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Biomedical subjects

D Beaubaton

Publications and source records attributed to D Beaubaton.

At least 19 recordsLinked to original sources
PubMed1989

Experimental bradykinesia in the monkey: speed control impairments after lesion of the substantia nigra.

Unilateral lesions of the substantia nigra were performed on baboons which had been previously trained to perform a visual pointing movement. The resulting motor impairment consisted of an increase in movement duration. This bradykinesia shows as a regular decrease in velocity. A possible change in mode of motor control caused by lesion of the SN is discussed. Partial exclusion of SN might bring about a shift from the feedforward to a feedback mode relaying more heavily on visual cues.

Acceleration↗
PubMed1987

The role of visual reafferents during a pointing movement: comparative study between open-loop and closed-loop performances in monkeys before and after unilateral electrolytic lesion of the substantia nigra.

In order to elucidate the compensatory role of visual feedback during movement, two experiments were designed to compare the motor performances of Papio papio baboons depending on whether the animals were able to visually control the limb trajectory (visual closed-loop condition) or not (visual open-loop condition). The visuomotor task used consisted of making trained pointing movements towards a stationary target. In experiment A, the baboons were successively presented with these two experimental conditions. The abolition of visual control was found to cause no change in either reaction time (RT) or movement time (MT), but brought about extensive pointing errors. It was also associated with a conspicuous increase in the mean velocity and the mean length of the trajectories. In experiment B, two groups of baboons were used. The monkeys in the first group were required to perform under closed loop conditions. The second group performed the pointing movement under open loop conditions. Once criterion was reached by each animal, a unilateral electrolytic lesion of the substantia nigra (SN) was performed. A comparison between the post operative performances of the animals in the two groups showed that suppression of visual cues resulted in a lengthening of the RT and a slowing of the movement speed. Moreover when visual feedback was lacking, the amplitude of the movement decreased and the finger fell short of the target. During the last post operative period, suppression of visual feedback brought about a more rapid return of RTs to their preoperative level and a more durable slowing of movement speed than with normal vision. The discussion deals with the role of visual feed-back in the control of movement preparation and execution, and with the change in mode of motor control caused by lesion of the SN. Partial exclusion of the SN might bring about a shift from the feedforward to a feedback mode relying more heavily on visual cues.

Animals↗
PubMed1986

Visual correction of a rapid goal-directed response.

The purpose of this study was to investigate the role of dynamic and static visual cues in improvement of accuracy during a pointing movement. In the experiment, subjects were required to point finger rapidly at visual targets as accurately as possible. Movement amplitude was 15 cm, and movement times ranged from 100 to 190 msec. Three visual feedback conditions were applied: no feedback, dynamic ongoing feedback on the complete hand trajectory, and static error feedback on the movement end-point. Two spatial movement outcomes were considered, mean constant error and intraindividual dispersion of pointings. Data were analyzed with regard to effects of feedback and speed. Under the no-feedback condition, accuracy was lowest; constant error was not speed-dependent, whereas dispersion increased with speed of movement. Accuracy was highest under the complete feedback condition and was speed-dependent, as shown by both constant error and dispersion. Under error feedback, accuracy was intermediate and was also speed-dependent. The results are discussed in terms of the interchange between correcting mechanisms vs delayed control within the motor regulatory processes.

Adult↗
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↗
PubMed1983

Left-hand advantage in right-handers for spatial constant error: preliminary evidence in a unimanual ballistic aimed movement.

While the superiority of the right hemisphere for the processing of spatial relationships in normal right-handers has been largely accepted, it is surprising that evidence for an advantage of the left "nondominant" hand over the right "dominant" hand in spatial motor tasks is up to now almost totally lacking. We report preliminary evidence that normal right-handers perform open-loop ballistic aimed movements with a smaller constant error when using the left rather than the right hand. In addition, constant error is found to be minimal for movements directed toward the left half-field.

Functional Laterality↗
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↗
PubMed1980

Role of structured visual field and visual reafference in accuracy of pointing movements.

In a visuo-motor pointing task, the accuracy of response was measured in situations which differ in the visual information available and the speed of execution of movement. Results confirm the role of visual cues received from self-produced movement in the control of the trajectory of a limb. Furthermore, it can be shown that a structured visual background is important in the treatment of sensory data concerned with the movement and in target localization. This effect is absent in rapidly executed pointing response.

Cues↗
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↗