Lateralized motor control processes determine asymmetry of interlimb transfer

Differences in brain activation and connectivity during unaffected hand exercise in subacute and convalescent stroke patients

Patients experiencing severe hemiplegia following a stroke struggle to rehabilitate their affected limbs. Cross-education (CE) training emerges as a promising rehabilitation method due to its safety, simplicity, low risk, and ability to effectively improve muscle strength in the affected limb. However, controversy surrounds the neural mechanisms and clinical applications of CE. To address this, we employed functional near-infrared spectroscopy to monitor the response of regions of interest (ROI) and functional connectivity in patients with stroke experiencing severe hemiplegia during one session of 50% maximal voluntary contraction (MVC) strength training with less-affected hand in both subacute and convalescent phases. Our objective was to compare the two stroke groups to gain insight into the potential utility for unilateral training of the less-affected limb as an effective rehabilitation approach during different phases post of stroke. The findings revealed varying degrees of activation in the ROIs within the affected hemisphere across both groups during the task. Additionally, we found that the subacute stroke patients with severe hemiplegia (SPS) had higher blood oxygen levels in the ipsilesional primary motor (iM1), ipsilesional pre-motor and supplementary motor area (iP-SMA) and contralesional P-SMA (cP-SMA). Functional connectivity strength between the iM1 and contralesional brain regions, as well as between the iP-SMA and ipsilesional ROIs, showed statistically significant differences in SPS compared to convalescent stroke patients with severe hemiplegia (CPS) during a 50% MVC strength training session using the less-affected hand. SIGNIFICANCE STATEMENT: Exploring the neural mechanisms underlying one session of 50% MVC strength training with less-affected hand sheds light on a safe therapy. The study enhances our understanding of less-affected hand training and investigates the feasibility as a future rehabilitation approach. Analyzing how one session of 50% MVC strength training with less-affected hand affects brain activation and connectivity could lead to more tailored and effective rehabilitation strategies.

Force drifts and matching errors in the lower extremities: implications for the control and perception of foot force

Accurate control of force on the environment is mechanically necessary for many tasks involving the lower extremities. We investigated drifts in the horizontal (shear) active force produced by right-footed seated subjects and the effects of force matching by the other foot. Subjects generated constant shear force at 15% and 30% of maximal voluntary contraction (MVC) using one foot. Visual feedback of shear force magnitude was provided for the first 5s, then turned off for 30s. During the 30% MVC task, we observed parallel drops in active shear and vertical force magnitudes leading to consistent drifts in the resultant force magnitude, not in its direction. Force matching by the other foot resulted in significantly lower forces when feedback was available throughout the trial. No feedback was provided for the matching foot. When the matching foot began exerting force, the task foot experienced a notable drop in all force components, with a change in force direction only for the task foot. After this initial drop, the downward drift in the task foot stopped or reversed. Subjects were unaware of these drifts and errors. Our findings suggest that shear force production involves setting a referent coordinate vector, which shows drifts and matching errors, while its direction remains stable. Involvement of the matching foot appears to perturb the neural commands to the task foot, with minor differences observed between feet. The discrepancy between the consistent force drifts and lack of awareness of the drifts indicates a difference between force perception-to-act and perception-to-report.

Lateralization of acquisition and consolidation in direction but not amplitude of a motor skill task

Previous research suggests that the neural processes underlying specification of movement direction and amplitude are independently represented in the nervous system. However, our understanding of acquisition and consolidation processes in the direction and distance learning remains limited. We designed a virtual air hockey task, in which the puck direction is determined by the hand direction at impact, while the puck distance is determined by the amplitude of the velocity. In two versions of this task, participants were required to either specify the direction or the distance of the puck, while the alternate variable did not contribute to task success. Separate groups of right-handed participants were recruited for each task. Each participant was randomly assigned to one of two groups with a counter-balanced arm practice sequence (right to left, or left to right). We examined acquisition and, after 24 h, we examined two aspects of consolidation: 1) same hand performance to test the durability and 2) the opposite hand to test the effector-independent consolidation (interlimb transfer) of learning. The distance task showed symmetry between hands in the extent of acquisition as well as in both aspects of consolidation. In contrast, the direction task showed asymmetry in both acquisition and consolidation: the dominant right arm showed faster and greater acquisition and greater transfer from the opposite arm training. The asymmetric acquisition and consolidation processes shown in the direction task might be explained by lateralized control and mapping of direction, an interpretation consistent with previous findings on motor adaptation paradigms.

Upper extremity asymmetry due to nerve injuries or central neurologic conditions: a scoping review

BACKGROUND

Peripheral nerve injuries and central neurologic conditions can result in extensive disabilities. In cases with unilateral impairment, assessing the asymmetry between the upper extremity has been used to assess outcomes of treatment and severity of injury. A wide variety of validated and novel tests and sensors have been utilized to determine the upper extremity asymmetry. The purpose of this article is to review the literature and define the current state of the art for describing upper extremity asymmetry in patients with peripheral nerve injuries or central neurologic conditions.

METHOD

An electronic literature search of PubMed, Scopus, Web of Science, OVID was performed for publications between 2000 to 2022. Eligibility criteria were subjects with neurological conditions/injuries who were analyzed for dissimilarities in use between the upper extremities. Data related to study population, target condition/injury, types of tests performed, sensors used, real-world data collection, outcome measures of interest, and results of the study were extracted. Sackett's Level of Evidence was used to judge the quality of the articles.

RESULTS

Of the 7281 unique articles, 112 articles met the inclusion criteria for the review. Eight target conditions/injuries were identified (Brachial Plexus Injury, Cerebral Palsy, Multiple Sclerosis, Parkinson's Disease, Peripheral Nerve Injury, Spinal Cord Injury, Schizophrenia, and stroke). The tests performed were classified into thirteen categories based on the nature of the test and data collected. The general results related to upper extremity asymmetry were listed for all the reviewed articles. Stroke was the most studied condition, followed by cerebral palsy, with kinematics and strength measurement tests being the most frequently used tests. Studies with a level of evidence level II and III increased between 2000 and 2021. The use of real-world evidence-based data, and objective data collection tests also increased in the same period.

CONCLUSION

Adequately powered randomized controlled trials should be used to study upper extremity asymmetry. Neurological conditions other than stroke should be studied further. Upper extremity asymmetry should be measured using objective outcome measures like motion tracking and activity monitoring in the patient's daily living environment.

Playing with your ears: Audio-motor skill learning is sensitive to the lateral relationship between trained hand and ear

A salient feature of motor and sensory circuits in the brain is their contralateral hemispheric bias-a feature that might play a role in integration and learning of sensorimotor skills. In the current behavioral study, we examined whether the lateral configuration between sound-producing hand and feedback-receiving ear affects performance and learning of an audio-motor skill. Right-handed participants (n = 117) trained to play a piano sequence using their right or left hand while auditory feedback was presented monaurally, either to the right or left ear. Participants receiving auditory feedback to the contralateral ear during training performed better than participants receiving ipsilateral feedback (with respect to the training hand). Furthermore, in the Left-Hand training groups, the contralateral training advantage persisted in a generalization task. Our results demonstrate that audio-motor learning is sensitive to the lateral configuration between motor and sensory circuits and suggest that integration of neural activity across hemispheres facilitates such learning.

Bilateral transfer of motor performance as a function of motor imagery training: a systematic review and meta-analysis

Objective

The objective of this review was to evaluate the efficacy of mental imagery training (MIT) in promoting bilateral transfer (BT) of motor performance for healthy subjects.

Data sources

We searched 6 online-databases (Jul-Dec 2022) using terms: "mental practice," "motor imagery training," "motor imagery practice," "mental training," "movement imagery," "cognitive training," "bilateral transfer," "interlimb transfer," "cross education," "motor learning," "strength," "force" and "motor performance."

Study selection and data extraction

We selected randomized-controlled studies that examined the effect of MIT on BT. Two reviewers independently determined if each study met the inclusion criteria for the review. Disagreements were resolved through discussion and, if necessary, by a third reviewer. A total of 9 articles out of 728 initially identified studies were chosen for the meta-analysis.

Data synthesis

The meta-analysis included 14 studies for the comparison between MIT and no-exercise control (CTR) and 15 studies for the comparison between MIT and physical training (PT).

Results

MIT showed significant benefit in inducing BT compared to CTR (ES = 0.78, 95% CI = 0.57-0.98). The effect of MIT on BT was similar to that of PT (ES = -0.02, 95% CI = -0.15-0.17). Subgroup analyses showed that internal MIT (IMIT) was more effective (ES = 2.17, 95% CI = 1.57-2.76) than external MIT (EMIT) (ES = 0.95, 95% CI = 0.74-1.17), and mixed-task (ES = 1.68, 95% CI = 1.26-2.11) was more effective than mirror-task (ES = 0.46, 95% CI = 0.14-0.78) and normal-task (ES = 0.56, 95% CI = 0.23-0.90). No significant difference was found between transfer from dominant limb (DL) to non-dominant limb (NDL) (ES = 0.67, 95% CI = 0.37-0.97) and NDL to DL (ES = 0.87, 95% CI = 0.59-1.15).

Conclusion

This review concludes that MIT can serve as a valuable alternative or supplement to PT in facilitating BT effects. Notably, IMIT is preferable to EMIT, and interventions incorporating tasks that have access to both intrinsic and extrinsic coordinates (mixed-task) are preferred over those that involve only one of the two coordinates (mirror-task or normal-task). These findings have implications for rehabilitation of patients such as stroke survivors.

Bilateral Transfer of Performance between Real and Non-Immersive Virtual Environments in Post-Stroke Individuals: A Cross-Sectional Study

(1) Background: Post-stroke presents motor function deficits, and one interesting possibility for practicing skills is the concept of bilateral transfer. Additionally, there is evidence that the use of virtual reality is beneficial in improving upper limb function. We aimed to evaluate the transfer of motor performance of post-stroke and control groups in two different environments (real and virtual), as well as bilateral transfer, by changing the practice between paretic and non-paretic upper limbs. (2) Methods: We used a coincident timing task with a virtual (Kinect) or a real device (touch screen) in post-stroke and control groups; both groups practiced with bilateral transference. (3) Results: Were included 136 participants, 82 post-stroke and 54 controls. The control group presented better performance during most parts of the protocol; however, it was more evident when compared with the post-stroke paretic upper limb. We found bilateral transference mainly in Practice 2, with the paretic upper limb using the real interface method (touch screen), but only after Practice 1 with the virtual interface (Kinect), using the non-paretic upper limb. (4) Conclusions: The task with the greatest motor and cognitive demand (virtual-Kinect) provided transfer into the real interface, and bilateral transfer was observed in individuals post-stroke. However, this is more strongly observed when the virtual task was performed using the non-paretic upper limb first.

Are reaching and grasping effector-independent? Similarities and differences in reaching and grasping kinematics between the hand and foot

While reaching and grasping are highly prevalent manual actions, neuroimaging studies provide evidence that their neural representations may be shared between different body parts, i.e., effectors. If these actions are guided by effector-independent mechanisms, similar kinematics should be observed when the action is performed by the hand or by a cortically remote and less experienced effector, such as the foot. We tested this hypothesis with two characteristic components of action: the initial ballistic stage of reaching, and the preshaping of the digits during grasping based on object size. We examined if these kinematic features reflect effector-independent mechanisms by asking participants to reach toward and to grasp objects of different widths with their hand and foot. First, during both reaching and grasping, the velocity profile up to peak velocity matched between the hand and the foot, indicating a shared ballistic acceleration phase. Second, maximum grip aperture and time of maximum grip aperture of grasping increased with object size for both effectors, indicating encoding of object size during transport. Differences between the hand and foot were found in the deceleration phase and time of maximum grip aperture, likely due to biomechanical differences and the participants’ inexperience with foot actions. These findings provide evidence for effector-independent visuomotor mechanisms of reaching and grasping that generalize across body parts.

A short review on emotion processing: a lateralized network of neuronal networks

Emotions are valenced mental responses and associated physiological reactions that occur spontaneously and automatically in response to internal or external stimuli, and can influence our behavior, and can themselves be modulated to a certain degree voluntarily or by external stimuli. They are subserved by large-scale integrated neuronal networks with epicenters in the amygdala and the hippocampus, and which overlap in the anterior cingulate cortex. Although emotion processing is accepted as being lateralized, the specific role of each hemisphere remains an issue of controversy, and two major hypotheses have been proposed. In the right-hemispheric dominance hypothesis, all emotions are thought to be processed in the right hemisphere, independent of their valence or of the emotional feeling being processed. In the valence lateralization hypothesis, the left is thought to be dominant for the processing of positively valenced stimuli, or of stimuli inducing approach behaviors, whereas negatively valenced stimuli, or stimuli inducing withdrawal behaviors, would be processed in the right hemisphere. More recent research points at the existence of multiple interrelated networks, each associated with the processing of a specific component of emotion generation, i.e., its generation, perception, and regulation. It has thus been proposed to move from hypotheses supporting an overall hemispheric specialization for emotion processing toward dynamic models incorporating multiple interrelated networks which do not necessarily share the same lateralization patterns.

Deficient Interhemispheric Connectivity Underlies Movement Irregularities in Parkinson's Disease

BACKGROUND

Movement execution is impaired in patients with Parkinson's disease. Evolving neurodegeneration leads to altered connectivity between distinct regions of the brain and altered activity at interconnected areas. How connectivity alterations influence complex movements like drawing spirals in Parkinson's disease patients remains largely unexplored.

OBJECTIVE

We investigated whether deteriorations in interregional connectivity relate to impaired execution of drawing.

METHODS

Twenty-nine patients and 31 age-matched healthy control participants drew spirals with both hands on a digital graphics tablet, and the regularity of drawing execution was evaluated by sample entropy. We recorded resting-state fMRI and task-related EEG, and calculated the time-resolved partial directed coherence to estimate effective connectivity for both imaging modalities to determine the extent and directionality of interregional interactions.

RESULTS

Movement performance in Parkinson's disease patients was characterized by increased sample entropy, corresponding to enhanced irregularities in task execution. Effective connectivity between the motor cortices of both hemispheres, derived from resting-state fMRI, was significantly reduced in Parkinson's disease patients in comparison to controls. The connectivity strength in the nondominant to dominant hemisphere direction in both modalities was inversely correlated with irregularities during drawing, but not with the clinical state.

CONCLUSION

Our findings suggest that interhemispheric connections are affected both at rest and during drawing movements by Parkinson's disease. This provides novel evidence that disruptions of interhemispheric information exchange play a pivotal role for impairments of complex movement execution in Parkinson's disease patients.

Neural mechanisms mediating cross education: With additional considerations for the ageing brain

CALVERT, G.H.M., and CARSON, R.G. Neural mechanisms mediating cross education: With additional considerations for the ageing brain. NEUROSCI BIOBEHAV REV 21(1) XXX-XXX, 2021. - Cross education (CE) is the process whereby a regimen of unilateral limb training engenders bilateral improvements in motor function. The contralateral gains thus derived may impart therapeutic benefits for patients with unilateral deficits arising from orthopaedic injury or stroke. Despite this prospective therapeutic utility, there is little consensus concerning its mechanistic basis. The precise means through which the neuroanatomical structures and cellular processes that mediate CE may be influenced by age-related neurodegeneration are also almost entirely unknown. Notwithstanding the increased incidence of unilateral impairment in later life, age-related variations in the expression of CE have been examined only infrequently. In this narrative review, we consider several mechanisms which may mediate the expression of CE with specific reference to the ageing CNS. We focus on the adaptive potential of cellular processes that are subserved by a specific set of neuroanatomical pathways including: the corticospinal tract, corticoreticulospinal projections, transcallosal fibres, and thalamocortical radiations. This analysis may inform the development of interventions that exploit the therapeutic utility of CE training in older persons.

Symmetric interlimb transfer of newly acquired skilled movements

In this study, we aimed to examine features of interlimb generalization or "transfer" of newly acquired motor skills, with a broader goal of better understanding the mechanisms mediating skill learning. Right-handed participants (n = 36) learned a motor task that required them to make very rapid but accurate reaches to one of eight randomly presented targets, thus bettering the typical speed-accuracy tradeoff. Subjects were divided into an "RL" group that first trained with the right arm and was then tested on the left and an "LR" group that trained with the left arm and was subsequently tested on the right. We found significant interlimb transfer in both groups. Remarkably, we also observed that participants learned faster with their left arm compared with the right. We hypothesized that this could be due to a previously suggested left arm/right hemisphere advantage for movements under variable task conditions. To corroborate this, we recruited two additional groups of participants (n = 22) that practiced the same task under a single target condition. This removal of task level variability eliminated learning rate differences between the arms, yet interlimb transfer remained robust and symmetric, as in the first experiment. Additionally, the strategy used to reduce errors during learning, albeit heterogeneous across subjects particularly in our second experiment, was adopted by the untrained arm. These findings may be best explained as the outcome of the operation of cognitive strategies during the early stages of motor skill learning.NEW & NOTEWORTHY How newly acquired motor skills generalize across effectors is not well understood. Here, we show that newly learned skilled actions transfer symmetrically across the arms and that task-level variability influences learning rate but not transfer magnitude or direction. Interestingly, strategies developed during learning with one arm transfer to the untrained arm. This likely reflects the outcome of learning driven by cognitive mechanisms during the initial stages of motor skill acquisition.

Differences in the Magnitude of Motor Skill Acquisition and Interlimb Transfer between Left- and Right-Handed Subjects after Short-Term Unilateral Motor Skill Practice

Motor skill practice improves performance not only in the trained - but also in the untrained contralateral limb - a phenomenon called as interlimb transfer. Handedness affects motor skill acquisition and interlimb transfer, but it remains unknown whether handedness affects interlimb transfer when practicing with the dominant or non-dominant limb. We have hypothesized that interlimb transfer of skill acquisition differs between left- and right-handed participants, and that right- as compared with left-hand motor skill practice shows greater interlimb transfer, regardless of handedness. Strongly left-hand (n = 12, aged 27.3 ± 4.4 years; 3 female) and right-hand dominant (n = 12, 20.7 ± 3.8 years; 5 female) subjects with no history of neurological or orthopedic disorders performed the grooved pegboard test before and after 4 blocks of practice on the same apparatus. Subjects were timed on their speed of the task. Right-handed subjects failed to improve manual performance in their right hand after right- or left-hand motor practice. In contrast, they showed improvement on the left hand in each condition. These data suggest greater interlimb transfer after right-hand motor skill practice, but no interlimb transfer after left-hand practice. On the other hand, our results show consistent interlimb transfer effects in left-handed subjects, irrespective of whether the dominant left or the non-dominant right arm has been initially trained. In conclusion, our results add to the body of literature by detecting the differences in the magnitude of motor skill acquisition and interlimb transfer between left- and right-handed subjects after short-term unilateral motor skill practice.

Interlimb differences in coordination of rapid wrist/forearm movements

We have previously proposed a model of motor lateralization that attributes specialization for predictive control of intersegmental coordination to the dominant hemisphere/limb system, and control of limb impedance to the non-dominant system. This hypothesis was developed based on visually targeted discrete reaching movement made predominantly with the shoulder and elbow joints. The purpose of this experiment was to determine whether dominant arm advantages for multi-degree of freedom coordination also occur during continuous distal movements of the wrist that do not involve visual guidance. In other words, are the advantages of the dominant arm restricted to controlling intersegmental coordination during discrete visually targeted reaching movements, or are they more generally related to coordination of multiple degrees of freedom at other joints, regardless of whether the movements are discrete or invoke visual guidance? Eight right-handed participants were instructed to perform alternating wrist ulnar/radial deviation movements at two instructed speeds, slow and fast, with the dominant or the non-dominant arm, and were instructed not to rotate the forearm (pronation/supination) or move the wrist up and down (flexion/extension). This was explained by slowly and passively moving the wrist in each plane during the instructions. Because all the muscles that cross the wrist have moment arms with respect to more than one axis of rotation, intermuscular coordination is required to prevent motion about non-instructed axes of rotation. We included two conditions, a very slow condition, as a control condition, to demonstrate understanding of the task, and an as-fast-as-possible condition to challenge predictive aspect of control, which we hypothesize are specialized to the dominant controller. Our results indicated that during as-fast-as-possible conditions the non-dominant arm incorporated significantly more non-instructed motion, which resulted in greater circumduction at the non-dominant than the dominant wrist. These findings extend the dynamic dominance hypothesis, indicating that the dominant hemisphere-arm system is specialized for predictive control of multiple degrees of freedom, even in movements of the distal arm and made in the absence of visual guidance.

Competition for limited neural resources in older adults leads to greater asymmetry of bilateral movements than in young adults

We previously demonstrated that lateralization in the neural control of predictive and impedance mechanisms is reflected by interlimb differences in control of bilateral tasks. Aging has been shown to reduce lateralization during unilateral performance, presumably due to greater recruitment of the ipsilateral hemisphere. We now hypothesize that aging-related reduction in the efficiency of neural resources should produce greater behavioral asymmetry during bilateral actions that require hemispheric specialization for each arm. This is because simultaneous control of dominant and nondominant arm function should induce competition for hemisphere-specific resources. To test this hypothesis, we now examine the effect of aging (young, n = 20; old, n = 20) on performance of a mechanically coupled task, in which one arm reaches toward targets while the other arm stabilizes against a spring that connects the two arms. Results indicate better dominant arm reaching performance and better nondominant arm stabilizing performance for both groups. Most notably, limb and joint compliance was lower in the dominant arm, leading to dominant arm deficits in stabilizing performance. Group analysis indicated that older adults showed substantially greater asymmetry in stabilizing against the spring load than did the younger adults. We propose that competition for limited neural resources in older adults is associated with reduced contributions of right hemisphere mechanisms to right-dominant arm stabilizing performance, and thus to greater asymmetry of performance.NEW & NOTEWORTHY We provide evidence for greater asymmetry of interlimb differences in bilateral coordination for stabilizing and preserved asymmetry of reaching with aging. These results provide the first evidence for increased lateralization with aging within the context of a complementary bilateral task.

Interlimb transfer and generalisation of learning in the context of persistent failure to accomplish a visuomotor task

Transfer, in which capability acquired in one situation influences performance in another is considered, along with retention, as demonstrative of effectual learning. In this regard, interlimb transfer of functional capacity has commanded particular attention as a means of gauging the generalisation of acquired capability. Both theoretical treatments and prior empirical studies suggest that the successful accomplishment of a physical training regime is required to bring about generalised changes that extend to the untrained limb. In the present study, we pose the following question: Does interlimb transfer occur if and only if the training movements are executed? We report findings from JG-an individual recruited to a larger scale trial, who presented with (unilateral) deficits of motor control. We examined whether changes in the performance of the untrained right limb arose following practice undertaken by the impaired left limb, wherein the majority of JG's attempts to execute the training task were unsuccessful. Comparison was made with a group of "control" participants drawn from the main trial, who did not practice the task. For JG, substantial gains in the performance of the untrained limb (registered 3 days, 10 days and 1 year following training) indicated that effective learning had occurred. Learning was, however, expressed principally when the unimpaired (i.e. untrained) limb was utilised to perform the task. When the impaired limb was used, marked deficiencies in movement execution remained prominent throughout.

Handedness results from complementary hemispheric dominance, not global hemispheric dominance: evidence from mechanically coupled bilateral movements

Two contrasting views of handedness can be described as 1) complementary dominance, in which each hemisphere is specialized for different aspects of motor control, and 2) global dominance, in which the hemisphere contralateral to the dominant arm is specialized for all aspects of motor control. The present study sought to determine which motor lateralization hypothesis best predicts motor performance during common bilateral task of stabilizing an object (e.g., bread) with one hand while applying forces to the object (e.g., slicing) using the other hand. We designed an experimental equivalent of this task, performed in a virtual environment with the unseen arms supported by frictionless air-sleds. The hands were connected by a spring, and the task was to maintain the position of one hand while moving the other hand to a target. Thus the reaching hand was required to take account of the spring load to make smooth and accurate trajectories, while the stabilizer hand was required to impede the spring load to keep a constant position. Right-handed subjects performed two task sessions (right-hand reach and left-hand stabilize; left-hand reach and right-hand stabilize) with the order of the sessions counterbalanced between groups. Our results indicate a hand by task-component interaction such that the right hand showed straighter reaching performance whereas the left hand showed more stable holding performance. These findings provide support for the complementary dominance hypothesis and suggest that the specializations of each cerebral hemisphere for impedance and dynamic control mechanisms are expressed during bilateral interactive tasks. NEW & NOTEWORTHY We provide evidence for interlimb differences in bilateral coordination of reaching and stabilizing functions, demonstrating an advantage for the dominant and nondominant arms for distinct features of control. These results provide the first evidence for complementary specializations of each limb-hemisphere system for different aspects of control within the context of a complementary bilateral task.

Use-dependent directional bias does not transfer to the untrained limb during bimanual contractions

Skills learned through practice with one limb can often be transferred to the untrained limb. In the present report, we sought to determine whether movement direction biases, acquired through repeated movement with one limb, transfer to the untrained limb. In order to do so, we asked participants to perform synchronized bilateral contractions of muscles in both wrists, followed by the unilateral contraction of muscles in one wrist. In four experiments, we manipulated the position of the unilateral target to create use-dependent directional biases; changed the direction of the cursor in relation to the wrist movement to control for attentional biases; and sought to induce directional biases with both right and left unilateral movements. The results showed clear movement-related biases for the wrist that performed unilateral contractions, but no evidence that movement-related bias transferred to the opposite limb during bilateral action. Thus, motor preparation and execution of unilateral contractions does not affect the direction of movement made by the opposite limb during subsequent bilateral contractions.