Goal conceptualization has distinct effects on spatial and temporal bimanual coordination after left- and right- hemisphere stroke.

Perception of task goal influences motor performance and coordination. In bimanual actions, it is unclear how one's perception of task goals influences bimanual coordination and performance in individuals with unilateral stroke. We characterized inter-limb coordination differences in individuals with chronic right- and left-hemisphere damaged (RCVA: n = 24, LCVA: n = 24) stroke and age-matched neurotypical controls (n = 24) as they completed bimanual reaching tasks under distinct goal conditions. In the dual-goal condition, participants reached to move two virtual bricks (cursors) assigned to each hand toward independent targets. In the common-goal condition, they moved a central common virtual brick representing both hands to a single, central target. Spatial and temporal coordination (cross-correlation coefficients of hand velocity and their time-lag), the redundant axis deviations (the hand deviations in the axis orthogonal to the axis along the cursor-target direction), and the contribution ratio of the paretic hand were measured. Compared to the dual-goal condition, reaching actions to the common-goal demonstrated better spatial bimanual coordination in all three participant groups. Temporal coordination was better during common-goal than dual-goal actions only for the LCVA group. Additionally, and novel to this field, sex, as a biological variable, differently influenced movement time and redundant axis deviation in participants with stroke under the common-goal condition. Specifically, female stroke survivors showed larger movements in the redundant axes and, consequently, longer movement times, which was more prominent in the LCVA group. Our results indicate that perception of task goals influences bimanual coordination, with common goal improving spatial coordination in neurotypical individuals and individuals with unilateral stroke and providing additional advantage for temporal coordination in those with LCVA. Sex influences bimanual performance in stroke survivors and needs to be considered in future investigations.

Post-stroke deficits in the anticipatory control and bimanual coordination during naturalistic cooperative bimanual action.

BACKGROUND: Unilateral stroke leads to asymmetric deficits in movement performance; yet its effects on naturalistic bimanual actions, a key aspect of everyday functions, are understudied. Particularly, how naturalistic bimanual actions that require the two hands to cooperatively interact with each other while manipulating a single common object are planned, executed, and coordinated after stroke is not known. In the present study, we compared the anticipatory planning, execution, and coordination of force between individuals with left and right hemisphere stroke and neurotypical controls in a naturalistic bimanual common-goal task, lifting a box. METHOD: Thirty-three individuals with chronic stroke (15 LCVA, 18 RCVA) and 8 neurotypical age-matched controls used both hands to lift a box fitted with force transducers under unweighted and weighted conditions. Primary dependent variables included measures of anticipation (peak grip and load force rate), execution (peak grip force, load force), and measures of within-hand (grip-load force coordination) and between-hand coordination (force rate cross-correlations). Primary analyses were performed using linear mixed effects modeling. Exploratory backward stepwise regression examined predictors of individual variability within participants with stroke. RESULTS: Participants with stroke, particularly the RCVA group, showed impaired scaling of grip and load force rates with the addition of weight, indicating deficits in anticipatory control. While there were no group differences in peak grip force, participants with stroke showed significant impairments in peak load force and in grip-load force coordination with specific deficits in the evolution of load force prior to object lift-off. Finally, there were differences in spatial coordination of load force rates for participants with stroke, and especially the RCVA group, as compared to controls. Unimanual motor performance of the paretic arm and hemisphere of lesion (right hemisphere) were the key predictors of impairments in anticipatory planning of grip force and bimanual coordination among participants with stroke. CONCLUSIONS: These results suggest that individuals with stroke, particularly those with right hemisphere damage, have impairments in anticipatory planning and interlimb coordination of symmetric cooperative bimanual tasks.

Sex differences in corticospinal excitability and quadriceps performance after anterior cruciate ligament reconstruction.

Anterior cruciate ligament (ACL) ruptures result in lasting quadriceps dysfunction that contributes to secondary injury risk and development of osteoarthritis. There is evidence of persistent reduced nervous system drive (corticospinal excitability [CSE]) to the quadriceps and sex differences in both quadriceps performance and CSE post-ACL reconstruction (ACLR). The purposes of this study were to investigate the differences in CSE and quadriceps dysfunction after ACLR between sexes and relative to controls. Twenty subjects 4-9 months post-ACLR and 20 age, sex, and activity matched controls participated in this study. Quadriceps performance (peak torque, PT; rate of torque development from onset to 100 ms, RTD100; and RTD from 100 to 200ms, RTD200) and CSE (active motor threshold; slope of the stimulus response (SR) curve, SR curve slope) were measured using an isokinetic dynamometer (HUMAC NORM) and transcranial magnetic stimulation respectively. Significant group differences were found for SR curve slope, PT, RTD100, and RTD200 on the surgical limb. Males after ACLR had higher slopes (higher CSE) than females. Females after ACLR had worse surgical limb quadriceps PT than control males and slower RTD100 and RTD200 than control males and control females. Higher CSE in males after ACLR may point to a potentially adaptive neurological change in males post-ACLR and indicate greater need for novel interventions to address cortical drive in females after ACLR.

Remote ischaemic conditioning combined with bimanual task training to enhance bimanual skill learning and corticospinal excitability in children with unilateral cerebral palsy: a study protocol of a single centre, phase II randomised controlled trial.

INTRODUCTION: Children with unilateral cerebral palsy (UCP) have difficulty in bimanual coordination that restricts the child's independence in daily activities. Although several efficacious interventions to improve bimanual coordination exist, these interventions often require higher training doses and have modest effect sizes. Thus, there is a critical need to find an effective priming agent that, when paired with task-specific training, will facilitate neurobiological processes to enhance the magnitude of training effects and subsequently improve functional capabilities of children with UCP. The aim of this study is to determine the effects of a novel priming agent, remote ischaemic conditioning (RIC), combined with bimanual training on bimanual skill learning and corticospinal excitability in children with UCP. METHODS AND ANALYSES: 46 children, aged 8-16 years, will be randomly assigned to receive RIC or sham conditioning combined with 5 days of bimanual skill (cup stacking) training (15 trials per session). RIC or sham conditioning will be performed with a standard conditioning protocol of five cycles of alternative inflation and deflation of a pressure cuff on the affected arm with the pressure of at least 20 mm Hg above systolic blood pressure for RIC and 25 mm Hg for sham conditioning. Primary outcomes will be movement time and corticospinal excitability measures determined with a single-pulse transcranial magnetic stimulation (TMS). Secondary outcomes include Assisting Hand Assessment, spatio-temporal kinematic variables and paired pulse TMS measures. All measures will be conducted before and immediately after the intervention. A mixed model analysis of variance will test the group×time interaction for all outcomes with group (RIC and sham) as between-subject and time (preintervention, postintervention) as within-subject factors. ETHICS AND DISSEMINATION: The study has been approved by the University Medical Centre Institutional Review Board (UMCIRB #21-001913). We will disseminate the study findings via peer-reviewed publications and presentations at professional conferences. TRIAL REGISTRATION NUMBER: NCT05777070.

Bimanual Movement Characteristics and Real-World Performance Following Hand-Arm Bimanual Intensive Therapy in Children with Unilateral Cerebral Palsy.

The purpose of this study was to quantify characteristics of bimanual movement intensity during 30 h of hand-arm bimanual intensive therapy (HABIT) and bimanual performance (activities and participation) in real-world settings using accelerometers in children with unilateral cerebral palsy (UCP). Twenty-five children with UCP participated in a 30 h HABIT program. Data were collected from bilateral wrist-worn accelerometers during 30 h of HABIT to quantify the movement intensity and three days pre- and post-HABIT to assess real-world performance gains. Movement intensity and performance gains were measured using six standard accelerometer-derived variables. Bimanual capacity (body function and activities) was assessed using standardized hand function tests. We found that accelerometer variables increased significantly during HABIT, indicating increased bimanual symmetry and intensity. Post-HABIT, children demonstrated significant improvements in all accelerometer metrics, reflecting real-world performance gains. Children also achieved significant and clinically relevant changes in hand capacity following HABIT. Therefore, our findings suggest that accelerometers can objectively quantify bimanual movement intensity during HABIT. Moreover, HABIT enhances hand function as well as activities and participation in real-world situations in children with UCP.

Bimanual coordination during reach-to-grasp actions is sensitive to task goal with distinctions between left- and right-hemispheric stroke.

The perceptual feature of a task such as how a task goal is perceived influences performance and coordination of bimanual actions in neurotypical adults. To assess how bimanual task goal modifies paretic and non-paretic arm performance and bimanual coordination in individuals with stroke affecting left and right hemispheres, 30 participants with hemispheric stroke (15 right-hemisphere damage-RHD); 15 left-hemisphere damage-LHD) and 10 age-matched controls performed reach-to-grasp and pick-up actions under bimanual common-goal (i.e., two physically coupled dowels), bimanual independent-goal (two physically uncoupled dowels), and unimanual conditions. Reach-to-grasp time and peak grasp aperture indexed motor performance, while time lags between peak reach velocities, peak grasp apertures, and peak pick-up velocities of the two hands characterized reach, grasp, and pick-up coordination, respectively. Compared to unimanual actions, bimanual actions significantly slowed non-paretic arm speed to match paretic arm speed, thus affording no benefit to paretic arm performance. Detriments in non-paretic arm performance during bimanual actions was more pronounced in the RHD group. Under common-goal conditions, movements were faster with smaller peak grasp apertures compared to independent-goal conditions for all groups. Compared to controls, individuals with stroke demonstrated poor grasp and pick-up coordination. Of the patient groups, patients with LHD showed more pronounced deficits in grasp coordination between hands. Finally, grasp coordination deficits related to paretic arm motor deficits (upper extremity Fugl-Meyer score) for LHD group, and to Trail-Making Test performance for RHD group. Findings suggest that task goal and distinct clinical deficits influence bimanual performance and coordination in patients with left- and right-hemispheric stroke.

Linking Pain and Motor Control: Conceptualization of Movement Deficits in Patients With Painful Conditions.

When people experience or expect pain, they move differently. Pain-altered movement strategies, collectively described here as pain-related movement dysfunction (PRMD), may persist well after pain resolves and, ultimately, may result in altered kinematics and kinetics, future reinjury, and disability. Although PRMD may manifest as abnormal movements that are often evident in clinical assessment, the underlying mechanisms are complex, engaging sensory-perceptual, cognitive, psychological, and motor processes. Motor control theories provide a conceptual framework to determine, assess, and target processes that contribute to normal and abnormal movement and thus are important for physical therapy and rehabilitation practice. Contemporary understanding of motor control has evolved from reflex-based understanding to a more complex task-dependent interaction between cognitive and motor systems, each with distinct neuroanatomic substrates. Though experts have recognized the importance of motor control in the management of painful conditions, there is no comprehensive framework that explicates the processes engaged in the control of goal-directed actions, particularly in the presence of pain. This Perspective outlines sensory-perceptual, cognitive, psychological, and motor processes in the contemporary model of motor control, describing the neural substrates underlying each process and highlighting how pain and anticipation of pain influence motor control processes and consequently contribute to PRMD. Finally, potential lines of future inquiry-grounded in the contemporary model of motor control-are outlined to advance understanding and improve the assessment and treatment of PRMD. IMPACT: This Perspective proposes that approaching PRMD from a contemporary motor control perspective will uncover key mechanisms, identify treatment targets, inform assessments, and innovate treatments across sensory-perceptual, cognitive, and motor domains, all of which have the potential to improve movement and functional outcomes in patients with painful conditions.

Feasibility and longitudinal effects of repeated participation in an annual, brief and intense exercise program in individuals with Parkinson's disease: A case report.

BACKGROUND: Functional decline is expected over time in persons with Parkinson's disease (PD). Intense exercise (RPE ≥ 5-7/10), incorporating motor learning principles, may be beneficial. Purpose:The purpose of this case report is to describe the feasibility and longitudinal effects after individuals with PD participated in multiple, 3.5-day, intensive exercise programs called Movement Camp (Camp). METHODS: Developed based on the principles of skill, capacity, and motivation, the Camp was offered four times (spring 2014-spring 2017) over the course of three years. Camp consisted of 3.5 days, with approximately 5.5 hours of exercise per day. The four participants on whom we are reporting were selected because they participated in three or more Camps, thus providing longitudinal data. Participants rotated through high-intensity, one-hour exercise stations targeting balance, endurance, gait, upper extremity function and three 30-minute group training sessions. Balance (Mini-BESTest), endurance (six-minute walk test), gait speed, and function (five times sit-to-stand) were examined. RESULTS: Testing was completed prior to, post, and six weeks post intervention. Over three years, participants maintained or improved performance on most measures. CONCLUSION: The outcomes of this case report suggest that brief, intensive exercise based on motor learning principles is feasible and may maintain or improve function in persons with PD over three years.

The 4-Element Movement System Model to Guide Physical Therapist Education, Practice, and Movement-Related Research.

The movement system has been adopted as the key identity for the physical therapy profession, and recognition of physical therapists' primary expertise in managing movement dysfunction is an important achievement. However, existing movement system models seem inadequate for guiding education, practice, or research. Lack of a clear, broadly applicable model may hamper progress in physical therapists actually adopting this identity. We propose a model composed of 4 primary elements essential to all movement: motion, force, energy, and control. Although these elements overlap and interact, they can each be examined and tested with some degree of specificity. The proposed 4-element model incorporates specific guidance for visual, qualitative assessment of movement during functional tasks that can be used to develop hypotheses about movement dysfunction and serve as a precursor to more quantitative tests and measures. Human movement always occurs within an environmental context and is affected by personal factors, and these concepts are represented within the model. The proposed scheme is consistent with other widely used models within the profession, such as the International Classification of Functioning, Disability and Health and the Patient Management Model. We demonstrate with multiple examples how the model can be applied to a broad spectrum of patients across the lifespan with musculoskeletal, neurologic, and cardiopulmonary disorders.

Contralesional motor cortex is causally engaged during more dexterous actions of the paretic hand after stroke-A Preliminary report.

Bilateral activation in motor cortex is observed during paretic hand performance after stroke; however the functional significance of contralesional motor cortex (C-M1) activation is highly debated. Particularly, it is not known if task characteristics such as dexterity influence the causal engagement of C-M1 during paretic hand performance. Transcranial magnetic stimulation (TMS) was used to quantify motor corticospinal physiology of the CM1 projecting to the contralateral resting extensor carpi radialis brevis (ECRB) and first dorsal interosseous (FDI) while eleven participants with unilateral stroke performed unimanual tasks of differing dexterity with their paretic hand. The novel finding was that compared to rest and less dexterous task (LDT), more dexterous task (MDT) performance led to increased corticospinal excitability and decreased intracortical inhibition of the C-M1 projecting to the resting FDI, but not resting ECRB. Further, using trains of repetitive TMS during MDT and LDT, we tested the behavioral relevance of C-M1 for paretic hand performance. Online rTMS perturbation to C-M1, but not to the vertex or sham stimulation led to significantly more movement errors during MDT without consistently affecting LDT performance. The present results argue for a beneficial role of C-M1 for accurate performance during dexterous motor actions with the paretic hand after stroke.

Synthesis and characterization of Abhraka (mica) bhasma by two different methods.

BACKGROUND: Bhasmas are traditional Ayurvedic medicines prepared from minerals and metals by tedious process which removes toxic properties of metals and minerals and enhances medicinal properties. We have synthesized abhraka bhasma by two traditional methods and were analyzed during each stage of preparation. OBJECTIVE: The present study deals with the synthesis and characterization of abhraka bhasma by two different methods, method-1 is commonly used for treating anemia and tropical sprue and method-2 for treating chronic cough. Hence attempts have been made to see the physico-chemical differences between these methods by using different analytical techniques. MATERIAL AND METHODS: Different steps in preparation of abhraka bhasma includes shodhana (purification), dhanyabhraka, marana (incineration) and amritikarana. The prepared bhasma were analyzed by classical ayurvedic tests and modern analytical techniques like XRD, FTIR, Raman spectroscopy, SEM, TEM, EDX, BET, DLS and TGA/DTA. RESULTS: The morphological characterization revealed that as-prepared abhraka bhasma products were nano crystalline in nature. Elemental analysis confirms presence of various elements along with carbon suggesting bhasma as herbo-mineral compound. The XRD studies revealed the presence of KMg3(Si3Al)O10(OH)2 in bhasmas. CONCLUSION: Characterization study revealed presence of various bonds of different functional groups and formation of nano particles. Abhraka bhasma prepared by method-2 has more proportion of nano particles than that prepared by method-1 and hence will be more effective in its use.

WITHDRAWN: Immediate Adaptations to Poststroke Walking Performance Using a Wearable Robotic Exoskeleton.

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Behavioral and neurophysiological mechanisms underlying motor skill learning in patients with post-stroke hemiparesis.

OBJECTIVE: Given the presence of execution deficits after stroke, it is difficult to determine if patients with stroke have deficits in motor skill learning with the paretic arm. Here, we controlled for execution deficits while testing practice effects of the paretic arm on motor skill learning, long-term retention, and corticospinal excitability. METHODS: Ten patients with unilateral stroke and ten age-matched controls practiced a kinematic arm skill for two days and returned for retention testing one-day and one-month post-practice. Motor skill learning was quantified as a change in speed-accuracy tradeoff from baseline to retention tests. Transcranial magnetic stimulation (TMS) was used to generate an input-output curve of the ipsilesional motor cortex (M1), and measure transcallosal inhibition from contralesional to ipsilesional M1. RESULTS: While the control group had greater overall accuracy than the stroke group, both groups showed comparable immediate and long-term improvements with practice. Skill improvements were accompanied by greater excitability of the ipsilesional corticospinal system and reduced transcallosal inhibition from contralesional to ipsilesional M1. CONCLUSIONS: When execution deficits are accounted for, patients with stroke demonstrate relatively intact motor skill learning with the paretic arm. Paretic arm learning is accompanied by modulations in corticospinal and transcallosal mechanisms. SIGNIFICANCE: Functional recovery after stroke relies on ability for skill learning and the underlying mechanisms.

Bimanual coordination: A missing piece of arm rehabilitation after stroke.

Inability to use the arm in daily actions significantly lowers quality of life after stroke. Most contemporary post-stroke arm rehabilitation strategies that aspire to re-engage the weaker arm in functional activities have been greatly limited in their effectiveness. Most actions of daily life engage the two arms in a highly coordinated manner. In contrast, most rehabilitation approaches predominantly focus on restitution of the impairments and unilateral practice of the weaker hand alone. We present a perspective that this misalignment between real world requirements and intervention strategies may limit the transfer of unimanual capability to spontaneous arm use and functional recovery. We propose that if improving spontaneous engagement and use of the weaker arm in real life is the goal, arm rehabilitation research and treatment need to address the coordinated interaction between arms in targeted theory-guided interventions. Current narrow focus on unimanual deficits alone, difficulty in quantifying bimanual coordination in real-world actions and limited theory-guided focus on control and remediation of different coordination modes are some of the biggest obstacles to successful implementation of effective interventions to improve bimanual coordination in the real world. We present a theory-guided taxonomy of bimanual actions that will facilitate quantification of coordination for different real-world tasks and provide treatment targets for addressing coordination deficits. We then present evidence in the literature that points to bimanual coordination deficits in stroke survivors and demonstrate how current rehabilitation approaches are limited in their impact on bimanual coordination. Importantly, we suggest theory-based areas of future investigation that may assist quantification, identification of neural mechanisms and scientifically-based training/remediation approaches for bimanual coordination deficits post-stroke. Advancing the science and practice of arm rehabilitation to incorporate bimanual coordination will lead to a more complete functional recovery of the weaker arm, thus improving the effectiveness of rehabilitation interventions and augmenting quality of life after stroke.

Complex Skill Training Transfers to Improved Performance and Control of Simpler Tasks After Stroke.

BACKGROUND: Given limited therapy time, it is important to practice tasks that optimize transfer to other tasks that cannot be practiced during therapy. However, little is known about how tasks can be selected for practice to optimize generalization. OBJECTIVE: One dimension of task selection is the complexity of the task. The purpose of the current study was to test if learning of a complex motor skill with the paretic arm would transfer to a simpler unpracticed goal-directed reaching task. DESIGN: This is an observational study, repeated measures design. METHODS: Fifteen participants with mild-to-moderate stroke practiced a complex motor skill using their paretic arm for 2 consecutive days. Complex skill learning was quantified using change in the speed-accuracy trade-off from baseline to 1 day and 1 month post-practice. Motor transfer was assessed as the change in goal-directed planar reaching performance and kinematics from 2 baselines to 1 day and 1 month post-practice. Nine additional participants with stroke were recruited as the test-alone group who only participated in the transfer tests to rule out the effects of repeated testing. RESULTS: Practice improved the speed-accuracy trade-off for the practiced complex skill that was retained over a period of 1 month. Importantly, complex skill practice, but not repeated testing alone, improved the long-term performance and kinematics of the unpracticed simpler goal-directed planar reaching task. Improvements in the unpracticed transfer task (reaching) strongly correlated with improvements in the practiced complex motor skill. LIMITATIONS: We did not have a comparison stroke group that practiced task-specific reaching movements. CONCLUSIONS: Given the limited number of tasks that can be practiced during therapy, training complex tasks may have an added advantage of transfer to improved simpler task performance.

Goal conceptualization and symmetry of arm movements affect bimanual coordination in individuals after stroke.

Coordination during goal-directed movements emerges from an interaction of task and individual constraints. It is not known how individuals with unilateral stroke and age-matched controls coordinate their arms when performing symmetric and asymmetric movements to accomplish common task goals compared to independent task goals. Eleven individuals with chronic stroke and ten age-matched controls executed a bimanual task under virtual conditions that allowed systematic manipulation of symmetry and goal conditions. Spatial and temporal bimanual coordination was characterized using the cross-correlation coefficients and time lag between the tangential velocities between the two hands. While task conditions had little effect on coordination of control participants, individuals with stroke were less coordinated in space and time during common-goal bimanual actions employing asymmetric arm movements. Further, patients demonstrated lesser contribution of their paretic arm compared to their non-paretic arm during common-goal conditions. These findings indicate that conceptualization of task goals (common vs. independent) and symmetry of arm movements influence coordination and contribution of the two hands during bimanual tasks in patients with stroke.

Task-Dependent Bimanual Coordination After Stroke: Relationship With Sensorimotor Impairments.

OBJECTIVES: To determine (1) bimanual coordination deficits in patients with stroke using 3-dimensional kinematic analyses as they perform naturalistic tasks requiring collaborative interaction of the 2 arms; and (2) whether bimanual coordination deficits are related to clinical measures of sensorimotor impairments and unimanual performance of the paretic arm. DESIGN: Case-control study. SETTING: Rehabilitation hospital research institute. PARTICIPANTS: Participants (N=24) were patients with unilateral chronic stroke (n=14) and age-matched controls (n=10). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Temporal coordination between the 2 hands as participants performed (1) a symmetric task: reach to pick up a box using both hands; and (2) an asymmetric task: open a drawer with 1 hand to press a button inside with the other hand. RESULTS: During the symmetric task, patients and controls showed preserved temporal coupling while transporting the hands to the box. However, on reaching the box, patients demonstrated an impaired ability to cooperatively interact their 2 arms for an efficient pickup. This led to significantly longer pickup times compared with controls. Pickup time positively correlated with proprioceptive deficits of the paretic arm. During the asymmetric task, patients had a longer time delay between drawer opening and button pressing movements than controls. The deficits in asymmetric coordination did not significantly correlate with sensorimotor impairments or unimanual paretic arm performance. CONCLUSIONS: Bimanual coordination was impaired in patients poststroke during symmetric and asymmetric bimanual tasks that required cooperative interaction between the 2 arms. While the proprioceptive system contributes to symmetric cooperative coordination, commonly tested measures of paretic arm impairment or performance, or both, do not strongly predict deficits in bimanual coordination.

Reduced asymmetry in motor skill learning in left-handed compared to right-handed individuals.

Hemispheric specialization for motor control influences how individuals perform and adapt to goal-directed movements. In contrast to adaptation, motor skill learning involves a process wherein one learns to synthesize novel movement capabilities in absence of perturbation such that they are performed with greater accuracy, consistency and efficiency. Here, we investigated manual asymmetry in acquisition and retention of a complex motor skill that requires speed and accuracy for optimal performance in right-handed and left-handed individuals. We further determined if degree of handedness influences motor skill learning. Ten right-handed (RH) and 10 left-handed (LH) adults practiced two distinct motor skills with their dominant or nondominant arms during separate sessions two-four weeks apart. Learning was quantified by changes in the speed-accuracy tradeoff function measured at baseline and one-day retention. Manual asymmetry was evident in the RH group but not the LH group. RH group demonstrated significantly greater skill improvement for their dominant-right hand than their nondominant-left hand. In contrast, for the LH group, both dominant and nondominant hands demonstrated comparable learning. Less strongly-LH individuals (lower EHI scores) exhibited more learning of their dominant hand. These results suggest that while hemispheric specialization influences motor skill learning, these effects may be influenced by handedness.

Improvement in Paretic Arm Reach-to-Grasp following Low Frequency Repetitive Transcranial Magnetic Stimulation Depends on Object Size: A Pilot Study.

Introduction. Low frequency repetitive transcranial magnetic stimulation (LF-rTMS) delivered to the nonlesioned hemisphere has been shown to improve limited function of the paretic upper extremity (UE) following stroke. The outcome measures have largely included clinical assessments with little investigation on changes in kinematics and coordination. To date, there is no study investigating how the effects of LF-rTMS are modulated by the sizes of an object to be grasped. Objective. To investigate the effect of LF-rTMS on kinematics and coordination of the paretic hand reach-to-grasp (RTG) for two object sizes in chronic stroke. Methods. Nine participants received two TMS conditions: real rTMS and sham rTMS conditions. Before and after the rTMS conditions, cortico-motor excitability (CE) of the nonlesioned hemisphere, RTG kinematics, and coordination was evaluated. Object sizes were 1.2 and 7.2 cm in diameter. Results. Compared to sham rTMS, real rTMS significantly reduced CE of the non-lesioned M1. While rTMS had no effect on RTG action for the larger object, real rTMS significantly improved movement time, aperture opening, and RTG coordination for the smaller object. Conclusions. LF-rTMS improves RTG action for only the smaller object in chronic stroke. The findings suggest a dissociation between effects of rTMS on M1 and task difficulty for this complex skill.