An Edge essay by V S Ramachandran on What is self?
It has recently been shown that if a
conscious awake human patient has his parietal lobe stimulated during
neurosurgery, he will sometimes have an “out of body” experience — as
if he was a detached entity watching his own body from up near the
ceiling. I suggest that this arises because of a dysfunction in the
mirror neuron system in the parieto-occipital junction caused by the
stimulating electrode. These neurons are ordinarily activated when we
temporarily “adopt” another’s view of our body and mind (as outlined
earlier in this essay). But we are always aware we are doing this
partly because of other signals (both sensory and reafference/command
signals) telling you you are not literally moving out of yourself.
(There may also be frontal inhibitory mechanisms that stop you from
involuntarily mimicking another person looking at you). If these
mirror neuron-related mechanisms are deranged by the stimulating
electrode the net result would be an out-of-body experience. Some
years ago we examined a patient with a syndrome called anosognosia who
had a lesion in his right parietal lobe and vehemently denied the
paralysis. Remarkably the patient also denied the paralysis of another
patient sitting in an adjacent wheelchair! (who failed to move the arm
on command from the physician.) Here again was, evidence that two
seemingly contradictory aspects of self — its the individuation and
intense privacy vs. its social reciprocity — may complement each other
and arise from the same neural mechanism, mirror neurons.