Biomedical subjects

F el Massioui

Publications and source records attributed to F el Massioui.

9 recordsLinked to original sources

PubMed1996

Attention deficits in depression: an electrophysiological marker.

EVENT-RELATED POTENTIALS were recorded in young depressed subjects and compared with results from controls. Subjects were required to respond to targets (rare high-frequency sounds) presented to a designated ear, and to ignore targets presented to the non-designated ear as well as standards (frequent low-frequency sounds) presented to either ear. The results confirm those previously obtained with elderly depressed patients, showing the same general profile of electrophysiological and behavioural differences, and in particular a substantial reduction of the N200 amplitude in response to attended targets in depressed subjects. It is suggested that the N200 component could be a marker of depression.

Adult↗

PubMed1996

Depression as a dynamical disease.

Mathematical models are helpful in the understanding of diseases through the use of dynamical indicators. A previous study has shown that brain activity can be characterized by a decrease of dynamical complexity in depressive subjects. The present paper confirms and extends these conclusions through the use of recent methodological advances: first episode and recurrent patients strongly differ in their dynamical response to therapeutic interventions. These results emphasize the need for clinical follow-ups to avoid recurrence and the necessity of specific therapeutic intervention in the case of recurrent patients.

Adult↗

PubMed1995

Temporal localization of the response selection processing stage.

Response choice is one of the stages in the information processing model proposed by Sanders. It is influenced by stimulus-response (S-R) compatibility. Segmentation of the processing window in intervals between RT and peak latencies and between peak latencies, was used to test the assumption that the decisional processes would be concomitant with the N200 rather than the P300 component. ERPs were recorded in ten subjects during a spatial S-R compatibility auditory task. The S-R compatibility effect is observed on P300 latencies but is only a trend on the N200 component. An effect also observed on the interval between RT and N200 and especially between N200 and P300 while no effect is observed on the interval between RT and P300. These results support the idea that the selection processes ending with P300 occurrence could start as early as the N200 peak component.

Acoustic Stimulation↗

PubMed1995

[Study of the organization of sensorimotor stages in man using delayed evoked potentials].

The main aim of this study was to test the relative organization of three of the stages of Sanders' 1990 information processing model: "features extraction", "response choice", and "motor adjustment". The variables influencing these stages: stimulus degradation, stimulus-response (SR) compatibility and preparatory period have been manipulated. Event related potentials (N100, N200, P300) and reaction time were recorded from ten healthy subjects, in a dichotic listening task. Reaction times are lengthened for degraded stimuli, in the absence of a preparatory period and for SR non compatible conditions. However, the interaction between preparatory period and stimulus degradation variables, suggests an overlapping of the corresponding stages contrary to Sanders' postulate. The non compatible condition increases the latency of N200 and P300 components. The results suggest that the response choice processing would be contemporary to the N200 component. They are discussed within the framework of models of early communication between sensory and motor systems.

Adult↗

PubMed1994

Decrease of complexity in EEG as a symptom of depression.

Nonlinear dynamic analysis provides new methods for the processing of the electroencephalogram (EEG). We demonstrate here that the EEG dynamics of major depressive subjects is more predictable, that is less complex, than that of control subjects. Moreover, the consequence of treatment upon the EEG dynamics seems to be dependent on the appearance of the illness. Although the specificity of this dynamic signature for different stages of depression is to be confirmed, the assumption of a strong link between a healthy system and a high level of complexity in dynamics is further supported.

Adult↗

PubMed1993

Time for reorienting of attention: a premotor hypothesis of the underlying mechanism.

The paradigm of the covert orienting of attention (COA) has shown that the displacement of visual attention may be assessed even in the absence of eye movement. Stimuli correctly cued before their presentation are usually detected faster than uncued stimuli. However, miscued stimuli induce an increased detection time, which has been attributed to the time required for the reorientation of attention from the incorrect to the correct spatial location. Currently, the mechanism of such a displacement of visual attention remains unknown. Rizzolatti et al. Neuropsychologia 25, 31-40 (1987) have suggested a premotor hypothesis which suggests that an oculomotor disprogramming and reprogramming is necessary to reorient visual attention, even if the eye movement is inhibited. Since shifting of auditory attention from one ear to the other does not require any motor control, we further investigated the model of COA in 20 normal subjects who performed two tasks requiring a reorienting of auditory attention: (1) a choice RT task that requires a response readjustment during the auditory reorienting; (2) a simple RT task that does not require a response readjustment during the auditory reorienting; (2) a simple RT task that does not require a response readjustment during the auditory reorienting. Results indicate that correctly cued stimuli significantly reduce the RT in both tasks and that this reduction is greater in the choice than in the simple RT task. This suggests that a correct cue may produce a pre-programming of the response, in addition to the pre-engagement of the perceptual attention.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗

PubMed1991

[Evaluation by evoked potentials of attentional abilities in patients with depression under amoxapine or imipramine].

ERPs are described as a new dependent variable class allowing a dynamic exploration of cognitive activities. Attentional processes play a fundamental role in those activities. An original conception of attention is outlined. In this view, attention is considered as responsible of managing of different cognitive processes. The interest of attentional impairment assessment with ERPs particularly in psychiatric disorders such as depression is underlined. This is illustrated by Buchsbaum M.S. et al. (1988) study. These authors recorded EPs, during a continuous performance test, in 3 groups of depressive patients under amoxapine, imipramine or placebo. Results showed in the amoxapine group and enhanced N120 amplitude in midline and right parietal cortex. In normal subjects, an amplitude increase in those areas usually reflects a selective attention effect. Behavioral performance was improved in the amoxapine group compared to that of patients who received imipramine or placebo. This improvement as soon as 48 h after drug administration could be related to the higher amoxapine affinity for serotonin S2 receptors.

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

[Electrophysiological study of attention mechanisms in depressed patients with characteristics of psychomotor retardation].

The ERPs and RTs of 8 drug-free depressed in-patients (mean age 58, with marked psycho-motor retardation) were recorded during a dichotic listening 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: whereas the controls would perform quickly this easy task thanks to quasi-automatic matching processes (reflected by the vertex N2), the depressed would need further effortful, controlled processing (reflected by the LFN) in order to perform the same task. The ERPs of 6 of these depressed were recorded a second time, after anti-depressive treatment and clinical improvement. A tendency to improved RTs and ERPs (amplitude decrease of the LFN and increase of N2) was seen in most patients, but these improvements were far from being as marked as the clinical improvement.

Depressive Disorder↗