Effect of positive social comparative feedback on the resting state connectivity of dopaminergic neural pathways: A preliminary investigation.

Positive social comparative feedback is hypothesized to generate a dopamine response in the brain, similar to reward, by enhancing expectancies to support motor skill learning. However, no studies have utilized neuroimaging to examine this hypothesized dopaminergic mechanism. Therefore, the aim of this preliminary study was to investigate the effect of positive social comparative feedback on dopaminergic neural pathways measured by resting state connectivity. Thirty individuals practiced an implicit, motor sequence learning task and were assigned to groups that differed in feedback type. One group received feedback about their actual response time to complete the task (RT ONLY), while the other group received feedback about their response time with positive social comparison (RT + POS). Magnetic resonance imaging was acquired at the beginning and end of repetitive motor practice with feedback to measure practice-dependent changes in resting state brain connectivity. While both groups showed improvements in task performance and increases in performance expectancies, ventral tegmental area and the left nucleus accumbens (mesolimbic dopamine pathway) resting state connectivity increased in the RT + POS group but not in the RT ONLY group. Instead, the RT ONLY group showed increased connectivity between ventral tegmental area and primary motor cortex. Positive social comparative feedback during practice of a motor sequence task may induce a dopaminergic response in the brain along the mesolimbic pathway. However, given that absence of effects on expectancies and motor learning, more robust and individualized approaches may be needed to provide beneficial psychological and behavioral effects.

Effect of behavioural practice targeted at the motor action selection network after stroke.

Motor action selection engages a network of frontal and parietal brain regions. After stroke, individuals activate a similar network, however, activation is higher, especially in the contralesional hemisphere. The current study examined the effect of practice on action selection performance and brain activation after stroke. Sixteen individuals with chronic stroke (Upper Extremity Fugl-Meyer motor score range: 18-61) moved a joystick with the more-impaired hand in two conditions: Select (externally cued choice; move right or left based on an abstract rule) and Execute (simple response; move same direction every trial). On Day 1, reaction time (RT) was longer in Select compared to Execute, which corresponded to increased activation primarily in regions in the contralesional action selection network including dorsal premotor, supplementary motor, anterior cingulate and parietal cortices. After 4 days of practice, behavioural performance improved (decreased RT), and only contralesional parietal cortex significantly increased during Select. Higher brain activation on Day 1 in the bilateral action selection network, dorsolateral prefrontal cortex and contralesional sensory cortex predicted better performance on Day 4. Overall, practice led to improved action selection performance and reduced brain activation. Systematic changes in practice conditions may allow the targeting of specific components of the motor network during rehabilitation after stroke.

Neural correlates of within-session practice effects in mild motor impairment after stroke: a preliminary investigation.

While the structural integrity of the corticospinal tract (CST) has been shown to support motor performance after stroke, the neural correlates of within-session practice effects are not known. The purpose of this preliminary investigation was to examine the structural brain correlates of within-session practice effects on a functional motor task completed with the more impaired arm after stroke. Eleven individuals with mild motor impairment (mean age 57.0 ± 9.4 years, mean months post-stroke 37.0 ± 66.1, able to move ≥ 26 blocks on the Box and Blocks Test) due to left hemisphere stroke completed structural MRI and practiced a functional motor task that involved spooning beans from a start cup to three distal targets. Performance on the motor task improved with practice (p = 0.004), although response was variable. Baseline motor performance (Block 1) correlated with integrity of the CST (r = - 0.696) while within-session practice effects (change from Block 1 to Block 3) did not. Instead, practice effects correlated with degree of lesion to the superior longitudinal fasciculus (r = 0.606), a pathway that connects frontal and parietal brain regions previously shown to support motor learning. This difference between white matter tracts associated with baseline motor performance and within-session practice effects may have implications for understanding response to motor practice and the application of brain-focused intervention approaches aimed at improving hand function after stroke.

Targeted Engagement of the Action Selection Network during Task-Oriented Arm Training after Stroke.

Action selection (AS), or selection of an action from a set of alternatives, is an important movement preparation process that engages a frontal-parietal network. The addition of AS demands to arm training after stroke could be used to engage this motor planning process and the neural network that supports it. The purpose of this case series is to describe the feasibility and outcomes associated with task-oriented arm training aimed at engaging the AS behavioral process and the related neural network in three individuals with chronic stroke. Three participants with mild to moderate motor deficits completed 13 to 15 sessions of task-oriented arm training that included AS cues for each movement repetition; cues dictated movement direction, height, or distance. Before and after training, individuals completed an AS brain-behavior probe during functional MRI. AS behavioral performance improved after training (increased accuracy, decreased reaction time) in all participants while brain activation in the AS network (dorsal premotor, parietal, dorsolateral prefrontal cortices) decreased in two participants. Gains in motor function were also found in all three participants, especially on patient-reported measures of perceived difficulty and confidence to complete upper extremity functional tasks. It was feasible to target the AS behavioral process and the related neural network through the addition of AS demands to functional, task-oriented arm training in three individuals with mild to moderate motor dysfunction poststroke.

Instrument-assisted soft tissue mobilization and proprioceptive neuromuscular facilitation techniques improve hamstring flexibility better than static stretching alone: a randomized clinical trial.

Objectives: Tight hamstrings contribute to inefficiency of movement and increased risk for injury. Static stretching is the most common intervention for this problem, but the use of alternatives like instrument-assisted soft tissue mobilization (IASTM) and proprioceptive neuromuscular facilitation (PNF) is increasing among clinicians. This study examined two prospective studies with the common aim of demonstrating the effectiveness of IASTM or PNF over static stretching for improving hamstring tightness. Methods: Nondisabled adults were recruited on a university campus. IASTM study: N = 17 (11 males and 6 females). PNF study: N = 23 (7 males and 16 females). Hip flexion range of motion was measured with a passive straight leg raise (for IASTM) or active straight leg raise (for PNF) before and after stretching. Participants performed a self-static stretch on one leg and received the alternative intervention on the contralateral leg. The two studies were analyzed separately for reliability indices and significant differences between interventions. Results: Hip flexion measures showed good reliability in both studies (intraclass correlation coefficient = 0.97) with a minimal detectable change of <4.26. Both studies showed significant interactions between time and intervention (p < 0.05). Follow-up analyses revealed PNF and IASTM interventions resulted in greater increases in hip flexion range than static stretching. Discussion: These findings demonstrate the effectiveness of PNF and IASTM techniques over static stretching for hamstring flexibility. These interventions provide more efficient alternatives for improving flexibility in the clinic, allowing greater progress in a shorter period of time than an equivalent static stretching program. Level of Evidence: 1b.

The effect of energy-matched exercise intensity on brain-derived neurotrophic factor and motor learning.

BACKGROUND: Pairing a bout of high-intensity exercise with motor task practice can enhance motor learning beyond task practice alone, which is thought, in part, to be facilitated by an exercise-related increase in brain-derived neurotrophic factor (BDNF). The purpose of the current study was to examine the effect of different exercise intensities on BDNF levels and motor learning while controlling for exercise-related energy expenditure. METHODS: Forty-eight young, healthy participants were assigned to one of three groups: high-intensity exercise [High], low-intensity exercise [Low], or quiet rest [Rest]. The duration of the exercise bouts were individually adjusted so that each participant expended 200 kcals regardless of exercise intensity. BDNF was measured before and after exercise or rest. After exercise or rest, all participants practiced a 3-dimensional motor learning task, which involved reach movements made to sequentially presented targets. Retention was tested after 24-h. BDNF genotype was determined for each participant to explore its effects on BDNF and motor learning. RESULTS: All participants equally improved performance, indicated by a reduction in time to complete the task. However, the kinematic profile used to control the reach movement differed by group. The Rest group travelled the shortest distance between the targets, the High group had higher reach speed (peak velocity), and the Low group had earlier peak velocities. The rise in BDNF post-exercise was not significant, regardless of exercise intensity, and the change in BDNF was not associated with motor learning. The BDNF response to exercise did not differ by genotype. However, performance differed between those with the polymorphism (Met carriers) and those without (Val/Val). Compared to the Val/Val genotype, Met carriers had faster response times throughout task practice, which was supported by higher reach speeds and earlier peak velocities. CONCLUSION: Results indicated that both low and high-intensity exercise can alter the kinematic approach used to complete a reach task, and these changes appear unrelated to a change in BDNF. In addition, the BDNF genotype did not influence BDNF concentration, but it did have an effect on motor performance of a sequential target reach task.

Sequence-specific implicit motor learning using whole-arm three-dimensional reach movements.

Implicit motor learning is essential to the acquisition of motor skills. Examination of implicit motor learning, however, has largely involved single-finger button presses or two-dimensional movements of a computer mouse or joystick. The purpose of this study was to examine sequence-specific implicit motor learning during practice of  a three-dimensional (3D) whole-arm reach task. Fifteen young, non-disabled individuals completed two consecutive days of practice of a 3D target task presented in a virtual environment with the dominant, right arm. Stimuli were displayed one at a time and alternated between an eight-target random sequence and an eight-target repeated sequence. Movement of the shoulder and elbow was required to successfully capture a target. Performance was indicated by time to complete a sequence (response time) and analyzed by sequence type (random, repeated). Kinematic data (total distance to complete a sequence, peak velocity, and time to peak velocity) were used to determine how movement changed over time. Results showed significant improvements in performance early in practice, regardless of sequence type. However, individuals completed the repeated sequence faster than the random sequence, indicating sequence-specific implicit motor learning. The difference in response time between the sequence types was driven by the total distance of the hand path; the distance traveled for the repeated sequence was shorter than the distance of the random sequence. Examination of implicit motor learning using 3D reach movements provides the opportunity to study learning using whole-arm movements, an important component of many real-world, functional tasks.

Biomarkers of Rehabilitation Therapy Vary according to Stroke Severity.

Biomarkers that capture treatment effects could improve the precision of clinical decision making for restorative therapies. We examined the performance of candidate structural, functional, and angiogenesis-related MRI biomarkers before and after a 3-week course of standardized robotic therapy in 18 patients with chronic stroke and hypothesized that results vary significantly according to stroke severity. Patients were 4.1 ± 1 months poststroke, with baseline arm Fugl-Meyer scores of 20-60. When all patients were examined together, no imaging measure changed over time in a manner that correlated with treatment-induced motor gains. However, when also considering the interaction with baseline motor status, treatment-induced motor gains were significantly related to change in three functional connectivity measures: ipsilesional motor cortex connectivity with (1) contralesional motor cortex (p = 0.003), (2) contralesional dorsal premotor cortex (p = 0.005), and (3) ipsilesional dorsal premotor cortex (p = 0.004). In more impaired patients, larger treatment gains were associated with greater increases in functional connectivity, whereas in less impaired patients larger treatment gains were associated with greater decreases in functional connectivity. Functional connectivity measures performed best as biomarkers of treatment effects after stroke. The relationship between changes in functional connectivity and treatment gains varied according to baseline stroke severity. Biomarkers of restorative therapy effects are not one-size-fits-all after stroke.

Genetic Variation and Neuroplasticity: Role in Rehabilitation After Stroke.

BACKGROUND AND PURPOSE: In many neurologic diagnoses, significant interindividual variability exists in the outcomes of rehabilitation. One factor that may impact response to rehabilitation interventions is genetic variation. Genetic variation refers to the presence of differences in the DNA sequence among individuals in a population. Genetic polymorphisms are variations that occur relatively commonly and, while not disease-causing, can impact the function of biological systems. The purpose of this article is to describe genetic polymorphisms that may impact neuroplasticity, motor learning, and recovery after stroke. SUMMARY OF KEY POINTS: Genetic polymorphisms for brain-derived neurotrophic factor (BDNF), dopamine, and apolipoprotein E have been shown to impact neuroplasticity and motor learning. Rehabilitation interventions that rely on the molecular and cellular pathways of these factors may be impacted by the presence of the polymorphism. For example, it has been hypothesized that individuals with the BDNF polymorphism may show a decreased response to neuroplasticity-based interventions, decreased rate of learning, and overall less recovery after stroke. However, research to date has been limited and additional work is needed to fully understand the role of genetic variation in learning and recovery. RECOMMENDATIONS FOR CLINICAL PRACTICE: Genetic polymorphisms should be considered as possible predictors or covariates in studies that investigate neuroplasticity, motor learning, or motor recovery after stroke. Future predictive models of stroke recovery will likely include a combination of genetic factors and other traditional factors (eg, age, lesion type, corticospinal tract integrity) to determine an individual's expected response to a specific rehabilitation intervention.

Dorsal premotor activity and connectivity relate to action selection performance after stroke.

Compensatory activation in dorsal premotor cortex (PMd) during movement execution has often been reported after stroke. However, the role of PMd in the planning of skilled movement after stroke has not been well studied. The current study investigated the behavioral and neural response to the addition of action selection (AS) demands, a motor planning process that engages PMd in controls, to movement after stroke. Ten individuals with chronic, left hemisphere stroke and 16 age-matched controls made a joystick movement with the right hand under two conditions. In the AS condition, participants moved right or left based on an abstract, visual rule; in the execution only condition, participants moved in the same direction on every trial. Despite a similar behavioral response to the AS condition (increase in reaction time), brain activation differed between the two groups: the control group showed increased activation in left inferior parietal lobule (IPL) while the stroke group showed increased activation in several right/contralesional regions including right IPL. Variability in behavioral performance between participants was significantly related to variability in brain activation. Individuals post-stroke with relatively poorer AS task performance showed greater magnitude of activation in left PMd and dorsolateral prefrontal cortex (DLPFC), increased left primary motor cortex-PMd connectivity, and decreased left PMd-DLPFC connectivity. Changes in the premotor-prefrontal component of the motor network during complex movement conditions may negatively impact the performance and learning of skilled movement and may be a prime target for rehabilitation protocols aimed at improving the function of residual brain circuits after stroke. Hum Brain Mapp 37:1816-1830, 2016. © 2016 Wiley Periodicals, Inc.

Age-related variability in performance of a motor action selection task is related to differences in brain function and structure among older adults.

Task performance for behaviors that engage motor cognitive processes may be particularly sensitive to age-related changes. One well-studied model of cognitive motor function involves engagement of action selection (AS) processes. In young adults, task conditions that add AS demands result in increased preparation times and greater engagement of bilateral dorsal premotor (PMd) and parietal cortices. The current study investigated the behavioral and neural response to a change in motor cognitive demands in older adults through the addition of AS to a movement task. Sixteen older adults made a joystick movement under two conditions during functional magnetic resonance imaging. In the AS condition, participants moved right or left based on an abstract rule; in the execution only (EO) condition, participants moved in the same direction on every trial. Across participants, the AS condition, as compared to the EO condition, was associated with longer reaction time and increased activation of left inferior parietal lobule. Variability in behavioral response to the AS task between participants related to differences in brain function and structure. Overall, individuals with poorer AS task performance showed greater activation in left PMd and dorsolateral prefrontal cortex and decreased structural integrity of white matter tracts that connect sensorimotor, frontal, and parietal regions-key regions for AS task performance. Additionally, two distinct patterns of functional connectivity were found. Participants with a pattern of decreased primary motor-PMd connectivity in response to the AS condition, compared to those with a pattern of increased connectivity, were older and had poorer behavioral performance. These neural changes in response to increased motor cognitive demands may be a marker for age-related changes in the motor system and have an impact on the learning of novel, complex motor skills in older adults.

Control of reach extent with the paretic and nonparetic arms after unilateral sensorimotor stroke: kinematic differences based on side of brain damage.

Scaling of reach kinematics to targets that vary in distance is indicative of the use of planning and feedback-based adjustments. The control of reach extent, however, has not been reported for the paretic arm after stroke. The purpose of this study was to determine whether individuals post-stroke utilized planning (scaling acceleration magnitude) and feedback-based adjustments (scaling acceleration duration) to reach to targets that varied in distance. Individuals with mild-to-moderate motor impairment after stroke and nondisabled adults reached with both arms to targets presented at three distances (8, 16, 24 cm). Kinematic data were used to determine scaling of peak acceleration magnitude and duration to target distance and compared between arms (control, nonparetic, paretic). Despite differences in the magnitude of movement variables, individuals post-stroke utilized both planning and feedback-based adjustments to meet the demands of the task with the nonparetic and paretic arms in a similar manner as controls. However, there was variability in the use of planning with the paretic arm, some individuals utilized planning while others did not. After right brain damage, differences in reach control related to the specialized role this hemisphere plays in endpoint control were found in both arms; no hemisphere-specific changes were found after left brain damage (LBD). The appearance of hemispheric-specific effects after right but not LBD were not due to age, degree of motor impairment, or time post-stroke, but, instead, may be related to relative differences in visual-motor processing ability, lesion characteristics, or interhemispheric inhibition changes between groups.

Control of reach extent with the paretic and nonparetic arms after unilateral sensorimotor stroke II: planning and adjustments to control movement distance.

Nondisabled adults utilize both planning and feedback-based compensatory adjustments to control actual distance moved for skilled reach actions. The purpose of this study was to determine whether individuals post-stroke utilize planning and compensatory adjustments to control movement distance for reaches to targets that vary in distance. Individuals with mild to moderate motor impairment after stroke and nondisabled adults reached with both arms to targets presented at three distances (8, 16, 24 cm). The control of movement distance was compared between arms (control, nonparetic, and paretic) as to the use of planning (correlation of peak acceleration with movement distance), compensatory adjustments prior to peak velocity (correlation of time to peak velocity with movement distance), and compensatory adjustments after peak velocity (variance in movement distance accounted for by deterministic statistical model). The correlation of peak acceleration with movement distance for reaches with the paretic arm was significantly less than controls suggesting a decreased reliance on planning. Feedback-based compensatory adjustments, however, were present prior to and after peak velocity that assisted in achievement of movement distance in a similar manner as controls. Overall reach performance with the paretic arm was impaired, however, as evidenced by greater endpoint error and longer movement times than controls. The decreased use of planning to control movement distance after stroke suggests that the selected motor command was suboptimal in producing the desired movement outcome and may be related to an inability to generate muscle force quickly, lack of knowledge of arm dynamics due to decreased arm use, or lesion characteristics.

Brain-Hand Function Relationships Based on Level of Grasp Function in Chronic Left-Hemisphere Stroke.

BACKGROUND AND OBJECTIVE: The biomarkers of hand function may differ based on level of motor impairment after stroke. The objective of this study was to determine the relationship between resting state functional connectivity (RsFC) and unimanual contralesional hand function after stroke and whether brain-behavior relationships differ based on level of grasp function. METHODS: Sixty-two individuals with chronic, left-hemisphere stroke were separated into three functional levels based on Box and Blocks Test performance with the contralesional hand: Low (moved 0 blocks), Moderate (moved >0% but <90% of blocks relative to the ipsilesional hand), and High (moved ≥90% of blocks relative to the ipsilesional hand). RESULTS: RsFC in the ipsilesional and interhemispheric motor networks was reduced in the Low group compared to the Moderate and High groups. While interhemispheric RsFC correlated with hand function (grip strength and Stroke Impact Scale Hand) across the sample, contralesional RsFC correlated with hand function in the Low group and no measures of connectivity correlated with hand function in the Moderate and High groups. Linear regression modeling found that contralesional RsFC significantly predicted hand function in the Low group, while no measure correlated with hand function in the High group. Corticospinal tract integrity was the only predictor of hand function for the Moderate group and in an analysis across the entire sample. CONCLUSIONS: Differences in brain-hand function relationships based on level of motor impairment may have implications for predictive models of treatment response and the development of intervention protocols aimed at improving hand function after stroke.

Patient-reported measures provide unique insights into motor function after stroke.

BACKGROUND AND PURPOSE: Patient-reported outcome measures have been found useful in many disciplines but have received limited evaluation after stroke. The current study investigated the relationship that patient-reported measures have with standard impairment and disability scales after stroke. METHODS: Patients with motor deficits after stroke were scored on standard assessments including the National Institutes of Health Stroke Scale, modified Rankin Scale, and Fugl-Meyer motor scale, and on 2 patient-reported measures, the hand function domain of the Stroke Impact Scale, which documents difficulty of hand motor usage, and the amount of use portion of the Motor Activity Log, which records amount of arm motor usage. RESULTS: The 43 participants had mild disability (median modified Rankin Scale=2), moderate motor deficits (Fugl-Meyer motor scale=46 ± 22), and mild cognitive/language deficits. The 2 patient-reported outcome measures, Stroke Impact Scale and Motor Activity Log, were sensitive to the presence of arm motor deficits. Of 21 patients classified as having minimal or no impairment or disability by the National Institutes of Health Stroke Scale or modified Rankin Scale (score of 0-1), 15 (71%) reported difficulty with hand movements by the Stroke Impact Scale score or reduced arm use by the Motor Activity Log score. Furthermore, of 14 patients with a normal examination, 10 (71%) reported difficulty with hand movements or reduction in arm use. CONCLUSIONS: Patient-reported measures were a unique source of insight into clinical status in the current population. Motor deficits were revealed in a majority of patients classified by standard scales as having minimal or no disability, and in a majority of patients classified as having no deficits.

Planning and adjustments for the control of reach extent in a virtual environment.

BACKGROUND: Skilled performance of reach actions includes both anticipatory planning and compensatory adjustments made while moving. The execution of reach actions in a virtual environment (VE) demonstrates similar characteristics to reaches performed in the real-world, however, it is unclear whether the VE itself significantly impacts movement planning or compensatory adjustments. The purpose of this study was to directly compare the use of planning and adjustments to control extent for unconstrained reach actions performed in an immersive VE to those performed in an analogous real-world environment (RWE). METHODS: Five non-disabled adults (29±5 years) reached with the dominant, right arm to six targets presented in two directions (+45°, -45°) and three distances (8, 16, 24 cm) in a VE and an analogous RWE. Position data were sampled at 120 Hz from an electromagnetic marker on the index finger and differentiated to determine velocity and acceleration. The control of reach extent was compared between the two environments (paired t-test) as to the use of planning (correlation of peak acceleration with movement distance), compensatory adjustments prior to peak velocity (correlation of time to peak velocity with movement distance), and compensatory adjustments after peak velocity (variance in movement distance accounted for by deterministic statistical model). RESULTS: Reach movements were relatively fast (<400 msec) and scaled to target distance in both the VE and RWE. Overall, the control of reach extent was similar in all respects between the two environments. In both environments, a hybrid control pattern was observed. That is, individuals utilized a combined strategy that relied on both planning and compensatory adjustments to capture the target. Adjustments to the reach were evident prior to peak velocity through changes in acceleration duration as well as after peak velocity based on target information. The two factor deterministic statistical model (peak velocity, target distance) explained >92% of the variance in movement distance across participants and environments. CONCLUSIONS: The VE did not impact movement planning or subsequent compensatory adjustments for the control of reach extent when directly compared to an analogous RWE. An immersive VE is a valid environment for the study of unconstrained reach actions.

Task-Based Functional Connectivity and Blood-Oxygen-Level-Dependent Activation During Within-Scanner Performance of Lumbopelvic Motor Tasks: A Functional Magnetic Resonance Imaging Study.

There are a limited number of neuroimaging investigations into motor control of the lumbopelvic musculature. Most investigation examining motor control of the lumbopelvic musculature utilize transcranial magnetic stimulation (TMS) and focus primarily on the motor cortex. This has resulted in a dearth of knowledge as it relates to how other regions of the brain activate during lumbopelvic movement. Additionally, task-based functional connectivity during lumbopelvic movements has not been well elucidated. Therefore, we used functional magnetic resonance imaging (fMRI) to examine brain activation and ROI-to-ROI task-based functional connectivity in 19 healthy individuals (12 female, age 29.8 ± 4.5 years) during the performance of three lumbopelvic movements: modified bilateral bridge, left unilateral bridge, and right unilateral bridge. The whole brain analysis found robust, bilateral activation within the motor regions of the brain during the bilateral bridge task, and contralateral activation of the motor regions during unilateral bridging tasks. Furthermore, the ROI-to-ROI analysis demonstrated significant connectivity of a motor network that included the supplemental motor area, bilateral precentral gyrus, and bilateral cerebellum regardless of the motor task performed. These data suggest that while whole brain activation reveals unique patterns of activation across the three tasks, functional connectivity is very similar. As motor control of the lumbopelvic area is of high interest to those studying low back pain (LBP), this study can provide a comparison for future research into potential connectivity changes that occur in individuals with LBP.

Effects of positive social comparative feedback on motor sequence learning and performance expectancies.

Introduction: Positive social comparative feedback indicates to the learner that they are performing better than others. While this type feedback supports motor skill learning in some tasks, the effect of social comparative feedback on implicit motor sequence learning remains unknown. The aim of this study was to determine the effect of positive social comparative feedback on the learning of and expectancies for a motor sequence task. Methods: Forty-eight individuals practiced a joystick-based sequence task and were divided into three feedback groups: CONTROL (no performance feedback), RT ONLY (response time only feedback), and RT+POS (response time plus positive social comparison). Participants attended sessions on two consecutive days: Day 1 for repetitive motor practice/skill acquisition and Day 2 for retention testing. Performance related expectancies, like perceived competence, were measured before and after motor practice on Day 1 and at retention on Day 2. Results: While all groups improved with practice, the CONTROL group showed better overall performance/learning (faster response times) compared with the RT ONLY group. Despite similar response times, the RT+POS showed higher peak velocities than the RT ONLY group. Overall, the RT+POS and CONTROL demonstrated increases in perceived competence while the RT ONLY group did not. Discussion: The results of this study suggest that feedback content is an important consideration during motor practice sessions since feedback without context (RT ONLY) may be detrimental to motor sequence learning. The results also suggest that, if providing performance related feedback during practice of a skill that relies on implicit sequence learning processes, comparative context may be necessary for enhancing expectancies and supporting.

Mechanisms of the contextual interference effect in individuals poststroke.

Although intermixing different motor learning tasks via random schedules enhances long-term retention compared with "blocked" schedules, the mechanism underlying this contextual interference effect has been unclear. Furthermore, previous studies have reported inconclusive results in individuals poststroke. We instructed participants to learn to produce three grip force patterns in either random or blocked schedules and measured the contextual interference effect by long-term forgetting: the change in performance between immediate and 24-h posttests. Nondisabled participants exhibited the contextual interference effect: no forgetting in the random condition but forgetting in the blocked condition. Participants at least 3 mo poststroke exhibited no forgetting in the random condition but marginal forgetting in the blocked condition. However, in participants poststroke, the integrity of visuospatial working memory modulated long-term retention after blocked schedule training: participants with poor visuospatial working memory exhibited little forgetting at 24 h. These counterintuitive results were predicted by a computational model of motor memory that contains a common fast process and multiple slow processes, which are competitively updated by motor errors. In blocked schedules, the fast process quickly improved performance, therefore reducing error-driven update of the slow processes and thus poor long-term retention. In random schedules, interferences in the fast process led to slower change in performance, therefore increasing error-driven update of slow processes and thus good long-term retention. Increased forgetting rates in the fast process, as would be expected in individuals with visuospatial working memory deficits, led to small updates of the fast process during blocked schedules and thus better long-term retention.