Monday, May 28, 2012

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.