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L Defebvre

Publications and source records attributed to L Defebvre.

85 records · Page 5Linked to original sources
PubMed1994

Spatiotemporal study of Bereitschaftspotential and event-related desynchronization during voluntary movement in Parkinson's disease.

Bereitschaftspotential (BP) and Event-Related Desynchronization (ERD) were simultaneously recorded during a voluntary wrist flexion in 10 patients with Parkinson's disease (PD) treated with L-Dopa therapy and 10 control subjects. BP and ERD were analyzed 2 s before and 0.5 s after the movement, during two successive left and right experimental conditions. ERD (9-11 Hz) was computed from 11 source derivations (frontocentral, central, parietocentral). The BP was averaged from these 11 electrodes. For the BP, no spatiotemporal difference was found between the two groups. BP began bilaterally over the 3 groups of electrodes, 1250 ms before movement onset for the right flexion and 1500 ms for the left flexion. A contralateral predominance appeared 500 ms before movement onset over the central area. ERD began in the control group 1750 ms before movement over the contralateral central area, and then appeared bilaterally after its execution. In the PD group, the ERD appeared with a shorter latency than in the control group, 1250 ms (left flexion) and 1000 ms (right flexion) before movement onset; diffusion over the ipsilateral side was found 500 ms before movement onset. ERD also involved the frontocentral area and could be interpreted as a compensatory activity of the supplementary motor area. These findings suggest that with Parkinsonian and control subjects, ERD gives additional and maybe more information than the BP about changes of cortical activity during the motor preparation period. In the PD group the delay of ERD appearance seems to confirm that the programming of movement would be affected, thus explaining partially akinesia.

Aged↗
PubMed1993

Evaluation of event-related desynchronization (ERD) during a recognition task: effect of attention.

Event-related desynchronization (ERD) was studied in 10 subjects during a verbal recognition task. The attentional load of the task varied according to the difficulty to discriminate targets and distractors. The EEG recorded from 29 electrodes was used to compute ERD from 14 source derivations in 125 msec intervals and displayed as spatio-temporal maps. The results show that large brain areas of both hemispheres are significantly activated when the attentional load is high. This cerebral activation pattern is less pronounced when the load is low. ANOVA reveals main effects of attention and time and a significant interaction between attention and time.

Adolescent↗
PubMed1993

Effect of aging on the spatio-temporal pattern of event-related desynchronization during a voluntary movement.

Event-related desynchronization (ERD) of alpha components was studied in young and elderly subjects during planning of voluntary movement. ERD was quantified from 11 source derivations covering regions of the scalp corresponding to the supplementary motor area, the left and right primary sensorimotor areas, the vertex, and the medial posterior parietal cortex. Spatio-temporal display of ERD showed a very different pattern in elderly subjects, with mainly a spatial diffusion of ERD over the parietal and frontal regions. On the contrary, ERD in young subjects was limited to the central regions. ERD was also more lasting in elderly subjects. Changes of the ERD pattern in elderly subjects could indicate a change of cortical activation during voluntary movement. The data also confirm that ERD study is a useful electrophysiological exploration to observe the changes of cortical activation during cerebral aging.

Adult↗
PubMed1993

[Spatiotemporal study of event-related desynchronization during self-paced movement].

The desynchronization of Alpha band components during a self-paced movement of the thumb was studied in 7 subjects. The EEG was recorded from 23 electrodes located on the frontocentral, central, and parietocentral regions, referred to the right mastoïde, 4 s before and 2 s after movement onset. The data were then transformed to obtain 11 source derivations. The temporal evolution of the power of the signal within the Alpha band, every 250 ms, associated to the non parametric statistic test of Wilcoxon, authentifies the event-related desynchronization (ERD). The spatiotemporal analysis of ERD underlines on the central regions, two principal locations of ERD: one controlateral to the movement, starting more than 1 s before the movement; the other, ipsilateral, shorter, during the movement. However, no significance desynchronization was underlined on the vertex. The ANOVA used to analyse these results confirms the principal location of ERD on the central region, and seems to indicate a right lateralisation during the right or the left movement.

Adult↗
PubMed1993

[Senator's neuromyositis associated with Hashimoto's thyroiditis].

The concept and even the reality of Senator neuromyositis are discussed. One case is reported confirming its reality. The diagnosis is based on clinical signs (polymyositis and peripheric neuropathy), biological (muscular enzymes increase) and electrophysiological disturbances (myogenic syndrome, decrease of nerve conduction velocities), and histological lesions (polymyositis and denervation). The association with a Hashimoto thyroiditis could support the hypothesis of an autoimmune mechanism in the neuromyositis pathogenesis.

Acute Disease↗
PubMed1991

[Hereditary parkinsonism-dystonia syndrome of juvenile onset with diurnal fluctuations].

Symptoms of fluctuating dystonia developed in 4 subjects of the same family during childhood or adolescence. In the 2 sisters, these symptoms were initially or subsequently associated with signs of parkinsonism, whereas in the 2 brothers they disappeared, spontaneously in at least 1 case, and signs of parkinsonism appeared later after a free interval. Anticholinergic agents and L-Dopa proved very effective against all extrapyramidal signs. These cases are similar to those gathered by Nygaard et al. in 1988 under the term "Dopa-responsive dystonia". Yet laboratory data seem to confirm that the common physiological mechanism is a disorder of tetrahydrobiopterin metabolism. Serum and urinary biopterin levels were lowered in our 4 cases but were normal in an unaffected sister. However, like the subjects affected this third sister showed a decrease of platelet serotonin which was taken as being a consequence of aromatic aminoacid hydroxylation defect due to tetrahydrobiopterin deficiency.

Adolescent↗
PubMed1990

[Spinal cord ependymoma: contribution of MRI using gadolinium].

In a case of panmedullary ependymoma, a rare tumour, MRI was performed before and after gadolinium injection. The latter clearly demonstrated the borders of the tumour. Throughout the procedure, neurophysiological exploration was carried out with recording of motor and somatosensory evoked potentials.

Adult↗
PubMedDate not supplied

Is there a typical pattern of brain SPECT imaging in Alzheimer's disease?

The identification of new nosological forms such as Lewy body disease (LBD) requires a re-evaluation of the patterns observed in brain functional imaging in the various forms of dementia. We studied 60 demented patients, divided into three groups and fulfilling the clinical criteria for Alzheimer's disease (AD), LBD and frontotemporal dementia (FTD), using Tc-HMPAO and a brain-dedicated SPECT system. After normalisation we applied a cut-off at two levels according to previously established criteria. We reaffirmed the already established data concerning FTD (mainly a bilateral frontal decrease) and for LBD (a severe diffuse decrease in the frontal regions and also in the posterior association cortex). In contrast, the decrease in AD was strictly limited to the parieto-occipital cortex, irrespective of the severity of the cognitive decline. We hypothesise that the major simplification concerning the pattern observed in AD can be explained by the fact that patients suffering from LBD have previously been included in the groups of AD patients.

Aged↗
PubMedDate not supplied

[Panmedullary ependymoma. A case report].

Panmedullary ependymoma is an unusual disease last reported by Fuentes in 1986. The present case is the first to have been studied by magnetic resonance, using gadolinium. The findings indicated a panmedullary lesion rather than a tumour. Histopathological investigation confirmed the hypothesis.

Adult↗