Pupil Diameter May Reflect Motor Control and Learning

Non–luminance-mediated changes in pupil diameter have been used since the first studies by Darwin in 1872 as indicators of clinical, cognitive, and arousal states. However, the relation between processes involved in motor control and changes in pupil diameter remains largely unknown. Twenty participants attempted to compensate random walks of a cursor with a computer mouse to restrain its trajectory within a target circle while the authors recorded their pupil diameters. Two conditions allowed the authors to experimentally manipulate the motor and cognitive components of the task. First, the step size of the cursor's random walk was either large or small leading to 2 task difficulties (difficult or easy). Second, they instructed participants to imagine controlling the cursor by moving the mouse, but without actually moving it (task modality: imagined movement or real movement condition). Task difficulty and modality allowed the authors to show that pupil diameters reflect processes involved in motor control and in the processing of feedback, respectively. Furthermore, the authors also demonstrate that motor learning can be quantified by pupil size. This noninvasive approach provides a promising method for investigating not only motor control, but also motor imagery, a research field of growing importance in sports and rehabilitation.     

Offline Improvement during Motor Sequence Learning Is Not Restricted to Developing Motor Chunks

Robust offline performance gains, beyond those that would be anticipated by being exposed to additional physical practice, have been reported during procedural learning and have been attributed to enhancement consolidation, a process by which memory is transformed in such a way that it is not only more resistant to forgetting but may also involve a reorganization of information that supports superior task execution. The authors assessed the impact of increasing within-session practice extent on the emergence of offline performance gains. Practice-dependent improvements occurred across 12 and 24 30-s practice trials of a 5-element motor sequencing task. Offline improvements were observed following both 12 and 24 trials. The improvement following 12 trials was associated with the formation of motor chunks important for establishing movement sequence structure. In contrast, the offline improvement after 24 trials was not related to further changes in movement structure beyond those that had emerged during practice. These data suggest that additional memory operations, beyond those needed to amalgamate subsequences of the SRT task, are susceptible to enhancement consolidation.     

Haptic Guidance Can Enhance Motor Learning of a Steering Task

Haptic guidance can improve the immediate performance of a motor task by enforcing a desired pattern of kinematics, but several studies have found that it impairs motor learning. In this study, we studied whether guidance from a robotic steering wheel can improve one's short-term learning of steering a simulated vehicle. We developed a computer algorithm that adapted the firmness of the guidance based on ongoing error. Training with "guidance-as-needed" or "fixed guidance" allowed participants to learn to steer without experiencing large errors and produced slightly better immediate retention than did training without guidance, apparently because participants were better able to learn when to initiate turns. Training with guidance-as-needed produced slightly better results than training with fixed guidance: the guidance-as-needed participants' errors were significantly smaller when guidance was removed. However, this difference quickly dissipated with more practice. We conclude that haptic guidance can benefit short-term learning of a steering-type task while also limiting performance errors during training.     

Molecular Mechanisms Associated with the Benefits of Variable Practice in Motor Learning

Abstract

Variable practice promotes a higher level of motor learning than constant practice. The glutamate receptors, n-methyl-d-aspartate (NMDA) and alfa-amino-3-hydroxy-5-methyl-4-isoxazolepropionic (AMPA), have been associated with the changes in motor cortex that occur throughout the process of motor learning. Considering that, it is possible that variable practice is more associated with the NMDA and AMPA receptors than constant practice. This study aimed ao investigating the association between the glutamate receptors, NMDA and AMPA, and constant and variable practice schedules. Seventy-eight male mice practiced the rotarod task in a constant or variable scheduling, in two consecutive days (acquisition phase). Learning tests were performed 24?h and 10?days after the end of the acquisition phase. Variable practice was more associated with the NMDA receptor and had a greater AMPA receptor expression than constant practice. The results suggest that the benefits of variable practice are result of both the greater dependency on the NMDA receptor and the greater AMPA receptor expression.     

Examining the Preferred Self-Controlled KR Schedules of Learners and Peers During Motor Skill Learning

In many practical situations, learners are provided with feedback in the form of knowledge of results (KR) by a peer. However, when peers provide KR is currently unknown. When given the opportunity to request KR in a self-controlled manner, some participants have reported a preference for requesting KR after good performances. Alternatively, peers may provide KR in a different fashion. Subsequently, a discrepancy between the learner's desire to receive KR and when a peer provides KR may arise. In our study, peer- and self-controlled KR schedules were compared. Participants were peers who controlled KR (PC; 8), learners with peers (P-L; 8), or learners with self-control (SC; 8). Participants in the two learning groups (P-L and SC groups) completed a serial-timing task with a goal time of 2500 ms. Absolute error data on KR and no-KR trials along with self-reports indicate that participants with self-control preferred KR after good trials and peers preferred to provide KR after both good and bad trials equally. Results from the delayed retention test indicated that peer-controlled learners were more consistent (i.e., in terms of variable error) than the self-control group.     

Transfer of Work Decrement in Motor Learning

Two experiments tested the hypothesis that the decremental effects of massed practice are due to the development of a negative drive (Hull’s I_r). The results indicated that the decremental effects of massed practice on either the pursuit rotor or the two-hand coordinator do not transfer to depress performance or reminiscence on the other task. The results did not support Hull’s drive interpretation but were explained by theories attributing decrement to a decreased level of arousal.     

效应器在动作序列学习中的作用机制探析

动作序列学习是动作技能学习的重要组成部分,其中大部分动作序列学习都有效应器参与。目前有关效应器在动作序列学习中的作用机制存在两种观点：一是依存于效应器的观点,即动作序列技能的获得依附于具体的效应器,不可向其他效应器迁移,其学习的本质是建立反应或肌肉间的联结。二是独立于效应器的观点,即动作序列技能的获得并不依存于具体效应器,某个效应器获得的技能可以向其他效应器迁移,其学习的本质是建立抽象的刺激表征联结。效应器作用机制随练习程度、意识状态及其他条件的不同而有所变化。     

The Relationship Between Balance Confidence and Cognitive Motor Interference in Individuals With Multiple Sclerosis

The authors examined and compared the development of oral and manual force control in preschool-aged children. In all, 50 typically developing children (aged 3-5 years) performed maximal strength tasks and submaximal visually guided tasks using tongue elevation, power, and precision grips. Dependent measures included strength, rate of force rise, initial force overshoot, force variability, and rate of force release. The authors performed age- and performance-related analyses. Results revealed similar changes for tongue, fingers, and hands across age- and performance-related measures for strength, initial force overshoot, and rate of force release. There were no significant changes in rate of force rise with increasing age. Force variability measures showed effector-specific changes with decreases across age- and performance-related measures for the hands and fingers but not for the tongue. Changes common across effector systems likely reflect biological development coupled with cognitive-strategic development. Effector-specific changes in force variability likely reflect experience gained through functional tasks influencing biological and cognitive-strategic development. Lack of change in force variability of the tongue suggests that fine control of the tongue is activity specific; thus, nonfunctional tasks are not likely to be sensitive to experience-related biological development.     

外显知识对运动技能内隐学习的影响

总结了近年来关于外显知识对运动技能内隐学习影响的研究。提出外显知识对内隐学习存在影响,但其作用的大小及其性质取决于外显知识的呈现时间、内容、内隐规则的可觉察程度、认知负荷以及压力等因素。提供外显知识既可能有利于任务的完成,也可能激发与任务规则无关的注意过程,阻碍内隐学习。外显知识可影响行为,却不一定能被有意识地提取。外显知识对学习者的认知过程和动作模式均会产生影响。     

Learning,Motor Skill,and Long-Range Correlations

Long-range correlations have been evidenced in a number of experiments, generally using overlearned and overpracticed tasks. The authors hypothesized that long-range correlation could represent the byproduct of learning. They analyzed the series of periods produced by a group of expert and a group of novices during prolonged trials on a ski simulator. Results showed a very low variability in expert's series, as compared to novices. Fractal analyses showed that fluctuations were significantly more structured and correlated in experts. These results suggest that learning could be conceived as the progressive installation of complexity in the system.     

Dyad Practice Impacts Self-Directed Practice Behaviors and Motor Learning Outcomes in a Contextual Interference Paradigm

We studied dyad practice to determine whether and how alternating practice blocks with a partner impacts self-directed practice scheduling, learning, and perceptions of practice. Participants were assigned to be Partner 1 (P1) or 2 (P2). P1s had a blocked, random, or self-directed schedule, while all P2s self-directed practice of 3, differently-timed keystroke-sequences. P2s showed both own error-dependent practice (switching sequences following better performance) and partner-dependent practice, with the partner's schedule impacting sequence selection and switching frequency. A partner's schedule also impacted learning. Random practice resulted in better timing accuracy than blocked practice for both partners in an immediate and delayed retention test. These data give evidence that self-directed practice behaviors and learning outcomes are modulated by a partner's practice schedule.     

Dealing with Possible Baseline Inequalities Between Experimental Groups – The Case of Motor Learning

Abstract

One important concept of experimental design is the random assignment of participants to experimental groups. This randomization process is used to prevent selection bias, as well as to provide a strong basis for a cause-and-effect relationship between the independent variable/s and the dependent variable/s. In small sample sizes, simple randomization may not provide equal groups at baseline for one or more of the variables, and therefore more restricted types of randomization, such as the stratified permuted-block randomization, can be used. A code was written to calculate the probability that simple randomization will not lead to equality between groups at baseline, and then an example of stratified permuted-block randomization was examined. The findings suggest that for certain variables that are commonly measured in experiments in motor learning, there is a relatively high probability that groups will not be equal at baseline after simple randomization. This observation reflects the small sample sizes usually found in the literature on motor learning. However, stratified permuted-block randomization does lead to greater equality among groups. Implications for researchers are discussed, and a flowchart is proposed that will allow researchers to decide whether to use simple or stratified randomization.     

The Effects of Brain Lateralization on Motor Control and Adaptation

ABSTRACT

Lateralization of mechanisms mediating functions such as language and perception is widely accepted as a fundamental feature of neural organization. Recent research has revealed that a similar organization exists for the control of motor actions, in that each brain hemisphere contributes unique control mechanisms to the movements of each arm. The authors review present research that addresses the nature of the control mechanisms that are lateralized to each hemisphere and how they impact motor adaptation and learning. In general, the studies suggest an enhanced role for the left hemisphere during adaptation, and the learning of new sequences and skills. The authors suggest that this specialization emerges from a left hemisphere specialization for predictive control—the ability to effectively plan and coordinate motor actions, possibly by optimizing certain cost functions. In contrast, right hemisphere circuits appear to be important for updating ongoing actions and stopping at a goal position, through modulation of sensorimotor stabilization mechanisms such as reflexes. The authors also propose that each brain hemisphere contributes its mechanism to the control of both arms. They also discuss the potential advantages of such a lateralized control system.     

Using Reinforcement Learning to Examine Dynamic Attention Allocation During Reading

A fundamental question in reading research concerns whether attention is allocated strictly serially, supporting lexical processing of one word at a time, or in parallel, supporting concurrent lexical processing of two or more words (Reichle, Liversedge, Pollatsek, & Rayner, 2009). The origins of this debate are reviewed. We then report three simulations to address this question using artificial reading agents (Liu & Reichle, 2010; Reichle & Laurent, 2006) that learn to dynamically allocate attention to 1–4 words to “read” as efficiently as possible. These simulation results indicate that the agents strongly preferred serial word processing, although they occasionally attended to more than one word concurrently. The reason for this preference is discussed, along with implications for the debate about how humans allocate attention during reading.     

Attention to Visual Feedback in Motor Learning

Visual guidance and movement to a stop were used to train subjects to make a simple movement without experiencing error in practice. Movement to a stop led to test performance as accurate as that after training with KR, but visual guidance did not. If a continuous visual cue as well as a stop were present during practice, subjects also performed less accurately, although they did not need to attend to the visual cue. All types of training were better than no training at all. Results are discussed in terms of the role of visual feedback in the development and assessment of programs for movement.     

The Effect of Fatigue on Learning and Performance of a Gross Motor Task

40 college males were sequentially assigned to 1 of 2 groups to examine the effects of induced physical fatigue upon the performance and learning of a gross motor task, the stabilometer. All Ss were given 32 practice trials over 3 practice sessions, with 48 hr. rest interpolated between sessions. Trials 1 and 2 were performed under control conditions (no fatigue) for both groups. The Experimental Group was then required to perform under conditions of physical fatigue during Trials 3-26. Trials 27-32 (Session 3) were performed under control conditions. The condition of fatigue was achieved on Trials 3-26 by having Ss pedal a bicycle ergometer until a heart rate of 180 beats/min was attained prior to each trial. The Control Group cancelled vowels. The results indicated that physical fatigue was detrimental to the performance and learning of the Experimental Group.     

The Neural Basis of Motor-Skill Learning

Recent work indicates that motor-skill learning is supported by four processes: a strategic process that selects new goals of what to change in the environment, a perceptual-motor integration process that adjusts to new relationships between environmental stimuli and the appropriate motor response, a sequencing process that learns sequences of motor acts, and a dynamic process that learns new patterns of muscle activations. These four processes can operate in one of two modes: an unconscious mode, in which one is aware only of the goal of the movement, or a conscious mode, in which one consciously controls detailed aspects of the movement. This article provides an overview of these four processes and two modes, and describes their neural bases.     

Motor Programming Within a Sequence of Responses

Choice reaction time prior to a motor response has been shown to depend on the nature of the response to be made. This effect is assumed to represent variations in programming time. However, as the length of a response sequence increases this effect becomes smaller, suggesting that some response programming is postponed until after the response sequence is initiated. The present experiment studied this assumed programming within a sequence of responses. For sequences comprised of two Morse Code responses (e.g. dit-dah) the initial reaction time was independent of the terminal response. However, programming of this terminal response was apparent as a lengthening of the duration of intervals within the response when the terminal response was dah rather than dit. When programming of parts of the sequence is postponed beyond the reaction time interval, the programming occurs later and influences the timing of the sequence of responses.     

Influence of Motor Cortex Stimulation During Motor Training on Neuroplasticity as a Potential Therapeutic Intervention

Rehabilitation options to promote neuroplasticity may be enhanced when patients are engaged in motor practice during repetitive transcranial magnetic stimulation (rTMS). Twelve participants completed 3 separate sessions: motor practice, motor practice with rTMS, and rTMS only: motor practice consisted of 30 isometric contractions and subthreshold rTMS was 30, 3-s trains at 10 Hz. Assessments included the Box and Block Test (BBT), force steadiness (10% of the maximum voluntary contraction), and TMS (cortical excitability, intracortical inhibition, and intracortical facilitation). Participants significantly increased BBT scores following the combined condition. Force steadiness improved after all 3 conditions (p < .05). TMS outcomes depended on intervention condition with significant increases in facilitation following the motor practice plus rTMS condition. All interventions influenced motor control, yet are likely modulated differently when combining motor practice plus rTMS. These results help guide the clinical utility of rTMS as an intervention to influence motor control.     

Engaging Environments Enhance Motor Skill Learning in a Computer Gaming Task

Engagement during practice can motivate a learner to practice more, hence having indirect effects on learning through increased practice. However, it is not known whether engagement can also have a direct effect on learning when the amount of practice is held constant. To address this question, 40 participants played a video game that contained an embedded repeated sequence component, under either highly engaging conditions (the game group) or mechanically identical but less engaging conditions (the sterile group). The game environment facilitated retention over a 1-week interval. Specifically, the game group improved in both speed and accuracy for random and repeated trials, suggesting a general motor-related improvement, rather than a specific influence of engagement on implicit sequence learning. These data provide initial evidence that increased engagement during practice has a direct effect on generalized learning, improving retention and transfer of a complex motor skill.