Important Role In Motor Learning Research Articles

Changes in excitability and GABAergic neuronal activity of the primary somatosensory cortex after motor learning.

IntroductionIt is widely known that motor learning changes the excitability of the primary motor cortex. More recently, it has been shown that the primary somatosensory cortex (S1) also plays an important role in motor learning, but the details have not been fully examined. Therefore, we investigated how motor skill training affects somatosensory evoked potential (SEP) in 30 neurologically healthy subjects.MethodsSEP N20/P25_component and N20/P25 SEP paired-pulse depression (SEP-PPD) were assessed before and immediately after complex or simple visuomotor tasks.ResultsMotor learning was induced more efficiently by the complex visuomotor task than by the simple visuomotor task. Both the N20/P25 SEP amplitude and N20/P25 SEP-PPD increased significantly immediately after the complex visuomotor task, but not after the simple visuomotor task. Furthermore, the altered N20/P25 SEP amplitude was associated with an increase in motor learning efficiency.ConclusionThese results suggest that motor learning modulated primary somatosensory cortex excitability.

Increase of vesicular glutamate transporter 2 co-expression in the deep cerebellar nuclei related to skilled reach learning

Motor learning induces plasticity in multiple brain regions involving the cerebellum as a crucial player. Synaptic plasticity in the excitatory collaterals to the cerebellar output, the deep cerebellar nuclei (DCN), have recently been shown to be an important part of motor learning. These synapses are composed of climbing fiber (CF) and mossy fiber synapses, with the former conveying unconditioned and the latter conditioned responses in classical conditioning paradigms. The CF synapse on to the cerebellar cortex and the DCN express vesicular transporter 2 (vGluT2), whereas mossy fibers express vGluT1 and /or vGluT2 in their terminals. However, the underlying regulatory mechanism of vGluT expression in the DCN remains unknown. Here we confirm the increase of vGluT2 in a specific part of the DCN during the acquisition of a skilled reaching task in mice. Furthermore, our findings show that this is due to an increase in co-expression of vGluT2 in vGluT1 presynapses instead of the formation of new vGluT2 synapses. Our data indicate that remodeling of synapses – in contrast to synaptogenesis - also plays an important role in motor learning and may explain the presence of both vGluT’s in some mossy fiber synapses.

Sensorimotor vs. Motor Upper Limb Therapy for Patients With Motor and Somatosensory Deficits: A Randomized Controlled Trial in the Early Rehabilitation Phase After Stroke.

Background: Somatosensory function plays an important role in motor learning. More than half of the stroke patients have somatosensory impairments in the upper limb, which could hamper recovery.Question: Is sensorimotor upper limb (UL) therapy of more benefit for motor and somatosensory outcome than motor therapy?Design: Randomized assessor- blinded multicenter controlled trial with block randomization stratified for neglect, severity of motor impairment, and type of stroke.Participants: 40 first-ever stroke patients with UL sensorimotor impairments admitted to the rehabilitation center.Intervention: Both groups received 16 h of additional therapy over 4 weeks consisting of sensorimotor (N = 22) or motor (N = 18) UL therapy.Outcome measures: Action Research Arm test (ARAT) as primary outcome, and other motor and somatosensory measures were assessed at baseline, post-intervention and after 4 weeks follow-up.Results: No significant between-group differences were found for change scores in ARAT or any somatosensory measure between the three time points. For UL impairment (Fugl-Meyer assessment), a significant greater improvement was found for the motor group compared to the sensorimotor group from baseline to post-intervention [mean (SD) improvement 14.65 (2.19) vs. 5.99 (2.06); p = 0.01] and from baseline to follow-up [17.38 (2.37) vs. 6.75 (2.29); p = 0.003].Conclusion: UL motor therapy may improve motor impairment more than UL sensorimotor therapy in patients with sensorimotor impairments in the early rehabilitation phase post stroke. For these patients, integrated sensorimotor therapy may not improve somatosensory function and may be less effective for motor recovery.Clinical Trial Registration: www.ClinicalTrials.gov, identifier NCT03236376.

Effect of the brain-derived neurotrophic factor gene Val66Met polymorphism on sensory-motor integration during a complex motor learning exercise

The brain-derived neurotrophic factor (BDNF) gene Val66Met polymorphism may cause impairment in short-term motor learning by reducing activity-dependent BDNF expression, which causes alterations in synaptic plasticity by changing glutamatergic and GABAergic synaptic transmissions. Sensory-motor integration (SMI) plays an important role in motor learning. In this study, we investigated the role of this polymorphism on SMI during a complex motor learning practice. Forty-three healthy participants performed standardized 5-day basketball shooting exercises under supervision. Electrophysiologic SMI studies were performed before the first day exercise (T0) and after the first and fifth day exercises (T1 and T2, respectively). SMI was studied using electrical median nerve stimulation at the wrist, followed by transcranial magnetic stimulation (TMS) of the contralateral motor cortex with various inter-stimulus intervals (ISIs). Recordings were made from the thenar and forearm flexor muscles. Participants were divided into two groups according to their BDNF genotype. Group 1 consisted of 26 subjects with the Val66Val genotype and group 2 included 17 subjects with the BDNF Met allele. Group 2 had a lower increase in basketball scores at day 5. Moreover, they had higher afferent facilitation for the responses recorded from both thenar and forearm flexor muscles at T1, but these changes could not be maintained until T2. This non-persistent early hyper-responsivity of the sensory-motor cortex in subjects with the BDNF Met allele might be explained by a transient upsurge of cortical excitability to compensate the insufficient cortical plasticity during motor learning, which could be considered as a sign of lower performance in motor skill learning.

Развитие взглядов на взаимосвязь произвольного движения и его мысленного образа

Введение. Широко известно, что проработка двигательного навыка посредством мысленного представления способствует повышению его скоординированности и результативности. Однако образ рассматривался как гипотетическая основа произвольного движения еще до начала своего практического применения. Статья впервые представляет текущее понимание образа движения как разрешения противоречий, присущих более ранним взглядам, и рассматривает совместимость последних с современной точкой зрения, чем обосновывает необходимость пересмотра некоторых существующих рекомендаций по применению мысленного образа в спорте.
 Теоретическое обоснование. Отправной точкой в рассмотрении мысленного образа как основы произвольного движения явилась идеомоторная теория. Моторным эффектам, описанным как неконтролируемое выражение доминирующей идеи, посвящены работы Т. Лэйкока и У. Б. Карпентера. Однако их видение как проявления системной роли образа в контроле движения пришло благодаря трудам И. Ф. Гербарта, Г. Р. Лотце и Э. Харлесса. Экспериментальное подтверждение подобных явлений было получено в ряде инструментальных исследований непроизвольной двигательной активности при ее мысленном представлении, которые поддержали научный интерес к идеомоторной теории в условиях ее критики со стороны бихевиоризма. Разрешение противоречий было предложено на современном этапе М. Джиннеродом, рассматривающим двигательный образ как осознанную репрезентацию лежащих в основе соответствующего движения нейрофизиологических процессов, которая формируется при отсутствии инактивирующей обратной связи от исполнительных органов.
 Результаты и их обсуждение. Современное понимание двигательного образа фокусируется на его эквивалентности фактическому движению с точки зрения реализующих его центральных нейрофизиологических процессов и присущих ему свойств, в т. ч. формирования навыка при повторении соответствующего движения. Важную роль в двигательном обучении, особенно на начальных этапах, которую подчеркивал еще П. Ф. Лесгафт, играют когнитивный анализ движения и познание его смысловой структуры с помощью образа. При этом, как показывают исследования, когнитивные и моторные процессы тесно переплетены между собой.

Visuomotor learning is dependent on direction-specific error saliency.

People perceive better in cardinal directions compared with oblique ones. This directional effect, called oblique effect, has been documented in perception studies for a long time. However, typical motor studies do not differentiate learning in different directions. In this study we identify a significant directional effect in motor learning using visuomotor rotation paradigms. We find that adaptation to visual perturbations yields more savings when both initial learning and relearning are performed in cardinal directions than in oblique directions. We hypothesize that this directional effect arises from relatively higher error saliency in cardinal directions. Consistent with this hypothesis, we successfully increased savings in the oblique directions, which showed no saving effect before, by enhancing the error saliency with augmented visual feedback during learning. Our findings suggest that movement direction plays an important role in motor learning, especially when learning signals are direction specific. Our results also provide new insights about the role of motor errors in the formation and retrieval of motor memory and practical implications for promoting learning in motor rehabilitation and athletic training. NEW & NOTEWORTHY People perceive better when the stimulus is in cardinal directions than in oblique directions. Whether a similar directional effect exists in motor learning is unknown. Using a motor learning paradigm, we show that people relearn to compensate for a previously encountered perturbation faster when they move in cardinal directions than when they move in oblique directions. Further experimentation supports that this motor directional effect likely results from better sensory saliency of motor errors in cardinal directions.

High variability impairs motor learning regardless of whether it affects task performance.

Motor variability plays an important role in motor learning, although the exact mechanisms of how variability affects learning are not well understood. Recent evidence suggests that motor variability may have different effects on learning in redundant tasks, depending on whether it is present in the task space (where it affects task performance) or in the null space (where it has no effect on task performance). We examined the effect of directly introducing null and task space variability using a manipulandum during the learning of a motor task. Participants learned a bimanual shuffleboard task for 2 days, where their goal was to slide a virtual puck as close as possible toward a target. Critically, the distance traveled by the puck was determined by the sum of the left- and right-hand velocities, which meant that there was redundancy in the task. Participants were divided into five groups, based on both the dimension in which the variability was introduced and the amount of variability that was introduced during training. Results showed that although all groups were able to reduce error with practice, learning was affected more by the amount of variability introduced rather than the dimension in which variability was introduced. Specifically, groups with higher movement variability during practice showed larger errors at the end of practice compared with groups that had low variability during learning. These results suggest that although introducing variability can increase exploration of new solutions, this may adversely affect the ability to retain the learned solution. NEW & NOTEWORTHY We examined the role of introducing variability during motor learning in a redundant task. The presence of redundancy allows variability to be introduced in different dimensions: the task space (where it affects task performance) or the null space (where it does not affect task performance). We found that introducing variability affected learning adversely, but the amount of variability was more critical than the dimension in which variability was introduced.

High-intensity Interval Exercise Promotes Motor Cortex Disinhibition and Early Motor Skill Consolidation.

Gamma-aminobutyric acid (GABA) inhibition shapes motor cortex output, gates synaptic plasticity in the form of long-term potentiation, and plays an important role in motor learning. Remarkably, recent studies have shown that acute cardiovascular exercise can improve motor memory, but the cortical mechanisms are not completely understood. We investigated whether an acute bout of lower-limb high-intensity interval (HIT) exercise could promote motor memory formation in humans through changes in cortical inhibition within the hand region of the primary motor cortex. We used TMS to assess the input-output relationship, along with inhibition involving GABAA and GABAB receptors. Measures were obtained before and after a 20-min session of HIT cycling (exercise group) or rest (control group). We then had the same participants learn a new visuomotor skill and perform a retention test 5 hr later in the absence of sleep. No differences were found in corticomotor excitability or GABAB inhibition; however, synaptic GABAA inhibition was significantly reduced for the exercise group but not the control group. HIT exercise was found to enhance motor skill consolidation. These findings link modification of GABA to improved motor memory consolidation after HIT exercise and suggest that the beneficial effects of exercise on consolidation might not be dependent on sleep.

Cerebellar degeneration affects cortico-cortical connectivity in motor learning networks.

The cerebellum plays an important role in motor learning as part of a cortico-striato-cerebellar network. Patients with cerebellar degeneration typically show impairments in different aspects of motor learning, including implicit motor sequence learning. How cerebellar dysfunction affects interactions in this cortico-striato-cerebellar network is poorly understood. The present study investigated the effect of cerebellar degeneration on activity in causal interactions between cortical and subcortical regions involved in motor learning. We found that cerebellar patients showed learning-related increase in activity in two regions known to be involved in learning and memory, namely parahippocampal cortex and cerebellar Crus I. The cerebellar activity increase was observed in non-learners of the patient group whereas learners showed an activity decrease. Dynamic causal modeling analysis revealed that modulation of M1 to cerebellum and putamen to cerebellum connections were significantly more negative for sequence compared to random blocks in controls, replicating our previous results, and did not differ in patients. In addition, a separate analysis revealed a similar effect in connections from SMA and PMC to M1 bilaterally. Again, neural network changes were associated with learning performance in patients. Specifically, learners showed a negative modulation from right SMA to right M1 that was similar to controls, whereas this effect was close to zero in non-learners. These results highlight the role of cerebellum in motor learning and demonstrate the functional role cerebellum plays as part of the cortico-striato-cerebellar network.

Practice and nap schedules modulate children's motor learning.

Night- or day-time sleep enhances motor skill acquisition. However, prominent issues remained about the circadian (time-of-day) and homeostatic (time since last sleep) effects of sleep on developmental motor learning. Therefore, we examined the effects of nap schedules and nap-test-intervals (NTIs) on the learning of finger tapping sequences on computer keyboards. Children aged 6-7, 8-9, and 10-11 years explicitly acquired the short and long tapping orders that share the same movement strings (4-2-3-1-4, 4-2-3-1-4-2-3-1-4). Following a constant 8- or 10-hr post-learning period in one of the four NTIs (2, 4, 5, 7 hr), children in the morning napping groups, the afternoon napping groups, or the waking group performed the original long sequence in retention test (4-2-3-1-4-2-3-1-4) and the mirrored-order sequence in transfer test (1-3-2-4-1-3-2-4-1). Age and treatment differences in the movement time (MT, ms) and sequence accuracy (SA, %) were compared during skill learning and in retrieval tests. Results suggest that practice or nap affects MT and SA in a greater extent for the younger learners than for the older learners. The circadian effects might not change nap-based skill learning. Importantly, the longer NTIs resulted in superior retention performance than the shorter ones, suggesting that children require a relatively longer post-nap period to form motor memory. Finally, nap-based motor learning was more marked in skill retention than in skill transfer. Brain development may play an important role in motor learning. Our discussion centers on memory consolidation and its relevance for skill acquisition from early to late childhood.

The cerebellum is not necessary for visually driven recalibration of hand proprioception

Decades of research have implicated both cortical and subcortical areas, such as the cerebellum, as playing an important role in motor learning, and even more recently, in predicting the sensory consequences of movement. Still, it is unknown whether the cerebellum also plays a role in recalibrating sensory estimates of hand position following motor learning. To test this, we measured proprioceptive estimates of static hand position in 19 cerebellar patients with local ischemic lesions and 19 healthy controls, both before and after reach training with altered visual feedback of the hand. This altered visual feedback, (30° cursor-rotation) was gradually introduced in order to facilitate reach adaptation in the patient group. We included two different types of training (in separate experiments): the typical visuomotor rotation training where participants had full volition of their hand movements when reaching with the cursor, and sensory exposure training where the direction of participants׳ hand movements were constrained and gradually deviated from the cursor motion (Cressman, E. K., Henriques, D. Y., 2010. Reach adaptation and proprioceptive recalibration following exposure to misaligned sensory input. J. Neurophysiol., vol. 103, pp. 1888–1895). We found that both healthy individuals and patients showed equivalent shifts in their felt hand position following both types of training. Likewise, as expected given that the cursor-rotation was introduced gradually, patients showed comparable reach aftereffects to those of controls in both types of training. The robust change in felt hand position across controls and cerebellar patients suggests that the cerebellum is not involved in proprioceptive recalibration of the hand.

Motor learning in individuals with autism spectrum disorder: activation in superior parietal lobule related to learning and repetitive behaviors.

Motor-linked implicit learning is the learning of a sequence of movements without conscious awareness. Although motor symptoms are frequently reported in individuals with autism spectrum disorder (ASD), recent behavioral studies have suggested that motor-linked implicit learning may be intact in ASD. The serial reaction time (SRT) task is one of the most common measures of motor-linked implicit learning. The present study used a 3T functional magnetic resonance imaging scanner to examine the behavioral and neural correlates of real-time motor sequence learning in adolescents and adults with ASD (n = 15) compared with age- and intelligence quotient-matched individuals with typical development (n = 15) during an SRT task. Behavioral results suggested less robust motor sequence learning in individuals with ASD. Group differences in brain activation suggested that individuals with ASD, relative to individuals with typical development, showed decreased activation in the right superior parietal lobule (SPL) and right precuneus (Brodmann areas 5 and 7, and extending into the intraparietal sulcus) during learning. Activation in these areas (and in areas such as the right putamen and right supramarginal gyrus) was found to be significantly related to behavioral learning in this task. Additionally, individuals with ASD who had more severe repetitive behavior/restricted interest symptoms demonstrated greater decreased activation in these regions during motor learning. In conjunction, these results suggest that the SPL may play an important role in motor learning and repetitive behavior in individuals with ASD.

Cdk5/p35 is required for motor coordination and cerebellar plasticity.

Previous studies have implicated the role of Purkinje cells in motor learning and the underlying mechanisms have also been identified in great detail during the last decades. Here we report that cyclin-dependent kinase 5 (Cdk5)/p35 in Purkinje cell also contributes to synaptic plasticity. We previously showed that p35(-/-) (p35 KO) mice exhibited a subtle abnormality in brain structure and impaired spatial learning and memory. Further behavioral analysis showed that p35 KO mice had a motor coordination defect, suggesting that p35, one of the activators of Cdk5, together with Cdk5 may play an important role in cerebellar motor learning. Therefore, we created Purkinje cell-specific conditional Cdk5/p35 knockout (L7-p35 cKO) mice, analyzed the cerebellar histology and Purkinje cell morphology of these mice, evaluated their performance with balance beam and rota-rod test, and performed electrophysiological recordings to assess long-term synaptic plasticity. Our analyses showed that Purkinje cell-specific deletion of Cdk5/p35 resulted in no changes in Purkinje cell morphology but severely impaired motor coordination. Furthermore, disrupted cerebellar long-term synaptic plasticity was observed at the parallel fiber-Purkinje cell synapse in L7-p35 cKO mice. These results indicate that Cdk5/p35 is required for motor learning and involved in long-term synaptic plasticity.

A Magnetic Resonance Imaging Study of Cerebellar Volume in Tuberous Sclerosis Complex

The cerebellum plays an important role in motor learning and cognition, and structural cerebellar abnormalities have been associated with cognitive impairment. In tuberous sclerosis complex, neurologic outcome is highly variable, and no consistent imaging or pathologic determinant of cognition has been firmly established. The cerebellum calls for specific attention because mouse models of tuberous sclerosis complex have demonstrated a loss of cerebellar Purkinje cells, and cases of human histologic data have demonstrated a similar loss in patients. We hypothesized that there might be a common cerebellar finding in tuberous sclerosis complex that could be measured as morphometric changes with magnetic resonance imaging. Using a robust, automated image analysis procedure, we studied 36 patients with tuberous sclerosis complex and age-matched control subjects and observed significant volume loss among patients in the cerebellar cortices and vermis. Furthermore, this effect was strongest in a subgroup of 19 patients with a known, pathogenic mutation of the tuberous sclerosis 2 gene and impacted all cerebellar structures. We conclude that patients with tuberous sclerosis complex exhibit volume loss in the cerebellum, and this loss is larger and more widespread in patients with a tuberous sclerosis 2 mutation.

Active versus Passive Training of a Complex Bimanual Task: Is Prescriptive Proprioceptive Information Sufficient for Inducing Motor Learning?

Perceptual processes play an important role in motor learning. While it is evident that visual information greatly contributes to learning new movements, much less is known about provision of prescriptive proprioceptive information. Here, we investigated whether passive (proprioceptively-based) movement training was comparable to active training for learning a new bimanual task. Three groups practiced a bimanual coordination pattern with a 1∶2 frequency ratio and a 90° phase offset between both wrists with Lissajous feedback over the course of four days: 1) passive training; 2) active training; 3) no training (control). Retention findings revealed that passive as compared to active training resulted in equally successful acquisition of the frequency ratio but active training was more effective for acquisition of the new relative phasing between the limbs in the presence of augmented visual feedback. However, when this feedback was removed, performance of the new relative phase deteriorated in both groups whereas the frequency ratio was better preserved. The superiority of active over passive training in the presence of augmented feedback is hypothesized to result from active involvement in processes of error detection/correction and planning.

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.

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.

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.

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.