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B Bioulac

Publications and source records attributed to B Bioulac.

At least 91 records · Page 5Linked to original sources
PubMed1991

A quantitative study of neuronal discharge in areas 5, 2, and 4 of the monkey during fast arm movements.

1. The properties of parietal neurons were studied in four adult rhesus monkeys during fast arm movements. The animals were trained to perform flexion or extension of the forearm about the elbow in response to specific auditory cues. Single neuron activity was recorded in 272 area 5 neurons, 81 neurons of the somatosensory cortex, and 92 neurons of the motor cortex. 2. In area 5, 42% of neuronal changes occurred before movement onset (early changes) and 58% after (late changes), with 21% before the earliest electromyogram. The range of modification in activity took place between 260 ms before movement onset and 180 ms after. Complex receptive fields were found in area 5 with a greater proportion among the late neurons (72%) than among the early neurons (32%). 3. Different patterns of activity were observed in neurons recorded in both movement directions. Reciprocal neurons represented 52% of the motor cortex neurons and 41% of the neurons in the somatosensory cortex but only 14% of the area 5 neurons. Of the remainder area 5 neurons, 46% were direction-sensitive neurons and 39% coactivated neurons. This suggests a more complex encoding of movement direction in area 5 than in area 2 or 4. 4. Temporal characteristics of the neuronal bursts were quantitatively analyzed in areas 5, 2, and 4. Neuronal burst duration was longer in area 5 than in the other areas. Above all, a variability of burst parameters, which did not depend on variable movement execution, was noticed in area 5. Therefore neuronal activity in this cortical area cannot be simply explained by a convergence of sensory and motor inputs but may depend on the behavioral context in which the movement is performed. 5. A correlation between neuronal burst duration and movement duration was found in 41% of area 2 neurons. In area 5, this correlation was observed in 20% of the late neurons and in 14% of the early neurons. A correlation between neuronal discharge frequency and movement velocity was found in 34% of area 2 neurons and 24% of area 4 neurons. About 16% of both late and early neurons in area 5 showed such a correlation. These neurons received polyarticular input, and it is suggested that they may be involved in the kinematic encoding of polyarticular movements. 6. A topographic and functional organization of area 5 was noticed. In anterior area, 5, 83% of the neurons had receptive fields and most of the reciprocal neurons and those exhibiting a correlation with movement parameters were found there.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1990

Modifications of precentral cortex discharge and EMG activity in monkeys with MPTP-induced lesions of DA nigral neurons.

1. Individual neurons were recorded extracellularly in the precentral forelimb area of two monkeys trained to perform rapid, large amplitude flexion and extension movements of the contralateral forearm in response to auditory signals. Electromyographic (EMG) activity in the biceps/triceps muscles was recorded separately under the same conditions. The dopaminergic (DA) neurons of the substantia nigra (SN) were destroyed selectively by repeated series of intravenous injections of MPTP. The lesion was verified on serial slices using both tyrosine hydroxylase immunocytochemistry and classical staining methods. 2. In normal monkeys, the frequency of firing of precentral neurons shows rapid changes shortly before the onset of displacement. In our sample (n = 102), most of the neurons (49%) tested during movement in both directions (flexion, extension) showed a reciprocal pattern of activity for the two directions of movement, a small percentage (19%) exhibited a change for only one direction (unidirectional neurons), and the remaining 32% displayed a similar change for both directions of movement (bidirectional neurons). 3. In MPTP-treated monkeys, movement-related modification of neuronal activity was more gradual, beginning earlier and lasting longer relative to the onset of movement. The cellular reaction time (the time between the auditory cue and a significant change in neuronal activity) was not significantly altered. Spontaneous firing of precentral neurons (n = 124) did not increase significantly, and the dynamic discharge rate was unchanged after the nigral lesion. However, only 18% of cortical neurons still presented a reciprocal pattern of discharge for the two directions of movement, while the percentage of unidirectional neurons increased (50%), and the percentage of bidirectional neurons remained the same (32%). 4. After MPTP treatment, alterations in movement parameters and EMG activity were observed. Mean reaction time and movement duration increased by 20-25% and 25-30% respectively. The movements were slower and were associated with a generalized depression in the shape and the amplitude of EMG activity in the agonist muscle. 5. The neuronal basis for the observed central and peripheral disturbance in the MPTP-treated monkeys is discussed. We conclude that SN lesion leads to two main disturbances of cortical activity: i) the loss of the reciprocal pattern of response of movement-related cortical cells, and ii) an inability of the motor cortex to modify its activity in response to peripheral input.

Animals↗
PubMed1988

Postural adjustments in the monkey: effects of velocity on EMG sequence.

Monkeys were trained to perform flexion or extension movements of the elbow in a strictly restrained position. Even in these conditions, postural adjustments were still recorded. They appeared to be organized in a consistent pattern. When trials were ranked with increasing velocity, two kinds of EMG changes could be described: (i) those in the upper part of the body which may be triggered by anticipatory postural motor programs; (ii) those in lower limbs recruited only with higher velocities and that may correspond to semi-automatic programs organized at a lower level of the central nervous system.

Animals↗
PubMed1985

Peripheral inputs and early unit activity in area 5 of the monkey during a trained forelimb movement.

Previous studies on area 5 in the monkey showed that an early neuronal activity up to 300 ms before the onset of movement was encountered in this cortical area after deafferentation of the trained forelimb (C1-T7). This present work indicates that none of the EMG activity recorded in other parts of the body may account for these early changes and lends weight to the hypothesis that their activation is purely central.

Animals↗
PubMed1985

MPTP primate model of Parkinson's disease: a mechanographic and electromyographic study.

Movement parameters and electromyographic (EMG) studies were carried out in two macaque monkeys performing a rapid arm movement before and after administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Hypokinesia and rigidity were seen after repeated doses. Disturbances in both movements and EMG activity were similar to those reported in Parkinsonian patients.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1985

[Activity of substantia nigra pars reticulata neurons after lesion of the ipsilateral neostriatum by kainic acid in rats].

Huntington's chorea is a degenerative disorder of the human brain characterized by a marked loss of intrinsic neostriatal neurons. This situation can be reproduced by kainic acid injection in the caudate nucleus. Activity of pars reticulata neurons ipsilateral to the injected neostriatum was studied in normal, control (saline-injected) and lesioned rats. They were identified by electrophysiological and histological criteria (Fig. 1). Results obtained in normal and control rats were very similar (Table I). As previously described, the mean frequency of these neurons was high. An important percentage (respectively 72.5 and 73%) and these neurons presented the characteristics of a regular firing pattern (so called "organized neurons"). Results obtained in kainic acid lesioned rats were significantly different (Table I). The mean frequency was lower and only 11% of reticulata cells remained organized after neostriatal lesion. This important dysfunction may be explained in various ways: The neostriato-nigral pathway's destruction involves both the inhibitory GABAergic tract and the excitatory substance P tract (GALE et al., 1978). Other inputs arising from many structures in the brain continue to exert their own action on SN neurons, resulting in an unbalance in the SN inputs. It is well known that the nigral dopamine influences the neuronal activity of pars reticulata neurons (Ruffieux et Schultz, 1980; Waszczak et Walters, 1983). Doudet et al. (1984 b) previously reported a dysfunction of neuronal activity of dopaminergic cells after striatal lesion. A disturbance in the electrical activity may induce a similar disturbance in the intranigral dendritic release of DA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

[A model of Parkinson's disease: effect of L-dopa therapy on movement parameters and electromyographic activity in monkeys treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)].

A primate model of Parkinson's disease was obtained by i. v. administration of 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP). A behavioural, a mechanographic and an electromyographic (EMG) study were carried out during the execution of a rapid elbow movement, in two normal monkeys and, after the MPTP administration, before and after a L-DOPA therapy. Disturbances in behavior, movement parameters and EMG activity observed in MPTP-treated monkeys mimic those reported in Parkinsonian patients. Treatment with L-DOPA was effective in greatly correcting these disturbances. These results lend weight to the assumption that use of MPTP in primate provides a good model to study Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1985

[Hashimoto's thyroiditis and myoclonic encephalopathy. Pathogenic hypothesis].

A 49 year old caucasian female with Hashimoto thyroiditis, developed during two years a neurological disorder with tonic-clonic and myoclonic seizures and confusional states. Some attacks were followed by a transient postictal aphasia. Some parallelism was noted between the clinical state and TSH levels. Neurological events disappeared with the normalisation of thyroïd functions. This association of Hashimoto thyroiditis and myoclonic encephalopathy has been rarely published. Pathogenesis could be double. Focal signs could be due to an auto-immune mechanism, perhaps through a vasculitis. A non-endocrine central action could explain diffuse signs: tonic-clonic seizures, myoclonus and confusional episodes.

Confusion↗
PubMed1984

Activity of nigral dopaminergic neurons after lesion of the neostriatum in rats.

As shown by post-mortem analysis the major neuropathological trait of Huntington's chorea is a degeneration of the intrinsic neurons of the neostriatum (caudate nucleus and putamen). Such a situation can be reproduced by a destruction of the neostriatum by kainic acid. When injected into the caudate nucleus this excitatory amino acid destroys the intrinsic neurons of the neostriatum and spares fairly well the passing fibers. In the present work, we have chosen to examine the influence of neostriatal destruction on the activity of identified dopaminergic cells in the pars compacta of the substantia nigra. As a key element in the nigro-neostriato-nigral loop, this structure is a relevant site for observing the functional effects of neostriatal lesion. Our research hypothesis was based on the generally accepted view that the suppression of the important neostriato-nigral pathway and in particular the inhibitory GABAergic contingent, could generate a hyperactivity of nigral dopaminergic cells. One may therefore consider that the dopaminergic hyperactivity produces abnormal messages which can influence via several pathways the motoneurons, and which participates in the genesis of the hyperkinetic movements characteristic of chorea. After destruction of the neostriatum, we have shown that the pattern of discharge of most identified nigral dopaminergic neurons becomes greatly disorganized. This drastic change in the pattern of activity cannot be interpreted as the simple 'lift of a brake' on these cells by the suppression of the inhibitory GABAergic striato-nigral tract.

Animals↗
PubMed1984

[Activity of dopaminergic neurons of the substantia nigra: a functional significance?].

In this study, neuronal activity of dopamine (DA) containing neurons located in pars compacta of the substantia nigra is analysed by the use of the time interval histograms and autocorrelograms. These cells display a regular and rhythmic firing pattern which may possibly subserve the striatal regular spontaneous release of DA, and, then exert an homeostatic function within this part of the extrapyramidal system.

Action Potentials↗
PubMed1984

[Activity of dopaminergic neurons of the substantia nigra following lesions of the neostriatum by kainic acid].

Neostriatal lesions by kainic acid provide a good model for studying Huntington's chorea. The pattern of discharge of nigral dopaminergic neurons of rats subjected to a kainate lesions of the caudate nucleus was compared to the nigral activity in control (saline-injected) and normal rats. The observed changes suggest that neostriatal degeneration does not simply induce a nigral dopaminergic hyperactivity but rather a disorganization of their slow and rhythmic pattern of discharge, thus eliciting in the nigral neurons abnormal messages which may reach the motoneurons and participate in the genesis of choreic movements.

Action Potentials↗
PubMed1983

A statistical method for the estimation of neuronal response latency and its functional interpretation.

The functional role of many central nervous structures has been inferred from the temporal relationship of a neuronal response with the different sensory and motor events in an experimental design such as when an animal performs a trained movement in response to a conditioned stimulus. However, this kind of data analysis leads to problems in estimating the occurrence and latency of any neuronal response. We examine these problems and propose a novel technique of data analysis to estimate the point of change in a sequence of neuronal discharge. Furthermore, data can be tested to see whether the neuronal response is related to the conditioned stimulus or the motor act. The method can also be used in the simple situation of determining the latency of a neuronal response after a stimulus.

Animals↗
PubMed1983

Instruction-related changes of neuronal activity in area 5 during a simple forearm movement in the monkey.

Unit recordings were made in area 5 of monkeys during the performance of a sound-triggered movement of the forearm. Changes in neuronal activity prior to the movement were observed in 188 neurons recorded in both normal and deafferented animals. When the discharge of these cells was analyzed as peristimulus histograms, it was seen that 152 neurons presented a pattern of discharge which was characterized by a brief modification in activity with a relatively constant latency after the auditory cue. Similar changes were observed in normal and deafferented animals but the latency was not the same for the two groups. These neurons may reflect the presence of a sensorimotor interface for the integration of instructions for movement and the subsequent genesis of motor commands.

Afferent Pathways↗
PubMed1982

Activity of neurons in area 5 during a simple arm movement in monkeys before and after deafferentation of the trained limb.

Unit recordings were performed in the postcentral cortex and focused on area 5 of awake monkeys during the execution of a learned movement of the contralateral forearm so that the time relationship between the motor act and any modification of neuronal activity could be precisely correlated. Recordings were obtained from intact animals (561 neurons) and after deafferentation (C1-T7) of the trained limb (344 neurons). Of the movement-related neurons in normal animals, 243 cells were located in area 5 and these cells were divided into two populations. The first population (66% of movement-related neurons) presented modifications of activity after the onset of movement and receptive fields, often complex, were identifiable for these somaesthetic-like cells. No such neurons were found in the same cortical area after deafferentation. The second population (34% of movement-related neurons) presented modifications of activity related to movement but these changes occurred well before the onset of movement, up to 280 ms before. These cells were also characterized by an absence of sensory modulation and they represented the entire population of movement-related neurons recorded in area 5 after deafferentation (124 neurons). The first population appears to subserve a complex somaesthetic function. The second population is subject to purely central influences which, in part, may be due to corollary discharge or internal feedback. However, this population most likely represents a command apparatus for movement located 'upstream' to the motor cortex.

Afferent Pathways↗