Eagleman, the orbitofrontal and Libet


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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