| Abstract #158, Date 2/14/99, Session E6, Poster (B126) |
| Pitch sequence in the Japanese monkey |
| *H. Riquimaroux (Doshisha University and PRESTO); K. Manabe (Doshisha University) |
We have investigated pitch extraction mechanisms in the central auditory system. Pitch perception is not always directly related to frequency or spectral information. A typical example is the missing fundamental perception. The missing fundamental perception is believed to be created in the central auditory system above the superior olive, where information from both ears meets for the first time, and is not due to the physical distortion such as the difference tone or the nonlinearity in the peripheral auditory system. Previous human studies with brain surgery have shown that the area around the primary auditory cortex appears to play an essential role in the missing fundamental perception. On the other hand, animal behavioral researches have indicated that non-human animals also posses the missing fundamental perception. Thus, neural correlates for the missing fundamental perception were studied in the primary auditory cortex of the Japanese monkey (Macaca fuscata), which has much more similar brain structure to humans than rodents or cats. We found that the neurons in the primary auditory cortex, which were tuned to the fundamental frequency, also responded very well to a combination of successive higher harmonics of the fundamental frequency without the fundamental frequency itself. However, these neurons did not or little responded to each frequency component of the harmonics. The neurophysiological data basically agreed well with the human psychoacoustical results. Our findings suggested that the pitch perception originated from spectral information and the one created by time information were integrated at or below the primary auditory cortex. Next, we stepped into experiments to investigate the dynamic pitch sequence which is related to music perception and speech communication. The water deprived monkey was trained to discriminate the direction of change in frequency or pitch, rising (S-) or falling (S+), by pushing a button. Tone bursts and/or complex tone bursts were sequentially presented. After the training, a transfer from sequential tone burst discrimination to sequential pitch discrimination with complex tones was found. The data suggest that the monkey may have a categorical perception for rising pitch and falling pitch similar to humans. Pitch perception in the monkey auditory system will be discussed. |