Biomedical subjects

N Lesèvre

Publications and source records attributed to N Lesèvre.

At least 19 recordsLinked to original sources

PubMed1990

[Evoked potentials and the mode of cognitive development in boys 6 to 8 years of age presenting hyperactivity with attention deficit].

Event-related potentials were recorded in 2 groups (attention deficit hyperactivity disorder--ADHD--and normal controls) of 12 male children aged between 6-8 years during 4 categorization tasks. Each task was performed with a different type of visual stimulus; pictures, words, geometrical figures or digits. The amplitudes and latencies of a fronto-central P250 and a parieto-occipital P350 were examined. The overall amplitude of the fronto-central P250 was larger in the ADHD group. However, the overall latency of the parieto-occipital P350 decreased with age; coincidentally, in the control group, the P350 latency measured in the left hemisphere became shorter with age for the words than for the pictures. This was not the case in the ADHD group. These results are discussed in relation to the level of the orienting reaction and the modes (general or differentiated) of cognitive development.

Attention Deficit Disorder with Hyperactivity↗

PubMed1989

Hemisphere asymmetry of alpha burst sequential organization in depression.

A new quantitative EEG index based on the sequential variability of the frequency of occurrence of alpha bursts (alpha-BVI) was utilized for investigating the respective role of the two hemispheres in depression and their relationship with two clinical dimensions of this illness: psychomotor retardation and blunted affect. The EEG (at P3 and P4 referred to Fz) was recorded during rest periods in two groups of patients selected according to their scores on various clinical scales: one consisted of 12 patients characterized by psychomotor retardation (PMR group), the other of 9 patients characterized by blunted affect (BA group). A control group of 12 normal subjects was recorded in the same conditions. All subjects were dextral. The following main results were obtained: (1) in both groups of patients the right and the left alpha-BVI were, before treatment, significantly lower than those of the controls. (2) In controls, the sequential alpha burst variability was identical on both hemispheres. (3) In patients, before treatment, the right hemisphere alpha-BVI was significantly lower than the left. (4) Electro-clinical correlations were also observed: (A) in the BA group, before treatment, (a) between the degree of blunted affect and the decrease of the right alpha-BVI, (b) between ideoverbal retardation and the decrease of the left alpha-BVI (these correlations disappeared after treatment); (B) in the PMR group, ideoverbal retardation was, on the contrary, correlated to a right alpha-BVI decrease, this correlation persisting after treatment. These results are discussed according to the role of each hemisphere in depression.

Adult↗

PubMed1988

Attention impairment and psychomotor retardation in depressed patients: an event-related potential study.

The cerebral event-related potentials (ERPs) and reaction times (RTs) of 8 drug-free depressed in-patients (mean age 58, with marked psychomotor retardation) were recorded during a dichotic listening and choice RT task and compared to those of 9 healthy, age-matched controls. The depressed showed significantly longer, more variable RTs than the controls and made more mistakes. Their ERPs for targets in the attended ear differed significantly from those of the controls by the small amplitude (or absence) of the N2 vertex component elicited by the controls in such a situation and by the presence in the same situation of a late frontal slow negativity (LFN) that did not show up in the grand average ERP of the control group. These results were discussed in terms of the two components of the processing negativity described by Näätänen (1982, 1985) and according to resource models of attention: whereas the controls would perform this easy task quickly thanks to quasi-automatic matching processes (reflected by the vertex N2), the depressed would need further effortful, controlled processing (reflected by the LFN) to perform the task.

Aged↗

PubMed1988

[Concepts underlying the analysis of late evoked potentials applied to the study of information processing and its disturbances in psychopathology].

This paper gives a rapid overview of the information processing approach taken when recording and analysing endogenous event-related potentials (ERPs) with psychiatric patients, and its theoretical framework, born from information theory and cognitive psychology. The triarchic model of P 300 amplitude recently proposed by Johnson (1986) is given as an example of a particularly coherent framework that should help determine the various sources of the P 300 amplitude reduction usually observed in psychiatric patients, probably related to the impairment of a number of different processes. The concept of "functional component" is underlined and some examples are given concerning different ERP components reflecting normal and abnormal attention processes of either automatic or controlled mode of processing. The difference between this information processing approach of the cognitive electro-physiologist, aiming at shedding some light on the strategies utilized by patients in order to cope with the experimental situation, and the electro-clinical approach seeking chiefly for a diagnostic, is emphasized.

Cognition↗

PubMed1988

[Changes in various activation indices as a function of the value given by a stimulus in anhedonic and deprossogenic subjects].

The aim of this experiment was to investigate, in "normal" subjects, the relationship between personality characteristics (anhedonia and depressogenic attitudes) and various tonic and phasic activation indices (EEG power spectra, CNV (at Fz and Cz), heart rate and reaction time) recorded during auditory stimulations, and the influence of the affective value of stimuli on phasic activation indices. Eighteen subjects were divided into two opposite groups according to their scores on two self-rating questionnaires (the Chapman Physical Anhedonia Scale and the Beck-Weissman Dysfunctional Attitude Scale): the A group (anhedonic with depressogenic attitudes) and the H group (hedonic and non-depressogenic). The experiment was divided into three phases. The first and third phase utilised an identical classical CNV paradigm. During the second phase, two of the three neutral warning tones of the first phase were given, by conditioning, a positive or a negative value. The results showed that: 1) before conditioning, when all stimuli were neutral, all activation indices (tonic and phasic) were significantly higher in the A group than in the H group; 2) after conditioning, the two groups differed mainly by their cortical reactivity to the positively conditioned sound: the amplitude of the two CNV components increased in the H group whereas a tendency to a CNV decrease was seen in the A group; 3) all the between-group CNV differences were significant only at Fz. These results were discussed in terms of differences of optimal level of activation.

Acoustic Stimulation↗

PubMed1987