Signs of Consciousness in Vegetative Patients?
I was interviewed for a column appearing in today’s Wall Street Journal on an intriguing case of possible conscious states in a vegetative patient (“There May Be More To a Vegetative State Than Science Thought” by Sharon Begley).
In the case in question, scientists recorded brain activity in a vegetative patient in response to being asked to imagine playing tennis.
Remarkably, this made neurons fire in the premotor cortex, a region that hums with activity when you mentally practice sophisticated movement, from a jump shot to a backhand. Then they asked her to imagine walking through each room of her house. This time her parahippocampal gyrus, which generates spatial maps, became active, again just as in healthy volunteers.
I think that if the same activity also shows up in patients under general anesthesia, then that activity doesn’t suffice for consciousness. The proposal that people under general anesthetic are conscious after all is an intolerable skeptical hypothesis (do you really want to believe that people suffer their major surgeries?). Only a tiny bit of my point got into the article, though:
There also is the possibility that people in other mental states regarded as unconscious, such as patients under general anesthesia, may show similar brain activity, suggests philosopher Peter Mandik of William Paterson University, Wayne, N.J., who studies consciousness.
Lamme et al (1998) suggest that the responses elicited by stimuli in anesthetized animals constitute merely feed-forward activation of representations in perceptual networks and lack feed-back activations from representations higher in the processing hierarchy. I suggested (but it didn’t make it into the article) that a good case for consciousness in the vegetative patient could be made if the following was found in the vegetative but not anesthetized patients: reciprocal activity of higher-level representations (like abstract representations of tennis) and lower-level representations (like motor-representations in a body-centered reference frame) as in Mandik (2005).
(Cross-posted at Brains)
Update Sept. 12, 2006: On this elsewhere: @Mind Hacks; @Rebecca Skloot; @Milinda’s Questions.
References:
Begley, S. There May Be More To a Vegetative State Than Science Thought. Wall Street Journal September 8, 2006.
Lamme, V. A. F., et al. (1998). Feedforward, horizontal, and feedback processing in the visual cortex. Current Opinion in Neurobiology, 8, 529 – 535.
Mandik, P. (2005) Phenomenal Consciousness and the Allocentric-Egocentric Interface. In: R. Buccheri et al. (eds.); Endophysics, Time, Quantum and the Subjective. World Scientific Publishing Co.
September 8th, 2006 at 7:04 am
I read the BBC on-line version of the report on this research. It isn’t clear to me from that report the degree to which activation in the comatose matched those of conscious subjects. They showed fMRI scans that showed impressive overlap. But surely there must be *some* neural difference between normal and comatose responses to verbal stimuli. So then the question becomes, why should what the two populations have in common be considered sufficient for consciousness instead of what they do not have in common?
September 8th, 2006 at 8:14 am
It is disheartening that this article made it into Science without the anesthesia control. It is the key experiment. The paper says:
Moreover, her decision to cooperate with the authors by imagining particular tasks when asked to do so represents a clear act of intention, which confirmed beyond any doubt that she was consciously aware of herself and her surroundings.
This is BS. How, in a top-tier journal, did they allow phrases like “confirmed beyond any doubt” for a first-pass study without proper controls?
The WSJ article leaves open the interpretation that if the same results are seen in patients under anesthesia, that would be sufficient to show that people under anesthetics are conscious. That is, I think the author either missed your point, or didn’t make it well. That’s too bad.
September 8th, 2006 at 3:33 pm
I would like to comment the ethical reading of the case. If there is an inherent statistical uncertainty in medical decision making due to human errors either in clinical judgements or utilization of high-tech equippment or simply we still not knowing precisely the neural correlates of consciousness, as it seems, why people decide to disconnect themselves (family members choose for them) from mechanical machines that sustain their life? Until we cannot establish the functional cluster of nerve cell coalitionary activity in conscious states from multiple level perspective (molecular=neurotrasmitters… , cellular= which anatomical areas are involve and how they behave, and finally behavioural= overt gazing, overt language etc.), i prefer to abide by the cautionary principle and orient myself toward the well-being movement of the 70´s, its maxim was: “there are not terminal illnesses only terminal patients”, to pinpoint that science always advance ussually disconfirming previosly hold ideas but a decision to die is irreversible.
September 12th, 2006 at 11:28 am
Tad: What do you think of the following suggestion? If both populations are conscious then they are both conscious in virtue of something they have in common and if only one population is conscious, then that failure is due to something that they don’t have in common. I think this suggestion has a non-trivial reading whereby it’s neither obviously correct nor obviously incorrect, but constitutes a better initial hypothesis than its negation.
Eric: Good point. I speculate the problem is due to a mixture of a rush to publish something with popular appeal and a high tolerance for sloppiness many still have when discussing consciousness.
Anibal: I interpret your ethical recommendation as being something like “If you can’t be certain you won’t be killing someone, err on the side of life.†What I worry about, though, is that people won’t take sufficiently seriously the ethical imperative to figure out who is conscious. We often don’t have the resources to simply let live everybody who we aren’t sure about. Also, there might be conscious beings capable of suffering that we were heretofore unaware of. (At one time surgeons didn’t realize that curare wasn’t an anesthetic!) Erring on the side of life is fine, as long as it doesn’t become an excuse for continued ignorance.
September 12th, 2006 at 2:08 pm
Sounds good to me. Don’t know what the non-trivial meaning is, other than anti-dualism, i.e., there must be a detectable neural difference in virtue of which one is conscious and the other is not, or in virtue of which both are conscious.
I didn’t mean anything metaphysically contentious… Just the obvious observation that neural similarities don’t necessarily imply similarities in conscious states. It’s long been known that comatose brains have blood vessels, just as conscious brains. That’s no proof that the former are really conscious. How do we know whether the activation on which the research focuses are not similarly irrelevant to consciousness? The only way I suppose is by running other experiments, such as the one you propose on anaesthetized patients. It would be nice if you could design an experiment that showed a conscious patient without activity in that area. Perhaps if you knocked out activity to that area with transcranial magnetic stimulation (nice recent post on this in the blog ‘Developing Intelligence’). That would show such activity is not necessary for consciousness. I suppose you need to find an unconscious person (like the anaesthetized patient) with the activity to show that it’s not sufficient, which is probably the more interesting and controversial claim.
September 12th, 2006 at 3:33 pm
Ahh, thanks Tad. I thought you were initially making a point about neural identity theory v. multi-realizability. Along those lines, the non-trivial reading I had in mind wasn’t simply anti-dualism, but specifically neural id.
On to your real point, I think we are in agreement. I tried to wave my hands in the post toward a whole collection of converging evidence by citing my paper which gets into, among other things, transcranial magnetic stimulation.
February 18th, 2007 at 7:34 am
[…] Ever wonder if one is actually conscious when under the knife? Or, if vegetative patients are more awake then we think? Blogger Pete Mandik from the Brain Hammer was interviewed for Sharon Begley’s post in Wall Street Journal entitled “There may be more to a vegetative state than science thought.” Mandik comments on Begley’s piece, pointing out cautions for those who stray off the scientific path in reaching conclusions. […]