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Defective motor learning in ideomotor apraxia.

Liepmann suggested that the left hemisphere contained the engrams for motor sequences. Other investigators have suggested that ideomotor apraxia may be caused by either a destruction of these engrams or a disconnection of these engrams from motor systems in the nondominant hemisphere. If these hypotheses are correct, then ideomotor apraxics should not only show a defect on previously learned motor tasks but also a defect in new motor learning. Nine right-handed, hemiparetic, aphasic apraxics were given six trials on a rotary pursuit meter. Eight right-handed hemiparetic, aphasic, nonaprixic patients served as controls. All subjects were instructed to use their left (nonparetic) hand. The performance of the control group on the sixth trial was significantly better than that on the first trial, showing a distinct learning effect. In the apraxic group, however, there was no significant difference between the first and sixth trial, suggesting a defect in motor learning. This defect appeared to be caused by a combined defect of both acquisition and retention.

Aphasia↗

Adaptation motor learning of arm movements in patients with cerebellar disease.

OBJECTIVE: To design a test of motor learning using arm movements in normal subjects and patients with cerebellar disease. METHODS: Elbow angle was continuously displayed as a cursor (a dot) on a computer screen, and subjects made ballistic elbow flexion and extension movements to try to move the cursor between two targets on the screen. The relation between the arm movement and its visual feedback was changed, and the subjects reacted by adapting the amplitude of their movements in subsequent trials. RESULTS: The consecutive errors showed exponential learning curves during adaptation, which were quantified by their steepness. Ten patients with isolated cerebellar or olivopontocerebellar degeneration had less steep learning curves than normal subjects, indicating a failure of adaptation motor learning in cerebellar disease. The results show that this test may be useful for the analysis of motor learning.

Adaptation, Physiological↗

Motor learning following unilateral stroke.

OBJECTIVE: To determine the effect of different motor learning schedules on stroke patients' rate of acquisition and retention of a functional movement sequence using the hemiparetic upper limb. DESIGN: Randomized controlled group study using a retention design with two retention trials. SETTING: Outpatient neurorehabilitation clinic. PATIENTS: Twenty-four patients with chronic hemiparesis secondary to a single unilateral cerebral stroke without evidence of severe cognitive or language impairment. MAIN OUTCOME MEASURE: The primary hypothesis was that hemiparetic motor learning that occurred under conditions of contextual interference (ie, random practice) would be retained better than learning that occurred under conditions of repetitive drill (blocked practice). RESULTS: A significant difference was found among the three groups (ie, random-practice, blocked-practice, control) on both the first retention measure (chi 2 = 13.50, p < .01) and the second retention measure (chi 2 = 12.59, p < .01). More importantly, a significant difference was found between the random-practice and blocked-practice groups on both the first retention measure (U = 68.5, p < .01) and the second retention measure (U = 62.0, p = .05). CONCLUSIONS: Findings provide empirical evidence to support the contention that random practice is more effective than blocked practice, with respect to retention over time, when hemiparetic stroke patients attempt to learn functional motor skills.

Adult↗

Motor learning in Ts65Dn mice, a model for Down syndrome.

Ts65Dn mice are a genetic model for Down syndrome. Both individuals with Down syndrome and Ts65Dn mice have reduced cerebellar volumes and the cerebellum is involved in motor learning. Conflicting results have been reported on the motor learning abilities of Ts65Dn mice, which may be related to procedural differences between the motor learning tasks used in different laboratories and/or variability in phenotype because of the segregating background on which the mice are maintained. In this study, we examined learning in three types of motor tasks (peg running, accelerating rotorod, and rotating rod) which were initially easy for mice and gradually increased in difficulty. Ts65Dn mice learned the peg running task as well as controls, and learned the accelerating rotorod and rotating rod tasks as well as, and even better than, controls. These data indicate that Ts65Dn mice are not impaired in motor learning.

Animals↗

Motor learning.

Bilateral damage of the medial temporal lobe system prevents the formation of new declarative memories but leaves intact knowledge that was acquired before damage. For motor learning, no structure has been identified that plays a comparable role for the consolidation of motor memories. The deficits of motor learning are focal and show a similar allocation to the various sensorimotor subsystems, as do the corresponding non-mnemonic functions. The involvement of sensorimotor circuitries changes during motor learning so that association areas are preferentially activated in the early stages, and cerebello- and striato-motor-cortical loops are preferentially activated in the late stages of motor learning. Recent neuroanatomical and neurophysiological findings on the effects of brain lesions in human and non-human primates are discussed.

Animals↗

MAP2 and synaptophysin protein expression following motor learning suggests dynamic regulation and distinct alterations coinciding with synaptogenesis.

Learning a new motor skill can induce neuronal plasticity in rats. Within motor cortex, learning-induced plasticity includes dendritic reorganization, synaptogenesis, and changes in synapse morphology. Behavioral studies have demonstrated that learning requires protein synthesis. It is likely that some of the proteins synthesized during learning are involved in, or the result of, learning-induced structural plasticity. We predicted the expression of proteins involved in neural plasticity would be altered in a learning dependent fashion. Long-Evans rats were trained on a series of motor tasks that varied in complexity, so that the effects of activity could be teased apart from the effects of learning. The motor cortices were examined for MAP2 and synaptophysin protein using Western blotting and immunohistochemistry. Western blotting revealed that expression of MAP2 was not detectably influenced by learning, whereas synaptophysin expression increased on day 1, 3, and 5 of complex motor skill learning. Expression of MAP2 does not seem to indicate difficulty of task or duration of training time, whereas increases in synaptophysin expression, which appear diffusely across the cortex, seem to be correlated with the first 5 days of motor skill learning. Similar findings with GAP-43 suggest the change in synaptophysin may coincide with synapse formation. Immunohistochemistry did not reveal any localized changes in protein expression. These data indicate a difference in learning-induced expression in the mammalian brain compared to reports in the literature, which have often focused on stimulation to induce alterations in protein expression.

Adaptation, Physiological↗

Verbal actions of physiotherapists to enhance motor learning in children with DCD.

In this study, the motor teaching principles taxonomy (MTPT) was developed to investigate which teaching principles physiotherapists use to treat children with developmental coordination disorder during Neuromotor Task Training (NTT). In NTT, special attention is paid to the best ways to instruct and provide feedback. Based on motor learning theory and video observations of NTT treatments, teaching principles aimed at improving motor learning were categorised into three categories: giving instruction, providing or asking feedback, and sharing knowledge. The MTPT's reliability and validity were satisfactory. Therapists gave instructions very frequently. In addition, the principle frequency showed hardly any correlation with the children's initial motor performance level, indicating that the principles used are not related to the child's entry level.

Child↗

Application of motor learning principles in occupational therapy.

The processes underlying skill acquisition depend on the nature of the task and the stage of the learner. In addition, feedback and practice are two potent learning variables when used appropriately in the instruction of motor tasks. Occupational therapists involved in the training and retraining of motor skills can benefit from knowledge of instructional methods used by coaches and physical educators. This paper reviews commonly accepted principles of motor learning and applies these principles to occupational therapy treatment. The stage of the learner, type of task, feedback, practice, and facilitation of skill acquisition are emphasized. Specific examples of how occupational therapists can use motor learning principles in treatment are given.

Biofeedback, Psychology↗

Motor learning and occupational therapy: the organization of practice.

This article addresses implications for the practice of occupational therapy when that therapy is guided by theories of motor learning. In occupational therapy, clients must learn or relearn motor skills through the use of activities. The occupational therapist must present activities in a manner that elicits the retention and transfer of the desired skills for use in functional settings. Therefore, the therapist should strive for acquisition conditions that facilitate retention and transfer of the learned skills. The processes that underlie motor learning should guide therapy. Three major factors that affect motor learning are environmental conditions, cognitive processes, and movement organization. Examination of the clinical implications of these factors, however, results in contradictory predictions regarding optimal practice conditions for motor skills. This article explores the successful integration of these factors and its application in occupational therapy practice. It is suggested that increasing the difficulty of the learning context during practice is beneficial for retention.

Humans↗

Influence of cholinergic system on motor learning during aging in mice.

Three, 12- and 20-month-old C57Bl6 mice, reared in standard conditions or in an enriched environment, were administered subcutaneously either scopolamine hydrobromide (SIGMA), 0.6 and 1.2 mg kg(-1), or physiological saline 15 min before testing their motor skills (muscular strength, dynamic equilibrium and motor coordination) and motor learning abilities (number of trials needed to reach a learning criterion on a rotorod rotating at 27 revolutions per min). The results demonstrated a lack of correlation between motor skill scores and between motor skill and motor learning scores, suggesting that the rotorod training procedure measures motor learning and not motor skills or is insensitive to changes in motor skills. They also demonstrated that motor skills decreased with age but were insensitive to environmental rearing and to scopolamine. In contrast, the learning scores, which also decreased with age, were very sensitive to scopolamine, particularly in the oldest mice. These results are discussed according to the role of cholinergic system in motor learning during aging.

Aging↗

Probability detection mechanisms and motor learning.

The automatic detection of patterns or regularities in the environment is central to certain forms of motor learning, which are largely procedural and implicit. The rules underlying the detection and use of probabilistic information in the perceptual-motor domain are largely unknown. We conducted two experiments involving a motor learning task with direct and crossed mapping of motor responses in which probabilities were present at the stimulus set level, the response set level, and at the level of stimulus-response (S-R) mapping. We manipulated only one level at a time, while controlling for the other two. The results show that probabilities were detected only when present at the S-R mapping and motor levels, but not at the perceptual one (experiment 1), unless the perceptual features have a dimensional overlap with the S-R mapping rule (experiment 2). The effects of probability detection were mostly facilitatory at the S-R mapping, both facilitatory and inhibitory at the perceptual level, and predominantly inhibitory at the response-set level. The facilitatory effects were based on learning the absolute frequencies first and transitional probabilities later (for the S-R mapping rule) or both types of information at the same time (for perceptual level), whereas the inhibitory effects were based on learning first the transitional probabilities. Our data suggest that both absolute frequencies and transitional probabilities are used in motor learning, but in different temporal orders, according to the probabilistic properties of the environment. The results support the idea that separate neural circuits may be involved in detecting absolute frequencies as compared to transitional probabilities.

Adolescent↗

Failure of motor learning for large initial errors.

For certain complex motor tasks, humans may experience the frustration of a lack of improvement despite repeated practice. We investigate a computational basis for failure of motor learning when there is no prior information about the system to be controlled and when it is not practical to perform a thorough random exploration of the set of possible commands. In this case, if the desired movement has never yet been performed, then it may not be possible to learn the correct motor commands since there will be no appropriate training examples. We derive the mathematical basis for this phenomenon when the controller can be modeled as a linear combination of nonlinear basis functions trained using a gradient descent learning rule on the observed commands and their results. We show that there are two failure modes for which continued training examples will never lead to improvement in performance. We suggest that this may provide a model for the lack of improvement in human skills that can occur despite repeated practice of a complex task.

Computer Simulation↗

Cerebellar stroke impairs temporal but not spatial accuracy during implicit motor learning.

OBJECTIVE: Numerous studies have demonstrated cerebellar activity during implicit motor learning, but few have addressed its specific role. The purpose of this study was to determine if specific components (spatial or temporal) of an implicit motor-tracking task were affected by cerebellar stroke. METHODS: The authors studied the performance of individuals with unilateral cerebellar stroke (n = 7)and a control group (n = 10) across 3 acquisition days and at a delayed retention test as they practiced a unimanual tracking task with the contralesional upper extremity. RESULTS: After cerebellar stroke, participants demonstrated reduced tracking errors for repeating sequences compared to random sequences; however, decomposition of tracking performance into temporal and spatial components revealed persistent deficits in tracking time lag despite improved spatial accuracy. A lesion analysis showed that the dentate nucleus was the only common region affected by all cerebellar strokes. CONCLUSIONS: During implicit motor learning, the cerebellum appears to participate in the formation of predictive strategies for the timing of motor responses, rather than for the accuracy of motor execution. Because deficits were found in the contralesional upper extremity, the authors suggest that this function is not lateralized to 1 hemisphere; cerebellar output may affect the formation of an internal model for timing movements in both upper extremities.

Adult↗

[Anticipatory postural adjustment in bimanual unloading: role of the motor cortex in motor learning].

The role of the motor cortex was investigated during learning unusual postural adjustment. Healthy subjects held their right (postural) forearm in a horizontal position while supporting a 1-kG load via an electromagnet. The postural forearm position was perturbed by the load release triggered by other elbow voluntary movement. Repetition of the imposed unloading test resulted in a progressive reduction of the maximal forearm rotation, accompanied by the anticipatory decrease in m. biceps brachii activity (learning). Control situation consisted of the voluntary forearm loading. Using the transcranial magnetic stimulation we examined changes in the motor evoked potential of the m. biceps brahii at the beginning and at the end of learning. The evoked potential amplitude did not significantly change in process of the decrease of m. biceps brachii activity. At the end of learning, motor evoked potential / baseline electromyogram ratio increased as compared to the beginning of learning and to the control situation. The results highlight the fundamental role of the motor cortex in suppression of synergies which interfere with formation of a new coordination during motor learning.

Adult↗

Mechanisms of motor learning in the cerebellum.

How the elaborate neuronal circuit in the cerebellum operates and is involved in motor learning is a question addressed in earnest in studies on the cerebellum. During the past four decades, experimental studies have revealed circuit and module structures of the cerebellum, established long-term depression (LTD) as a unique and characteristic type of synaptic plasticity in the cerebellum, and analysed signal contents of activates of cerebellar neurons related to motor learning. In the 1990s, these studies were developed to detailed analyses of the signal transduction underlying LTD, and to uncovering the involvement of the cerebellum in cognitive function. On the other hand, theoretical studies yielded epochal Marr-Albus network models of the cerebellum around 1970, and introduced control system principles explaining the essential roles of the cerebellum in motor learning as providing internal models, both forward and inverse. The author maintains the hypothesis that reorganisation of the neuronal circuit by error-driven induction of LTD constitutes the major memory and learning mechanisms of the cerebellum. In this article, we examine the validity of the hypothesis in light of currently available data in recent studies of the cerebellum.

Animals↗

Interlimb coordination in patients with Parkinson's disease: motor learning deficits and the importance of augmented information feedback.

The basal ganglia have traditionally been associated with motor control functions and this view has prevailed since the late nineteenth century. Recent experimental studies suggest that this neuroanatomical system is also critically involved in motor learning. In the present study, motor learning/transfer capabilities were compared between patients with Parkinson's disease and a group of normal elderly people. Subjects practiced a bimanual coordination task that required continuous flexion-extension movements in the transverse plane with a 90 degrees phase offset between the forearms. During acquisition, augmented visual feedback of the relative motions was provided in real time. The findings revealed improvements in the bimanual coordination pattern across practice in both groups when the augmented concurrent feedback was present. However, when transferred to performance conditions in which the augmented information was withheld, performance deteriorated (relative to the augmented condition) and this effect was more prevalent in the Parkinson patients. More specifically, no improvement in interlimb coordination was observed under nonaugmented feedback conditions across practice. Instead, a drift toward the preferred in-phase and antiphase coordination patterns was evident. The present findings suggest that Parkinson patients can improve their performance on a new motor task, but they remain strongly dependent on augmented visual information to guide these newly acquired movements. The apparent adoption of a closed-loop control mode is accompanied with decreases in movement speed in order to use the feedback to ensure accuracy. When the augmented feedback is withheld and the movement pattern is to be controlled by means of intrinsic information feedback sources, performance is severely hampered. The findings are hypothesized to indicate that learning/transfer is affected in Parkinson patients who apparently prefer some constancy in the environmental contingencies under which practice takes place. The present findings are consistent with the notion that the basal ganglia form a critical neuroanatomical substrate for motor learning.

Aged↗

Motor learning changes GABAergic terminals on spinal motoneurons in normal rats.

The role of spinal cord plasticity in motor learning is largely unknown. This study explored the effects of H-reflex operant conditioning, a simple model of motor learning, on GABAergic input to spinal motoneurons in rats. Soleus motoneurons were labeled by retrograde transport of a fluorescent tracer and GABAergic terminals on them were identified by glutamic acid decarboxylase (GAD)67 immunoreactivity. Three groups were studied: (i) rats in which down-conditioning had reduced the H-reflex (successful HRdown rats); (ii) rats in which down-conditioning had not reduced the H-reflex (unsuccessful HRdown rats) and (iii) unconditioned (naive) rats. The number, size and GAD density of GABAergic terminals, and their coverage of the motoneuron, were significantly greater in successful HRdown rats than in unsuccessful HRdown or naive rats. It is likely that these differences are due to modifications in terminals from spinal interneurons in lamina VI-VII and that the increased terminal number, size, GAD density and coverage in successful HRdown rats reflect and convey a corticospinal tract influence that changes motoneuron firing threshold and thereby decreases the H-reflex. GABAergic terminals in spinal cord change after spinal cord transection. The present results demonstrate that such spinal cord plasticity also occurs in intact rats in the course of motor learning and suggest that this plasticity contributes to skill acquisition.

Analysis of Variance↗

Robot-aided functional imaging: application to a motor learning study.

The purpose of this study was to examine the neural activity underlying an implicit motor learning task. In particular, our goals were to determine whether initial phases of procedural learning of a motor task involve areas of the brain distinct from those involved in later phases of learning the task, and what changes in neural activity coincide with performance improvement. We describe a novel integration of robotic technology with functional brain imaging and its use in this study of implicit motor learning. A portable robotic device was used to generate forces that disturbed the subjects' arm movements, thereby generating a "virtual mechanical environment" that the subjects learned to manipulate. Positron emission tomography (PET) was used to measure indices of neural activity underlying learning of the motor task. Eight health, right-handed male subjects participated in the study. Results support the hypothesis that different stages of implicit learning (early and late implicit learning) occur in an orderly fashion, and that distinct neural structures may be involved in these different stages. In particular, neuroimaging results indicate that the cortico-striatal loop may play a significant role during early learning, and that the cortico-cerebellar loop may play a significant role during late learning.

Adult↗