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.
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