ABSTRACT
A major role of tonotopic organization in primary auditory cortex (AI) is to analyze sound frequency. To date, we have a good understanding of the responses to pure tones (PT) in the auditory cortex. Electrophysiological studies have revealed a tonotopic organization and isofrequency contours in AI, and variations of neuronal properties like frequency tuning, rate-intensity functions to PT, binaural and azimuthal tuning, and distribution of these neurons along and across the isofrequency contours. We also start to have an insight into how AI represents frequency modulated sounds (FM). However, we have not yet understood the dynamic properties of the responses of neuron populations of AI to PTs and FMs, that is, spatial and temporal developments of the responses within the tonotopic organization. Therefore, we studied in AI of guinea pigs the relationship between PT and FM responses, both obtained by an optical recording technique using a voltage sensitive dye. This article describes the similarity and difference of the spatiotemporal patterns of responses to PTs and FMs and possible synaptic mechanisms producing such spatiotemporal patterns in AI.
