Features of Neuronal Synchrony in Mouse Visual Cortex

1 Abteilung Neurophysiologie, Max-Planck-Institut für Hirnforschung, 60528 Frankfurt 2 Abt. Klinische Neurobiologie, Universität Heidelberg, 69120 Heidelberg 3 Institut für Neurophysiologie und Pathophysiologie, Universitätsklinikum Hamburg-Eppendorf, 20246 Hamburg, Germany Submitted 1 July 2002; accepted in final form 31 March 2003 Synchronization of neuronal discharges has been hypothesized to play a role in defining cell assemblies representing particular constellations of stimulus features. In many systems and species, synchronization is accompanied by an oscillatory response modulation at frequencies in the -band. The cellular mechanisms underlying these phenomena of synchronization and oscillatory patterning have been studied mainly in vitro due to the difficulty in designing a direct in vivo assay. With the prospect of using conditional genetic manipulations of cortical network components, our objective was to test whether the mouse would meet the criteria to provide a model system for the study of -band synchrony. Multi-unit and local field potential recordings were made from the primary visual cortex of anesthetized C57BL/6J mice. Neuronal responses evoked by moving gratings, bars, and random dot patterns were analyzed with respect to neuronal synchrony and temporal patterning. Oscillations at -frequencies were readily evoked with all types of stimuli used. Oscillation and synchronization strength were largest for gratings and decreased when the noise level was increased in random-dot patterns. The center peak width of cross-correlograms was smallest for bars and increased with noise, yielding a significant difference between coherent random dot patterns versus patterns with 70% noise. Field potential analysis typically revealed increases of power in the -band during response periods. Our findings are compatible with a role for neuronal synchrony in mediating perceptual binding and suggest the usefulness of the mouse model for testing hypotheses concerning both the mechanisms and the functional role of temporal patterning. Address for reprint requests: G. Nase, Abt. Neurophysiologie, Max-Planck-Institut für Hirnforschung, Deutschordenstr. 46, 60528 Frankfurt, Germany (E-mail: nase{at}mpih-frankfurt.mpg.de ).