| Budget Amount *help |
¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1993: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1992: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1991: ¥400,000 (Direct Cost: ¥400,000)
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| Research Abstract |
A negative potential at a latency of 3 msecin the auditory brain stem responses (ABRs) was studied in this project from 1991 to 1993. This large negative deflection at the latency of 3 msec was termed the "N3 potential". The results conclusions are summarized as follows.
1.The N3 potential was found in 46 cases (6.2%), 57 ears (5.6%) among the 3319 ABR waveforms recorded clinicallyat our departmentfrom 1978 to 1990. The appearance was independent of age and sex.
2.The response appeared at the intensity of 80dBnHL or more. As the intensity of stimulationincreased, the amplitude became larger and the latency decreased.
3.The N3 potential had was a far-field potential by nature, and a replicability was found in retesting.
The patients with the N3 potential had no central disorder. The audiogram showed profound deafness.
From the results above, it was suggested that the N3 potential was not an electricalartifact but rather a physiological response to acoustic stimuli. However, the origin of the
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N3 potentialis unknown. It is possibly a vestibularevoked potential, since it occurred in the context of profound or total deafness.
Next, the effects of the stimulus repetitionrate and click polarity on the N3 potential were examined and compared with the findings of Wit et al.in pigeons, which concern the vestibular evoked potential from a semicircularcanal to acoustic stimulation.
5.The latency remained almost unchanged at 10 to 40/sec.but it was definitely prolonged at 83.3/sec. Also, the amplitude decreased to about one half of that observed at the lower repetition rates. The shortest average latency occurred with the rarefaction click, and the longest with the condensation click.
6.No patients with the N3 potential experienced so-called Tullio phenomenon during ABR testing. Furthermore, in one case the ENG failed to show nystagmus in the presence of a loud auditory stimulus.
On the basis of these results, the N3 potential was not the same as the vestibular evoked potential from a semicircular canal to acoustic stimulation and was unlikely to be a vestibular evoked potential. However, a saccular acoustic response in the guinea pig after complete cochlear hair cell destruction was observed by Cazals Y and Aran JM.Additionalinvestigations are needed to determine the origin of the N3 potential. Less
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