Changes In Movement Time Research Articles

Performance Trends During Sleep Deprivation on a Tilt-Based Control Task.

Understanding human behavior under the effects of sleep deprivation allows for the mitigation of risk due to reduced performance. To further this goal, this study investigated the effects of short-term sleep deprivation using a tilt-based control device and examined whether existing user models accurately predict targeting performance. A task in which the user tilts a surface to roll a ball into a target was developed to examine motor performance. A model was built to predict human performance for this task under various levels of sleep deprivation. Every 2 h, 10 subjects completed the task until they reached 24 h of wakefulness. Performance measurements of this task, which were based on Fitts' law, included movement time, task throughput, and time intercept. The model predicted significant performance decrements over the 24-h period with an increase in movement time (R2 = 0.61), a decrease in throughput (R2 = 0.57), and an increase in time intercept (R2 = 0.60). However, it was found that in experimental trials there was no significant change in movement time (R2 = 0.11), throughput (R2 = 0.15), or time intercept (R2 = 0.27). The results found were unexpected as performance decrement is frequently reported during sleep deprivation. These findings suggest a reexamination of the initial thought of sleep loss leading to a decrement in all aspects of performance.Bolkovsky JB, Ritter FE, Chon KH, Qin M. Performance trends during sleep deprivation on a tilt-based control task. Aerosp Med Hum Perform. 2018; 89(7):626-633.

Nonlinear mixed-effects model reveals a distinction between learning and performance in intensive reach training post-stroke

BackgroundWe recently showed that individuals with chronic stroke who completed two sessions of intensive unassisted arm reach training exhibited improvements in movement times up to one month post-training. Here, we study whether changes in movement times during training can predict long-term changes.MethodsSixteen participants with chronic stroke and ten non-disabled age-matched participants performed two sessions of reach training with 600 movements per session. Movement time data during training were fitted to a nonlinear mixed-effects model consisting of a decreasing exponential term to model improvements of performance due to learning and an increasing linear term to model worsening of performance due to activity-dependent fatigability and/or other factors unrelated to learning.ResultsFor non-disabled age-matched participants, movement times gradually decreased overall during training and overall changes in movement times during training predicted long-term changes. In contrast, for participants post-stroke, movement times often worsened near the end of training. As a result, overall changes in movement times during training did not predict long-term changes in movement times in the stroke group. However, improvements in movement times due to training, as estimated by the exponential term of the model, predicted long-term changes in movement times.ConclusionParticipants post-stroke showed a distinction between learning and performance in unassisted intensive arm reach training. Despite worsening of performance in later trials, extended training was beneficial for long-term gains.

Role of BDNF genetic variations in motor skill acquisition: a pilot study

Background: Motor learning induces neural plasticity which ismodulated primarily byBrain-DerivedNeurotrophic Factor (BDNF). Recent studies have shown that BDNF Val66Met polymorphism influences learning of a visualmotor tracking task and the neural changes associated to it. This polymorphism has also been shown to affect stroke outcomes. However, there are no studies that have examined the role of this polymorphism in the learning of a sequential motor task which engages different sets of processes from those of the tracking task. Purpose: The purpose of this study was to determine the role of BDNF genetic variation in learning of a finger sequence movement. We hypothesized that individuals with Val66Met polymorphismwould show inferior learning of the task compared to those without. Methods: 40 young healthy adults (mean age = 23.9 years old) were recruited. Buccal swap sample was collected and genotype was determined by using Taqman SNP genotyping assay (rs6265). The participants then practiced a 4-element finger sequence task with their dominant hand for 144 trials. The participants were instructed to improve the task performance by reducing the time required to finish the sequence (movement time). Learning of the task was evaluated on the next day, approximately 24 hours later, with a delayed retention test. The tester was blinded to the genotype of participants. The genotyping results were revealed after all the behavioural task data were collected and analyzed. The data were then divided into two groups (val66met carriers vs. non-carriers). We used two-way repeated measure ANOVA and independent t-test to compare the task performance and learning between the two groups. Results: 24 out of the 40 participants were val66met carriers (60%). Both groups (val66met carriers and non-carriers) showed improved movement time during the training phase (p= .04). There was a significant group by practice effect (p= .047) with the val66met carriers showed a greater change in movement time than the non-carriers. However, there was no difference noted in the index of learning (forgetting) between the groups (p= .56). Conclusion(s):Thefindings suggest that BDNFpolymorphism may not influence learning of a motor sequence task. However, the extensive practice in the present studymay have affected the effect of BDNFpolymorphism onmotor learning as a previous report showed that extensive practice may overcome the deficits in learning among the met allele carriers. Further investigation on the relationship between the amount of practice and polymorphism influence on motor learning is being conducted. Implications: Understanding the relationship between genetic variations andmotor learningwill aid to identify those who might require tailored program during motor rehabilitation.

Cerebellar direct current stimulation enhances on-line motor skill acquisition through an effect on accuracy.

The cerebellum is involved in the update of motor commands during error-dependent learning. Transcranial direct current stimulation (tDCS), a form of noninvasive brain stimulation, has been shown to increase cerebellar excitability and improve learning in motor adaptation tasks. Although cerebellar involvement has been clearly demonstrated in adaptation paradigms, a type of task that heavily relies on error-dependent motor learning mechanisms, its role during motor skill learning, a behavior that likely involves error-dependent as well as reinforcement and strategic mechanisms, is not completely understood. Here, in humans, we delivered cerebellar tDCS to modulate its activity during novel motor skill training over the course of 3 d and assessed gains during training (on-line effects), between days (off-line effects), and overall improvement. We found that excitatory anodal tDCS applied over the cerebellum increased skill learning relative to sham and cathodal tDCS specifically by increasing on-line rather than off-line learning. Moreover, the larger skill improvement in the anodal group was predominantly mediated by reductions in error rate rather than changes in movement time. These results have important implications for using cerebellar tDCS as an intervention to speed up motor skill acquisition and to improve motor skill accuracy, as well as to further our understanding of cerebellar function.

Extended practice of reciprocal wrist and arm movements of varying difficulties

An experiment was designed to determine the degree to which reciprocal aiming movements of the wrist and arm with various accuracy requirements (Fitts' tasks) are enhanced by extended practice. The vast majority of research on motor learning shows performance improvement over practice. However, literature examining the effect of practice on Fitts' task performance is limited and inconclusive. Participants were asked to flex/extend their limb/lever in the horizontal plane at the wrist (arm stabilized) or elbow joint (wrist stabilized) in an attempt to move back and forth between two targets as quickly and accurately as possible. The targets and current position of the limb were projected on the screen in front of the participant. Target width was manipulated with amplitude constant (16°) in order to create indexes of difficulty (ID) of 1.5, 3, 4.5, and 6. Contrary to the earlier reports, after 20days of practice, we found minimal changes in movement time or the movement time–ID relationships for the arm and wrist over practice. However, the variability in the movement endpoints decreased over practice and wrist movements at ID=6 were characterized by shorter movement times and longer dwell times relative to arm movements with dwell time for the wrist increasing over practice. These data are consistent with the notion that Fitts' tasks provide a stable measure of perceptual-motor capabilities.

Advance knowledge effects on kinematics of one-handed catching

The purpose of this experiment was to examine the effects of advance knowledge on the kinematics of one-handed catching. Balls were launched from a distance of 8.4 m by a ball-projection machine with adjustable launching speed. Fifteen skilled ball catchers caught 160 balls with their preferred hand under blocked-order (4 blocks, each comprising 20 trials at 1 of 4 different ball speeds) or random-order (4 blocks, each comprising 20 trials of 4 different ball speeds) conditions. By projecting balls with different ball speeds from a fixed position, it was possible to modify the temporal constraints of the catching task. In both the blocked-order and random-order conditions, catching performance (number of catches, touches and misses) decreased with increasing temporal constraints. Analysis of successful trials indicated that this equal level of catching performance was achieved with different movement kinematics. Specifically, there was a change in movement time, latency, wrist velocity profile, and coefficient of straightness. Based on expectancy of previous trials, movement kinematics was scaled to ball speed in the blocked-order condition whereas in the random-order condition, participants exhibited a more default initial response. However, this latter mode of control was functional in that it increased the likelihood of success for the higher ball speeds while also providing participants with a larger temporal window to negotiate the unexpected temporal constraint on-line for the lowest ball speed.

Practice Effects on Motor Control in Healthy Seniors and Patients with Mild Cognitive Impairment and Alzheimer's Disease

ABSTRACT This research was designed to test the hypothesis that motor practice can enhance the capabilities of motor control in healthy controls (NC) and patients with a diagnosis of probable Alzheimer's disease (AD) and mild cognitive impairment (MCI), and consequently results in better motor performance. Approximately half of the subjects in the NC (n = 31), AD (n = 28), and MCI (n = 29) either received or did not receive practice on a task of fast and accurate arm movement with a digitizer. Changes in movement time (MT), movement smoothness (jerk), and percentage of primary submovement (PPS) were recorded and compared among the three groups across six blocks of trials (baseline and five training sessions). For all subjects, practice improved motor functions as reflected by faster and smoother motor execution, as well as a greater proportion of programming control. Compared to unaffected matched controls, AD and MCI subjects exhibited a greater reduction in movement jerk due to practice. Movement time and PPS data revealed that motor practice appeared to reduce the use of “on-line” correction adopted by the AD or MCI patients while performing the aiming movements. Evidently, their arm movements were quicker, smoother, and temporally more consistent than their untrained peers. The findings of this study shed light on how MCI and AD may affect motor control mechanisms, and suggest possible therapeutic interventions aimed at improving motor functioning in these impaired individuals.

Systematic scaling of target width: dynamics, planning, and feedback

The target width of a single target in a two-target reciprocal aiming task was scaled from small (ID = 5.85) to large (ID = 2.85) and large-to-small within individual trials with movement amplitude fixed. Scaling target width produced a transition in the end-effector’s dynamics and based on a measure of movement harmonicity, the transition was sensitive to the initial conditions but not to the direction of target width scaling. Hysteresis emerged in a variety of kinematic measures suggesting that the interdependency of planning and feedback control processes was sensitive to initial conditions as well as the direction of target width scaling. Practice increased the efficiency of the reciprocal movements and produced changes in movement time and the measure of harmonic motion that revealed a tuning of the end-effector’s dynamics to cyclical motion over as large of range of IDs as possible. The tuning occurred through the modulation of time spent accelerating and decelerating the end-effector for IDs outside the range of 3.85–4.26. The results are discussed with reference to a critical ID boundary that separates regions of parameter space wherein the end-effector’s dynamics are more cyclical (limit-cycle) or discrete (fixed-point) in nature.

Temporal Changes in Movement Time during the Switch of the Stimulators in Parkinson’s Disease Patients Treated by Subthalamic Nucleus Stimulation

Objective: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a very effective therapy for the advanced phase of Parkinson’s disease (PD). The functional inhibition of this nucleus is responsible for a significant improvement of cardinal motor symptoms of PD. The aim of the study was the assessment of the effectiveness of STN DBS on bradykinesia by the analysis of movement time (MT) in 2 conditions: with the stimulators turned on (‘stim-on’) or off (‘stim-off’). Methods: After pharmacological wash-out, 10 patients submitted to bilateral STN DBS were studied with an MT analyser in 3 phases: stim-on, stim-off and stim-on again, in order to establish the time course of MT lengthening, the posteffect duration and the latency of the effect of STN DBS. MT data were then compared with the UPDRS motor scores. Results: After turning off the stimulators, MT progressively increases, reaching a plateau after about 30 min, which then lasts for the subsequent observation time (2 h). A significant elongation is achieved after the first 5 min. Upon pulse generator activation, MT shows a dramatic shortening, already significant after 2 min. Moreover, we observed a significant correlation between MT and the severity of PD, higher with bradykinesia than with rigidity or tremor. Conclusion: Our findings show a relevant effect of STN DBS on MT, a parameter strongly related to bradykinesia. This study confirms the effectiveness of STN inhibition on the whole parkinsonian triad, suggesting that this target can be considered a proper choice for the surgical treatment of advanced PD.

Apomorphine delays simple reaction time in Parkinsonian patients

Background. Parkinsonian patients have difficulty in the preparation and execution of movements, which translate into delayed performance of simple reaction time (SRT) paradigms. Objective. To examine short-term effects of an acute subcutaneous injection of the dopamine agonist apomorphine on the results of a SRT task. Methods. We studied a SRT paradigm in 26 non-fluctuating idiopathic Parkinsonian patients, before and 30, 60, 90 min after administration of apomorphine. Results. The reaction time (RT) was significantly delayed after apomorphine injection. We found no significant change in movement time (MT). Conclusion. Delay of RT and the lack of response of MT to apomorphine administration may result from the sedative effects of apomorphine, overstimulation of postsynaptic dopaminergic receptors with subsequent inhibition of prefrontal cholinergic neurotransmission, and at least partial binding of apomorphine to presynaptic dopaminergic autoreceptors, which cause inhibition of locomotor activity. We suggest that future studies testing the capacity for reaction in Parkinsonian patients should consider the exact timing of the delivery of dopamine substituting drugs prior to the test.

The dynamics of rhythmical aiming in 2D task space: Relation between geometry and kinematics under examination

We explored a two-dimensional task space variant of the classical rhythmical Fitts' task in which participants were asked to sequentially cross four targets arranged around the extreme points of the major axes of an ellipse. Fitts' law was found to adequately describe the changes in movement time with the variations in task difficulty (ID), but the 1/3 power-law relating curvature and tangential velocity of the trajectory did not resist the increase in ID. Kinematic analyses showed that the behavioral adaptation to the ID resulted in an increase in the contribution of non-linear terms to the kinematics along the two axes of task space. Moreover, a limit cycle model (combining Rayleigh damping and Duffing stiffness, as in one-dimensional Fitts' task) captured such a behavior. In such a context, Fitts' law and the 1/3 power law appear as surface relations that emerge from parametric changes in a dynamical structure that captures the nature of Fitts' task.

Medial prefrontal and neostriatal lesions disrupt performance in an operant delayed alternation task in rats

An operant version of the classical delayed alternation task is presented and applied to evaluate the effects of bilateral prefrontal and striatal lesions in rats. Retractable levers in a conventional operant chamber control discrete trial opportunities for making sequential choice responses to the two sides, and the rats are required to maintain repeated nose poke responses to a central panel during the delay interval, which is randomly varied. The operant task provides measures of the speed and accuracy of response alternation and side bias; analysis at different delay intervals provides an index of the memory demands of accurate performance; and analysis of accuracy depending on the response on preceding trials provides measures of proactive interference and perseveration. Following pretraining in the task contingencies, both striatal and prefrontal lesions induced profound deficits in task accuracy, with no change in side bias and only small changes in movement times. The deficit in the prefrontal lesion group recovered more rapidly, neither group showed any change in sensitivity to proactive interference, while the rats with striatal lesions alone exhibited an increased tendency to perseverate incorrect responses on either side. We conclude that the operant delayed alternation task should assist analysis of fronto-striatal function in rats as well as be useful for the analysis of strategies for fronto-striatal repair.

Children's development of reaching: temporal and spatial aspects of aimed whole-arm movements.

Age-related changes in movement time and spatial distribution of pointing errors were investigated using a whole-arm target-aimed task. 60 children (6 to 11 yr.) and 10 young adults were required to reach towards targets located on a vertical screen in four conditions: target lit for 4 sec. in light (1), in darkness (2), target lit for 200 msec. in light (3), in darkness (4). Accuracy was perfect in Conditions 1 and 2, with a significant increase of MT in Condition 2 between the ages 7 and 10. Accuracy decreased slightly in Condition 3 and strongly in Condition 4, despite a similar shortening of MT. In Condition 4 the subjects undershot the target position: horizontally from age 8 and vertically in all age groups, with an increase of vertical bias by girls at age 9. These results suggest age-related changes in computation of arm movement towards the target.

CHILDREN'S DEVELOPMENT OF REACHING: TEMPORAL AND SPATIAL ASPECTS OF AIMED WHOLE-ARM MOVEMENTS

Age-related changes in movement time and spatial distribution of pointing errors were investigated using a whole-arm target-aimed task. 60 children (6 to 11 yr.) and 10 young adults were required to reach towards targets located on a vertical screen in four conditions: target lit for 4 sec. in light (1), in darkness (2), target lit for 200 msec. in light (3), in darkness (4). Accuracy was perfect in Conditions 1 and 2, with a significant increase of MT in Condition 2 between the ages 7 and 10. Accuracy decreased slightly in Condition 3 and strongly in Condition 4, despite a similar shortening of MT. In Condition 4 the subjects undershot the target position: horizontally from age 8 and vertically in all age groups, with an increase of vertical bias by girls at age 9. These results suggest age-related changes in computation of arm movement towards the target.

A quantitative analysis of pallidal discharge during targeted reaching movement in the monkey

Neurons in the globus pallidus have been studied during reaching movements of the arm made at varying speeds. The reaching task is similar to one used in earlier experiments, in which disruption of normal pallidal output caused changes in movement time. The pallidal cells studied were those that showed task-related changes in activity and a modification of discharge when the arm was manipulated outside of the task. Neuronal discharge was assessed to evaluate two possible models, one in which the timing of task-related discharge varied as a function of movement time and the other in which the amplitude (mean firing rate) of the change in discharge varied as movement time varied. The relation between neuronal discharge and movement time was examined quantitatively on a trial-by-trial basis using a statistical algorithm that identified each phase of the change in neuronal discharge on each trial. A non-parametric statistic was used to determine the correlation between movement time and the duration or latency of changes in neural firing or the mean discharge during each phase of the cell's response. For fifty-five percent of the 40 neurons studied, the timing of the cell's response (duration or latency) varied as a function of movement time. For only 10 cells (25%) was there a significant correlation between movement time and the mean firing rate during one or more phases of the cell's response. Both timing and frequency modulation with movement time were limited to cells responsive to manipulation at the wrist or the shoulder.

An equilibrium-point model for fast, single-joint movement: I. Emergence of strategy-dependent EMG patterns.

We describe a model for the regulation of fast, single-joint movements, based on the equilibrium-point hypothesis. Limb movement follows constant rate shifts of independently regulated neuromuscular variables. The independently regulated variables are tentatively identified as thresholds of a length sensitive reflex for each of the participating muscles. We use the model to predict EMG patterns associated with changes in the conditions of movement execution, specifically, changes in movement times, velocities, amplitudes, and moments of limb inertia. The approach provides a theoretical neural framework for the dual-strategy hypothesis, which considers certain movements to be results of one of two basic, speed-sensitive or speed-insensitive strategies. This model is advanced as an alternative to pattern-imposing models based on explicit regulation of timing and amplitudes of signals that are explicitly manifest in the EMG patterns.

Basal ganglia motor control. III. Pallidal ablation: normal reaction time, muscle cocontraction, and slow movement

1. Inactivation of the portions of globus pallidus pars interna (GPi) containing the greatest concentration of wrist-related neurons was achieved in two rhesus monkeys with microinjections of muscimol (temporary) and kainic acid (permanent). 2. After muscimol injection, there was onset within 30 s of 1) tonic and phasic coactivation of wrist flexors and extensors; 2) slightly greater activation of the flexors, giving a flexor bias in postural holds and the endpoint of movements; and 3) slowness of all movements with a prolonged movement time. Nevertheless, 4) movements made by lessening prior loaded muscle activity (to move in the direction of the load) were slower than movement made by increasing muscle activity (to move against the direction of the load). Despite marked slowing of all movements, there was 5) a normal reaction time for movement onset. Finally, there was 6) a reduced amplitude of most movements. Open room behavior included 7) spiraling contralateral to the lesion while walking. Effects were reproducible (12 injections), were apparent for 7-8 h and were usually completely gone by the next day's testing. 3. After kainic acid injection, there was a period of mixed effects, followed by a period of permanent defects (observed for up to 24 days) that duplicated the temporary effects of muscimol. 4. By contrast, muscimol inactivation of the cerebellar dentate nucleus resulted in 1) a prolonged reaction time and 2) an increased variability of movement trajectory, but 3) without change in movement time or peak velocity. Open room behavior included overshoot in reaching for fruit with the forelimb ipsilateral to the injection. 5. From the facts that normal pallidal neurons fire constantly, that pallidal neurons inhibit their target neurons, and that the muscimol effect was immediate, we conclude that the release of the target neurons from the tonic inhibition allowed them to fire in patterns that promoted a maintained state of cocontraction of agonist and antagonist muscles. From the fact that movement time was prolonged, we conclude that the maintained state of neural activity that caused the muscle cocontraction interfered with the commands for voluntary movement, which were generated by other mechanisms. From the fact that reaction time for movement onset was normal, we conclude that the pallidal neurons may play little or no role in the voluntary initiation of these movements, which are instead generated by other structures that include the anterior cerebral cortex and the lateral cerebellum.

An examination of rapid positioning movements with spatiotemporal constraints.

Unidirectional positioning movements with spatiotemporal constraints were examined as a test of impulse-timing theory (Schmidt, 1976; 1980; Wallace, 1981). Movements were examined at the kinematic, kinetic, and neuromuscular levels in three experiments. In the first experiment, displacement was held constant while five different movement times were examined. Both amplitudes and durations of the EMG and the kinetic variables were related to movement time. The results generally support the impulse-timing model. In the second experiment, movements were performed to a target at each of four distances in a constant movement time. EMG and force amplitudes and, unexpectedly, accelerative-force duration were modulated to achieve changes in displacement when movement time was constant. In the third experiment, movement time and displacement were simultaneously varied resulting in four conditions with equal average velocities. The results of this experiment were not as clear and exhibited individual differences. EMG duration did not always vary with changes in movement time. The results of all three experiments could not be adequately accounted for by the impulse-timing model.

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.

Dentate cooling in monkeys performing a visuo-motor pointing task

Baboons were trained to perform a visuo-motor pointing task. Reversible exclusion of the cerebellar dentate nucleus was obtained by local cooling, after unilateral implantation of a cryoprobe. Increased reaction time, changes in movement time and impairment of the terminal accuracy of the pointing responses were observed. They are in agreement with the hypothesis that the dentate nucleus plays a rôle in the spatio-temporal organization of goal-directed limb movements.