1996 Fiscal Year Final Research Report Summary
OPTICAL IMAGING OF NEURAL ACTIVITY IN AUDITORY CORTEX TO AZIMUTHAL STIMULATION
| Project/Area Number |
07680866
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Neuroscience in general
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| Research Institution | TOKYO MEDICAL AND DENTAL UNIVERSITY |
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Principal Investigator |
HOSOKAWA Yutaka TOKYO MEDICAL AND DENTAL UNIVERSITY RESEARCH ASSOCIATE, 難治疾患研究所, 助手 (80181501)
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| Co-Investigator(Kenkyū-buntansha) |
HORIKAWA Junsei TOKYO MEDICAL AND DENTAL UNIVERSITY ASSOCIATE PROFESSOR, 難治疾患研究所, 助教授 (50114781)
TANIGUCHI Ikuo TOKYO MEDICAL AND DENTAL UNIVERSITY PROFESSOR, 難治疾患研究所, 教授 (60014255)
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| Project Period (FY) |
1995 – 1996
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| Keywords | SOUND LOCALIZATION / BINAURAL / OPTICAL IMAGING / GUINEA PIG / AUDITORY CORTEX |
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| Research Abstract |
Neural activities of the auditory cortex responding to binaural and azimuthal stimulation were studied by optical recording with a 12*12 photodiode array. Anterior (A) and dorsocaudal (DC) fields of the auditory cortex of guinea pigs (280-450g) anesthetized with sodium pentobarbital (30 mg/kg) were stained with a voltage-sensitive dye (RH795). Optical signals were recorded from the auditory cortex and were transformed into sequentail two-dimensional images.
Dichotic stimuli were used to study the effects of interaural intensity difference (IID) and interaural time difference (ITD) on neural activities of the auditory cortex. When both ears were stimulated dichtically by tone bursts at 14 kHz and 75 dB SPL,band-like excitatory responses running along the isofrequency bands appeared in both fields A and DC.Increase of intensity of ipsilateral stimulation from 75 to 95 dB SPL,while the contralateral intensity being kept constant (75 dB SPL), caused decrease of these excitatory responses. I
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ncrease of ipsilateral leads from 0 to 10 ms resulted in gradual decrease of the excitatory responses and increase of the strength of inhibition. Strong inhibition was observed in the ventral portion of field A and whole field DC.However, no topographic representation of azimuths was observed in both the fields. The ipsilateral lead inducing strong inhibition was much longer than the time difference (80 ms) calculated from the interaural distance of the guinea pig. These results indicate that IID is more important than ITD for azimutal sensitivity in the guinea pig.
In order to study the azimuth sensitivity of the auditory cortex, tone bursts were dilivered from loudspeakers placed at contralateral 90ﾟ to ipsilateral 90ﾟ by 15ﾟ steps. The strongest neural activities of the auditory cortex were obtained at contralateral 30ﾟ to 45ﾟ. However, not opographic representation of azimuths was observed in the auditory cortex, which conforms to the results obtained by dichotic stimuli described above. Less
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