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

carp at neuro.med.umn.edu carp at neuro.med.umn.edu
Thu Dec 7 13:06:43 EST 1995

laubach at biogfx.bgsm.wfu.edu (Mark Laubach) wrote:
>Does anyone know of any study, published or unpublished, that shows
>that the precise timing of action potentials encodes information in
>the CNS?
>Specifically, I am interested in studies that used behaving subjects,
>not reduced preparations.
>My own search of the literature indicates that there is no evidence
>for precise timing of spikes as a neural code in awake, behaving
>subjects.  Rather, those who have searched for such coding have
>instead found that local changes in firing rate, not the precise
>temporal pattern of spikes, may serve as a code for environmental
>stimuli, movements, task contingiencies, etc. (e.g., Richmond's work
>on visual cortex).  I know that some (e.g., Abeles) have reported that
>precise spike patterns across small ensembles of neurons can occur in
>behaving subjects, but have these patterns been shown to "be good for
>anything" with regard to the subject's performance of the  task?
>Thanks in advance for any info.
>Mark Laubach
>Wake Forest University

There was a poster from the Merzenich lab at this year's SFN meeting 
(461.13) which demonstrated stimulus encoding by temporal correlation of 
spikes.  Pairs of neurons were recorded from primary auditory cortex in 
anaesthetized monkeys during tone pulses - often, changes in firing 
rated would signal the onset and offset of the stimulus, but not the 
entire stimulus duration.  Cross correlations, on the other hand, were 
(at least in some examples) elevated during the entire stimulus 
duration, sometimes with no corresponding change in firing rate 
whatsoever.  Since the monkeys were anaesthetized one cannot 
assign any "behavioral significance" to such a finding - nevertheless I 
think this is a more compelling demonstration of temporal integration 
than those seen in slice preparations.

Adam Carpenter
University of Minnesota

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