Society for Neuroscience 2001
Prog#821.35

THE AMOUNT OF TRANSMITTED INFORMATION IS NOT IMPROVED BY POOLING OF NEURONAL ACTIVITIES IN INFERIOR TEMPORAL CORTEX.
H. Tamura1,2*; H. Kaneko2; I. Fujita1,3
1. Grad Sch Engin Sci, Osaka Univ, Toyonaka, Japan
2. AIST, Tsukuba, Japan
3. CREST, Toyonaka, Japan

Responses of single sensory neurons vary among repeated stimulus presentations. Pooling of activity across a population of neurons can reduce this variation (noise). For pooling to be effective for the noise reduction, neurons should share their stimulus preference, and noise should be uncorrelated among them. We examined how pooling of activities of adjacent neurons affects signal fidelity (signal to noise (S/N) ratio) and signal discriminability (the amount of transmitted information). We recorded simultaneously from 2 to 12 adjacent neurons in area TE of the inferior temporal cortex of 4 anesthetized and paralyzed monkeys (Macaca fuscata). A set of 64 visual stimuli consisting of object images and a variety of shapes were presented. Stimulus preference and noise were weakly correlated among adjacent neurons. The S/N ratio of pooled neuronal responses was evaluated by the slope of regression line for a plot of the mean versus the standard deviation of responses to the 64 stimuli. The S/N ratio became gradually improved as the pooling size was increased. Despite the improvement of the S/N ratio, pooling of activities from adjacent neurons decreased the amount of transmitted information due to the differences in stimulus preference among them. The results indicate that the improvement of the S/N ratio after pooling of neuronal activities does not contribute to decrease signal uncertainty.
Supported by: a CREST grant from the JST to IF, grants from the Japanese MESSC to HT and IF, and a grant from the AIST Japan to HT and HK