neural coding of behavior: evidence for precise timing of spikes ?

Mark Laubach laubach at biogfx.neuro.wfu.edu
Mon Dec 18 19:50:46 EST 1995


jan at neuroinformatik.ruhr-uni-bochum.de (Jan Vorbrueggen) wrote:

>In an electric eel, a frequecy selection cell changed behavious (selected a
>different frequency of the side organ) dependent on a one microsecond timing
>difference of two afferent cells. Somehow, the network is able to extract that
>information...Binaural cells are also an example.

I admitted in a reply to David Sparks that I agree that not all cells,
or nervous systems for that matter, are likely to be equivalent in
terms of how they process information.  Clearly, in some sensory
systems, and probably in other systems, precise spike timing may be
used to encode info.  Nevertheless, for my areas of interest, basal
ganglia and cerebral cortex, the neurons do not appear to be reliable
in that they do not fire repeating patterns of spikes that are
predictive of an animals behavior.  This also seems to happen in the
somatosensory system.  For example, Chapin and Nicolelis' stuff on
neural ensembles recorded across all levels of the central
somatosensory representation.  The cells DO mis-fire on occasion and
this has to be reckoned with!  But you'd only know this if you
recorded from lots of cells in lots of places over lots of stimuli and
to my knowledge this has not yet been done anyone but them.  So the
issue is still open.  

>So the challenge is to extract the information that is relevant to the cells
>you're measuring, not the changes caused by the general environment which is
>uncontrollable.

The point is that the behavior in my work  IS  controlled, that's why
we use operant techniques.  Also, one has to be a bit more open and
accept that some factors in the environmental, such as the animal's
reinforcement history, will change things even in areas like V1.




-----------------------------------
Mark Laubach
Dept. of Physiology & Pharmacology
Bowman Gray School of Medicine
Wake Forest University
Winston-Salem, NC 27157
laubach at biogfx.neuro.wfu.edu
-----------------------------------




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