Redding

[hazelk]

Book reviews that make you want to read books are doing something right. One in last week’s Nature on Seeing Red: A Study in Consciousness by Nicholas Humphrey.

It begins most temptingly by explaining the author’s role in the discovery of ‘blindsight.’ I’d never heard of this syndrome but in some people with severe damage to the visual cortex the ability to perceive visual stimuli and describe them accurately remains even though they insist they cannot see. As if the information now goes direct from eye to brain without creating the sensation of sight.

So do all those other things you know but don’t know how you know indicate the existence of yet more sensory systems for which no cortex exists. The one for direction or the answers to anagrams? Is the world really written over with the answers to crossword clues in ink only the mind's eye can see? The way that mediaeval monks believed the word of God was to be found everywhere in nature.

On sensation:

Sensation itself is a self-contained evaluative activity – in Humphrey’s terms, someone seeing red engages in the activity of redding.

and on a possible reason for the evolution of consciousness:

The apparent mystery of consciousness prompts us to see ourselves as more than mere biological machines, and so strive all the more to preserve our existence.

Fascinating stuff

Comments

[aycheb.livejournal.com]

The review began by discussing experiments on a monkey that had had its visual cortex removed in a way that implied this was a model for human blindsight. But it could be misleading or there could be more than one interpretation or one form of the syndrome. I'd like get the book or look up the original work but as it was in the late sixties that would mean going to the actual library instead of just the virtual one {g}

[aquaeri.livejournal.com]

There seems to be several kinds of blindsight, at least from recent publication s pulled up by PubMed. (I also no longer visit the dead tree library :-) ).

Visual cortex turned off:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16263934&query_hl=13&itool=pubmed_docsum

Severed hemispheres:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16714319&query_hl=13&itool=pubmed_docsum

Three classes, not categorised (at least in the abstract) by brain area:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16143169&query_hl=13&itool=pubmed_docsum