>From: Paul Hughes <email@example.com>
>Subject: Neuron Computational Requirements?
>Date: Wed, 19 Apr 2000 13:26:41 -0700
Actually, you also have to consider that the brain/mind system includes
another layer or layers of processing, involving the release of various
"hormones" and psychoactive agents not from neuron to neuron, but for the
purpose of affecting entire brain areas, in a multitude of ways, as in
emotional states. Imagine the difficulty of simulating this with current
>Iíve recently grown obsessed again with the requirements of
>accurately simulating the neurons role in *informational*
>processing. We do know that a majority of a neurons
>function is devoted to repair and self maintenance.
>However, the question of how much of a neurons function is
>directly related to cognitive processing remains in dispute.
>If you ask Hans Moravec he remains content is equating each
>neuron with a single transistor. He bases this claim on his
>analysis of the ocular neurons role in visual processing.
>The problem with this assumption is that the simple
>processing of visual data near the ocular region neglects
>the remaining processing thatís required to assess the
>context and meaning of that data and integrating it within
>the larger realm of cognitive life itself, to say nothing of
>emotional or other more subtle psychological states.
>My assertion is that the computation required within each
>neuron is far greater than can be met by a single
>transistor. A typical neuron has several thousand synapses
>connected to other neurons mediated by a complex array of
>neurotransmitter activity. Each neuron is responsible for
>regulating the transmission and reception of signals along
>these networks. Although synaptic transmission is quantal
>because an integer number of vesicles must fuse to release
>their neurotransmitters, the decision when to fire is
>determined ultimately by the degree and types of
>neurotransmitters involved. This is why various types of
>psychoactive drugs from Prozac to Marijuana have remarkably
>different effects on cognition and mood.
>**My contention then, is that although the pattern of the
>neural network determines in part who and what we are, the
>complex neurotransmitter activity within the neurons
>themselves also play a significant role in the quality of
>our subjective states. Therefore there is no way a single
>transistor has a chance of duplicating.
>So the question remains what amount of computational
>machinery is required to replace the current role that a
>neuron plays? Any takers?
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