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E Trouche

Publications and source records attributed to E Trouche.

At least 37 records · Page 2Linked to original sources
PubMed1986

Differential time-course of reaction time recovery depending on variations in the amplitude of a goal-directed movement after nigrostriatal lesion in monkeys.

Unilateral striatal dopamine depletion induced by 6-hydroxydopamine injections into the substantia nigra of behaving monkeys was found to increase the latency of a visually guided pointing movement performed by the contralateral forelimb. The time-course of recovery of the movement latency was faster in small displacements of the limb than in movements with larger amplitudes. The efficiency of putative compensatory mechanisms that may develop progressively in response to the striatal dopamine deficit depends on the amplitude of the movement to be initiated.

Animals↗
PubMed1983

Motor impairment after unilateral electrolytic lesions of the substantia nigra in baboons: behavioral data with quantitative and kinematic analysis of a pointing movement.

Unilateral electrolytic lesions of the substantia nigra (SN) were carried out stereotaxically on 4 baboons which had been previously trained to perform a visually guided pointing movement. For a few days after operation, all animals exhibited a behavioral impairment affecting the contralateral body half and consisting of dystonic flexed posture and akinesia. The animals were thus unable to perform the pointing task with the contralateral hand. After a delay which depended on the extent of the SN lesion, the animals began to make the pointing movement again. Postoperative changes were then observed only on the side opposite the SN lesion. These consisted of an increase in the latency and particularly the duration of the movement without any change in the accuracy. The kinematic analysis of the hand trajectory showed that the contralateral increase in the movement duration corresponded to a regular decrease in the velocities. Study of the recovery over 120 days after SN lesion showed a progressive improvement which was faster with regard to movement duration than to movement latency. These data clearly point to the functional role of the SN in the initiation and particularly in the execution of movement. Quantitative and kinematic analysis of this pointing movement makes it possible to detect and quantify very closely the changes in movement program and execution induced by a SN lesion. This experimental model will be useful for pharmacological in vivo studies allowing a more specific assessment of the functional role of the neurotransmitters involved in SN dysfunction.

Animals↗
PubMed1982

Participation of the cerebellar dentate nucleus in the control of a goal-directed movement in monkeys. Effects of reversible or permanent dentate lesion on the duration and accuracy of a pointing response.

Experiments carried out on seven adult baboons were addressed at specifying the participation of the cerebellar dentate nucleus (DN) in the control of duration and accuracy of a goal-directed movement. The visuo-motor task used in this experiment involved trained pointing movement towards stationary target. The monkeys trained to point with the index finger to a target light were required to perform stereotyped movements of constant amplitude and direction, or movements with variable amplitude and direction. Duration of response execution was measured by movement time and accuracy by terminal spatial errors. We analysed the effects of excluding the DN on the arm ipsilateral or contralateral to the partially inactivated nucleus. Two techniques have been used to impair the DN activity: in three monkeys the structure was reversibly cooled with a chronically implanted thermode; in four others partial electrolytic destruction of the DN was performed. In the arm ipsilateral to the lesioned DN we observed modifications of movement times, appearance of systematic errors with increased dispersion. Contralateral effects were restricted to movement times. Changes in movement times and spatial errors were studied over time (4 months) in permanently lesioned animals. Only the spatial dispersion presented a total recovery. These data show that the DN is concerned with the control of speed and accuracy during the execution of visually triggered movements in monkeys. Moreover comparison of results concerning ipsilateral and contralateral effects of DN dysfunction on movement times and errors, and evidence of different time course of recovery in these variables, suggest a differential control exerted by the DN on speed and accuracy of goal directed movements.

Animals↗
PubMed1981

Bradykinesia following unilateral lesions restricted to the substantia nigra in the baboon.

Unilateral lesions were made in the substantia nigra of baboons which had been previously trained to carry out a visually guided pointing movement. During the early post-operative period, the animals were unable to perform the task with the contralateral forelimb because of the severity of the akinesia affecting it. After one or two weeks, the animals began to make the movement; at this time, there was a purely contralateral increase in the latency and particularly the duration of the movement, while its accuracy remained unchanged.

Animals↗
PubMed1981

[Impairments in initiation and execution of a visually-guided movement in baboon during cooling or after lesion of the internal pallidal segment (author's transl)].

In the present experiment, the participation of the internal part of the globus pallidus (GP) in the initiation and the execution of a pointing movement was investigated in four baboons (Papio papio). The effects of GP exclusion on the response latency, the movement execution time and the pointing accuracy were analyzed. Two different methods were used to exclude the GP. In two cases, cryogenic blockade was induced using a chronic cryoprobe, implanted contralaterally to the operant hand. Two other animals underwent a partial electrolytic destruction of the GP, contralateral to the active hand. The effects of GP exclusion on reaction times, movement times and pointing accuracy were compared for movements with variable amplitudes and directions. For all animals, the GP exclusion resulted in a decrease in reaction time, but an increase in movement time and spatial error. None of these modifications was increased by variations in the biomechanic characteristics of the movement. These data show that the GP, in baboons, is concerned with: (a) the initiation of a pointing movement (without playing a critical role in the encoding of amplitude and direction parameters); and (b) the execution of this movement. The possible involvement of the GP in sensory-motor integration, postural adjustments and muscular synergy is discussed.

Animals↗
PubMed1980

Effects of putamen cooling on the latency, speed and accuracy of a pointing movement in the baboon.

The functional role of the putamen, in both initiation and execution of a motor act, was investigated in 3 baboons performing a visuomotor pointing task. Reversible blockade of the putamen differentially affected the spatiotemporal components of the response. The results stress the importance of the putamen in the triggering of a goal-directed movement, but show that this structure does not seem critically involved in the control of the speed and accuracy of the movement.

Animals↗
PubMed1980

Initiation of a goal-directed movement in the monkey. Role of the cerebellar dentate nucleus.

The participation of the dentate nucleus (DN) in the initiation of a voluntary movement was investigated in five baboons (Papio papio). In these experiments, we have analyzed the effects of excluding the DN on the latency (reaction time, RT) of a learned goal-directed movement. Two techniques were for excluding the DN. In three animals, the structure was cooled with a probe, stereotaxically implanted on the side ipsilateral to the active hand. In two others, a partial electrolytic destruction of the DN ipsilateral to the operant hand was undertaken. In one further animal, both DNs were destroyed electrolytically. A comparison was made of the effect of DN inactivation on the latency of stereotyped goal-directed movements of constant amplitude and direction, and of goal-directed movements whose amplitude and/or direction were varied in random fashion. The exclusion of DN brought about a prolongation of RTs in all animals. This prolongation was not accentuated by variation of different characteristics (amplitude and/or direction) of the impending goal-directed movement. A recovery of the RTs to their prelesion values was observed after irreversible unilateral DN lesion, but no so easily after bilateral destruction. These results show that in the monkey DN is concerned with the initiation of a goal-directed movement, but is not critically implicated in the encoding of direction and amplitude parameters. These findings are discussed in view of the role that is usually attributed to the neocerebellum in programming voluntary movements.

Animals↗
PubMed1979

[Manipulation box to measure the motor performance involving the distal musculature of the arm in primates (author's transl)].

For studies of motor performance in the baboon, regarding precise finger movements, a new latch-box was developed. The device was designed so as to involve mainly the distal musculature of the arm. Handling the different knobs or latches which open the compartments of the box had to be performed in a given motor sequence. Monkeys were trained to use two fingers of the hand: thumb and index. Data are presented which show that, after exclusion of a central nervous structure, it is possible to differentiate the performance obtained with the device described above that obtained in a pointing task, mainly involving the proximal musculature.

Animals↗
PubMed1979

Impairments and recovery of the spatial and temporal components of a visuomotor pointing movement after unilateral destruction of the dentate nucleus in the baboon.

In baboons trained to perform visuomotor pointing movements, unilateral electrolytic lesions are performed in the dentate nucleus. The consequences of these lesions on the following movement parameters are then studied:--temporal parameters: reaction time and movement time;--spatial parameters: pointing area and directional errors. From the observations taken 3 months after the dentate nucleus exclusion, a distinction can be made between parameters showing recovery phenomena (reaction time and pointing area) and components definitively affected (movement time and directional error).

Animals↗
PubMed1976

[Effect of ablation of the motor cortex or the cerebellum on postural-kinetic coordination in the cat].

1. A cat, restrained in a hammock, stands with its feet on supporting trays each furnished with strain gauges to measure the isometric upthrust. Placing reactions are elicited by contact of the left or right forelimb with a moving tray. The placing movement is preceded and accompanied by a postural adjustment characterized by an increase of the upthrust exerted by the opposite forelimb. 2. After ablation of the motor cortex on one side, the placing movement of the contralateral forelimb is abolished for the first few days after the operation and thereafter is delayed. However, the postural adjustment of the ipsilateral forelimb persists, with the same range of latencies as before the operation. 3. After unilateral motor cortical ablation, the contralateral forelimb still takes part in the postural adjustment associated with the placing movement of the other forelimb. 4. In two cats which had 2 years earlier undergone a total cerebellectomy, the placing movement was lacking or appeared with a long delay, whereas a postural adjustment of the other forelimb could be observed, although reduced. 5. The results indicate that the nervous structures responsible for the movement and for the associated postural adjustment are separate but partially linked.

Animals↗
PubMed1975

[Postural adjustment associated with cat movement].

The experiments were undertaken in order to investigate the relationship between movement and associated postural adjustment. Cats were accustomed to standing quietly in a restraining hammock. Each forelimb was supported by a tray equipped with strain gauge transducers in order to measure the postural forces exerted by the limbs. Flexion of one forelimb was elicited by stimulation of the motor cortex, the red nucleus or the superficial radial nerve. Unloading of the forelimb undergoing flesion was associated with loading of the other forelimb. The loading resulted from a postural adjustment which was elicited together with movement by the central or peripheral stimulation. Movement and postural adjustment are linked by a common central command.

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