while to list the other occasions that i can remember. i may be able to remember them all. before these past three, it happened twice earlier this year: once was during, uh, sex, which was weird, in China (within a few days of new years), and the second was on a sunday afternoon in late january or early february, when i was on my way to tkd, walking around cleveland circle.

before that, probably have to go back a year. it's happened several times with me just sitting here at my computer; probably half the times. i announced a few on facebook. i woke up once, early last year, with the SS starting right off. makes me wonder if it happens sometimes when i'm sleeping. it's happened after sex a couple of times. only once in the lab, i think, after j** checking my eyes. except for that morning one, i think it's almost always at night.

i would guess that, all together, this has happened 10-15 times in the last 2.5 years. until now, i don't think it had happened in summertime, only winter and spring. lots of headaches, maybe biweekly on average, without interesting symptoms.

i think these map data will be usable, and better quality than the paint drawings. not as pretty, but i can just generate post hoc pictures. i'll process them in the next couple of days, probably tomorrow. basically, it seemed very similar to the last two times, except that after the first minute or two of scotoma (again, i noticed it had started because, suddenly, i couldn't read), which i managed to record, the scotoma disappeared, or at least i couldn't find it. i thought maybe i had scared it away, but then it returned, right on track. anyways, update later when maps and stats are done.

*update*

some plots: sorry, didn't label any axes. descriptions accompany each:

This is the progression in spatial coordinates. color represents time in minutes, which you see in the colorbar. i also tied marker size to time, to help represent the thickening of the scotoma with time. 

This is progression in logpolar coordinates; x-axis is degrees from leftwards (in the last post, i was coding angle relative to 'up'), y-axis is log(degecc + 1). now it looks a lot more like a straight wave, though there is a bend to it, as if the wave has a 160° trailing angle. maybe that would be straighter with a more realistic cortical space transform? maybe not. i'll get around to finding out later this summer.
 

This last one is just binning the previous plot into 10° strips, plotting logecc+1 against time (like in the previous headache post). if i assume that the speed of the wave is closest to the fastest estimate that i get from these kinds of fits (it must be faster, since i'm only measuring at an angle to the wave), then i estimate that for this event, the speed of the wave was at least 0.248 logecc+1 / min. this compares with estimates of 0.250 and 0.258 for the last two events (i cited a lower number last time; that was the median, this is the max). once i learn to transform logpolar into v1 coordinates, i'll bother to do the extra geometry to measure the true transverse speed of the wave.

scintillating scotoma 2

another aura! (no post in a month, and now it is forced!)

right now it's flying out to the far left field, but there's also a weird 'rough patch', a bit nearer in that appeared late on. i got a good map. i didn't expect this one coming on at all, except for what i think is just sort of standard low-level paranoia which i've developed since this all started. it's hard to tell what's prodrome and what's just coincidental suspicion.

anyways, i was reading through a section of the classification image manuscript, and, yep, can't see the letters. i think that 8/10 of these things so far have begun while i was reading. not sure if that's because i spend the majority of my time working with text in one way or another, or if that actually pushes things over the edge.

***

it's been a few hours now. here's the map i drew of this last event:

similar to last time, except that it's in the left field this time. it started out below fixation, and did the slow arc outward, following a really similar path as the last one. below, i'll show you below just how similar they are.

as for the rough patch: in the plot above, notice that in the superior field there's some green (and hard-to-see gray) scribbles over the neat arcs; that was a region that i noticed late which wasn't blind, and wasn't flickering, but was clearly..  unclear. it's at about 10 degrees eccentricity, so it's hard to see well out there anyways, but it was obvious that something was wrong. i could see the scribbles that had already been drawn, but it was all very indistinct and jumbled, and i couldn't see the motion of the cursor even though i could tell that it was laying down green/gray scribbles of its own. without any other explanation, i'm going to guess that this was the fabled extrastriate scotoma - my V2 was getting some CSD!

ok, now some analysis. first, log-polar maps. i haven't gone and gotten/worked out a cortical remapping scheme, but putting things in in log-polar coordinates is almost as good. actually, what you do is put them in log(ecc+1)-polar space, so you can see where the fovea is (zero in case you're dull). here are logecc+1-polar-time plots for the last two events (lets say L = log(ecc+1), for easier reference):

time is measured here from start of recording. these data are smoothed versions of the drawn maps in 10 degree radial steps. the scales are the same except that these are for opposite hemifields. the z-axis is color coded.

i mean, you can just see that those two maps are almost identical. i got more data the second time because i wasn't occupied with working out a system (btw i was caught off-guard; i wrote a matlab script to record in real time, but it not work in matlab-64, and i put off doing the -32 install because... ah.. it's done now). the origin is similar - look at these plots:

sorry about the colors. these are the same data as in the scatter plots above, except these are collapsed over the x(angle)-axis. actually they aren't quite the same: here i've used linear regression to estimate the earliest time (before recording began) that the visual event could have begun, and subtracted it out of the time axis, so these plots start when recording began with respect to when i estimate the event began. so, basically, this aligns the data. 2 things: one, the rate of advance (remember that it's radial advance, so these technically are distorted plots; i assume that's why the slope changes with angle) is basically identical in the two cases, ~.16 L/m. and the origin, ie where it all begins, is ~180-170 degrees in both cases (that's directly below fixation).

i've got other analyses, but the above sums up the interesting stuff. i know i've seen these things do weirder things, following more difficult-to-understand courses, and i hope i see one of those next time i'm able to record this business.

scintillating scotoma

a few minutes ago (~22:35), reading, and i notice that letters are hard to see. that sensation of having a bright afterimage at fixation; it's moving rightward, usually it's been leftward (I haven't taken notes on the past 2 occurrences, sadly..); this it is at least the first of the last 4 to go through the right field, if not longer.

it begins with just a weird sense of scotoma-ness, very near fixation, but the blind areas are hard to pin down - they seem to change very rapidly, or else it's more a sensation of blindness rather than actual blindness. it's strange how it sticks at fixation even as it arcs out into the periphery; it seems it always arcs into the lower field, after arcing just a bit above fixation. i've not noticed yet one passing across the field, maybe it is restricted to hemisphere?

it's almost gone at this point (almost 30 minutes after the first signs), and all that's left is a flickering at the very top of my visual field, as if there's a light flashing on my eyebrows; interestingly, if i look up, it disappears, which is strange because it should be attached to the field location. i can look up, it disappears, look down again and it reappears. maybe was an interaction with the reflection of room/computer lights off my eyeglass frames? can't test, it's all gone now..

and i have a headache (actually it started a few minutes in; the light show was so slow to start, i thought we were skipping straight to the headache for a few minutes, a bit of disappointment, but it worked out!)

also, some hints: today and yesterday, i several times wondered if i wasn't going to get a headache soon, without understanding why. not sure what sets off those feelings.. this afternoon, i thought i saw some flashes at some point when i was walking down the hallway, and that really made me suspicious; and, all day, really tight, painful muscle spasm throughout my upper back, both sides trapezius.

23:05

map below: i have a few of these now, should get to processing them this summer..

Edit: look at what this guy has done: http://www.pvanvalkenburgh.com/MigraineAura/MigraineAuraMaps.html. pretty amazing.

also, i did wind up writing a script to analyze these plots; once I get some stuff settled, i'll post those in a new entry.

41

On orders from Michael Murphy, here are details of my return from Austin to Louisville.

These events took place on a Sunday, on November the 27th, in the year 2005 CE (or 60 MA depending on your region).

At the Austin airport I ate two tacos, which was easy because my flight was delayed about an hour. This is funny because my flight from Houston to Nashville was to leave only about 30 minutes after my flight from Austin to Houston was due to arrive. This meant that all the other people had to wait for us Austin-Houston-Nashvilliers. This was okay. At Houston, we had to get from gate 4 to gate 50. For some reason, to do this we had to leave the terminal and then go through security again, which was exciting.

The entire way I occasionally read through my new dictionary of Chinese words. I now know lots of Chinese words, but I still can't speak Chinese. I don't know what the critical mass is. I think I may be a few years away.

I arrived in Nashville at about 11 o' clock. This is Eastern time, which is officially the time which I am supposed to abide by. Strangely, I just got a weird sense that it was sometime in the afternoon, and that it was daylight out, and that it's business as usual, even though it's actually 8 forty-five, and it's dark out, and most people aren't here. Someone is out there slamming doors.

So, first, I thought, I'll just walk to my car, it will be nice to walk to my car, I don't really know where I parked it anyway, so I'll walk to my car. But I couldn't figure out how to get to the longterm parking lot. So I walked all the way back to the bus stop like a loser and rode the bus to stop 6, and found my car very quickly. I considered calling a girl on my new cell phone, but decided it would probably be rude and weird to do so so late at night, and without anything in particular to talk about, so instead I just started up my car and left the airport.

I took Briley Parkway to get to I-65. In doing this, I passed the Opryland Next Exit sign, which is pretty stupid. Then I was on my way, though I did stop somewhere up towards the north end of Tennessee, to get gas and some lame coffee, and some candy. So then I drove home. I am still getting this weird sensation that it's daytime right now and not nighttime, and that any minute someone's going to walk into my office from the hallway to ask me a question. Not that that happens often, you see, but it's something which could happen in the daytime with much more probability of happening than at nighttime.

Finally I got home, and apologized to my cat for being gone so long. Then I went to sleep. This was a little before 3 o' clock. I woke up this morning at 8 o' clock which was okay. Right now I have this weird pain in my forehead, or my temple, but I actually think it's a tooth. This is called referred pain. If that's what it is. It might also be a muscle by my eyeball, which makes a little more sense and is less worrisome.

Today I did a few things, less than explicitly expected but maybe about what was implicitly expected.

So, was this worth it. Really, I should be writing scientific essays and papers and ideas and things, but really, all I ever write are entries in this blog. I write a good amount of functional and fun Matlab code, which no one really cares about. But, really. Really, I write best in short bursts. When the writing comes, it's worthwhile. Unless it's about what I did the day before, in which case it's usually kind of pointless.