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Eagleman, the orbitofrontal and Libet
Eagleman, the orbitofrontal and Libet
Incognito
David Eagleman
This book represents a fairly standard exploration of the
unconscious aspects of the mind, but in at least two areas it fails to fully
explore its subject in the light of the most recent neuroscience.
The function
of the orbitofrontal region of the brain is presented here in a quasi-Freudian
style, in which some automated process in the orbitofrontal represses urges
towards various undesirable behaviour, which emerge as soon as the
orbitofrontal is compromised. This
description fails to give a full account of the importance of the orbitofrontal,
which serves to evaluate the reward/punisher status of inputs from all the
sensory cortices. Furthermore studies show that activation of the orbitofrontal
is correlated to the subjective appreciation of the input rather than the
strength of the signal.
It is probably not possible to conclusively say at
the present stage of neuroscience whether this is true of the repression of inappropriate
behaviours. However, it does seem very likely from what we already know about
the orbitofrontal that these options are assessed subjectively, with a
balancing of the reward/punisher values of the inappropriate behaviour and the possible
negative consequences. This balance is something which could be disrupted by damage
to the orbitofrontal.
The other problem with this book is a common one in
consciousness studies, which is the incomplete treatment of the Libet
experiments. These are trundled out once again as a definitive refutation of
the existence of freewill. What is not mentioned here is that these experiments
dealt exclusively with the timing of trivial movements, the nature of which had
been predetermined by the experimenter. Evaluations of conflicting choices such
as those made in the orbitofrontal, or longer-term planning performed by the dorsolateral
prefrontal do not appear relevant to the movements studied in these experiments,
but do look relevant to those behaviours that might be considered to involve
freewill.
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