Abstract
The processing of temporal information in the left and right auditory cortices of guinea pigs was investigated using click trains and optical imaging with a voltage-sensitive dye (RH795). Guinea pigs were anesthetized with ketamine (80mg/kg) and xylazine (40mg/kg). Click trains were presented at different repetition rates (4, 6, 8, 10, 12, 14, 20 Hz) and at 75 dBSPL ( equivalent to tone ). Neural activity was recorded from multiple auditory fields (primary: AI, dorsocaudal: AII, ventroanterior: VA) of both hemispheres. At the repetition rates of 4, 6 and 10 Hz, the neural activity followed well to each click and sometimes oscillated at the rate of the click even after the session of the stimulus. At 12 and 14 Hz, the neural activity showed one large peak followed by small peaks but at 20 Hz, it showed one large peak only. Repetition rate transfer functions (RRTF) in field AI were low-pass showing a sharp drop-off in evoked activity per click above 10 Hz but RRTFs in field AII were band-pass with the peak of 8 or 10 Hz. Synchronization to click trains was better in field AI than in other fields. In the same animals, the cut-off frequencies of RRTF in the left cortex were same as those in the right cortex but the slopes of the RRTF in the left cortex were sharper. We discuss the temporal processing in the left and right auditory cortices of guinea pigs. [Jpn J Physiol 55 Suppl:S160 (2005)]
