Abstract
The frequency dependency of directional sensitivity of the auditory cortex of barbiturate-anesthetized guinea pigs in response to tone bursts was studied by an optical equipment and a voltage sensitive dye (RH795). Tone bursts at 4, 8 and 14 kHz were presented from loudspeakers placed at the azimuths from contralateral 90° to ipsilateral 90° in 30° steps on a front-horizontal semi-circular board (100 cm in radius). The maximum responses were observed at around contralateral 30° (best azimuth). The onset and peak latencies were the shortest at the best azimuth. The best azimuth was the same for all these frequencies, but the azimuth selectivity became broader for the lower frequencies. These results indicate that the azimuth selectivity observed in the guinea pig auditory cortex is mainly associated with pinna characteristics.