Hitting head, seeing stars

[Stephen Black]

On Thu, 17 Oct 1996, Joseph Strout wrote:

> On Thu, 17 Oct 1996, PJ Skerrett wrote:
> 
> >       When you hit your head and see "stars," what are you really seeing?
> > 
> > Can anyone point me to an answer for that? I've tried a couple
> > neurologists/head injury experts, but haven't come up with much of an
> > explanation.
> 
> I believe that you are seeing activity in the primary visual cortex.  When
> you hit your head in back, the skull slams right into that part of the
> brain -- and the same thing happens when you hit your head in the front,
> by the recoil.  The pressure causes activity in the cells.  (Pressure can
> cause activity in almost ANY cell, as can light, electric current, and
> many other stimuli.)  The cells are not activated in any coherent pattern,
> so the result appears as random points of light.
> 
> I'm sorry that I don't have any references handy for this, but that is my
> understanding.  I hope you find it helpful.
> 

The question reminds me of that old principle with the quaint title called
"the law of specific nerve energies" which was enunciated by Johannes 
Muller in 1838, long before the birth of neurophysiology (which Muller 
undoubtedly helped to create). The gist of the "law" is that it doesn't 
matter how you bring a nervous pathway into activity; what matters is 
where the nerves terminate in the brain. 

Thus, if you receive a blow to the ear, you hear a ringing in the ears; if 
you get elbowed in the eye (or get hit on the head as above), you see stars.
Electrical stimulation of the brain will do it as well. Dobelle et al 
(1974, although there must be more recent reports) found that electrical 
stimulation of blind people in the visual cortex produced sensations of 
spots of light they called "phosphenes".

The early physiologists were fascinated with this idea and came up with a
number of weird and wonderful experiments to demonstrate it. Volta, for
example, the 19th century scientist, connected a large battery to metal
rods, which he stuffed into his ears, and reported a noise like "the
boiling of thick soup". Weber, being more cautious, tried this out on his
willing but unnamed *brother-in-law*, this time with vision, and he
reported a light which passed right through his head. (My notes on this
refer only to "Stein, An Introduction to Neurophysiology", presumably an
old textbook). 

This may also be my source of the 19th century speculation that "if the 
auditory and visual nerves were crossed, leaving their connections to the 
brain intact, then we could _see_ thunder and _hear_ lightning. I 
understand that this has actually been accomplished anatomically in the 
ferret (Roe et al, 1990). No word from the ferret yet on what this does 
to its perception of a thunderstorm.

References

Most textbooks of physiological psychology or history of neurosciences 
for the law of specific nerve energies

Roe, A. Hahm, J., & Sur, M. (1990). A map of visual space induced in
  primary auditory cortex. Science, 250, 818-

Dobelle, W., Mjadejovsky, M., & Girvin, J. (1974). Artificial vision
  for the blind: electrical stimulation of visual cortex offers hope
  for a functional prosthesis. Science, 183, 440-

-Stephen

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Stephen Black, Ph.D.                      tel: (819) 822-9600 ext 2470
Department of Psychology                  fax: (819) 822-9661
Bishop's University                    e-mail: sblack at ubishops.ca
Lennoxville, Quebec               
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