LONG-LATENCY NEURONS IN AUDITORY-CORTEX INVOLVED IN TEMPORAL INTEGRATION - THEORETICAL-ANALYSIS OF EXPERIMENTAL-DATA

A previous experimental study (He et al., 1997) found 132 duration-sel ective neurons with long latencies of greater than 30 ms in the dorsal zone of cat auditory cortex. The mechanism by which such long-latency neurons integrate information during their latent period is investiga ted by analysis of the temporal relationship between the stimulus and neuronal response. In the present study, we developed a one-layer perc eptron to examine the above temporal relationship of the experimental results. The acoustic stimulus was represented as a contiguous series of sequential short time epochs. The perceptron was trained by using t he spike data as the desired outputs and the acoustic stimuli (in digi tal format) as the inputs. The adaptive weights between the outputs an d the inputs after training indicated the temporal relationship betwee n neuronal responses and the stimuli. The contribution of each time ep och of the stimulus could be either positive or negative: the positive contribution corresponds to excitatory input and the negative contrib ution to inhibitory input. Long-duration-selective neurons were found to receive mainly excitatory input along the entire effective stimulus duration. However, duration-tuned neurons received excitatory input f or only the time period from the stimulus onset to their best duration s, and inhibitory thereafter. The temporal integration pattern of shor t-duration-selective neurons was similar to duration-tuned neurons. Ho wever, short-duration-selective neurons received excitatory input only at the beginning of the stimulus. Each of the duration-threshold neur ons integrated auditory information only for a restricted time period of the stimulus, suggesting that they have a time window over the stim ulus time domain. Non-duration-threshold neurons have time windows ext ending from the stimulus onset onward. The assembly of duration-thresh old neurons and non-duration-threshold neurons may collectively repres ent the time axis of the stimulus. (C) 1998 Elsevier Science B.V. All rights reserved.