Variability and Information in a Neural Code of the Cat Lateral Geniculate Nucleus

• Type of Material: Article
• Authors: Robert C. Liu, Emory University; Svilen Tzonev, University of California San Francisco; Sergei Rebrik, University of California San Francisco; Kenneth D. Miller, University of California San Francisco
• Language: English
• Date: 2001-12-01
• Publisher: American Physiology Society
• Publication Version: Final Published Version
• Copyright Statement: © 2001 The American Physiological Society
• Final Published Version (URL): https://doi.org/10.1152/jn.2001.86.6.2789
• Title of Journal or Parent Work: Journal of Neurophysiology
• Volume: 86
• Start Page: 2789
• End Page: 2806
• Grant/Funding Information: This work was supported by a grant from the Sloan Foundation (S. Tzonev and R. C. Liu), the University of California President's Postdoctoral Fellowship (R. C. Liu), National Institutes of Health Grants R01-NS-33787 and R01-EY-13595, and gifts from the Swartz Foundation.
• Keywords: variability; stimulus; response; potential capacity; Neural Code
• Research Categories: Biology, Neuroscience

Abstract

A central theme in neural coding concerns the role of response variability and noise in determining the information transmission of neurons. This issue was investigated in single cells of the lateral geniculate nucleus of barbiturate-anesthetized cats by quantifying the degree of precision in and the information transmission properties of individual spike train responses to full field, binary (bright or dark), flashing stimuli. We found that neuronal responses could be highly reproducible in their spike timing (∼1–2 ms standard deviation) and spike count (∼0.3 ratio of variance/mean, compared with 1.0 expected for a Poisson process). This degree of precision only became apparent when an adequate length of the stimulus sequence was specified to determine the neural response, emphasizing that the variables relevant to a cell's response must be controlled to observe the cell's intrinsic response precision. Responses could carry as much as 3.5 bits/spike of information about the stimulus, a rate that was within a factor of two of the limit the spike train could transmit. Moreover, there appeared to be little sign of redundancy in coding: on average, longer response sequences carried at least as much information about the stimulus as would be obtained by adding together the information carried by shorter response sequences considered independently. There also was no direct evidence found for synergy between response sequences. These results could largely, but not entirely, be explained by a simple model of the response in which one filters the stimulus by the cell's impulse response kernel, thresholds the result at a fairly high level, and incorporates a postspike refractory period.