Biphasic dose-related responses of the CNV (contingent negative variation) to I.V. nicotine in man.
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In 27 normal adult subjects, pre- and postimperative phases of the CNV had an homogeneous pattern. The return to the baseline was of short duration (320 +/- 170 msec) whatever the amplitude and surface. This is in favor of an active mechanism terminating the CNV. In 27 schizophrenic and 13 schizoaffective patients, pre- and postimperative phases of the CNV were heterogeneous in character suggesting the possibility of multiple disturbances. When present, the preimperative negativity was of lower amplitude and had a delayed return to the baseline with a wider dispersion. In the patients with preimperative negativity followed by a PINV (postimperative negative variation), a linear relationship has been found between the amplitudes of the two waves.
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The aim of this study was to examine the influence of interfering stimuli on subjects' C.N.V. With a labyrinthic stimulation before association S1-S2 and arithmetic calculation task between S1 and S2, the C.N.V. showed a statistically significant variation (P less than 0.025): it became prolonged after the response to S2. Provocation of a prolonged C.N.V. could be used as criterion to determine an individual threshold of stress.
The CNVs of three disorganized schizophrenics and three paranoid schizophrenics were studied longitudinally over a 5-year period. The CNV of the disorganized-type schizophrenics reached its maximum decrease within 3 years of disease onset. A more gradual and less accentuated decrease was noted in the paranoid group within a span of 5 years.
CNV magnitude was studied in a task involving spatial localization and discrimination Subjects were 18 children 10 years of age. The CNV amplitude of half the subjects increased when the performance decreased and, in the other half, CNV amplitude decreased when the performance decreased. However, it seems that CNV magnitude increases as task difficulty increases but only above a minimal threshold varying with the subject. The results suggest that CNV amplitude cannot be related to a single psychological factor.
The present study was designed to investigate the effect of verbal information processing upon CNV, using a lexical decision task. Subjects performed a choice reaction time (RT) task under possible combinations of sense and nonsense syllables serving as warning (S1) and imperative (S2) stimuli. The results showed that CNV developed exclusively when the expectant information for motor response was given at S1. It was also found that CNV resolution time as well as RT was shorter in the near meaning condition than in the far meaning condition. These findings were discussed in relation to verbal information processing.
Slow EEG potentials were recorded during performance of a simple reaction task in which warning signal intensity was varied from trial to trial under foreperiod durations of 1, 3 and 8 sec. As shown by speed of reaction, the warning signal had an activating effect which increased with its intensity and decreased with foreperiod duration. This effect was related to the amplitude of a slow potential which appears in the EEG shortly after presentation of the warning signal. This potential is interpreted as a component of the orienting response regulating sensitivity to subsequent stimulation, so that reaction time is affected through change in the effective intensity of the imperative signal.
After a review of the literature stressing the biological factors underlying CNV genesis, the author sets up a tentative biological model of CNV, based on the neurophysiological and neurochemical findings of Skinner and Yingling (1977) and Marczynski (1978). In terms of balance between excitatory and inhibitory processes this model encompasses different CNV abnormalities in amplitude or duration frequently observed in mental pathology. The interest of such a model lies in the physiopathologic and therapeutic hypotheses it may lead to. In this respect, CNVs of prolonged duration, which would reflect a catecholaminergic hyperactivity, could constitute an indication for treatment by neuroleptics and/or benzodiazepines. CNVs with a weak amplitude would rather invite one to prescribe antidepressant drugs.