Using an S 1-S2-S3 Reaction-Time task paradigm, the contingent negative variations (CNVs) for S2 and S3 were examined. In the task, a subject was informed by S2 of the occurrence or non-occurrence of the immediate S3 which was an imperative stimulus given in a half of the total trials (go-no go task). It was found that the negative potential-shift preceding the S2 presentation was larger when S2 was informative than when S2 was redundant. After the resolution of this shift, a second negative shift developed toward S3 when S2 informed its presentation, but did not when S2 informed its non-presentation. Based on the Principal Component Analysis, it was concluded that the first shift was the late CNV for S2 while the second shift was the late CNV for S3. It might be suggested that the former was not associated with a motor preparation but with anticipatory attention to an informative stimulus, and the latter with a motor preparation.
Effects of the physical properties of reflex-evoking sounds upon the magnitude of blinks and the subjective estimation of startle were examined. The electromyographic activity of orbicularis oculi was measured with eyes closed during wakefulness. Twenty young adults were assigned into one of following four experiments. In each experiment, the standard sound stimuli (noise in Exp. 1-3 and 1000 Hz tone in Exp. 4) were 100 dB, 50ms and less than 1 ms in their intensity, duration, and rise/fall time respectively. In Exp. 1, intensity was varied from 80 to 90,100,110, and 120dB. In Exp. 2, duration was varied from 10 to 30, 50, 70, and 90ms. In Exp. 3 and 4, r/f time was varied from 0 to 6, 12, 18, and 24ms. Results showed that the amplitude of the reflex increased linearly as functions of the noise intensity and the duration, but it decreased as a function of the r/f time. Subjective estimation for the magnitude of startles behaved alike to the reflex amplitude. The positive correlations between these two measures were significant in 17 out of 20 subjects. It is, therefore, concluded that the auditory evoked eyeblinks recorded by an EMG of orbicularis oculi are significant indexes of the startles in humans.
Event-related potentials (ERPs) were recorded from the left and right hemispheres of eight college students during a phonetic discrimination taks. Hemispheric asymmetry was observed in Ni amplitude of the ERP to consonant-vowel (C-V) syllables. More pronounced asymmetry of the ERP was found in the right ear presentation of the C-V-syllables.