A contingent negative variation (CNV) was recorded extracranially from 36 subjects during the interval between a warning stimulus (words or a pair of bursts of pure tones) and an imperative stimuius (flash of light) by means of the averaging computer technique. A typical pattern of the CNV was a monophasic negative wave with a latency of about 400 msec and an amplitude of about 10μ volts, and it disappeared abruptly after the second stimulus. The CNVs were identifiable in 94% of the subjects with notice method, in which the subjects were noticed the relationship between the two stimuli, and 85% with non-notice method, using the monosyllable test words as a warnig stimulus. And, they were in 89% with notice method using the meaningful test words. The identification of the CNV during the interval between a pair of tone bursts may be used as the parameters of the attention and the conation of the subjects. The diagnostic values as the objective audiometry, and the genesis of the CNV, and the variable factors to the measurement were discussed.
This investigation was undertaken to compare the auditory perception of aphasic individuals with that of normal adults by performing specific auditory discrimination tasks. Two groups of subjects were asked to listen to various interrupted pure tones and to judge whether they were continuous or interrupted tones. The test tones were consisted of three pure tones with duration time 100msec and pause time 10, 30, 50msec respectively. Most nonaphasics judged the pure tones with pause time 10msec as continuous tone and them with pause time 30 or 50msec as interrupted tone. However, aphasics performed three tasks less accurately than nonaphasics. It revealed that the more disturbed the auditory comprehension of aphasics, the poorer ability in discrimination. As for aging, the auditory discrimination decreased relatively and gradually until 70 years old, and there was a dramatic decrease in both normal adults and aphasics above 70 years of age. There were no differences in discrimination ability between males and females.
In order to study the usefullness of BSR for objective audiometry, patients with hearing impairments of various types of audiograms were tested by clicks, and subjective hearing threshold and response threshold of BSR was obtained. The results were as follows. 1) It is difficult to presume the hearing level or type of audiogram of moderate hearing impairments by the subjective hearing threshold to clicks. 2) The subjective threshold to clicks coincided with objective threshold of BSR by clicks except high tone hearing loss, because the response of BSR showed the acuity of hearing over 2kHz, but subjective threshold to clicks related to all frequencies. 3) The normal response of BSR only meaned the normal acuity of hearing in one part of frequencies above 2kHz. It is thus difficult to presume the hearing level or audiogram of hearing impairments by only BSR, and it is necessary to determine the audiological assessement by ERA and others.