Tuesday, July 17, 2007

The alien hand syndrome

We've had a lengthy discussion of consciousness recently, where I introduced the concept of the illusion of free will. For example it was shown by brain scans that the motor command to do something like grab an apple, precedes the actual conscious decision to grab it. Your brain then works its magic by either canceling that command in time, or if you do wish to grab the apple, make it seem seamless and purposeful. From the authors:

"a fully voluntary act is initiated unconsciously (non-consciously). That condition was in fact demonstrated experimentally by us (Libet et al. 1983) when we found that cerebral neural activity ("readiness potential") precedes the subject's awareness of his/her intention or wish to act by at least 350 msec. This applied to fully self-initiated acts that occurred without "pre-planning" by the subject of when to move. (Incidentally, those finding have been replicated by others--see Keller and Heckhansen, 1990 with commentary thereon by Libet 1992, and Wong et al. 1988)."

Case in point is the alien hand syndrome. This bizarre condition uncouples the motor planning area from the free will illusion decision making area of your brain and can lead to disturbing behavior from one of your hands, as if it were "processed":

"In one patient it was also seen as conflict with both feet (e.g. when putting on slippers) or as conflict of intentions (e.g. when planning to enter a room). The other form consisted of massive groping and grasping behaviour as the most dominant features, such as a "tug of war between hands" and was seen in five patients. Avoidance behaviour included sitting on the affected arm, holding it under the table, or keeping objects out of reach. "

Interestingly this uncoupling, often results from lesions in the corpus callosum, dominant medial frontal cortex, and posterior cortical/subcortical areas. A team in switzerland recently discovered the cause of this disorder and liken it to delusion in schizophrenia (soon to appear in the annals of neurology) . This disconnect may be similar to the involuntary uncoupling which occurs in other situations such as speaking in tongues or Ouija boards, but on a smaller scale:

"The experience of conscious will is the feeling that we are doing things. This feeling occurs for many things we do, conveying to us again and again the sense that we consciously cause our actions. But the feeling may not be a true reading of what is happening in our minds, brains, and bodies as our actions are produced. The feeling of conscious will can be fooled. This happens in clinical disorders such as alien hand syndrome, dissociative identity disorder, and schizophrenic auditory hallucinations. And in people without disorders, phenomena such as hypnosis, automatic writing, Ouija board spelling, water dowsing, facilitated communication, speaking in tongues, spirit possession, and trance channeling also illustrate anomalies of will--cases when actions occur without will or will occurs without action. This book brings these cases together with research evidence from laboratories in psychology to explore a theory of apparent mental causation. According to this theory, when a thought appears in consciousness just prior to an action, is consistent with the action, and appears exclusive of salient alternative causes of the action, we experience conscious will and ascribe authorship to ourselves for the action. Experiences of conscious will thus arise from processes whereby the mind interprets itself--not from processes whereby mind creates action. Conscious will, in this view, is an indication that we think we have caused an action, not a revelation of the causal sequence by which the action was produced."

So while the axiom "I think therefore I am" may be true, "I act, therefore I think" might not. Just another nail in the coffin of free will.


Bayman said...

I remember reading about the above example, but interestingly the interpretation did not pertain to consciousness, but rather the fact the damage to the corpus collosum simply abolishes communication between the two hemispheres of the brain. Therefore one hemisphere can initiate action without the knowledge or approval of the other. So whether the patient has free will might depend on which hemisphere you're talking to...

Anonymous Coward said...

Yeah people with detached hemisphere experience something similar and perhaps even more dramatic, they sometimes have split personalities and will try to put on two outfits at a time, or disagree with themselves over which eye is seeing what or which ear is hearing what in tests.