Abstract #21678, Date "Monday, Feb 5 2001 1:00PM - 12:00PM " Session "L17 Auditory Pathways, Cortex III "

Parametric changes in the cross correlation strength in rat primary auditory cortex as a function of experience

Jessica Lynn VAZQUEZ , Pritesh PANDYA , Daniel Rathbun , Raluca Moucha , Navzer D ENGINEER , Michael Paul KILGARD

"In sensory cortex, much of the synchronization between neuron pairs can be accounted for by the overlap of their stimulus preferences, however rapid modulation of cortical synchronization has also been documented and appears to play an important role in perceptual binding. Although both cortical synchronization and receptive field structure are altered by experience, the relationship between the two is far from clear. A better understanding of the interplay between spatial and temporal codes is likely to be essential for the development of a cohesive explanation of cortical function. Here we demonstrate that map expansion in response to a repeated tonal stimulus leads to increased synchronization of cortical responses, while cortical reorganization in response to a variety of spatially distinct stimuli leads to decreased synchronization across the cortical surface. Tuning curve broadening and expansion of the 9kHz region of the A1 frequency map as a result of repeatedly (300 times daily for four weeks) pairing 15Hz trains of 9kHz tones with electrical stimulation of the basal forebrain was accompanied by a 46% increase in normalized cross-correlation height and a 15% decrease in cross-correlation width at half height during spontaneous activity. In contrast, pairing tones of random frequency caused receptive field narrowing without map expansion that was accompanied by a 26% decrease in cross-correlation height and a 34% increase in cross-correlation width. Finally, no changes in cross-correlation height or width were observed when stimuli with features of both of the above acoustic stimuli were presented. Cross-correlation analysis was performed on multi-unit responses recorded from microelectrodes separated by 250 microns. We believe these findings are consistent with both receptive field overlap and perceptual (Gestalt) grouping models of cortical synchronization. "