Comments on: Neural correlates of consciousness

By: mitchell porter

mitchell porter — Sat, 22 Mar 2008 12:16:04 +0000

Koch quotes that article by Mark in his book on consciousness. I haven’t heard the online lectures yet.

IQ 75 is supposedly the upper bound of mental retardation. The question would have to be explained in shorter words, e.g. as meaning “Are you awake?”

By: mathemajician

mathemajician — Wed, 19 Mar 2008 12:32:02 +0000

I think the Koch example was a different person as I think in that case dominance was re-established after 2 weeks (which is usual). There are quite a few examples of this type of thing, indeed I believe doctors still perform the procedure.

Why would somebody with an IQ of 75 not be able to understand the question? Roughly 1 out of every 10 people has an IQ below 80.

I’ve never heard of alien memories after dominance is established. I suspect that it would be unlikely as the brain goes to considerable lengths to keep its model of the world consistent — even if this requires constructing and believing false memories.

By: mitchell porter

mitchell porter — Wed, 19 Mar 2008 10:42:13 +0000

That example is originally recounted here, in the chapter (12) by Victor Mark. I wonder if the patient (in either hemisphere) would understand the question; she's described as having an IQ of 75. You'd also have to watch for a Clever Hans effect. But I suppose we'll eventually get to the point of conducting philosophy-of-mind experiments on individuals with philosophically interesting neurological conditions. I'd still ask my question about the memories. After reunification, does anyone ever remember having been the silent hemisphere, even just as part of a newly unified identity? That would mean remembering themselves as the initiator of actions which the other hemisphere experienced as alien. I've never heard of it. It suggests that if there is a separate stream of consciousness there, it's a highly transient one that as consciousness is not reintegrated, though some of its powers may be.

By: mathemajician

mathemajician — Mon, 17 Mar 2008 14:44:08 +0000

We have no definitive way to measure consciousness in others. However, following a cut through the corpus callosum both sides of the brain are able to report independently, and can disagree with each other. This is well known in neuroscience. The online Koch lectures give a really nice example (but unfortunately with no video due to patient confidentiality): A woman is asked how many seizures she has had since her operation. Her voice gives a number (controlled by the left side of her brain), and then her left hand (controlled by the right side of her brain) raises up and shows a number of fingers to indicate something different. Her left brain objects and instructs her right hand to grab her left hand and pin it to the table. She then starts crying and says that strange things like this have been happening all week. Most people would agree that the left side of her brain that could speak to us was conscious. After all she generally seems quite normal except in special situations. Is the right side of her brain also conscious? It sounds reasonable that it is, given that it can report various things through the arm it controls.

Maybe somebody should try this simple experiment: show the patient via just their left eye the message “Are you consciously experiencing the world? If you are sure that you are, raise your left hand”, My guess is that the hand would go up. Of course, that doesn’t “prove” the right brain is conscious. It could think it is, mistakenly, or be lying. But, other things being equal, if it reports that it is, I guess we should probably believe it.

By: mitchell porter

mitchell porter — Mon, 17 Mar 2008 14:02:55 +0000

“people who have had their corpus callosum severed have reported that for a short period afterwards they experience two separate consciousnesses.”

This sounds like a myth. The reporting comes from a single consciousness – what did it actually report? Did it report memories from both sides of the alleged struggle? Or did it report just one sequence of memories, which includes bodily actions which were experienced as issuing from itself, and bodily actions which were experienced as not issuing from itself, and which were interpreted as issuing from a hypothesized other consciousness?

You brought this up, Jeff; it’s now your responsibility to do the homework and find out the actual details.

By: mathemajician

mathemajician — Tue, 11 Mar 2008 17:16:13 +0000

That is what I was referring to. The point is this: the only way we know this is because both sides of the brain can “report” via the side of the body that it controls. If a part of the brain wasn’t well enough connected to report to us, how would we know whether it was conscious or not? We wouldn’t know. In which case, maybe many parts of the “unconscious” brain are in fact conscious, it’s just that they can’t report this and so we assume that they aren’t.

By: Jeff

Jeff — Tue, 11 Mar 2008 17:05:13 +0000

In fact people who have had their corpus callosum severed have reported that for a short period afterwards they experience two separate consciousnesses. Sometimes even arguing against each other and fighting for control of the body. Eventually new connections form to route around the network failure, which results in a newly unified experience. The more interesting question is what are the algorithms and data structures required to compose consciousness, not where do they reside?

I think breaking down the neural correlates is just as valid a reverse engineering technique as others though. In a problem space this large you can never predict which questions will lead to the key insights.