Abstract
Recent studies on the human auditory cortex suggest that processing of spectral and temporal information differs between the left and the right hemisphere. In this study, processing of temporal information in the left and right auditory cortices of guinea pigs was investigated using repeated sounds and optical imaging with a voltage-sensitive dye (RH795). Guinea pigs were anesthetized with ketamine (80mg/kg) and xylazine (40mg/kg). Tone or noise trains were presented at different repetition rates (4, 6, 8, 10, 12, 14 Hz) and at 75 dBSPL. Neural activities were recorded from multiple auditory fields (primary: AI, dorsocaudal: AII, ventroanterior: VA and ventroposterior: VP) of both hemispheres. At the repetition rates of 4 and 6 Hz, the neural activity followed well to each sound and sometimes oscillated at the rate of the repeated sound. At 8 and 10 Hz, the neural activity showed one large peak followed by small peaks and at 12 and 14 Hz, it showed one large peak only. Repetition rate transfer functions (RRTF) were low-pass showing a sharp drop-off in evoked activity per tone above 6 Hz. Synchronization to tone trains was better in field AI than in other fields but synchronization to noise trains was the best in field AII. In the same animals, the cut-off frequencies of RRTF in the left cortex were higher than those in the right cortex. We discuss the temporal processing in the left and right auditory cortices of guinea pigs. [Jpn J Physiol 54 Suppl:S167 (2004)]
