The Animal Self: Neurobehavioral Correlates 155“9x6” b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanitycreate an aura, the patients always reported one experience at a time.^24
In fact, the singularity of self is the most exquisite product of our brain.
The nervous system is so intricately coordinated and integrated that the
whole functions as a harmonious “one,” or gives the subjective feeling of
one. The singularity of mind is taken for granted, and from there comes
the religious tenet of “one body, one soul.”
To many people’s surprise, this elegance of oneness is true only for
healthy brains, but not for some abnormal brains. To explain this, let me
start from the “bilaterality” of our body scheme, an inheritance from
our distant ancestors in the Cambrian period, about 500 million years
ago, when we were in the ranks of the trilobites. Like most animals, our
body has a left-right symmetry, which is roughly but not exactly true (the
limbs and kidneys are represented equally on both sides, but the heart is
single and toward the left). The brain is also composed of two parts (the
left and the right hemispheres), similar in appearance but unequal in
fine-tuning. The left cerebral hemisphere has a propensity for language,
reasoning, calculation, abstract thinking, whereas the right is good for
space orientation, emotion and intuition. For some unclear reasons,
extensive damage to the right cerebral hemisphere produces a left-sided
neglect, but a left hemispheric injury does not lead to a reciprocal deficit
(Fig. 7.17).^25
The most dramatic fragmentation of self happens when the two
cerebral hemispheres are disconnected surgically. This procedure, by
which the corpus callosum (a massive fiber tract connecting the two
hemispheres) is cut as a treatment for intractable epilepsy, produces a
person who is normal in terms of gross sensations and movements, but
lacks communication between the two hemispheres, so that knowledge
acquired by one is no longer shared with the other. In the 1960s, Roger
Sperry and his colleagues conducted detailed psycho-behavioral analysis
of these “split-brain” patients and found that, in certain instances, they
act like a person having two minds, sometimes even conflicting minds.
For example, since language function is performed only in the left hemi-
sphere, the patient can verbally report things that the left hemisphere