1998 Fiscal Year Final Research Report Summary
OPTICAL RECORDING OF AUDITORY CORTEX PLASTICITY IN DEAFENED GUINEA PIGS
| Project/Area Number |
09671736
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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 |
Otorhinolaryngology
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| Research Institution | TOKYO MEDICAL AND DENTAL UNIVERSITY |
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Principal Investigator |
TANIGUTI Ikuo MEDICAL RESEARCH INSTITUTE,PROF., 難治疾患研究所, 教授 (60014255)
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| Co-Investigator(Kenkyū-buntansha) |
HOSOKAWA Yutaka MEDICAL RESEARCH INSTITUTE,ASSIST.PROF., 難治疾患研究所, 助手 (80181501)
HORIKAWA Junsei TOYOHASHI UNIVERSITY OF TECHNOLOGY,FACULTY OF ENGINEERING,PROF., 工学部, 教授 (50114781)
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| Project Period (FY) |
1997 – 1998
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| Keywords | auditory cortex / optical recording / cortical plasticity / cochlcar stimulation / suditory deprivation / 難聴 |
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| Research Abstract |
Plastic changes in auditory cortex activities of deafened guinea pigs were studied using an optical recording system with a 12 x 12-channel photodiode array with the aide of a voltage-sensitive dye (RH795). One to 4 months before the recording, guinea pigs (150-200 g) were uni-or bilaterally deafened by injecting Kanamycin (25 mg/0.1 ml) into the middle ear. Whether the animal was deafened was checked by monitoring the startle reflex and the cortical activity in response to a large sound. The experiments were conducted in a dark soundproof room under Nembutal (30 mg/kg) anesthesia and neuroleptanalgesia (droperidol 0.3 mg /kg and pentazocine 1.1 mg/kg). Pure-tone stimulation (50-ms long and 10-ms rise-fall time) was applied to the intact ear of the unilaterally deafened animals. Electrical stimulation (200 mu s duration, 100 - 1000 mu A) was applied to the intact (for control) and deafened animals through bipolar electrodes located between scala vestibuli and scala tympani. The electro
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des were positioned at 1st and 2nd turns of the cochlea. In intact animals, cochlear stimulation induced band-like activity along the isofrequency contour of the auditory cortex (fields A and DC) and its location was shifted with the electrode location on the cochlea. These response patterns were similar to those to pure tones. However, the response to cochlear stimulation was more widely spread and its dynamic range of intensity function was much narrower than those to sound stimulation. In deafened animals, cochlear stimulation induced cortical responses in the manner similar to those of normal animal. However, after 3 months, band-like activity and tonotopic organization were unclear in bilaterally-deafened animals, while those were still remained in unilaterally-deafened animals. The ipsilateral inhibition observed in the intact animal was much reduced in the deafened animals, and in some cases, was changed to the ipsilateral excitation. These results indicate that the tonotopic architecture and the binaural interaction in the auditory cortex were changed drastically after auditory deprivation. Less
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