Peripheral Visions

A few days ago I came across the following video, and I thought I’d share it here for two reasons. The first reason is that you might find it surprising, possibly amusing and possibly also bit scary. Keep your eye on the cross in the centre of the screen and observe what happens to the faces either side:

Most people who I’ve shown this to report peculiar distortions of the (familiar) faces either side. This phenomenon is clearly related to the limitations of peripheral vision.

The second reason for posting this is much more personal and relates to my struggles over the years with a form of panic disorder (which I’ve blogged about before, e.g.,  here). The term `panic disorder’ has a very broad definition, so that different individuals experience different forms of panic attacks and they can also take very different forms for the same individual. For me, a “typical” panic episode begins with a  generalised feeling of apprehension or dread. Sometimes that’s as far as it goes. However, more often, there follows a period of increasingly heightened awareness of things moving  in my peripheral vision that I can’t keep track of,  accompanied by auditory and visual hallucinations.  I’ve tried to explain the latter in conversations with friends and colleagues and usually when I do so I describe how the faces of people around me become distorted in a grotesque and terrifying way. When that happens I usually run as fast as I can in whatever direction I can to get away.

On top of the effect of these attacks themselves, there is also the frustration, when they are over, of not really understanding what had happened. What is happening in my brain when a panic episode begins? What is going on with my peripheral vision when it goes awry like it does? Why do some particular places  or circumstances trigger an attack but other, apparently similar, ones don’t?

When I first saw the above video it struck me immediately that it might contain a big clue about these episodes, as the facial distortions that appear there are very similar to what I experience.  Perhaps what goes wrong is that peripheral vision takes over from central vision, i.e. a kind of opposite of tunnel vision,  as a result of some malfunction in the way my brain deals with peripheral data.

Most of the time we just discard data from outside our line-of-sight unless it’s something extremely dramatic and disturbing (whether good or bad); presumably we can’t process everything across our entire field of view so we usually filter out observations coming from the edges. What seems to happen with me is that something interferes with this filtering process so that almost everything gets flagged with a danger signal. My response to these is to look about manically trying to establish whether the threat is real before, usually, just getting out of there as quickly as I can when it becomes overwhelming.

Obviously, this isn’t a complete  answer to any of the many questions I’ve asked myself about this but somehow seeing the effect in the video makes me feel more comfortable with what happens because at least I can see that others can experience a similar phenomenon, even if in very different circumstances.

P.S.  I should say that although about two years ago I quit the medication I was taking to control them, I haven’t had any of these psychotic episodes since then. Reducing stress by leaving my job at Sussex was almost certainly a contributing factor.





5 Responses to “Peripheral Visions”

  1. One hypothesis that I quite like for anxiety-type disorders (and some others) is that what’s going wrong is your Bayesian weighting system. In normal operation, your brain takes inputs, applies some priors to them, and gets out a sensible result (person in peripheral vision is picking up groceries, no threat, all OK). In abnormal operation, brain gets same signal (person picking up groceries in peripheral vision), applies a deeply overweighted prior (OMG NO!), and gets out Panic, Panic Now, I really mean it.

    I personally find this helpful, because when e.g. I’m panicking about going to the GP or something, I can then explicitly call out the overweighted prior (i.e. I’ve visited my GP tens of times. It’s been desperately horrible <5% of the time. Therefore, etc…).

    Also, visual processing stuff is deeply cool. I was reading some notes on Computer Vision and how it differs from human vision – our brains do some incredibly complex processing and filtering and data mangling. It's not really surprising that other parts of our neurochemistr/neural system/whatever can cause it to do non-standard things – the more surprising thing is that it works in the first place!

  2. Diabetic Moron Says:

    Similar distortions in Peripheral Visions which are much more
    acute are quite common in diabetic retinopathy. You were lucky
    to have the luxury of quitting your job to reduce the stress that
    many of us can’t afford. According to some recent study after
    10 years of type 2 diabetes 65% and after 20 years 95%
    people would definitely end up developing retinopathy.

  3. I am glad to hear that less stress has helped. The distortions are funny. I can still see the colour so am still using the central part of the vision (in the periphery you should not see colour). There are more cones in the very centre of vision (there is enough resolution to read over a very small field of view. The funny distortions seem in part because you can’t see the eyes properly, but there is also a geometric distortion. I was wondering whether it is due to refraction of light entering the cones in the centre of your vision at an angle?

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