Spatiotemporal observation of guinea pig auditory cortex with optical recording.

The spatiotemporal characteristics of neural activity in the guinea pig auditory cortex were studied in order to clarify neural processing and coding mechanisms of complex sounds. We used a multi-channel optical recording system for a voltage-sensitive dye: RH795. The experimental results showed that a boomerang-shaped moving pattern of optical response appeared on the cortical surface in response to complex sounds (clicks) stimulation, but a rather fixed pattern appeared in response to tone burst stimulation. The tonotopical organization observed using microelectrode was not directly visible, but a similar topographic pattern was evidenced by selecting regions of a strong response evoked by tone-bursts. The correlative functions of regionwide responses may indicate a parallel and serial neural processing structure.