Cross-Correlation and Joint Spectro-Temporal Receptive Field Properties in Auditory Cortex
Journal of Neurophysiology
Tomita, Masahiko and Jos J. Eggermont. Cross-correlation and joint spectro-temporal receptive field properties in auditory cortex. . Recordings were made from the right primary auditory cortex in 17 adult cats using two eight-electrode arrays. We recorded the neural activity under spontaneous firing conditions and during random, multi-frequency stimulation, at 65 dB SPL, from the same units. Multiple single-unit (MSU) recordings (281) were stationary through 900 s of silence and during 900 s of
... and during 900 s of stimulation. The cross-correlograms of 545 MSU pairs with peak lag times within 10 ms from zero lag time were analyzed. Stimulation reduced the correlation in background activity, and as a result, the signal-to-noise ratio of correlated activity in response to the stimulus was enhanced. Reconstructed spectro-temporal receptive fields (STRFs) for coincident spikes showed larger STRF overlaps, suggesting that coincident neural activity serves to sharpen the resolution in the spectro-temporal domain. The cross-correlation for spikes contributing to the STRF depended much stronger on the STRF overlap than the cross-correlation during either silence or for spikes that did not contribute to the STRF (OUT-STRF). Compared with that for firings during silence, the cross-correlation for the OUT-STRF spikes was much reduced despite the unchanged firing rate. This suggests that stimulation breaks up the large neural assembly that exists during long periods of silence into a stimulus related one and maybe several others. As a result, the OUT-STRF spikes of the unit pairs, now likely distributed across several assemblies, are less correlated than during long periods of silence. Thus the ongoing network activity is significantly different from that during stimulation and changes afterng arousal during stimulation. Downloaded from FIG. 8. STRFs for coincident (Ϯ10 ms) spikes (top), noncoincident spikes (middle) and all spikes (bottom) for electrode 2 (left) and electrode 8 (middle column). Right: the overlap of the contour lines. 386 M. TOMITA AND J. J. EGGERMONT Abeles M. Corticonics: Neural Circuits of the Cerebral Cortex. London: Cambridge Univ. Press, 1991. Aertsen A, Erb M, and Palm G. Dynamics of functional coupling in the cerebral cortex: an attempt at a model-based interpretation. Physica D 75: 103-128, 1994. Alonso JM, Usrey WM, and Reid RC. Precisely correlated firing in cells of the lateral geniculate nucleus. Nature 383: 815-819, 1996. Bedenbaugh P and Gerstein GL. Multiunit normalized cross correlation differs from the average single-unit normalized correlation. Neural Comput 9: 1265-1275, 1997. Blake DT and Merzenich MM. Changes in AI receptive fields with sound density. J Neurophysiol 88: 3409 -3420, 2002. Brosch M and Schreiner CE. Correlations between neural discharges are related to receptive field properties in cat primary auditory cortex. Eur J Neurosci 11: 3517-3530, 1999. Cleveland WS. LOWESS: a program for smoothing scatterplots by robust locally weighted regression (Abstract).