[Relation between fast EEG rhythms and contingent negative variation]. / Relations entre rythmes rapides de l'EEG et variation contingente négative (VCN).

The experiments were done to investigate the relationships between activation level and contingent negative variation (CNV). Two groups of subjects, differing in their level of cortical arousal, were recorded with eyes open (OE, N = 17) or eyes closed (CE, N = 40). Beta activity, CNV, electro-oculogram, reaction time and heart rate were studied. In the CE group, beta activity and CNV were not significantly correlated. In the OE group, CNV was slightly extended with a higher amplitude and a higher post-imperative negativity when beta activity was higher; heart rate was also significantly correlated with beta activity in this group. The results are discussed as a function of the existence of two neurophysiological mechanisms of generation and regulation of CNV.

Electrophysiological measures (CNV--EEG) and nitrous oxide at low doses in man.

Nitrous oxide (N2O) is a widely used inhalational anesthetic gas, but its exact mode of action and its distribution in the CNS are not yet well known. The aim of this research was to study the effects of N2O at low doses (10 percent) in the CNS of humans. Five healthy volunteers were tested. Contingent Negative Variation (CNV), Reaction time (RT) and quantified EEG recordings were taken while subjects were breathing air and then N2O. A significant reduction of the post-imperative positive CNV components during N2O inhalation was observed; no changes in EEG power spectrum and RT values were seen. These results could be consistent with an early N2O interference with processes underlying CNV resolution, while vigilance and attention were still maintained.

A correlation study of contingent negative variation, reaction time, and EEG power spectrum in control and psychopathological populations.

Contingent negative variation (CNV), reaction time (RT), and EEG power spectrum were measured in a group of 27 neurotics and 26 controls subjects, male and female, aged 18 to 38. CNV was recorded with a 1 sec interstimulus interval and averaged over 48 trials. Two spectral analyses of the EEG were performed, the first during the 1 sec period preceding S1 (spontaneous EEG), the second during the S1-S2 interval (activated EEG). For each group of subjects, we calculated the correlations between four measures of CNV amplitude, RT duration, and the relative powers of the delta, theta, alpha and beta activities during spontaneous and activated EEG. In neurotic subjects there was an absence of correlation between the pre- and post-imperative segments of the CNV, and between early CNV amplitude and per cent alpha power. Both groups shared in common strong correlations relating CNV amplitude and RT length, on the one hand, and the different components of the EEG spectrum, on the other hand, Principal component analysis applied to the pooled data revealed different factors for CNV and EEG parameters, suggesting independence of the neurophysiological mechanisms implied in the two phenomena.

[Inversion of the polarity of contingent negative variation during falling asleep (author's transl)]. / Inversion de polarité de la variation contingente negative au cours d'etats d'endormissement.

In 25 subjects repeated examination of contingent negative variation (S1 - S2 = 1 sec) under relatively unconstrained experimental conditions (simple, monotonous task, long recording sessions with eyes closed) favorized drowsiness and falling asleep. These periods of low vigilance level, observed in 7 subjects, are characterized by: (1) a global reduction in spontaneous EEG, measured by a diminution in the alpha/theta + delta index (FFT on bipolar leads P3--P4); (2) an inversion in alpha reactivity in the S1 - S2 interval, which, instead of diminishing, tends to augment 'paradoxically'; and (3) an inversion in the polarity of the CNV, which can reach a positive value as high as + 15 to + 20 microV. These electrophysiological phenomena are not accompanied by significant modifications in reaction time. The results are interpreted as the translation of an active 'internal inhibition' process, induced by repetition of monotonic stimuli. They are compared with animal data obtained by MARCZYNSKI and SHERRY (1972) and SKINNER and YINGLING (1977).

[Comparative study of the CNV and the quantitative EEG during a simple motor task (author's transl)]. / Etude comparée de la V.C.N. et de l'E.EG.G. quantitatif au cours d'une tache motrice simple.

The purpose of this study was to evaluate CNV amplitude variability and its degree of covariance with the spontaneous EEG (quantified by FFT algorithm) and the reaction time. 14 healthy male subjects made from atypical for one hour, and they had to keep their eyes closed. Recordings were during this period. CNV experimental paradigm was performed (S1--S2 = 1500 msec). The major findings of this study were that: 1) the CNV amplitude progressively decreased during the first part of the test (habituation) and then tended to stabilize. While not correlated with the vigilance index of spontaneous EEG (alpha/theta + delta index) the CNV amplitude was significantly related to the alpha reactivity index (% alpha of spontaneous EEG--% alpha of the S1--S2 EEG), 2) the CNV slope (calculated by drawing two points situated at 600 msec and 1400 msec after S1) showed significant relationship to both these EEG indices and the reaction time. These data are discussed in terms of Cooper's distinction between "scopeutic" and "categoric" processes (1978) and in terms of the Tecce model of the CNV (1972).