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

Mark Laubach laubach at biogfx.neuro.wfu.edu
Sat Dec 9 10:32:09 EST 1995


kevin at gaba.neurology.wisc.edu (Kevin Hellman) wrote:

>It would appear neurons are more precise than we think... The order of magnitude
>of precision according to Mainen and Sejnowski also appears to increase in reliability
>with the injection of a random noise current(?)  

I agree.  Neurons in a dish can be made reliable and this means that
neurons in general are clearly capable of such reliable transmission.
However, in a whole brain during behavior, this reliability is the
issue.  Where is the evidence?

There are many variables that vary with performance of a task.
Richmond's group showed evidence at the neuro meeting that neurons in
_V1_ vary from trial to trial as a function of behavioral conditions
on previous trials.  Even under highly controlled experimental
conditions, chair-seated monkeys performing a well-learned task with
eye coils etc., one still finds an enormous complexity in neural
activity with variations from trial to trial.  I feel that this
variation is the thing we need to explain, not stuff found in dishes
with electrical stimulation.

My focus here is due to practical issues.  If one wants to understand
neural coding in behaving subjects, then one has to address the issues
that arise in these studies.  The tremendous convergence of neurons
onto the cells that are recorded implies that there are many
connections that could give rise to the patterns of spikes observed.
We need to think hard on this issue and to develop methods for
analysis that will allow for new insights into how neurons encode and
transmit information.
-----------------------------------
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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