Monday, November 03, 2008

Zany brainy (cont'd.) ...

A tuning fork is struck or a whistle is blown ... and a series of waves with the frequency of, let us say, 4,000 vibrations a second is propagated through the air. It strikes the observer's ear and a portion of the cochlea, attuned to this particular frequency, is caused to vibrate at the same rate. So far the subject has heard nothing. The vibration of this part of the cochlea starts a series of nerve-impulses in a certain fibre or fibres of the auditory nerve. No nerve-fibre in the body can carry impulses at so fast a rate. The frequency with which nerve-impulses can follow one another along a nerve depends upon the electro-chemical structure of nervous tissue and is never more than 1,500 a second, and often much less. ... The auditory nerve-fibre therefore conducts impulses at its accustomed rate, and by a series of relay paths, the impulses reach the auditory area of the cerebral cortex in the temporal lobe. ... the frequency of the sound-stimulus, and the electrical response which it evokes in the auditory cortex ... are entirely dissimilar.
The nervous impulses evoked by visual and olfactory stimuli are correspondingly dissimilar. This is taken from W. Russell Brain's Mind, Perception and Science. If this remains true - and I have no reason to believe it doesn't - then it would seem to have considerable bearing on what Andy Clark is quoted as saying in this earlier post.

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