Role In Motor Learning Research Articles

The role of motor learning in spatial adaptation near a tool.

Some visual-tactile (bimodal) cells have visual receptive fields (vRFs) that overlap and extend moderately beyond the skin of the hand. Neurophysiological evidence suggests, however, that a vRF will grow to encompass a hand-held tool following active tool use but not after passive holding. Why does active tool use, and not passive holding, lead to spatial adaptation near a tool? We asked whether spatial adaptation could be the result of motor or visual experience with the tool, and we distinguished between these alternatives by isolating motor from visual experience with the tool. Participants learned to use a novel, weighted tool. The active training group received both motor and visual experience with the tool, the passive training group received visual experience with the tool, but no motor experience, and finally, a no-training control group received neither visual nor motor experience using the tool. After training, we used a cueing paradigm to measure how quickly participants detected targets, varying whether the tool was placed near or far from the target display. Only the active training group detected targets more quickly when the tool was placed near, rather than far, from the target display. This effect of tool location was not present for either the passive-training or control groups. These results suggest that motor learning influences how visual space around the tool is represented.

Visuomotor Adaptation and Proprioceptive Recalibration

ABSTRACT Motor learning, in particular motor adaptation, is driven by information from multiple senses. For example, when arm control is faulty, vision, touch, and proprioception can all report on the arm's movements and help guide the adjustments necessary for correcting motor error. In recent years we have learned a lot about how the brain integrates information from multiple senses for the purpose of perception. However, less is known about how multisensory data guide motor learning. Most models of, and studies on, motor learning focus almost exclusively on the ensuing changes in motor performance without exploring the implications on sensory plasticity. Nor do they consider how discrepancies in sensory information (e.g., vision and proprioception) related to hand position may affect motor learning. Here, we discuss research from our lab and others that shows how motor learning paradigms affect proprioceptive estimates of hand position, and how even the mere discrepancy between visual and proprioceptive feedback can affect learning and plasticity. Our results suggest that sensorimotor learning mechanisms do not exclusively rely on motor plasticity and motor memory, and that sensory plasticity, in particular proprioceptive recalibration, plays a unique and important role in motor learning.

The role of motor learning and neuroplasticity in designing rehabilitation approaches for musculoskeletal pain disorders

The extent of cortical neuroplastic changes has been shown to be a key neurophysiological feature that correlates with the level of functional recovery. Therefore, rehabilitation efforts that attempt to maximize cortical reorganization provide the greatest potential for rehabilitation success. This paper reviews the evidence of cortical neuroplastic changes that have been shown to occur in association with experimental or chronic pain disorders. Further, the promising role of novel motor-skill training is discussed in order to best direct the clinician to optimize rehabilitation strategies for patients with musculoskeletal pain disorders.

Distinct consolidation outcomes in a visuomotor adaptation task: Off-line leaning and persistent after-effect

Consolidation is a time-dependent process responsible for the storage of information in long-term memory. As such, it plays a crucial role in motor learning. In two experiments, we sought to determine whether one’s performance influences the outcome of the consolidation process. We used a visuomotor adaptation task in which the cursor moved by the participants was rotated 30° clockwise. Thus, participants had to learn a new internal model to compensate for the rotation of the visual feedback. The results indicated that when participants showed good adaptation in the first session, consolidation resulted in a persistent after-effect in a no-rotation transfer test; they had difficulty returning to their normal no-rotation internal model. However, when participants showed poor adaptation in the first session, consolidation led to significant off-line learning (between sessions improvement) but labile after-effects. These observations suggest that distinct consolidation outcomes (off-line learning and persistent after-effect) may occur depending on the learner’s initial performance.

Differences in motor learning success are associated with differences in M1 excitability

Primary motor cortex (M1) plays a role in motor learning, although the exact nature of that involvement remains unclear. The present study examined the relationship between motor learning and cortical plasticity by manipulating augmented feedback during motor training. Two groups of 10 participants performed a wrist flexion–extension waveform-tracking task with either concurrent and terminal augmented feedback after every trial (100% FB) or only terminal feedback after every alternate trial (50% FB). Single- and paired-pulse transcranial magnetic stimulation (TMS) was used to assess cortical excitability short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) before, after, and 24 h following (retention) motor training. The 50% FB group performed better at retention than the 100% FB group, indicative of enhanced learning due to reduced FB scheduling. Cortical excitability did not change during acquisition for either group, however, the 50% FB group had elevated M1 excitability at retention, suggesting M1 involvement in the consolidation of learning. Reduced SICI following practice suggests a reduction of intracortical inhibition during motor skill acquisition. ICF was unchanged. It is concluded that the nature of M1 modulation associated with the acquisition and retention of a novel motor skill appears to vary with the nature and complexity of task requirements.

The role of motor learning in stuttering adaptation: Repeated versus novel utterances in a practice–retention paradigm

Most individuals who stutter become more fluent during repeated oral readings of the same material. This adaptation effect may reflect motor learning associated with repeated practice of speech motor sequences. We tested this hypothesis with a paradigm that used two integrated approaches to identify the role of motor learning in stuttering adaptation: to distinguish practice effects from situation effects, the texts contained both repeated and novel sentences; to differentiate learning effects from temporary performance effects, stuttering frequency was determined for both the initial adaptation readings and retention tests after 2 h and 24 h. Average group data for 7 stuttering individuals who showed adaptation indicate that (a) both repeated and novel sentences resulted in decreased stuttering frequency across five readings in the initial session, but the decrease was larger for repeated than for novel sentences; (b) after 2 h, stuttering frequency for both types of sentences was again similar, but with additional readings the repeated sentences once again showed larger improvements in fluency; (c) after 24 h, prior fluency improvements for the novel sentences had dissipated whereas retention was observed for the repeated sentences. These findings – supporting the hypothesis that motor learning plays a role in stuttering adaptation – were representative for most, but not all, individual subjects. Subjects whose data did not follow the group trend and showed comparable retention for repeated and novel sentences may adapt primarily on the basis of non-motor mechanisms. Alternatively, those subjects may in fact show more substantial generalization of motor learning effects to previously unpracticed movement sequences. Educational objectives: After reading this article, the reader will be able to: (1) summarize previous research on stuttering adaptation; (2) define motor learning and describe its essential characteristics; and (3) discuss why the results from this and previous studies suggest that stuttering adaptation may be a result of motor learning.

IMITATE: An intensive computer-based treatment for aphasia based on action observation and imitation

Background: Neurophysiological evidence from primates has demonstrated the presence of mirror neurons, with visual and motor properties, that discharge both when an action is performed and during observation of the same action. A similar system for observation–execution matching may also exist in humans. We postulate that behavioural stimulation of this parietal-frontal system may play an important role in motor learning for speech and thereby aid language recovery after stroke. Aims: The purpose of this article is to describe the development of IMITATE, a computer-assisted system for aphasia therapy based on action observation and imitation. We also describe briefly the randomised controlled clinical trial that is currently underway to evaluate its efficacy and mechanism of action. Methods & Procedures: IMITATE therapy consists of silent observation of audio-visually presented words and phrases spoken aloud by six different speakers, followed by a period during which the participant orally repeats the stimuli. We describe the rationale for the therapeutic features, stimulus selection, and delineation of treatment levels. The clinical trial is a randomised single blind controlled trial in which participants receive two pre-treatment baseline assessments, 6 weeks apart, followed by either IMITATE or a control therapy. Both treatments are provided intensively (90 minutes per day). Treatment is followed by a post-treatment assessment, and a 6-week follow-up assessment. Outcomes & Results: Thus far, five participants have completed IMITATE. We expect the results of the randomised controlled trial to be available by late 2010. Conclusions: IMITATE is a novel computer-assisted treatment for aphasia that is supported by theoretical rationales and previous human and primate data from neurobiology. The treatment is feasible, and preliminary behavioural data are emerging. However, the results will not be known until the clinical trial data are available to evaluate fully the efficacy of IMITATE and to inform theoretically about the mechanism of action and the role of a human mirror system in aphasia treatment.

Dynamic Associations in the Cerebellar–Motoneuron Network during Motor Learning

We assessed here true causal directionalities in cerebellar-motoneuron (MN) network associations during the classical conditioning of eyelid responses. For this, the firing activities of identified facial MNs and cerebellar interpositus (IP) nucleus neurons were recorded during the acquisition of this type of associative learning in alert behaving cats. Simultaneously, the eyelid conditioned response (CR) and the EMG activity of the orbicularis oculi (OO) muscle were recorded. Nonlinear association analysis and time-dependent causality method allowed us to determine the asymmetry, time delays, direction in coupling, and functional interdependences between neuronal recordings and learned motor responses. We concluded that the functional nonlinear association between the IP neurons and OO muscle activities was bidirectional and asymmetric, and the time delays in the two directions of coupling always lagged the start of the CR. Additionally, the strength of coupling depended inversely on the level of expression of eyeblink CRs, whereas causal inferences were significantly dependent on the phase information status. In contrast, the functional association between OO MNs and OO muscle activities was unidirectional and quasisymmetric, and the time delays in coupling were always of opposed signs. Moreover, information transfer in cerebellar-MN network associations during the learning process required a "driving common source" that induced the mere "modulating coupling" of the IP nucleus with the final common pathway for the eyelid motor system. Thus, it can be proposed that the cerebellum is always looking back and reevaluating its own function, using the information acquired in the process, to play a modulating-reinforcing role in motor learning.

Experience-Dependent Plasticity of Cerebellar Vermis in Basketball Players

The cerebellum is involved in the learning and retention of motor skills. Using animal and human models, a number of studies have shown that long-term motor skill training induces structural and functional plasticity in the cerebellum. The aim of this study was to investigate whether macroscopic alteration in the volume of cerebellum occurs in basketball players who had learned complex motor skills and practiced them intensively for a long time. Three-dimensional magnetic resonance imaging volumetry was performed in basketball players (n = 19) and healthy controls (n = 20), and the volumes of cerebellum and vermian lobules were compared between two groups. Although there was no macroscopic plasticity detected in the cerebellum as a whole, detailed parcellation of cerebellum revealed morphological enlargement in the vermian lobules VI-VII (declive, folium, and tuber) of basketball players (P < 0.0166), which might then be interpreted as evidence for plasticity. This finding suggests that the extensive practice and performance of sports-related motor skills activate structural plasticity of vermian lobules in human cerebellum and suggests that vermian VI-VII plays an important role in motor learning.

A Biological basis for Aphasia Treatment: Mirror Neurons and Observation-Execution Matching

Aphasia is caused by damage to the human brain, and recovery requires adaptive changes to the structure and function of this organ. Despite this obvious fact, biology plays little role in rehabilitation of persons with aphasia. Although linguistics can be useful in characterizing aphasic behaviour, thus providing a way to assess the effects of therapy, there is little evidence to suggest that linguistic models of impairment can themselves form the basis of effective therapy. Biological evidence from primates has demonstrated the presence of neurons that have both visual and motor properties, which discharge both when an action is performed and during observation of the same action. We postulate that behavioural stimulation of this system may play an important role in motor learning for speech and thereby aid language recovery after stroke. IMITATE is a computer-assisted system for aphasia therapy based on action observation and imitation. IMITATE therapy consists of silent observation of audio-visually presented words and phrases spoken aloud by six different speakers, followed by a period during which the participant orally repeats the stimuli. The treatment approach is motivated by the physiology of the brain in an effort to change specific anatomical connections, and the treatment method draws strongly from psychological evidence on learning. IMITATE is currently being used in a clinical trial, and results will not be known until these data are available in late 2010. At that juncture, it will be possible to evaluate fully the efficacy of IMITATE and to inform theoretically about the mechanism of action and the role of a human mirror system in aphasia treatment.

The Cerebellum Updates Predictions about the Visual Consequences of One's Behavior

Each action has sensory consequences that need to be distinguished from sensations arising from the environment. This is accomplished by the comparing of internal predictions about these consequences with the actual afference, thereby isolating the afferent component that is self-produced. Because the sensory consequences of actions vary as a result of changes of the effector's efficacy, internal predictions need to be updated continuously and on a short time scale. Here, we tested the hypothesis that this updating of predictions about the sensory consequences of actions is mediated by the cerebellum, a notion that parallels the cerebellum's role in motor learning. Patients with cerebellar lesions and their matched controls were equally able to detect experimental modifications of visual feedback about their pointing movements. When such feedback was constantly rotated, both groups instantly attributed the visual feedback to their own actions. However, in interleaved trials without actual feedback, patients did no longer account for this feedback rotation--neither perceptually nor with respect to motor performance. Both deficits can be explained by an impaired updating of internal predictions about the sensory consequences of actions caused by cerebellar pathology. Thus, the cerebellum guarantees both precise performance and veridical perceptual interpretation of actions.

Transient Spine Expansion and Learning-Induced Plasticity in Layer 1 Primary Motor Cortex

Experience-dependent regulation of synaptic strength in the horizontal connections in layer 1 of the primary motor cortex is likely to play an important role in motor learning. Dendritic spines, the primary sites of excitatory synapses in the brain, are known to change shape in response to various experimental stimuli. We used a rat motor learning model to examine connection strength via field recordings in slices and confocal imaging of labeled spines to explore changes induced solely by learning a simple motor task. We report that motor learning increases response size, while transiently occluding long-term potentiation (LTP) and increasing spine width in layer 1. This demonstrates learning-induced changes in behavior, synaptic responses, and structure in the same animal, suggesting that an LTP-like process in the motor cortex mediates the initial learning of a skilled task.

Cognitive Demands of Error Processing

This study used a dual-task methodology to assess attention demands associated with error processing during an anticipation-timing task. A difference was predicted in attention demands during feedback on trials with correct responses and errors. This was addressed by requiring participants to respond to a probe reaction-time stimulus after augmented feedback presentation. 16 participants (8 men, 8 women) completed two phases, the reaction time task only and the anticipation-timing task with the probe RT task. False feedback indicating error and a financial reward manipulation were used to increase relevance of errors. Data supported the hypothesis that error processing is associated with higher cognitive demands than processing feedback denoting a correct response. Individuals responded with quicker probe reaction times during presentation of feedback on correct trials than on error trials. These results are discussed with respect to the cognitive processes which might occur during error processing and their role in motor learning.

Cerebellum and motor learning

Introduction: Besides its well-established importance for motor coordination, the cerebellum plays a major role in motor learning including learning of skills and simple classical conditioning of skeletal muscle responses. The form of cerebellum-dependent motor learning, which has been examined in greatest detail, is classical conditioning of eyeblink responses. The aim of the talk is to give an update of findings in humans.

Neuronal Activity in the Cingulate Motor Areas During Adaptation to a New Dynamic Environment

Neurons in the cingulate motor areas (CMA) have been shown to be involved in many aspects of sensorimotor behavior, although their role in motor learning has received less attention. Here, we recorded single-cell activity in the CMA of monkeys while they adapted reaching movements to different dynamic environments. Specifically, we analyzed CMA activity during normal reaching to visual targets and during reaching in the presence of an applied velocity-dependent force field. We found that the cingulate neuronal activity was modulated during each phase of the task and in response to the applied forces. The neurons' involvement in the visuomotor transformation was influenced by their rostrocaudal location in the cingulate sulcus. Rostral CMA (CMAr) neurons were modulated by the visual instruction to a greater extent than caudal CMA (CMAc) neurons. In contrast, CMAc neurons had a greater amount of phasic and directionally tuned activity during movement than CMAr cells. Furthermore, compared with CMAr cells, the movement-related activity of CMAc cells was more frequently modulated by the applied force fields. The magnitude of the force-field-related neuronal response scaled with the amount of perturbation in each reaching direction. However, contrary to previous results from other cortical motor areas, force-field adaptation was not correlated with a shift in directional tuning of the CMA population. Based on these results, we suggest that although the CMA is clearly sensitive to applied forces, it is less involved in generating anticipatory responses to predictable forces than other cortical motor areas.

Non-primary motor areas in the human frontal lobe are connected directly to hand muscles

Structural studies in primates have shown that, in addition to the primary motor cortex (M1), premotor areas are a source of corticospinal tracts. The function of these putative corticospinal neuronal tracts in humans is still unclear. We found frontal non-primary motor areas (NPMAs), which react to targeted non-invasive magnetic pulses and activate peripheral muscles as fast as or even faster than those in M1. Hand muscle movements were observed in all our subjects about 20 ms after transcranial stimulation of the superior frontal gyrus (Brodmann areas 6 and 8). Stimulation of NPMA could activate both proximal and distal upper limb muscles with the same delay as a stimulation of the M1, indicating converging motor representations with direct functional connections to the hand. We suggest that these non-primary cortical motor representations provide additional capacity for the fast execution of movements. Such a capacity may play a role in motor learning and in recovery from motor deficits.

Model-free characterization of brain functional networks for motor sequence learning using fMRI

Neuroimaging experiments have identified several brain regions that appear to play roles in motor learning. Here we apply a novel multivariate analytical approach to explore the dynamic interactions of brain activation regions as spatio-temporally coherent functional networks. We acquired BOLD fMRI signal during explicit motor sequence learning task to characterize the adaptive functional changes in the early phase of motor learning. Subjects practiced a 10-digit, visually cued, fixed motor sequence during 15 consecutive 30 s practice blocks interleaved with similarly cued random sequence blocks. Tensor Independent Component Analysis (TICA) decomposed the data into statistically independent spatio-temporal processes. Two components were identified that represented task-related activations. The first component showed decreasing activity of a fronto-parieto-cerebellar network during task conditions. The other exclusively related to sequence learning blocks showed activation in a network including the posterior parietal and premotor cortices. Variation in expression of this component across individual subjects correlated with differences in behavior. Relative deactivations also were found in patterns similar to those described previously as “resting state” networks. Some of these deactivation components also showed task- and time-related modulations and were related to the behavioral improvement. The spatio-temporal coherence within these networks suggests that their elements are functionally integrated. Their anatomical plausibility and correlation with behavioral measures also suggest that this approach allows characterization of the interactions of functional networks relevant to the task. Particular value for multi-variant, model-free methods such as TICA lies in the potential for generating hypotheses regarding functional anatomical networks underlying specific behaviors.

What does the cerebellum really do?

Summary The cerebellum is a large part of the brain in all vertebrates. In humans it constitutes about ten percent of the total brain weight, but the small granule cells of the cerebellar cortex are densely packed so that the cerebellum contains more neurons than all of the rest of the brain. Although it has a uniform cellular structure in mammals and birds, there is great variability in the relative size of its parts. In mammals the cerebellum can be roughly divided into three parasagittal divisions; a midline vermis (Latin: a worm) and two lateral hemispheres. The hemispheres are large in the higher primates and they are very large in the human brain. Because the cerebellar hemispheres are particularly large in humans and the higher primates, from time to time claims have been made that in addition to its role in motor control, the cerebellum is important for cognitive functions, such as learning, attention, and language. Here I review some of the evidence for and against that claim.

Facilitation of Saccadic Eye Movements by Postsaccadic Electrical Stimulation in the Primate Caudate

Sensorimotor experience followed by positive feedback leads to motor learning. Although the striatum, an input channel of the basal ganglia, has been implicated to play a key role in motor learning, little is known about how reward information modulates the neuronal processes in the striatum that causes behavioral changes. Here, we report that direct manipulation of the neuronal signal in the primate caudate yields behavioral changes comparable with those induced by natural reward. Electrical stimulation in the oculomotor region of the caudate immediately after saccades to a fixed direction led to selective facilitation of saccades in that direction. The facilitation remained even after stimulation was stopped, indicating a plastic change. These effects were observed when stimulation was applied after, not before, saccades. We propose that the caudate plays a causal role in behavioral changes by integrating selective sensorimotor and reward information in a temporally specific manner.

Molecular Markers of Neuronal Progenitors in the Embryonic Cerebellar Anlage

The cerebellum, like the cerebrum, includes a nuclear structure and an overlying cortical structure. Experiments in the past decade have expanded knowledge beyond the traditional function of the cerebellum to include critical roles in motor learning and memory and sensory discrimination. The initial steps in cerebellar development depend on inductive signaling involving FGF and Wnt proteins produced at the mesencephalic/metencephalic boundary. To address the issue of how individual cerebellar cell fates within the cerebellar territory are specified, we examined the expression of transcription factors, including mammalian homologues of LIM homeodomain-containing proteins, basic helix-loop-helix proteins, and three amino acid loop-containing proteins. The results of these studies show that combinatorial codes of transcription factors define precursors of the cerebellar nuclei, and both Purkinje cells and granule neurons of the cerebellar cortex. Examination of gene expression patterns in several hundred lines of Egfp-BAC (bacterial artificial chromosome) transgenic mice in the GENSAT Project revealed numerous genes with restricted expression in cerebellar progenitor populations, including genes specific for cerebellar nuclear precursors and Purkinje cell precursors. In addition, we identified patterns of gene expression that link granule and Purkinje cells to their precerebellar nuclei. These results identify molecular pathways that offer new insights on the development of the nuclear and cortical structures of the cerebellum, as well as components of the cerebellar circuitry.