Abstract
The processing of spectral and temporal information in the core fields of the left and right auditory cortices of the guinea pig was investigated using optical imaging with a voltage-sensitive dye (RH795). 23 guinea pigs were anesthetized with ketamine (80mg/kg) and xylazine (40mg/kg). In order to compare the tonotopical organization between the left and the right auditory cortex, optical imaging patterns to tone stimulation at 2, 4, 8, 16 kHz were recorded from core auditory fields (primary (AI), dorsocaudal (DC) fields) of both sides and tonotopy maps were made. In the same animal, the tonotopic organization of AI and DC of one side was more clear than the other side. In 65% animals, the distance between 2kHz and 16kHz isofrequency bands in the left AI was longer than that of the right AI, whereas that of left DC was shorter than that of the right DC. To compare the temporal properties, click or noise trains were presented at different repetition rates (4-20 Hz). Repetition rate transfer functions (RRTF) in field AI were low-pass showing a sharp drop-off in evoked activity per click or noise above 10 Hz but RRTFs in field DC were band-pass with the peak of 8 or 10 Hz. The cut-off frequencies of RRTF in the left cortex were the same as those in the right cortex but the slopes of the RRTF in the left cortex were sharper. We discuss the functional difference between the left and right auditory cortices of guinea pigs. [J Physiol Sci. 2006;56 Suppl:S185]
