Hitting head, seeing stars

dog chrisb at webmedia.co.uk
Thu Oct 17 02:42:25 EST 1996

PJ Skerrett <skerrett at world.std.com> wrote in article
<skerrett-1610962057330001 at>...
>       When you hit your head and see "stars," what are you really seeing?

Well, it's likely you concussed some part of your visual cortex (damaging
optic nerve fibres would probably be more serious). Temporarily, some of
the cells that fire when they receive signals from the retina (retinal
cells in the eye send signals when light enters the eye) will fire in the
absence of the stimulus. Until the chemical balance is restored, which will
take a few seconds, your brain is telling you you're seeing something even
though the light didn't actually enter your eye. It seems like stars
because only a few, disparate stimuli are perceived; if you banged your
head really hard (without losing consciousness) you might describe it as
"snow". Is that a sufficient lay explanation?

| chrisb at webmedia.co.uk
| http://www.cogsci.ed.ac.uk/~dog/
| "Time for a less subtle approach." - Kira Nerys

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