少し読みやすくなってきたか。
Split brain - A putative biological model for the multiplicity of personality
Another topic to be discussed in this context is the “split brain” syndrome, a group of symptoms produced by a disconnection of brain hemispheres often as a result of the treatment of refractory epilepsy performed in 1960s’. There seems to be an increase of attention to this topic (Haan, et al. 2020). M. Gazzaniga, a leading researcher in this area thinks that the split brain paradigm creates a splendid opportunity to study the neurological mechanisms of consciousness in its potential dual states (Gazzaniga, 2000). Edelman and Tononi agree with his view from their standpoint of DC theory, as follows;
“The similarity between psychiatric dissociation syndrome and neurological disconnection syndromes is remarkable” although “unfortunately any date exist about the neuronal basis of psychiatric dissociative disorders….”(Edelman, Tononi, p.67).
Okano (2018) also
indicates that split-brain syndrome can be something akin to the multiplicity
of the DC within an individual, and considers this state as a step toward the
biological model of DID.
It might be worth
revisiting this split brain paradigm as there could still be much more to learn
from it in our search for the neurological correlate of personalities in DID. After
a surgical intervention and two hemispheres are disconnected, the verbal IQ of
a patient remains amazingly intact (Nass and Gazzaniga, 1987). Problem-solving
capacity remains unchanged for the left speaking hemisphere (Ledoux,
et al.,1988). However, with a proper set of examination, each hemisphere
appears to have a separate mind. “Cortical disconnection produces two
independent sensory information processing systems … (Gazzaniga, 1995)”,
with each hemisphere having its own set of specialized capacities, e.g.,
language and speech, problem solving capacities for the left, and facial
recognition, attentional monitoring, etc. for the right. When tested
separately, right hemisphere is seriously impoverished in cognitive tasks. It
is poor at problem solving and may other mental activities (Gazzaniga,
2000). Therefore, it has been debatable whether the right, mute
hemisphere has its conscious equal to its counterpart.
Joseph Ledoux,
however, maintains that brain bisection produces a state of double
consciousness (LeDeux, et al.1977). In their experiment with a patient
‘P.S.’ with a split brain, he concludes that the right hemisphere of ‘P.S.’ has
a sense of self with its own feeling. He states that the speaking left
hemisphere appears normal with intact intelligence, which is largely unaware of
its counterpart, right brain, except for the “emotional significance” of its
experience (LeDeux,
1996). It might be its limitation for verbal expression which might
make the left brain look like mindless.
（以下省略）
