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PubMed2000

The effect of switching between sequential and repetitive movements on cortical activation.

We used whole-head functional magnetic resonance imaging (fMRI) to investigate the effect of switching between different sequential and repetitive movements in the context of conditional and fixed tasks. Four different movement tasks were applied: (1) unpredictable switching between two movement sequences comprising six submovements each according to visual cues (SEQ-VC); (2) unpredictable switching between repetitive movement of one finger according to visual cues (REP-VC); (3) performance of the same sequential movements used for SEQ-VC but in a fixed mode triggered by a visual stimulus (SEQ-FIX); (4) performance of the repetitive movements used for REP-FIX but in a fixed mode by a visual stimulus (REP-FIX). The statistical group analysis of the hemodynamic responses revealed the following results: (1) the SEQ-VC compared to the SEQ-FIX condition (switching between movement sequences) engendered stronger activations in the left rostral supplementary motor area (pre-SMA), bilaterally in the posterior parietal lobule, the left ventral premotor area, and the visual cortices; (2) the REP-VC compared to the REP-FIX condition (switching between repetitive movements) only revealed stronger activation in extra-striate areas. We hypothesize that during switching of movement sequences higher motor control aspects are involved including movement selection, updating of motor plans, as well as recalling and restoring motor plans. The repetitive movements are too simple in order to evoke additional activations in the medial and lateral premotor areas, as well as in parietal areas.

Adult↗
PubMed1986

Motor strategies involved in the performance of sequential movements.

The present study analyses the strategies adopted by normal subjects when they are asked to make two separate movements as rapidly as possible one after the other. Five subjects performed the following sequential movements in their own time. 1) Squeeze an isometric force transducer between fingers and thumb to a force of 30 N and then flex the elbow of the same arm through 15 degrees. 2) Squeeze the transducer with one hand and then flex the elbow of the other arm. 3) Perform an isotonic opposition of finger and thumb and then flex the elbow of the same arm. 4) First flex the elbow through 15, 30 or 45 degrees and then squeeze the transducer. 5) Flex and then extend the elbow as rapidly as possible. In tasks 1-4 there was no correlation between the times taken to complete the two separate components of the sequence. Because of this we suggest that the two movements remained under the control of two separate motor programmes. In contrast, in task 5, the times taken for the two components were correlated and hence we suggest that in this case a single programme was used to perform the sequence. In tasks 1-3, in which the mean duration of the first movement was some 135-162 ms, there was a mean pause of about 85 ms before the start of the second movement. Subjects tended to chose a minimum inter-onset latency between the start of the first and the start of the second movement of a sequence of some 230 ms. The reason for this appeared to be that if subjects were encouraged to decrease their inter-onset latencies to less than 200 ms, the speed of the second movement decreased sharply. However, if the duration of the first movement was prolonged as in task 4, the second movement could be delayed, although there now was little or no pause between the two movements. We conclude that when a single motor programme is run, it is followed by a "relative refractory period". If a second programme is run within this period, it cannot be executed without loss of speed. Switching from one motor programme to another is achieved with an optimal minimum delay of 200 ms. Sequential movements which are controlled by a single programme do not share this limitation.

Adult↗
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↗
PubMed2004

Latency of adaptive vergence eye movements induced by vergence-vestibular interaction training in monkeys.

Clear vision of objects that move in depth toward or away from an observer requires vergence eye movements. The vergence system must interact with the vestibular system to maintain the object images on the foveae of both eyes during head movement. Previous studies have shown that training with sinusoidal vergence-vestibular interaction improves the frequency response of vergence eye movements during pitch rotation: vergence eye velocity gains increase and phase-lags decrease. To further understand the changes in eye movement responses in this adaptation, we examined latencies of vergence eye movements before and after vergence-vestibular training. Two head-stabilized Japanese monkeys were rewarded for tracking a target spot moving in depth that required vergence eye movements of 10 degrees/s. This target motion was synchronized with pitch rotation at 20 degrees/s. Both target and chair moved in a trapezoidal waveform interspersed with random inter-trial intervals. Before training, pitch rotation in complete darkness without a target did not induce vergence eye movements. Mean latencies of convergence and divergence eye movements induced by vergence target motion alone were 182 and 169 ms, respectively. After training, mean latencies of convergence and divergence eye movements to a target synchronized with pitch rotation shortened to 65 and 53 ms, and vergence eye velocity gains (relative to vergence target velocity) at the normal latencies were 0.68 and 1.53, respectively. Pitch rotation alone without a target induced vergence eye movements with similar latencies after training. These results indicate that vestibular information can be used effectively to initiate vergence eye movements following vergence-vestibular training.

Adaptation, Physiological↗
PubMed1999

Low sensitivity of dorsal spinocerebellar neurons to limb movement speed.

This paper reports the effect of limb movement speed on dorsal spinocerebellar tract (DSCT) activity recorded while the cat hindlimb was passively moved through two types of foot trajectories (figure eight and step cycle) at different speeds. While nearly all the DSCT neurons sampled (151/159; 94.5%) were significantly modulated by the direction of foot movement in these trajectories, they were only modestly influenced by movement speed. We quantified the speed effect and also accounted for intrinsic cell variability by computing a variability index (VI) between pairs of responses to trajectories made either at the same or at different speeds. The distribution of same-speed VIs across cells indicated a mean variability of about 10% over a trajectory cycle, whereas the two-speed distributions indicated a mean change of about 25% for a two- to fourfold change in movement speed. We also examined the relative contribution of movement speed to the activity of each DSCT cell by means of a multivariate regression model that also included as predictors the position, movement direction, and interactions between movement and position. We found that 28 of 103 (27.2%) neurons were not sensitive to movement speed. The rest were modulated in varying degrees by changes in speed, and the speed modulation depended on limb position for most of them (54/75). Overall, DSCT speed sensitivity resembles the 0.3-power relationship used to describe the velocity sensitivity of muscle spindles for large muscle stretches. We examined this by recording muscle spindle activity during these passive foot trajectories and found that their speed sensitivity was within the range observed for the DSCT and explained by the 0.3-power law. In total, movement speed accounted for about 15% of the variance in DSCT activity across cells, while the directional component of movement accounted for about 45%. The results suggest a separate processing of sensory information about the two components of movement velocity: namely, its direction and magnitude.

Animals↗
PubMed2000

Superposition of independent units of coordination during pointing movements involving the trunk with and without visual feedback.

Previous studies addressing the problem of the control of multiple degrees of freedom have examined the influence of trunk movement on pointing movements within the arm's reach. Such movements may be controlled by two functionally independent units of coordination (synergies): one involving only arm joints and producing the hand trajectory to the target (the transport synergy), and the other coordinating trunk and arm movements leaving the hand trajectory unchanged (the compensatory synergy). The question of whether or not this functional subdivision depends on visual feedback was addressed in the present study. We also tested whether or not the motor effects of different synergies are summated as independent components, a control strategy called "superposition." Finally, we investigated whether or not the relationship between different degrees of freedom within each synergy could be considered linear resulting in proportional changes in different joint angles. Seated subjects produced fast, uncorrected arm movements to an ipsi- or a contralateral target in the direction of +/-45 degrees to the sagittal midline of the trunk. Targets could be reached using the arm alone (control trials) or by combining the arm motion with a forward or backward trunk motion produced by hip flexion or extension (test trials), with and without visual feedback. The shape of the hand trajectory, its direction and tangential velocity, movement precision, joint angles and the sequence of the trunk and hand recruitment and de-recruitment were measured. In both visual conditions, the direction of the hand trajectory observed in control trials was generally preserved in test trials. In terms of sequencing, even in the absence of vision, the trunk movement was initiated before the onset of and outlasted the hand shift, indicating that the potential influence of the trunk on the hand movement was compensated by rotations in the elbow and shoulder joint. The analysis of other variables also implied that the effects of trunk recruitment on the hand trajectory were minor compared to those which could be observed if these effects were not compensated by appropriate changes in the arm joint angles. It was concluded that an arm-trunk compensatory synergy is present in pointing movements regardless of visual feedback. Principal component analysis showed that the relationship between elbow, shoulder and hip joint angles in individual arm and combined arm-trunk movements cannot be considered linear, implying that this relationship is adjusted according to the changing arm geometry. The changes in each arm joint angle (elbow, shoulder) elicited by a forward trunk bending in one block of trials were compared with those elicited by a backward bending in another block, whereas the hand moved to the same target in both blocks. These changes were opposite but of similar magnitude. As a result, for each moment of movement, the mean joint angle obtained by averaging across two directions of trunk motion was practically identical to that in control trials in which the trunk was motionless. It is concluded that the transport and arm-trunk compensatory synergies are combined as independent units, according to the principle of superposition. This principle may simplify the control of the coordination of a redundant number of degrees of freedom.

Adult↗
PubMed1985

Information processing deficits in Parkinson's disease during movement.

The capacity to process information during movement selection and execution was studied in Parkinsonian patients and controls in a task involving movement of a hand-held stylus between two targets whose size and separation could be systematicaly varied. Movement time and accuracy were evaluated when the size and required accuracy of movements were changed to modify movement difficulty. Movement time and inaccuracy of patients with Parkinson's disease were exaggerated by increasing target separation so as to increase movement extent (target size held constant) or by decreasing target size (target separation held constant). The fact that these changes in task difficulty caused greater deterioration of performance for patients than for controls is consistent with previous studies indicating that Parkinsonian patients have deficits in executing high-velocity movements. These data also show that performance deficits by Parkinsonian patients can be brought out by increasing movement difficulty through requiring increased movement accuracy. These findings are interpreted in relation to the relative contribution of deficits in movement execution vs motor programming in the motor disorders of Parkinson's disease.

Aged↗
PubMed1993

Early stages of load compensation in human aimed arm movements.

We investigated the kinematics of pointing movements in human subjects while varying the weight load carried by their hand. In accordance with our previous study, we found that movement velocity decreased and duration increased with load size, while skewness of velocity profiles and final pointing position were load-independent. When the load was changed without advance information about the new load size, kinematics of the first movement deviated initially (within the first 135 ms) from those of the preceding and following movements. Two types of deviation were found. Firstly, the initial rise of movement velocity was slower, independent of the new load size; we attributed this finding to a purposeful motor strategy to "probe" the new relationship between force and acceleration, and thus to determine the new load size. Secondly, the initial portions of movement trajectories deviated downwards after a load increase and upwards after a load decrease, depending in a graded way on the change of load size; this finding probably reflects incomplete load compensation. Deviating movement kinematics were found only for the first movement after a load change. This suggests that information required for appropriate load compensation is determined during the first movement, is stored in memory, and is available for the execution of subsequent movements. No deviating kinematics were found if prior to the first response after a load change, subjects moved the hand orthogonally to the direction of pointing or suspended the load against gravity. This suggests that the stored information is not specific for movements of similar spatial characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)

Acceleration↗
PubMed1989

Activity of digital area neurons of the primary somatosensory cortex in relation to sensorially triggered and self-initiated digital movements of monkeys.

Single-cell activity was examined in digital areas of the primary somatosensory cortex (SI) of monkeys performing sensorially triggered and self-initiated digital movements with the aim of rigorously determining the relative timing of onset of the neuronal activity with respect to movement onset. The activity of prime mover muscles for execution of a key-press movement was recorded simultaneously with the neuronal activity; movement onset was defined as the onset of muscle activity. Neuronal receptive fields were also identified. The following findings emerged from this study: (1) Few neurons, if any, in the SI(areas 3b, 1, 2), including pyramidal tract neurons, were active prior to movement onset. (2) The movement-related activity of SI neurons was basically similar in cases of signal-triggered and self-initiated movement. (3) No neuron in the SI showed activity associated with ipsilateral digital movement. (4) A majority of movement-related neurons in the precentral motor cortex, in contrast, started their activity before movement onset. These findings suggest that SI neuronal activity participates little in providing information necessary for developing motor responses in the initial phase of simple digital movements.

Afferent Pathways↗
PubMed1986

Mental health care and the opposition movement in The Netherlands.

In The Netherlands, there is a more or less recognized movement in the field of mental health care which is referred to as the psychiatric opposition movement or the patients movement. The nucleus of the Dutch movement consists of patients and ex-patients. As far as mental health professionals are participating in the movement, they do so as more or less passive supporters of a movement dominated by patients and ex-patients. This article is dealing with two questions. The first question is how and to what degree the opposition movement in The Netherlands has succeeded in breaking through or at least questioning the closed nature of Dutch mental health care system. The second question will be whether the dilemma between resistance and dependence in the position of patients and ex-patients is visible in the activities of the opposition movement, and whether this dilemma acted as an obstacle to their efforts to influence the mental health care debate in The Netherlands. An effort is being made to answer this question by describing the position of the opposition movement with respect to the Insanity Law and with respect to the organization of mental health care. In conclusion, three stages were found to be crucial in the development of Dutch opposition movement. In the 1970s, the opposition movement appeared to operate within the borders of a closed system in which the medical profession had a high degree of autonomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Attitude of Health Personnel↗
PubMed2003

Did a change in sensory control of skilled movements stimulate the evolution of the primate frontal cortex?

The classical view of the evolution of such skilled movements as use of the hand and digits for reaching and grasping posited that these movements had their origin in the primate lineage. The hypothesis was that the permissive influence of adaptations to an arboreal environment led to the evolution and elaboration of these skills. Associated with skilled movements were increases in the size of the frontal lobe, temporal lobe, and cerebellum and the elaboration of new connections between these structures and other cortical regions, the brainstem, and spinal cord. The classical view saw rodents as phylogenetically old and relatively unrelated animals, displaying no skilled movements, and whose normal repertoire of behavior had little dependence on the frontal lobes. Here, evidence is reviewed that shows that the classical view of the origins of skilled movements is incorrect. Skilled movements are phylogenetically old, evolved in relation to food handling, and are especially well developed in rodents. Behavioral evidence also shows that the skilled movements of rodents are dependent upon the function of the frontal cortex. Nevertheless, there are difference in the sensory control of skilled movement in primates and rodents. Skilled movements are largely directed by vision in primates but are directed by hapsis/olfaction in rodents. This difference in sensory control suggests that at a dividing point between primates and rodents, there was a profound behavior/brain transformation. Primates retained the skilled movements exemplified in rodents, but brought these movements under visual control. Correspondingly, along with many other anatomical changes, the primate frontal cortex became relatively larger and move complex under visual influence.

Animals↗
PubMed1997

Dose-response effects of adrenergic drugs on axial movements of the rat mandibular incisor and on arterial blood pressure.

Axial tooth movements and arterial blood pressure were measured following the intravenous injection of 0, 0.01, 0.1, 1, or 10 micrograms/kg of adrenaline, noradrenaline or isoprenaline. Adrenaline caused a dose-dependent, rapid, extrusive tooth movement with a nearly simultaneous increase in blood pressure, followed by a marked intrusive tooth movement and a decrease in blood pressure. Noradrenaline caused a dose-dependent, rapid, extrusive tooth movement and an increase in blood pressure, but a subsequent intrusive tooth movement and decrease in blood pressure were not so marked. Isoprenaline caused a marked intrusive tooth movement and a decrease in blood pressure, without an extrusive tooth movement and increase in blood pressure. The time required to reach the maximum intrusive tooth movement was delayed after that to reach the maximum decrease in blood pressure. The recovery time of the intrusive tooth movement was much more delayed than that of blood pressure. These results suggest that the extrusive movement of the rat incisor was primarily related to the rise of arterial blood pressure due to stimulation of vascular alpha-receptors. It is also suggested that stimulation of beta-receptors would probably cause vasodilatation of arteries that would make the pressure in the small vessels in the microcirculation of the socket fall, so reducing the volume of blood and interstitial fluid in the socket followed by a marked and continuing intrusive tooth movement.

Adrenergic Agonists↗
PubMed2000

Movement accuracy constraints in Parkinson's disease patients.

This study examined the hypothesis that the kinematics of movements performed by PD (Parkinson's disease) patients are differentially affected depending on whether or not the aiming movement has an accuracy constraint. The aiming movements required elbow extension in the horizontal plane on a digitizer. There were two movement conditions: (1) one having a spatial accuracy requirement in which the subjects moved to the defined target and stopped on it; and (2) one requiring the subjects to move toward the defined target without stopping precisely on it. Subjects were instructed to make their movements as fast and as accurate as possible in response to the auditory imperative signal. PD patients modified the movement speed and kinematics depending on the two accuracy conditions. However, when the accuracy constraint was imposed, movement slowness observed in the patients was much more pronounced. The most revealing result was localized to the deceleration phase, particularly as the target was approached. The patients also were found to make a higher number of acceleration zero crossings from negative to positive to reach the target, indicating that the movements were more irregular. For the patients, the first acceleration zero crossing from negative to positive occurred much earlier in the movement than that for the controls. In addition, when movement accuracy was constrained, the number of zero crossings was accentuated. These data show that when PD patients make aiming movements to a target, their deceleration phase becomes longer and more variable.

Aged↗
PubMed1999

A vector-integration-to-endpoint model for performance of viapoint movements.

Viapoint (VP) movements are movements to a desired point that are constrained to pass through an intermediate point. Studies have shown that VP movements possess properties, such as smooth curvature around the VP, that are not explicable by treating VP movements as strict concatenations of simpler point-to-point (PTP) movements. Such properties have led some theorists to propose whole-trajectory optimization models, which imply that the entire trajectory is precomputed before movement initiation. This paper reports new experiments conducted to systematically compare VP with PTP trajectories. Analyses revealed a statistically significant early directional deviation in VP movements but no associated curvature change. An explanation of this effect is offered by extending the vector-integration-to-endpoint (VITE) model (Bullock, D., & Grossberg, S. (1988a). Neural dynamics of planned arm movements: Emergent invariants and speed-accuracy properties during trajectory formation. Psychological Review, 95, 49-90; Bullock, D., & Grossberg, S. (1988b). The VITE model: A neural command circuit for generating arm and articulator trajectories. In J.A.S. Kelso, A.J. Mandell & M.F. Schlesinger (Eds.), Dynamic patterns in complex systems (pp. 305-326). Singapore: World Scientific Publishers.), which postulates that voluntary movement trajectories emerge as internal gating signals control the integration of continuously computed vector commands based on the evolving, perceptible difference between desired and actual position variables. The model explains the observed trajectories of VP and PTP movements as emergent properties of a dynamical system that does not precompute entire trajectories before movement initiation. The new model includes a working memory and a stage sensitive to time-to-contact information. These cooperate to control serial performance. The structural and functional relationships proposed in the model are consistent with available data on forebrain physiology and anatomy.

Journal Article↗
PubMed1997

An investigation into movement planning and execution deficits in individuals with schizophrenia.

The purpose of this study was to examine whether individuals with schizophrenia demonstrate slowing in movement planning (reaction time), or in movement execution (movement time and velocity), in comparison to normals. Twelve schizophrenic and 12 control right-handed males performed aiming movements with a mouse (controlled by either the left or right hand) on a graphics tablet towards targets of differing sizes and distances appearing on a computer screen. Results showed that, for reaction time, the controls were faster than the schizophrenics and the latter had a left hand advantage for movement preparation while the controls showed no such differences. For movement time, no group differences were found. However, as expected, movement times were shorter (i.e., movements were faster) to the large, and near targets. These results support Fitts' law (Fitts, 1954) which describes a relationship where aiming movement time decreases as target distance decreases, and target size increases. We provide evidence here for a movement planning deficit in schizophrenic patients with no decrement in movement execution compared to controls.

Adult↗
PubMed1981

Effects of a secondary task on the accuracy of single aiming movements.

Recently, Schmidt, Zelaznik, and Frank and Schmidt, Zelaznik, Hawkins, Frank, and Quinn have demonstrated that in rapid, single aiming movements, variability in the movement's kinetic requirements resulted in variability in the movement's amplitude. This new explanation of the speed-accuracy trade-off in motor control, however, does not predict or explain inaccuracy for slower movements (greater than 200 msec). In the two experiments reported, we demonstrate that the Schmidt et al. model can predict variability in slow aiming movements if attention is occupied with an additional task. Subjects were required to perform single aiming movements in either 500 (Experiment 1) or 200 (Experiment 2) msec. In both experiments, the movement amplitude (30, 45, 60, and 75 cm in Experiment 1, and 10, 20, and 30 cm in Experiment 2) and the probability of an auditory probe-reaction time (RT) task were manipulated. Results indicated that only when the movement time (MT) was 500 msec did the probe-RT task change the relationship between the effective target width and the movement's average velocity. This result extended the scope of the Schmidt et al. model to movements with a duration greater than 200 msec. In addition, it seems as though slow movements are controlled by attention-demanding mental processes.

Attention↗
PubMed1993

Fetal eye movements.

Since 1981, when eye movements of the human fetus were first reported, the study of fetal eye movements has increased, mainly focusing on the ontogenesis of eye movements and as one parameter of behavioral states. Using real-time ultrasound, fetal eye movements can be clearly observed from 14 weeks of gestational age. Fetal eye movements may be described in terms of their pattern, frequency and incidence of periods containing eye movements and no eye movements. Furthermore, the relationship of eye movements to other behaviors may be used to give information on the integration of central nervous system function. A picture of normal fetal eye movements can be constructed and used to detect abnormalities in eye movements which can indicate underlying abnormalities of the central nervous system. This paper concludes that, although in its early stages, the study of fetal eye movements holds promise for a greater understanding of brain development and the assessment of the condition of the fetus.

Journal Article↗
PubMedDate not supplied

Movement analysis of asymptomatic normal shoulders: a preliminary study.

The dynamic pattern of scapulothoracic rhythm during arm forward flexion in the scapular plane has been studied radiographically. The technique involves dynamic radiographic screening of shoulder movement in elevation. It has low levels of radiation compared with plane x-ray examination techniques of scapular movement analysis, and the results are comparable to those of previously published studies. We analyzed real-time video images of shoulder movement in 10 young male volunteers (group I; mean age, 35 years) and 9 older male volunteers (group II; mean age, 70 years) with the use of computer-aided software. Group I showed mean arm elevation of 154 degrees, glenohumeral movement of 107 degrees, and total scapular movement of 55 degrees. Group II showed mean arm elevation of 118 degrees, glenohumeral movement of 77 degrees, and total scapular movement of 40 degrees. No statistically significant difference was found in the glenohumeral-scapular or glenohumeral-arm movement ratios of these 2 groups. We conclude that although the total range of arm elevation reduces with increasing age, the glenohumeral-to-scapular movement ratio does not change. The technique of movement analysis described is dynamic, safe, and applicable to clinical studies of shoulder movement.

Adult↗