Analysis of temporal structure in spike trains of visual cortical area MT

Computation and Neural Systems

Bair, Wyeth ; Koch, Christof

University:California Institute of Technology

Department:Biology

关键词: Computation and Neural Systems;   

Others  :  https://thesis.library.caltech.edu/7600/2/Bair%201996.pdf

美国|英语

来源: Caltech THESIS

【 摘 要 】

The temporal structure of neuronal spike trains in the visual cortex can providedetailed information about the stimulus and about the neuronal implementation ofvisual processing. Spike trains recorded from the macaque motion area MT in previousstudies (Newsome et al., 1989a; Britten et al., 1992; Zohary et al., 1994) areanalyzed here in the context of the dynamic random dot stimulus which was usedto evoke them. If the stimulus is incoherent, the spike trains can be highly modulatedand precisely locked in time to the stimulus. In contrast, the coherent motionstimulus creates little or no temporal modulation and allows us to study patternsin the spike train that may be intrinsic to the cortical circuitry in area MT. Longgaps in the spike train evoked by the preferred direction motion stimulus are found,and they appear to be symmetrical to bursts in the response to the anti-preferreddirection of motion. A novel cross-correlation technique is used to establish that thegaps are correlated between pairs of neurons. Temporal modulation is also found inpsychophysical experiments using a modified stimulus. A model is made that canaccount for the temporal modulation in terms of the computational theory of biologicalimage motion processing. A frequency domain analysis of the stimulus revealsthat it contains a repeated power spectrum that may account for psychophysical and electrophysiological observations.

Some neurons tend to fire bursts of action potentials while others avoid burstfiring. Using numerical and analytical models of spike trains as Poisson processeswith the addition of refractory periods and bursting, we are able to account for peaksin the power spectrum near 40 Hz without assuming the existence of an underlyingoscillatory signal. A preliminary examination of the local field potential reveals thatstimulus-locked oscillation appears briefly at the beginning of the trial.