J.C. Rousseau

Slow potential changes in psychiatry: I. Contingent negative variation.

Abstract Contingent negative variation (CNV) amplitude, morphology, and duration have been studied in 370 subjects, distributed in 3 groups: controls (100 subjects), neurotics (135 subjects) and psychotics (135 subjects). Neurotics, especially those with hysterical characteristics, have a tendency to present small amplitude and Type A “field dependency” CNVs ( P > 0.05). Small amplitude or prolonged CNVs (Type III and Type IV curves with a “plateau” or “dome” aspect) occur significantly more often among psychotics than either normal or neurotic subjects ( P >0.001). It appears that psychotic patients seem able to respond only on the principle of “all or nothing” to the CNV paradigm.

Slow potential changes in psychiatry. II. Motor potential

Abstract The study of the motor potential was carried out on a population of 252 subjects, divided into three groups: controls (72 subjects), neurotics (86 subjects) and psychotics (94 subjects). Mainly among psychotics, and to a lesser degree among neurotics, a very different type of motor potential appears, not at all like that described in the literature concerning normal subjects (Type P motor potential). It is interesting because no inversion of polarity occurs during the muscular contraction. The negative readiness potential may present variable amplitude and duration, but in all cases it persists after the end of the motor activity and ends with a more gradual slope than is seen in the normal motor potential.

CNV and functional state changes during long-lasting and repetitive recording sessions.

Publisher Summary This chapter discusses contingent negative variation (CNV) and functional state changes during long-lasting and repetitive recording sessions. The data presented here clearly indicate that CNV undergoes amplitude change (experiment 1) within as well as between recording sessions. After a phase of decrement of amplitude negativity, that one shall call the “habituation phase,” CNV stabilizes around some mean value. During long-lasting sessions (experiment 2), the decrease in amplitude is not paralleled by a decrease in arousal level, as evaluated by quantitative spontaneous electroencephalography (EEG), but it is correlated with the orderly decrement of alpha desynchronization that occurs during the preparatory period between S1 and S2. Post-S2 positivity has a different evolution, as it tends to increase slightly during both long-lasting (experiment 2) and repetitive (experiment 1) session. Whatever explanation is preferred, the occurrence of such positive variations while a quasi-normal performance is maintained shows that the link between electrophysiological and behavioral data is not unequivocal: some “decoupling” of both functional systems may happen under special conditions.

Some Problems and Tentative Solutions to Questions Raised by Slow Potential Changes in Psychiatry

Publisher Summary Contingent Negative Variation (CNV) research in psychiatry is of increasing practical interest to the clinician. Nevertheless, the detection of an abnormal waveform does not provide a formal diagnosis because a nonspecific anomaly is found in most clinical categories. The chapter describes four different types of CNV according to their mode of resolution: (1) normal duration, where baseline return occurs immediately after the imperative stimulus; (2) long duration, where baseline return is delayed and the drop begins immediately after the imperative stimulus; (3) baseline return is delayed, but there is no drop after the imperative stimulus; and (4) baseline return is delayed, and the negative deflection increases in amplitude after the imperative stimulus, producing a characteristic “dome” appearance. The chapter also describes three types of problems raised by the discovery of prolonged CNVs: (1) problem of artifacts, (2) problems of the stability and variability of these phenomena, and (3) the question of significance.

Étude comparée de la V.C.N. et de l'E.E.G. quantitatif au cours d'une tache motrice simple*

Summary 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 Coopers distinction between « scopeutic » and « categoric » processes (1978) and in terms of the Tecce model of the CNV (1972) .