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From: brp@dino.berkeley.edu (Bruce Raoul Parnas)
Newsgroups: bionet.neuroscience
Subject: Re: Auditory Impulse Travel and Distance
Message-ID: <1991Jun18.190748.14855@agate.berkeley.edu>
Date: 18 Jun 91 19:07:48 GMT
References: <9106171949.AA20716@genbank.bio.net> <1991Jun18.033141.11511@agate.berkeley.edu> <SLEHAR.91Jun18084520@park.bu.edu>
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In article <SLEHAR.91Jun18084520@park.bu.edu> slehar@park.bu.edu (Steve Lehar) writes:
>
>The  reason why  the brain  uses  neural spiking, and  encodes  signal
>magnitude as spiking frequency  is exactly  to avoid   the degredation
>with distance that is experienced by the  alternative method of neural
>signaling, i.e. the density of ions of a particular charge.
>

i think the question here is not one of active vs. electrotonic spread of
electrical activity through nerves, but of information transfer.  signals
which are weak, i.e. produce only a few spikes, could lose their identity in
background firing rates of subsequent neurons.  thus, spikes still
propagate rather than dissipating, but the signal is lost.

it turns out that in the auditory system this is probably not the case.  the
preponderance of the noise is at the front end, and signals are actually
refined by ensemble processing as they travel along.  thus, any signal
that is lucky enough to make it past the cochlea and get transduced, i.e.
pulled out from the noise, will very likely make it to the auditory cortex.

>(O)((O))(((               slehar@park.bu.edu               )))((O))(O)
>(O)((O))(((    Steve Lehar Boston University Boston MA     )))((O))(O)


bruce
(brp@bandit.berkeley.edu)