Two experiments were conducted to determine whether subjects can learn to control the amplitudes of their contingent negative variation (CNV) through biofeedback training. In Experiment 1, the effect of feedback training on the subjects' discriminability of CNV amplitudes was examined using a simple reaction time task paradigm. Sixteen subjects were asked to try to discriminate their own CNV amplitude levels by pressing a key. Feedback information on discrimination performance was given after the S2 presentation. It was found that biofeedback training led to a significant improvement in discrimination performance. In Experiment 2, ten subjects were given immediate feedback about the amplitudes of CNV observed between S1 and S2. Subjects were instructed to either increase or decrease their CNV amplitude with the aid of immediate feedback information. Results indicated that subjects could learn to regulate their CNV amplitudes in the required directions. It was also found that subjects were able to extend the effects of feedback training to the post-feedback period when feedback signals were no longer presented.
Negative shifts in event-related potentials (ERPs) associated with selective attention were compared between fixed and varying tone pips. The fixed and varying tones were presented with noise bursts in random order within a single sequence. In selective listening to tones varying systematically in pitch and spatial location, subjects were told in advance to expect changes in these attributes from moment to moment. If they had not expected any changes, they would not have been able to selectively track and attend those varying tones. For selective attention to fixed tones, no such preliminary instruction was required. Fronto-centrally dominant negative shifts of ERPs, beginning around 80 ms post-stimulus, were observed when the eliciting tones were selectively attended. The developing phase of these negative shifts followed a similar pattern for the fixed and varying tones although the negative shift to varying tones declined a little earlier (by about 25 ms in grand average waveform) than it did to the fixed tones. These results indicated that expectations based on contextual information from prior stimuli can play an important role in early input selection. Some models of attention which emphasize the role of such expectations were discussed.
Nocturnal polygraphic sleep studies were conducted with 10 mentally retarded infants (2 months to 4 years of age ) suffering from hydrocephaly. In two cases of aqueduct stenosis with ventriculitis (A) and unknown etiology (B), it was not possible to distinguish between EEG patterns of wakefulness, sleep Stage 1, sleep Stage 2 and REM sleep because of abnormally high voltage fast activity during each of these periods. Spindles were observed in the latter case (B) but not in the former case (A). These four stages could, however, be differentiated on the basis of EOG, respiration and submental EMG patterns. One case each of postmeningitis and subdural effusion exhibited no spindles. In the remaining 6 cases, the EEG patterns characteristic of the sleep-wakefulnss cycle were observed. In one of these cases (postmeningitis), extreme spindles were evident. A periodic rhythmicity in the integrated delta levels was found in all cases.