An examination of lower limb asymmetry in ankle isometric force control

While asymmetries have been observed between the dominant and non-dominant legs, it is unclear whether they have different abilities in isometric force control (IFC). The purpose of this study was to compare ankle IFC between the legs. IFC is important for stabilization rather than object manipulation, and people typically use their non-dominant leg for stabilization tasks. Additionally, studies suggested that a limb can better acquire a motor task when the control mechanism of the task is related to what the limb is specialized for. We hypothesized that the non-dominant leg would better (1) control ankle IFC with speed and accuracy, and (2) acquire an ankle IFC skill through direct learning and transfer of learning. Two participant groups practiced an IFC task using either their dominant or non-dominant ankle. In a virtual environment, subjects moved a cursor to hit 24 targets in a maze by adjusting the direction and magnitude of ankle isometric force with speed (measured by the time required to hit all targets or movement time) and accuracy (number of collisions to a maze wall). Both groups demonstrated similar movement time and accuracy between the dominant and non-dominant limbs before practicing the task. After practice, both groups showed improvement in both variables on both the practiced and non-practiced sides (p < .01), but no between-group difference was detected in the degree of improvement on each side. The ability to control and acquire the IFC skill was similar between the legs, which did not support the brain is lateralized for ankle IFC.     

正念训练对康复期精神分裂症患者抑制控制的影响

探究正念训练对康复期精神分裂症患者正念觉知水平和抑制控制能力的影响。选取54名康复期精神分裂症住院患者随机分为正念组和对照组。对照组予以常规康复治疗,正念组在常规康复治疗基础上进行8周正念训练。结果发现：（1）在正念觉知方面,正念组后测得分显著高于前测,对照组前后测得分无显著差异;正念组后测得分显著高于对照组。（2）在抑制控制方面,正念组后测Stroop任务反应时显著低于前测,对照组前后测反应时无显著差异;正念组后测反应时显著低于对照组。结果表明,正念训练有助于提高康复期精神分裂症患者正念觉知水平和改善其抑制控制能力。     

The influence of robotic guidance on error detection and correction mechanisms

New technologies have expanded the available methods to help individuals learn or re-learn motor skills. Despite equivocal evidence for the impact of robotic guidance for motor skill acquisition (Marchal-Crespo, McHughen, Cramer, & Reinkensmeyer, 2010), we have recently shown that robotic guidance mixed with unassisted practice can significantly improve the learning of a golf putting task (Bested & Tremblay, 2018). To understand the mechanisms associated with this new mixed approach (i.e., unassisted and robot-guided practice) for the learning of a golf putting task, the current study aimed to determine if such mixed practice extends to one’s ability to detect errors. Participants completed a pre-test, an acquisition phase, as well as immediate, delayed (24-h), and transfer post-tests. During the pre-test, kinematic data from the putter was converted into highly accurate, consistent, and smooth trajectories delivered by a robot arm. During acquisition, 2 groups performed putts towards 3 different targets with robotic guidance on either 0% or 50% of acquisition trials. Only the 50% guidance group significantly reduced ball endpoint distance and variability, as well as ball endpoint error estimations, between the pre-test and the post-tests (i.e., immediate retention, 24-h retention, and 24-h transfer). The current study showed that allowing one to experience both robotic guidance and unassisted (i.e., errorful) performances enhances one’s ability to detect errors, which can explain the beneficial motor learning effects of a mixed practice schedule.     

Retroactive interference and mental practice effects on motor performance: a pilot study

This study examined the effect of similar versus dissimilar retroactive interference on the mental practice effects for performing a novel motor skill. Research has shown that mental practice of a motor task can interfere with learning and performance of the task; however, little is known about how different retroactive interference activities affect mental practice effects. 90 volunteers ages 18 to 51 years (M=26.8, SD=9.6) completed a pre-test and post-test of 10 sets of five trials of a throwing task with the non-preferred hand. In the practice phase, participants mentally practiced the throwing task and then mentally practiced a task that was similar, dissimilar, or completed an unrelated reading task. Performance for all groups improved from pre- to post-test; however, there were no differences in increases for the three groups. The findings suggest that mental practice of similar and dissimilar tasks produced no significant interference in performance.     

Joystick acquisition in tufted capuchins (<Emphasis Type="Italic">Cebus apella</Emphasis>)

A number of nonhuman primate species have demonstrated the ability to use a joystick to control a cursor on a computer screen, yet the acquisition of this skill has not been the focus of systematic inquiry. Here, we examined joystick acquisition in four tufted capuchins under two directional relationships of joystick movement and resultant cursor displacement, isomorphic and inverted. To document the natural history of the acquisition of this skill, we recorded the development of visual tracking of the cursor and body tilting. Rates of acquisition were comparable between the two conditions. After mastering the task in one condition, subjects remastered the task at an accelerated rate in the opposing condition. All subjects significantly increased or maintained high proportions of cursor tracking throughout acquisition. All subjects demonstrated a postural tilt while moving the cursor from the mid-phase of acquisition through task mastery. In the isomorphic condition, all subjects tilted significantly more often in the direction of goal location than in the opposite direction. In three of the four series of tilting that were scored for subjects in the inverted condition, tilting occurred significantly more often toward the direction of goal location than the direction of required hand movement. Together these findings suggest that body tilting participates in the organization of directional movement of the cursor rather than reflecting merely the motoric requirements of the task (to manipulate a joystick).     

Neural correlates of skill acquisition with a cortical brain-machine interface

Research into the development of brain-machine interfaces (BMIs) has led to demonstrations of rodents, nonhuman primates, and humans controlling prosthetic devices in real time through modulation of neural signals. In particular, cortical BMI studies have shown that improvements in performance require learning and are associated with changes in neuronal tuning properties. These studies have further shown evidence of long-term improvements in performance with practice. The authors conducted experiments to understand long-term skill acquisition with BMIs and to characterize the neural correlates of improvements in task performance. They specifically assessed long-term acquisition of neuroprosthetic skill (i.e., accurate task performance readily recalled across days). In 2 monkeys performing a center-out task using a brain-controlled (BC) computer cursor, they closely monitored daily performance trends and the neural correlates under different conditions. Importantly, they assessed BC performance using a continuous-control multistep task. The authors first conducted experiments that mimicked experimental conditions commonly used. Specifically, a large set of neurons was incorporated with daily recalibration of the transform of neural activity to BC. Under such conditions, they found evidence of variable daily performance. In contrast, when a fixed transform was applied to stable recordings from an ensemble of neurons across days, there was consistent evidence of long-term skill acquisition. Such skill acquisition was associated with the crystallization of a cortical map for prosthetic control. Taken together, the results suggest that the primate motor cortex can achieve skilled control of a neuroprosthetic device through consolidation of a cortical representation.     

How am I doing? Performance feedback mitigates the effects of mental fatigue on endurance exercise performance

Mental fatigue induced by an earlier cognitive task can impair performance on a subsequent physical task. The current study investigated whether such performance impairment could be mitigated by performance feedback. In an experimental sequential-task design, 63 sport science students completed a series of three tasks: 5-min physical (pre-test), 20-min cognitive, 5-min physical (post-test). Participants were randomly allocated to one of three groups: feedback (n = 23), no feedback (n = 20), control (n = 20). The physical tasks, which assessed force production during a self-paced rhythmic handgrip task as a measure of physical endurance performance, were performed with (feedback group) or without (no feedback group, control group) visual performance feedback. The cognitive tasks involved either completing a 2-back memory task to induce mental fatigue (feedback and no feedback groups) or watching a didactic film (control group). Self-report measures (fatigue, exertion, vigor, motivation) were collected throughout. The 2-back cognitive task increased mental fatigue, mental exertion and general fatigue in the feedback and no feedback groups compared to the control group. Relative to the pre-test physical task, post-test endurance performance declined in the no feedback group (−14.4%) but did not change in the control (−2.6%) and feedback (−2.4%) groups. This mitigation of performance effect was not accompanied by parallel changes in fatigue, exertion, vigor, or motivation. In conclusion, visual performance feedback mitigates the negative effects of mental fatigue on physical endurance performance.     

Does self-efficacy mediate transfer effects in the learning of easy and difficult motor skills?

The effect of task difficulty on inter-task transfer is a classic issue in motor learning. We examined the relation between self-efficacy and transfer of learning after practicing different versions of a stick balancing task. Practicing the same task or an easier version led to significant pre- to post-test transfer of learning, whereas practicing a more difficult version did not. Self-efficacy increased modestly from pre- to post-test with easy practice, but decreased significantly with difficult practice. In addition, self-efficacy immediately prior to the post-test was significantly lower after difficult practice than easy or intermediate practice. Self-efficacy immediately prior to the post-test, performance at the end of practice, and pre-test performance explained 75% of the variance in post-test performance. The mediating role of self-efficacy on transfer of learning offers an alternative explanation for recent findings on the superiority of easy-to-difficult transfer and may help clarify inconsistencies in earlier research.     

Force Control of Ankle Dorsiflexors in Young Adults: Effects of Bilateral Control and Leg Dominance

Abstract

We investigated whether bilateral lower-limb control and leg dominance affect force control ability in 15 healthy young adults (9 males and 6 females, age =26.8?±?4.1 years). Participants performed isometric ankle dorsiflexion force control tasks, matching a visual target (10% of maximal effort) as quickly and precisely as possible in ballistic and tonic tasks. Performance was evaluated using force error, force steadiness, amount of muscle activity of the tibialis anterior, and response time characteristics. Results showed no significant effects of leg dominance during both ballistic and tonic tasks, while bilateral condition resulted in significantly larger error, less force steadiness, compared to unilateral condition, and only during the tonic task. Consequently, bilateral control, specifically in tasks utilizing feedback control (i.e., tonic task) might affect force control ability, possibly because of the interhemispheric inhibition to meet bilateral task complexity and integrate afferent bilateral sensory information from both right and left legs.     

H-reflexes during a motor skill acquisition task

H-reflex amplitudes were studied during the acquisition of a motor skill involving coordinated isometric plantarflexion at the ankle joints as subjects learned to trace a triangular pattern on an oscilloscope screen by controlling plantarflexion torque applied against load cells. Torque feedback was presented on a subject oscilloscope with the right foot controlling a vertical cursor and the left foot a horizontal cursor. Eleven subjects reached criterion performance. H-reflexes were recorded from the right soleus and timed to the initiation of soleus muscle activity to plantarflex the foot. Average time to complete one trial decreased from 9 sec. in the prelearning block to 4 sec. postlearning. No single learning strategy was evident as subjects varied widely in their levels of H-reflex amplitude, but during postlearning, H-reflex amplitude became consistent within subjects as tracing performance became faster and accurate.     

Sleep-related improvements in motor learning following mental practice

A wide range of experimental studies have provided evidence that a night of sleep may enhance motor performance following physical practice (PP), but little is known, however, about its effect after motor imagery (MI). Using an explicitly learned pointing task paradigm, thirty participants were assigned to one of three groups that differed in the training method (PP, MI, and control groups). The physical performance was measured before training (pre-test), as well as before (post-test 1) and after a night of sleep (post-test 2). The time taken to complete the pointing tasks, the number of errors and the kinematic trajectories were the dependent variables. As expected, both the PP and the MI groups improved their performance during the post-test 1. The MI group was further found to enhance motor performance after sleep, hence suggesting that sleep-related effects are effective following mental practice. Such findings highlight the reliability of MI in learning process, which is thought consolidated when associated with sleep.     

Children show limited movement repertoire when learning a novel motor skill

Examining age differences in motor learning using real‐world tasks is often problematic due to task novelty and biomechanical confounds. Here, we investigated how children and adults acquire a novel motor skill in a virtual environment. Participants of three different age groups (9‐year‐olds, 12‐year‐olds, and adults) learned to use their upper body movements to control a cursor on a computer screen. Results showed that 9‐year‐old and 12‐year‐old children showed poorer ability to control the cursor at the end of practice. Critically, when we investigated the movement coordination, we found that the lower task performance of children was associated with limited exploration of their movement repertoire. These results reveal the critical role of motor exploration in understanding developmental differences in motor learning.     

The effect of implicit and explicit practice in the development of decision making in volleyball serving

This experiment investigated the effect of explicit, implicit, and sequential learning (implicit-explicit) on the acquisition and retention of decision-making skill in volleyball. The participants were 60 female novices, ages 10 to 12 years. The experimental groups followed three different methods of training: (a) explicit practice for the development of declarative knowledge, (b) implicit practice for the development of the procedural knowledge, (c) sequential practice (implicit first and then explicit), and (d) control group that participated only in the measurements. A pre-test, a post-test, and a retention test measured the response time and accuracy of the decision-making skill. Analysis indicated that all experimental groups improved over time while the control group did not. The sequential group was faster and more accurate than the implicit group, and the latter was faster and more accurate than the explicit one. The sequential group outperformed implicit and explicit groups on both speed and accuracy of decision. It seems that both explicit and implicit processes, when they take place in sequence, interact positively, and this method improves speed and accuracy of decision making rather than when each mode of learning (implicit or explicit) occurs separately. If the role of working memory is reduced at the early stages of learning, the accumulation of declarative knowledge (explicit learning) may benefit from accumulation of procedural knowledge and enhance decision-making skill.     

Effects of A Dual-Task Intervention in Postural Control and Cognitive Performance in Adolescents

Abstract

The aim was to assess dual- versus single-task training for motor performance and cognitive performance in adolescents. Two experiments were performed. In the first, 30 adolescents were randomized to three groups to determine the effect of dual-task difficulty on postural control: α-scaling and root mean square (RMS). In the second, 20 adolescents were randomized to two groups to determine the effect of dual-task practice to improve working memory. RMS in the post-test was lower than the pre-test in both dual-task groups, while α-scaling was lower in post-test than pre-test only in the high-difficulty dual-task group. A practice effect was observed on the percentage of correct answers only in the dual-task group (p?=?0.035). Thus, dual-task training could enhance motor and cognitive performance more than single-task training.     

Effect of mental imagery on realizing affordances

Using a reaction time experiment, we examined whether imagining a response would lead to an increase in the frequency of its execution. During a pre-test and a post-test, participants had to respond as quickly as possible with either their left or their right hand, as they preferred, to the illumination of one of 17 target positions arrayed in front of them in a semicircle. Between these two phases, participants performed a practice condition. Each of 40 right-handed participants was assigned to one of four groups that differed in their practice condition: One group made only dominant-hand responses to all target locations, two imagery groups imagined dominant hand responses to all target locations, and the last group received a no-practice, control task. One imagery group received instructions emphasizing that imagery has a strong effect; the second group received instructions suggesting that imagery was not effective. The results showed an increased incidence of the practised response for both imagery groups during the post-test. No effect was found for the physical performance group and the control group. The change in performance for the imagery groups was not accompanied by a change in reaction time. The results are discussed in terms of imagining the realization of action possibilities and from a neuropsychological point of view.     

Changes in muscle and joint coordination in learning to direct forces

While it has been suggested that bi-articular muscles have a specialized role in directing external reaction forces, it is unclear how humans learn to coordinate mono- and bi-articular muscles to perform force-directing tasks. Participants were asked to direct pedal forces in a specified target direction during one-legged cycling. We expected that with practice, performance improvement would be associated with specific changes in joint torque patterns and mono- and bi-articular muscular coordination. Nine male participants practiced pedaling an ergometer with only their left leg, and were instructed to always direct their applied pedal force perpendicular to the crank arm (target direction) and to maintain a constant pedaling speed. After a single practice session, the mean error between the applied and target pedal force directions decreased significantly. This improved performance was accompanied by a significant decrease in the amount of ankle angular motion and a smaller increase in knee and hip angular motion. This coincided with a re-organization of lower extremity joint torques, with a decrease in ankle plantarflexor torque and an increase in knee and hip flexor torques. Changes were seen in both mono- and bi-articular muscle activity patterns. The mono-articular muscles exhibited greater alterations, and appeared to contribute to both mechanical work and force-directing. With practice, a loosening of the coupling between bi-articular thigh muscle activation and joint torque co-regulation was observed. The results demonstrated that participants were able to learn a complex and dynamic force-directing task by changing the direction of their applied pedal forces through re-organization of joint torque patterns and mono- and bi-articular muscle coordination.     

An acute application of transcranial random noise stimulation does not enhance motor skill acquisition or retention in a golf putting task

Transcranial random noise stimulation (tRNS) is a brain stimulation technique that has been shown to increase motor performance in simple motor tasks. The purpose was to determine the influence of tRNS on motor skill acquisition and retention in a complex golf putting task. Thirty-four young adults were randomly assigned to a tRNS group or a SHAM stimulation group. Each subject completed a practice session followed by a retention session. In the practice session, subjects performed golf putting trials in a baseline test block, four practice blocks, and a post test block. Twenty-four hours later subjects completed the retention test block. The golf putting task involved performing putts to a small target located 3 m away. tRNS or SHAM was applied during the practice blocks concurrently with the golf putting task. tRNS was applied over the first dorsal interosseus muscle representation area of the motor cortex for 20 min at a current strength of 2 mA. Endpoint error and endpoint variance were reduced across the both the practice blocks and the test blocks, but these reductions were not different between groups. These findings suggest that an acute application of tRNS failed to enhance skill acquisition or retention in a golf putting task.     

Sex-related differences and visual-spatial mental imagery as factors affecting symbolic motor skill acquisition

The ability of males and females to use visual-spatial imagery as a facilitator of symbolic motor skill acquisition was investigated. Subjects, ordered by gender into control and mental imagery groups, performed 15 trials on a mirrored drawing task. The results indicated that, although both male and female mental imagery groups performed the task more skillfully than the control groups, the male mental imagery group scores over the early stages of performance were better as compared to the female mental imagery group scores. This difference was eradicated during the latter stages of performance. The findings, in addition to supporting the positive effects of mental imagery, lend support to the hypothesis that sex-related differences in selected visual-spatial tasks may be amendable through training followed by practice.     

Predicting individual differences in complex skill acquisition: dynamics of ability determinants.

Substantial controversy exists about ability determinants of individual differences in performance during and subsequent to skill acquisition. This investigation addresses the controversy. An information-processing examination of ability-performance relations during complex task acquisition is described. Included are ability testing (including general, reasoning, spatial, perceptual speed, and perceptual/psychomotor abilities) and skill acquisition over practice on the terminal radar approach controller simulation. Results validate and extend Ackerman's (1988) theory of cognitive ability determinants of individual differences in skill acquisition. Benefits of ability component and task component analyses over global analyses of ability-skill relations are demonstrated. Implications are discussed for selection instruments to predict air traffic controller success and for other tasks with inconsistent information-processing demands.