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

[azdak.livejournal.com]

Hee, this almost sounds like a BtVS analysis - "Seeing Red: A Study in Conscience".

I first came across blindsight as a prepubescent schoolkid, thanks to a science teacher who was thrilled by the mystery of it (though he didn't call it blindight and he'd come across it as the result of experiments - not done by him, I hasten to add - to cure epilepsy, where some of the nerves connecting the two hemispheres were severed, with the result that - ooh, I'm having to think back an awfully lonmg way now; I think the point was that if you showed the left eye a moving dot, the subject could indicate where it was but couldn't describe it, and when asked they would say they had just guessed). I must admit, I'd never thought of extending it to other cognitive processes - does Humphrey use it as a metaphor or is he seriously suggesting that we make use of "sensory systems for which no cortex exists"? (Or is that your own extrapolation?).

I can't say I'm impressed by the evolutionary explanation - "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". That seems to me to suffer from a definite lack of hormonal oomph (I suspect sheer blind panic will do a better job at preserving your existence than "Oh shit, big nasty predator coming, as something more than mere biological machine I'd better do a runner"), not to mention the fact that creatures (apparently) without consciousness don't see themselves as mere biological machines anyway.

I had an acquaintance at university who suffered from depression, for which she blamed consciousness, and she took the view that consciousness was an evolutionary bungle (like placentas - they developed, and we're stuck with them, but we'd all be better off if we reproduced like marsupials). Since I'm not depressed, I tend not to see consciousness as such a disadvantage, but I'm not convinced that it isn't simply an emergent property of complex cortical systems, rather than a feature that could be actively selected for. And I'm certain it was adaptive in all sorts of useful ways beyond the mere recognition that "I am more than a machine".

[aycheb.livejournal.com]

"Seeing Red: A Study in Conscience"
Yes that’s probably what caught my eye about the review :-) But he's probably referencing A Study in Scarlet

Other sensory systems is just me riffing, although I do wonder if a case could be made for directional sense. I think there’s reasonable evidence that homing pigeons use a magnetic sense to help them navigate so maybe we have a vestigial version of the system. Alternatively we just have a better memory for other cues than we think we do.

The consciousness does sound like the usual hand waving, the reviewer wasn’t too impressed either. But the guy seems capable of some quite original thinking so I’d like to read his whole argument. Though if he’s going by analogy with blindsight, given that people with actual sight do get more detailed information from it than single dot location you’d think that being conscious of a process just might be associated with greater efficacy.

[aquaeri.livejournal.com]

I was aware of blindsight (fascinating stuff) but I didn't realise that was the model for it. I was under the impression that visual processing was working, but the results weren't becoming available to consciousness, so the person with blindsight had to be prompted to guess, and would then guess correctly.

[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