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Behavioral/Systems/Cognitive Non-Gaussian Membrane Potential Dynamics Imply Sparse,
 

Summary: Behavioral/Systems/Cognitive
Non-Gaussian Membrane Potential Dynamics Imply Sparse,
Synchronous Activity in Auditory Cortex
Michael R. DeWeese and Anthony M. Zador
Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724
Many models of cortical dynamics have focused on the high-firing regime, in which neurons are driven near their maximal rate. Here we
consider the responses of neurons in auditory cortex under typical low-firing rate conditions, when stimuli have not been optimized to
drive neurons maximally. We used whole-cell patch-clamp recording in vivo to measure subthreshold membrane potential fluctuations
in rat primary auditory cortex in both the anesthetized and awake preparations. By analyzing the subthreshold membrane potential
dynamics on single trials, we made inferences about the underlying population activity. We found that, during both spontaneous and
evoked responses, membrane potential was highly non-Gaussian, with dynamics consisting of occasional large excursions (sometimes
tensofmillivolts),muchlargerthanthesmallfluctuationspredictedbymostrandomwalkmodelsthatpredictaGaussiandistributionof
membrane potential. Thus, presynaptic inputs under these conditions are organized into quiescent periods punctuated by brief highly
synchronous volleys, or "bumps." These bumps were typically so brief that they could not be well characterized as "up states" or "down
states."Weestimatethathundreds,perhapsthousands,ofpresynapticneuronsparticipateinthelargestvolleys.Thesedynamicssuggest
acomputationalschemeinwhichspiketimingiscontrolledbyconcertedfiringamonginputneuronsratherthanbysmallfluctuationsin
a sea of background activity.
Key words: auditory; cortex; whole-cell recording; rat; synchrony; random walk; neural coding
Introduction
Most of what we know about the dynamics of neuronal popula-

  

Source: Andrzejak, Ralph Gregor - Departament de Tecnologia, Universitat Pompeu Fabra
Pillow, Jonathan - Department of Psychology, University of Texas at Austin
Zadorlab, Tony - Cold Spring Harbor Laboratory

 

Collections: Biology and Medicine; Computer Technologies and Information Sciences