[From Bruce Gregory (2004.01.23.1035)]
This week Nova ran a TV program based on the research of V.S.
Ramachandran (co-author of _Phantoms in the Brain_). The show dealt
with a number of individuals who had suffered brain damage and the
lessons Ramachandran had draw from these cases.
One case that I found particularly interesting involved an individual
who suffered a severe head injury in an accident. He seemed to heal
completely but he had one bizarre after effect of the accident -- he
believed that both his parents had been replaced by impostors. These
impostors looked exactly like his parents, but he was sure that they
were not his parents. Even more strangely, this "impostor delusion"
seemed to vanish when he talked with them on the telephone. At these
times, they were his "real" parents. This rare condition is called
Capgras's illusion.
No amount of reasoning could convince him that the impostors were, in
fact, not impostors. Ramachandran interpreted this behavior in terms of
a break in the pathway from the temporal lobes (where the recognition
of faces is centralized) to the amygdala (where emotional responses are
centralized). Thus the patient had no trouble recognizing his parent's
faces, but apparently had no emotional response to this recognition.
This lack of emotional response, Ramachandran hypothesized, led the
patient to conclude that no matter how much these people resembled his
parents, they must be impostors. (Apparently the link from the temporal
lobes to the amygdala was unaffected by the accident, which was why he
did not think his parents were imposters when he spoke to them on the
phone and could not see them.) Ramachandran conducted a experiment with
galvanic skin responses that proved to be consistent with this
interpretation.
The story is also related in the book referenced above for those who
might be interested in more details. One conclusion the Ramachandran
drew from the experience is that we have a hard time accepting
reasoning that conflicts with our "gut reactions."
Bruce Gregory
"Everyone is entitled to his or her own opinions; everyone is not
entitled to his or her own facts."
Daniel Patrick Moynihan
"Everything that needs to be said has already been said. But since no
one was listening, everything must be said again."
Andre Gide