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Biomedical subjects

M Timsit-Berthier

Publications and source records attributed to M Timsit-Berthier.

At least 55 records · Page 3Linked to original sources
PubMed1985

Sleep and wake after benzodiazepine hypnotics: a 20-hour EEG comparison of lormetazepam and flunitrazepam.

In an electropharmacokinetic study, the effects of lormetazepam and flunitrazepam were compared by the means of a sleep EEG and waking EEG during the following daytime. At a 1-week interval, 6 normal subjects received at random either 2 mg lormetazepam or 2 mg flunitrazepam in a double-blind, crossover fashion. Sleep EEG was recorded throughout the night; 6-min EEG samples were recorded every hour during 10 hours on the following daytime for spectral analysis. Night sleep after flunitrazepam showed lower Stage IV sleep than after lormetazepam. During daytime, only flunitrazepam induced an increased percentage of beta 2 frequencies, which remained above baseline up to 10 hours after awakening, indicating a prolonged impregnation time. This study permitted comparison of the relative intensity and duration of these two benzodiazepines: lormetazepam appeared to be a short-acting hypnotic while flunitrazepam displayed longer modification of the brain electrical activity.

Adult↗
PubMed1985

[Contribution of contingent negative variation (CNV) to the study of schizophrenia].

The authors first review neurobiological and psychopathological data supporting the use of Contingent Negative Variation (CNV) for the study of Schizophrenia. Next, results obtained with the method are presented (i.e. with S1-S2 interval = 1 sec, and recording leads = Cz and Fz) comparing 34 control subjects with 29 schizophrenic patients, all diagnosed with the "Present State Examination" test or PSE (Wing and Sartorius). In patients, reduced CNV amplitude (p less than 0.0001), together with reduced CNV resolution (p less than 0.02) and less differentiated topographical spreading (p less than 0.02) were observed relatively to controls. There is also a slower reaction time (p less than 0.02). Such abnormalities are sufficiently frequent as to allow CNV as a helping diagnostic tool, with a sensitivity rate of 83% and a specificity rate of 85%. These results are discussed with respect to the psychopathological and neurobiological problems in relation with schizophrenia.

Contingent Negative Variation↗
PubMed1984

[Contingent negative variation and endogenous components of the evoked potential].

After having evoked the problems raised by the definition of the different endogenous components of evoked potentials, the author reviews the experimental data related to contingent negative variation (CNV), the processing negativity, the N200, P300 and the slow waves (SW1 and SW2). Their characteristics of amplitude, latency, duration, topography and their functional significance are examined. Then, the particular point of these waves' variability is pointed out, in relation to maturation, level of arousal and personality. Finally, the different theories which preside over their interpretation are reviewed.

Adult↗
PubMed1984

[Is there a correlation between the phases of CNV and the power spectrum of the EEG?].

In 14 volunteers, the relationships between CNV and EEG power spectrum were studied during 3 periods of 1 sec: before S1, between S1 and S2, and after S2. We noted first a relation between CNV amplitude and EEG spectrum over the 3 periods: there was an inverse correlation for the alpha band, and a direct correlation for the beta band. We also observed a direct, strong correlation (r = 0.94) between CNV slope and alpha band reactivity during the S1-S2 interval, but this held only for subjects showing a decrease of alpha activity during the S1-S2 interval. There was no correlation at all between the positive phase (post-S2) of the CNV and EEG. These results are discussed in terms of functional states of the brain influencing CNV development, as well of the various modes of activation and reactivity at the individual level that modify the relationships between CNV and EEG.

Adolescent↗
PubMed1983

[Relation between fast EEG rhythms and contingent negative variation].

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.

Adult↗
PubMed1982

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.

Adult↗
PubMed1982

[Quantified EEG and CNV changes during inhalation of nitrous oxide].

The present study constitutes an approach to the action mechanisms of nitrous oxide (N2O) by assessing both the subjective effects induced by the inhalation of this anaesthetic gas, and their electrophysiological correlates, i.e., spontaneous EEG, analyzed by a Fourier algorithm, AEP and CNV. The experiment was conducted single blind in 9 volunteers under 3 recording conditions: inhalation of air, of a mixture of 25% N2O--75% O2, and of a mixture of 50% N2O--50% O2. A latin-square design was used. Polymorphic effects of N2O were evidenced on behaviour and on CNS: some of the behavioural manifestations could evoke a depression of SNC: muscle relaxation with difficulty of motor initiation, psychomotor slowing, slower EEG with diminution of the percent alpha component and increase in the percent theta and delta, loss of amplitude of both exogenous (N1) and endogenous (P300) components of the AEP. Conversely, other manifestations were observed that are compatible with an activation of the CNS: increase of sensory perceptions, appearance of perceptual illusions, maintenance of a high CNV amplitude and lengthening of its duration. This dual effect of N2O suggests a dissociative action at the different levels of the CNS.

Adult↗
PubMed1982

[Positron tomographic study of the behavior of 13N-labeled nitrous oxide in the human brain].

The synthesis of 13N-labelled nitrous oxide was made following NICKLES' method. After a partial denitrogenisation by breathing pure oxygen for 3 min, the subject inhaled a bolus of 13N-labelled nitrous oxide diluted in 2 l of oxygen (a mixture of 5% 13N2O and 95% O2). After an apnea of 30 sec the subject began to breathe in a closed respiratory system containing a mixture of 10% N2O and 90% O2. Eight images of the brain taken at level OM + 3 in 4 subjects showed an important uptake in the cerebellum and in the frontal and temporal cortex. Six min after inhalation of the bolus, the radioactivity in the cerebellum showed a clear decrease, whereas little decrease was observed in the frontal cortex and only a slight decrease in the temporal cortex. In order to suppress the activity due to the vascular comportment, an experiment was performed under the same conditions as the previous one, but using sodium pyrophosphate containing tin and 25 mCi of Tc-99m pertechnetate. The correction factors vary from 0.394 to 0.894 depending on the R.O.I. The activity curves after correction showed a predominance in the frontal cortex. It can therefore be concluded that some specific zones of the brain are receptive to N2O and in particular the frontal cortex. These results were compared with the data obtained from the electrophysiological recording of the frontal region of the brain (C.N.V.: Contingent Negative Variation).

Adult↗
PubMed1982

Action of lysine-vasopressin on human electroencephalographic activity. Night sleep pattern, auditory evoked potential, contingent negative variation.

This study is an investigation of the central effects of vasopressin in man, as this hormone proved able to modify learning processes in animals and was applied successfully to post-traumatic, amnesic patients. Electrophysiological techniques were used to assess the effects of lysine-vasopressin (LVP) given by nasal spray (7 and 14 IU) on night sleep pattern (12 subjects), auditory evoked potentials (AEP; 26 subjects), and contingent negative variation (CNV; 26 subjects). Night sleep EEG was not modified to a great extent: in particular REM sleep did not undergo any change after LVP. Nor were AEPs modified, either in the 6-hour period following drug administration or 1 week after; CNV, however, reacted in a significant manner 6 h after drug intake, and the modifications were still present after 1 week. LVP did not affect CNV amplitude itself but its evolution through time, as CNV habituation was prevented. Such effects are discussed with regard to the neurochemical mechanisms of vasopressin action and CNV genesis.

Administration, Intranasal↗
PubMed1981

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.

Adolescent↗
PubMed1981

[Inversion of the polarity of contingent negative variation during falling asleep (author's transl)].

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).

Adult↗
PubMed1981

[Concerning the interpretation of the contingent negative variation in psychiatry (author's transl)].

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.

Acetylcholine↗