Naked Science Forum

Life Sciences => Physiology & Medicine => Topic started by: Jonathan Shapiro on 06/01/2010 10:30:01

Title: What is "blindsight" ?
Post by: Jonathan Shapiro on 06/01/2010 10:30:01

Jonathan Shapiro  asked the Naked Scientists:
   Dear Drs

I came across a news item of a case in which a patient with brain damage was totally blind, but had full "stereo" vision.

Can you find a source for this article?

Thanks for all the education and enjoyment (http://www.thenakedscientists.com/HTML/podcasts/).

Jonathan
Pardes Hanna
Israel

What do you think?

Title: What is \
Post by: Pwee on 06/01/2010 21:14:14

Blindsight is a well described phenomenon where the patient with primary visual cortex lesion and no conscious experience of vision (consciously blind) can perform some tasks that would otherwise be impossible for a perfectly blind patient.
For example they show him a moving dot on a screen. The patient sais he can't see anything, but he can non the less guess the direction of the movement of the dot far better then random chance.
All the while he still denies that he sees anything, and claims that he is just randomly guessing.

Here is a recent full text article about a single case study (I only red the abstract):
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2507770/?tool=pubmed (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2507770/?tool=pubmed)

The explanation for the phenomenon is that there are projections of the visual nerves that go right to the "upper" visual areas (specialized areas like the area for the detection of movement and direction, for colour perception, for shape perception etc.) leaving out the primary visual cortex (also called V1). An other implication of this phenomenon is that V1 is a necessary part of the neural correlates of visual consciousness.