Functional implications of ipsilesional motor deficits after unilateral stroke

Motor recovery of the ipsilesional upper limb in subacute stroke

OBJECTIVE

To investigate the time-related changes in motor performance of the ipsilesional upper limb in subacute poststroke patients by using clinical and kinematic assessments.

DESIGN

Observational, longitudinal, prospective, monocentric study.

SETTING

Physical medicine and rehabilitation department.

PARTICIPANTS

Stroke patients (n=19; mean age, 62.9y) were included less than 30 days after a first unilateral ischemic/hemorrhagic stroke. The control group was composed of age-matched, healthy volunteers (n=9; mean age, 63.1y).

INTERVENTIONS

Clinical and kinematic assessments were conducted once a week during 6 weeks and 3 months after inclusion. Clinical measures consisted of Fugl-Meyer Assessment, Box and Block Test (BBT), Nine-Hole Peg Test (9HPT), and Barthel Index. We used a 3-dimensional motion recording system during a reach-to-grasp task to analyze movement smoothness, movement time, and peak velocity of the hand. Healthy controls performed both clinical (BBT and 9HPT) and kinematic evaluation within a single session.

MAIN OUTCOME MEASURES

BBT and 9HPT.

RESULTS

Recovery of ipsilesional upper arm capacities increased over time and leveled off after a 6-week period of rehabilitation, corresponding to 9 weeks poststroke. At study discharge, patients demonstrated similar ipsilesional clinical scores to controls but exhibited less smooth reaching movements. We found no effect of the hemispheric side of the lesion on ipsilesional motor deficits.

CONCLUSIONS

Our findings provide evidence that ipsilesional motor capacities remain impaired at least 3 months after stroke, even if clinical tests fail to detect the impairment. Focusing on this lasting ipsilesional impairment through a more detailed kinematic analysis could be of interest to understand the specific neural network underlying ipsilesional upper-limb impairment.

Bilateral impairments in task-dependent modulation of the long-latency stretch reflex following stroke

OBJECTIVE

Modulation of the long-latency reflex (LLR) is important for sensorimotor control during interaction with different mechanical loads. Transcortical pathways usually contribute to LLR modulation, but the integrity of pathways projecting to the paretic and non-paretic arms of stroke survivors is compromised. We hypothesize that disruption of transcortical reflex pathways reduces the capacity for stroke survivors to appropriately regulate the LLR bilaterally.

METHODS

Elbow perturbations were applied to the paretic and non-paretic arms of persons with stroke, and the dominant arm of age-matched controls as subjects interacted with Stiff or Compliant environments rendered by a linear actuator. Reflexes were quantified using surface electromyograms, recorded from biceps.

RESULTS

LLR amplitude was significantly larger during interaction with the Compliant load compared to the Stiff load in controls. However, there was no significant change in LLR amplitude for the paretic or non-paretic arm of stroke survivors.

CONCLUSION

Modulation of the LLR is altered in the paretic and non-paretic arms after stroke.

SIGNIFICANCE

Our results are indicative of bilateral sensorimotor impairments following stroke. The inability to regulate the LLR may contribute to bilateral deficits in tasks that require precise control of limb mechanics and stability.

Relationship between arm usage and instrumental activities of daily living after unilateral stroke

OBJECTIVE

To determine whether the preferred pattern of arm use after unilateral hemispheric damage was associated with better everyday functioning. Our previous work showed that right-handed stroke patients with right hemisphere damage (RHD) used their right, ipsilesional arm most frequently, while those with left hemisphere damage (LHD) used both arms together most frequently. This effect was explained by right-hand preference, but its relationship to functional performance is not known.

DESIGN

Observational cohort.

SETTING

Research laboratory.

PARTICIPANTS

Stroke patients (n=60; 30 RHD, 30 LHD) and healthy controls (n=52).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The Functional Impact Assessment was used to assess performance on instrumental activities of daily living (IADLs).

RESULTS

The preferred patterns of arm use were similar to those in our previous report. However, it was the greater use of both arms together that was associated with better IADL performance in both stroke groups. Ipsilesional arm use alone was not significantly associated with IADL performance in the RHD group and was associated with poorer performance in the LHD group.

CONCLUSIONS

The modal arm use pattern did not always optimize IADL functioning. Better IADL functioning in both stroke groups was associated with the use of both arms together, which is the most common arm use pattern of healthy individuals doing these same IADLs. An important practical question that arises from these findings is whether bilateral arm rehabilitation should be emphasized, because using both arms together is the best predictor of better performance on everyday tasks.

Dynamic brain structural changes after left hemisphere subcortical stroke

This study aimed to quantify dynamic structural changes in the brain after subcortical stroke and identify brain areas that contribute to motor recovery of affected limbs. High-resolution structural MRI and neurological examinations were conducted at five consecutive time points during the year following stroke in 10 patients with left hemisphere subcortical infarctions involving motor pathways. Gray matter volume (GMV) was calculated using an optimized voxel-based morphometry technique, and dynamic changes in GMV were evaluated using a mixed-effects model. After stroke, GMV was decreased bilaterally in brain areas that directly or indirectly connected with lesions, which suggests the presence of regional damage in these "healthy" brain tissues in stroke patients. Moreover, the GMVs of these brain areas were not correlated with the Motricity Index (MI) scores when controlling for time intervals after stroke, which indicates that these structural changes may reflect an independent process (such as axonal degeneration) but cannot affect the improvement of motor function. In contrast, the GMV was increased in several brain areas associated with motor and cognitive functions after stroke. When controlling for time intervals after stroke, only the GMVs in the cognitive-related brain areas (hippocampus and precuneus) were positively correlated with MI scores, which suggests that the structural reorganization in cognitive-related brain areas may facilitate the recovery of motor function. However, considering the small sample size of this study, further studies are needed to clarify the exact relationships between structural changes and recovery of motor function in stroke patients.

Theories and control models and motor learning: clinical applications in neuro-rehabilitation

INTRODUCTION

In recent decades there has been a special interest in theories that could explain the regulation of motor control, and their applications. These theories are often based on models of brain function, philosophically reflecting different criteria on how movement is controlled by the brain, each being emphasised in different neural components of the movement. The concept of motor learning, regarded as the set of internal processes associated with practice and experience that produce relatively permanent changes in the ability to produce motor activities through a specific skill, is also relevant in the context of neuroscience. Thus, both motor control and learning are seen as key fields of study for health professionals in the field of neuro-rehabilitation.

DEVELOPMENT

The major theories of motor control are described, which include, motor programming theory, systems theory, the theory of dynamic action, and the theory of parallel distributed processing, as well as the factors that influence motor learning and its applications in neuro-rehabilitation.

CONCLUSIONS

At present there is no consensus on which theory or model defines the regulations to explain motor control. Theories of motor learning should be the basis for motor rehabilitation. The new research should apply the knowledge generated in the fields of control and motor learning in neuro-rehabilitation.

Force control of quadriceps muscle is bilaterally impaired in subacute stroke

We tested the hypothesis that force variability and error during maintenance of submaximal isometric knee extension are greater in subacute stroke patients than in controls and are related to motor impairments. Contralesional (more-affected) and ipsilesional (less-affected) legs of 33 stroke patients with sufficiently high motor abilities (62 ± 13 yr, 16 ± 2 days postinjury) and the dominant leg of 20 controls (62 ± 10 yr) were tested in sitting position. After peak knee extension torque [maximum voluntary contraction (MVC)] was established, subjects maintained 10, 20, 30, and 50% of MVC as steady and accurate as possible for 10 s by matching voluntary force to the target level displayed on a monitor. Coefficient of variation (CV) and root-mean-square error (RMSE) were used to quantify force variability and error, respectively. The MVC was significantly smaller in the more-affected than less-affected leg, and both were significantly lower than in controls. The CV was significantly larger in the more-affected than less-affected leg at 20 and 50% MVC, whereas both were significantly larger compared with controls across all force levels. Both more-affected and less-affected legs of patients showed significantly greater RMSE than controls at 30 and 50% MVC. The CV and RMSE were not related to the Fugl-Meyer motor score or to the Rivermead Mobility Index. The CV negatively correlated with MVC in controls but only in the less-affected leg of patients. It is concluded that isometric knee extension strength and force control are bilaterally impaired soon after stroke but more so in the more-affected leg. Future studies should examine possible mechanisms and the evolution of these changes.

Hemispheric specialization for movement control produces dissociable differences in online corrections after stroke

In this study, we examine whether corrections made during an ongoing movement are differentially affected by left hemisphere damage (LHD) and right hemisphere damage (RHD). Our hypothesis of motor lateralization proposes that control mechanisms specialized to the right hemisphere rely largely on online processes, while the left hemisphere primarily utilizes predictive mechanisms to specify optimal coordination patterns. We therefore predict that RHD, but not LHD, should impair online correction when task goals are unexpectedly changed. Fourteen stroke subjects (7 LHD, 7 RHD) and 14 healthy controls reached to 1 of the 3 targets that unexpectedly "jumped" during movement onset. RHD subjects showed a considerable delay in initiating the corrective response relative to controls and LHD subjects. However, both stroke groups made large final position errors on the target jump trials. Position deficits following LHD were associated with poor intersegmental coordination, while RHD subjects had difficulty terminating their movements appropriately. These findings confirm that RHD, but not LHD, produces a deficit in the timing of online corrections and also indicate that both stroke groups show position deficits that are related to the specialization of their damaged hemisphere. Further research is needed to identify specific neural circuits within each hemisphere critical for these processes.

Meal preparation abilities after left or right hemisphere stroke

OBJECTIVE

To examine meal preparation ability after right or left hemisphere damage (RHD, LHD) caused by stroke and whether cognitive (spatial abilities, aphasia, limb apraxia) and motor deficits are differentially associated with meal preparation.

DESIGN

Observational cohort design.

SETTING

Primary care Veterans Affair Medical Center and private medical center.

PARTICIPANTS

Volunteer right-handed sample of adults with LHD (n=30) or RHD (n=16) caused by stroke and healthy demographically matched adults (n=63) (N=109).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Total completion time, number and type of errors, and level of independence for a meal preparation task consisting of making a hot beverage and toast, eating part of the meal, and clean-up.

RESULTS

Both stroke groups took significantly more time to complete the meal preparation task than the control group. Total errors and level of independence were worse in the group with LHD than other groups, but individual errors did not significantly differ between the 2 stroke groups. While correlations should be interpreted cautiously, especially in the relatively small RHD group, poorer ipsilesional motor performance was associated with longer completion time in the RHD group, and poorer contralesional motor performance and greater aphasia were associated with less independence in the LHD group.

CONCLUSIONS

These findings demonstrate impaired meal preparation after LHD or RHD but greater impairment after LHD. Poorer meal preparation is associated with different cognitive and motor deficits in the 2 stroke groups.

Volumetric effects of motor cortex injury on recovery of ipsilesional dexterous movements

Damage to the motor cortex of one hemisphere has classically been associated with contralateral upper limb paresis, but recent patient studies have identified deficits in both upper limbs. In non-human primates, we tested the hypothesis that the severity of ipsilesional upper limb motor impairment in the early post-injury phase depends on the volume of gray and white matter damage of the motor areas of the frontal lobe. We also postulated that substantial recovery would accompany minimal task practice and that ipsilesional limb recovery would be correlated with recovery of the contralesional limb. Gross (reaching) and fine hand motor functions were assessed for 3-12 months post-injury using two motor tests. Volumes of white and gray matter lesions were assessed using quantitative histology. Early changes in post-lesion motor performance were inversely correlated with white matter lesion volume indicating that larger lesions produced greater decreases in ipsilesional hand movement control. All monkeys showed improvements in ipsilesional hand motor skill during the post-lesion period, with reaching skill improvements being positively correlated with total lesion volume indicating that larger lesions were associated with greater ipsilesional motor skill recovery. We suggest that reduced trans-callosal inhibition from the lesioned hemisphere may play a role in the observed skill improvements. Our findings show that significant ipsilesional hand motor recovery is likely to accompany injury limited to frontal motor areas. In humans, more pronounced ipsilesional motor deficits that invariably develop after stroke may, in part, be a consequence of more extensive subcortical white and gray matter damage.

Short-term effects of unilateral lesion of the primary motor cortex (M1) on ipsilesional hand dexterity in adult macaque monkeys

Although the arrangement of the corticospinal projection in primates is consistent with a more prominent role of the ipsilateral motor cortex on proximal muscles, rather than on distal muscles involved in manual dexterity, the role played by the primary motor cortex on the control of manual dexterity for the ipsilateral hand remains a matter a debate, either in the normal function or after a lesion. We, therefore, tested the impact of permanent unilateral motor cortex lesion on the manual dexterity of the ipsilateral hand in 11 macaque monkeys, within a time window of 60 days post-lesion. For comparison, unilateral reversible pharmacological inactivation of the motor cortex was produced in an additional monkey. Manual dexterity was assessed quantitatively based on three motor parameters derived from two reach and grasp manual tasks. In contrast to the expected dramatic, complete deficit of manual dexterity of the contralesional hand that persists for several weeks, the impact on the manual dexterity of the ipsilesional hand was generally moderate (but statistically significant) and, when present, lasted less than 20 days. Out of the 11 monkeys, only 3 showed a deficit of the ipsilesional hand for 2 of the 3 motor parameters, and 4 animals had a deficit for only one motor parameter. Four monkeys did not show any deficit. The reversible inactivation experiment yielded results consistent with the permanent lesion data. In conclusion, the primary motor cortex exerts a modest role on ipsilateral manual dexterity, most likely in the form of indirect hand postural control.

Defining and measuring residual deficits of the upper extremity following stroke: a new perspective

PURPOSE

To propose and test a new measure to quantify residual deficits (Rd) following stroke and provide preliminary evidence supporting its usefulness.

METHODS

Patients (N = 46) were stratified based on projected rate of upper extremity recovery and were randomly assigned to task-oriented (control) or task-oriented plus functional electrical stimulation (FES) training groups. All performed the Box & Blocks and the Jebsen-Taylor light object lift tests with the nonparetic and paretic upper extremities. A modified Fugl-Meyer test was performed on the paretic upper extremity. The calculation Rd = 100 - (paretic/nonparetic x 100) was made for each subgroup: task-specific training alone (control subgroup) or task-specific training plus functional electrical stimulation (FES subgroup). Data from each of these two groups were analyzed separately.

RESULTS

Intrasession and between-sessions tests of the nonparetic or paretic extremity yielded interclass correlation (ICC) values between 0.77 and 0.99. After training for 12 weeks, the Rd of the paretic upper extremity of patients who used the FES was significantly less compared to the control group (p < .05). The deficits of patients with slow recovery profile were as expected much greater.

CONCLUSIONS

Rd is a valid, highly reproducible, and dimensionless outcome measure. It should permit objective comparison of effectiveness between and within various rehabilitative intervention options regardless of the outcome measure(s) used.

The impact of left hemisphere stroke on force control with familiar and novel objects: neuroanatomic substrates and relationship to apraxia

Fingertip force scaling for lifting objects frequently occurs in anticipation of finger contact. An ongoing question concerns the types of memories that are used to inform predictive control. Object-specific information such as weight may be stored and retrieved when previously encountered objects are lifted again. Alternatively, visual size and shape cues may provide estimates of object density each time objects are encountered. We reasoned that differences in performance with familiar versus novel objects would provide support for the former possibility. Anticipatory force production with both familiar and novel objects was assessed in six left hemisphere stroke patients, two of whom exhibited deficient actions with familiar objects (ideomotor apraxia; IMA), along with five control subjects. In contrast to healthy controls and stroke participants without IMA, participants with IMA displayed poor anticipatory scaling with familiar objects. However, like the other groups, IMA participants learned to differentiate fingertip forces with repeated lifts of both familiar and novel objects. Finally, there was a significant correlation between damage to the inferior parietal and superior and middle temporal lobes and impaired anticipatory control for familiar objects. These data support the hypotheses that anticipatory control during lifts of familiar objects in IMA patients are based on object-specific memories and that the ventro-dorsal stream is involved in the long-term storage of internal models used for anticipatory scaling during object manipulation.

Ipsilateral deficits in 1-handed shoe tying after left or right hemisphere stroke

Poole JL, Sadek J, Haaland KY. Ipsilateral deficits in 1-handed shoe tying after left or right hemisphere stroke.

OBJECTIVE

To examine 1-handed shoe tying performance and whether cognitive deficits more associated with left or right hemisphere damage differentially affect it after unilateral stroke.

DESIGN

Observational cohort comparing ipsilesional shoe tying, spatial and language skills, and limb praxis.

SETTING

Primary care Veterans Affairs and private medical center.

INTERVENTIONS

Not applicable.

PARTICIPANTS

Volunteer right-handed sample of adults with left or right hemisphere damage and healthy demographically matched adults.

MAIN OUTCOME MEASURE

The number of correct trials and the total time to complete 10 trials tying a shoe using the 1-handed method.

RESULTS

Both stroke groups had fewer correct trials and were significantly slower tying the shoe than the control group. Spatial skills predicted accuracy and speed after right hemisphere damage. After left hemisphere damage, accuracy was predicted by spatial skills and limb praxis, while speed was predicted by limb praxis only.

CONCLUSIONS

Ipsilesional shoe tying is similarly impaired after left or right hemisphere damage, but for different reasons. Spatial deficits had a greater influence after right hemisphere damage, and limb apraxia had a greater influence after left hemisphere damage. Language deficits did not affect performance, indicating that aphasia does not preclude using this therapy approach. These results suggest that rehabilitation professionals should consider assessment of limb apraxia and ipsilesional skill training in the performance of everyday tasks.

Hemispheric specialization and functional impact of ipsilesional deficits in movement coordination and accuracy

Previous studies have demonstrated that following unilateral stroke, motor impairment occurs both contralateral, as well as ipsilateral, to the lesion. Although ipsilesional impairments can be functionally limiting, they can also provide important insight into the role of the ipsilateral hemisphere in controlling movement and the lateralization of specific motor control mechanisms, given that unilateral arm movements are thought to recruit processes in each hemisphere. The purpose of this study was to examine whether left and right hemisphere damage following stroke produces different ipsilesional deficits, and whether our dynamic dominance model of motor lateralization can predict such deficits. Specifically, the dynamic dominance model attributes control of multijoint dynamics to the left hemisphere, and control of steady-state position to the right hemisphere. Chronic stroke patients with either left or right hemisphere damage (LHD or RHD) used their ipsilesional arm, and the control subjects used either their left or right arm (LHC or RHC), to perform targeted reaching movements in different directions within the workspace ipsilateral to their reaching arm. We found that the LHD group showed deficits in controlling the arm's trajectory due to impaired multijoint coordination, but no deficits in achieving accurate final positions. In contrast, the RHD group showed deficits in final position accuracy but not in the ability to coordinate multiple joints during movement, thereby providing additional evidence for the hemisphere-specific nature of motor deficits. Furthermore, while both the LHD and RHD groups were functionally impaired to the same degree on the Jebsen Hand Function Test (JHFT), our results suggest that the underlying mechanisms for such impairment may be hemisphere-dependent.

Arm use after left or right hemiparesis is influenced by hand preference

BACKGROUND AND PURPOSE

Despite strong evidence for hand preference and its impact on motor performance, its influence on stroke rehabilitation has not been routinely considered. Previous research demonstrates that patients with hemiparetic stroke use their ipsilesional, nonparetic arm 5 to 6 times more frequently than their paretic arm, but it is unknown if such use varies with laterality of hemiparesis. The purpose of our study was to determine if the right arm is used more frequently in right-handed patients with stroke.

METHODS

We assessed relative use of the right, left, and both arms with wrist accelerometers on patients with unilateral, paretic stroke matched for degree of paresis (12 with right hemisphere damage, 17 with left hemisphere damage) and 25 neurologically intact control participants as they performed the Arm Motor Ability Test.

RESULTS

We showed: (1) ipsilesional arm use was greater after right hemisphere damage than left hemisphere damage; (2) the left hemisphere damage group used both arms together more often than the right hemisphere damage group but less often than the control group; and (3) both stroke groups used their contralesional, paretic arm to the same degree.

CONCLUSIONS

These findings emphasize the influence of hand preference on arm use after stroke for the ipsilesional but not the contralesional arm. Although both stroke groups used their ipsilesional more than their contralesional arm, the difference was greater for the right hemisphere damage group who used their ipsilesional arm 4 times more frequently than their contralesional arm, whereas the left hemisphere damage group used their ipsilesional arm 2 times more frequently than their contralesional arm.

Reliability and Sensitivity of a Wrist Rig to Measure Motor Control and Spasticity in Poststroke Hemiplegia

Background. Objective assessment of impairments after stroke is vital for evidence-based therapy and progress monitoring. Objective. This study determines the utility of outcome measures obtained from an instrumented wrist rig for future rehabilitation trials. The tests undertaken were evaluated in terms of sensitivity to detect differences between normal and impaired participants, test-retest repeatability (repeatability coefficient and intraclass correlation coefficient [ICC]), and interrater agreement (Bland and Altman limits of agreement). Methods . Twelve participants with chronic poststroke hemiparesis (mean 5.6 years); and 12 unimpaired volunteers performed a series of tasks in the rig. The hemiparetic arm (impaired group) and dominant arm (unimpaired group) were tested in 3 sessions on the same day by 2 assessors. Signals were analyzed to derive a tracking index (motor control), stretch index (spasticity), flexor modulation index (FMI) (muscle activation), force angle index (FAI) (stiffness), range of movement, and isometric force. Results and Conclusions. The means of all tests differed between impaired and unimpaired participants except for range of movement into flexion, the FAI, and the FMI. Repeatability coefficients for each test are presented as benchmark values for use in future trials in which the wrist rig tests may be used to detect change. Test-retest reliability was excellent in the impaired group (ICC = 0.88-0.98) and poor to excellent in the unimpaired group (ICC = 0.06-0.89). The Bland-Altman ranges showed no bias between assessors, and that the interassessor variability was similar to that between repeats by the same assessor for most tests.

Differentiating between two models of motor lateralization

This study was designed to differentiate between two models of motor lateralization: "feedback corrections" and dynamic dominance. Whereas the feedback correction hypothesis suggests that handedness reflects a dominant hemisphere advantage for visual-mediated correction processes, dynamic dominance proposes that each hemisphere has become specialized for distinct aspects of control. This model suggests that the dominant hemisphere is specialized for controlling task dynamics, as required for coordinating efficient trajectories, and the nondominant hemisphere is specialized for controlling limb impedance, as required for maintaining stable postures. To differentiate between these two models, we examined whether visuomotor corrections are mediated differently for the nondominant and dominant arms. Participants performed targeted reaches in a virtual reality environment in which visuomotor rotations occurred in two directions that elicited corrections with different coordination requirements. The feedback correction model predicts a dominant arm advantage for the timing and accuracy of corrections in both directions. Dynamic dominance predicts that correction timing and accuracy will be similar for both arms, but that interlimb differences in the quality of corrections will depend on the coordination requirements, and thus, direction of corrections. Our results indicated that correction time and accuracy did not depend on arm. However, correction quality, as reflected by trajectory curvature, depended on both arm and rotation direction. Nondominant trajectories were systematically more curvilinear than dominant trajectories for corrections with the highest coordination requirement. These results support the dynamic dominance hypothesis.

Ipsilateral versus contralateral cortical motor projections to a shoulder adductor in chronic hemiparetic stroke: implications for the expression of arm synergies

An increase in ipsilateral descending motor pathway activity has been reported following hemiparetic stroke. In axial muscles, increased ipsilateral cortical activity has been correlated with good recovery whereas in distal arm muscles it is correlated with poor recovery. Currently, little is known about the control of proximal upper limb muscles following stroke. This muscle group is less impaired than the distal arm muscles following stroke, yet contributes to the abnormal motor coordination patterns associated with movements of the arm which can severely impair reaching ability. This study used transcranial magnetic stimulation (TMS) to evaluate the presence and magnitude of ipsilateral and contralateral projections to the pectoralis major (PMJ) muscle in stroke survivors. A laterality index (LI) was used to investigate the relationship between ipsilateral and contralateral projections and strength, clinical impairment level, and the degree of abnormal coordination expressed in the arm. The ipsilateral and contralateral hemispheres were stimulated using 90% TMS intensity while the subject generated shoulder adduction torques in both arms. Motor evoked potentials (MEPs) were measured in the paretic and non-paretic PMJ. The secondary torque at the elbow was measured during maximal adduction as an indicator of the degree of extensor synergy. Ipsilateral MEPs were most common in stroke survivors with moderate to severe motor deficits. The LI was correlated with clinical impairment level (P = 0.05) and the degree of extension synergy expressed in the arm (P = 0.03). The LI was not correlated with strength. These results suggest that increased excitability of ipsilateral pathways projecting to the proximal upper arm may contribute to the expression of the extension synergy following stroke. These findings are discussed in relation to a possible unmasking or upregulation of oligosynaptic cortico-bulbospinal pathways following stroke.

Functional significance of ipsilesional motor deficits after unilateral stroke

OBJECTIVE

To determine whether ipsilesional motor skills, which have been related to independent functioning, are present chronically after unilateral stroke and are more common in people with apraxia than in those without apraxia.

DESIGN

Observational cohort comparing the performance of an able-bodied control group, stroke patients with left- or right-hemisphere damage matched for lesion volume, and left-hemisphere stroke patients with and without ideomotor limb apraxia.

SETTING

Primary care Veterans Affairs and private medical center.

PARTICIPANTS

Volunteer right-handed sample; stroke patients with left- or right-hemisphere damage about 4 years poststroke; a control group of demographically matched, able-bodied adults.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Total time to perform the (1) Williams doors test and the (2) timed manual performance test (TMPT), which includes parts of the Jebsen-Taylor Hand Function Test.

RESULTS

Ipsilesional motor deficits were present after left- or right-hemisphere stroke when using both measures, but deficits were consistently more common in patients with limb apraxia only for the TMPT.

CONCLUSIONS

These findings add to a growing literature that suggests that ipsilesional motor deficits may have a functional impact in unilateral stroke patients, especially in patients with ideomotor limb apraxia.

Ipsilesional motor deficits following stroke reflect hemispheric specializations for movement control

Recent reports of functional impairment in the 'unaffected' limb of stroke patients have suggested that these deficits vary with the side of lesion. This not only supports the idea that the ipsilateral hemisphere contributes to arm movements, but also implies that such contributions are lateralized. We have previously suggested that the left and right hemispheres are specialized for controlling different features of movement. In reaching movements, the non-dominant arm appears better adapted for achieving accurate final positions and the dominant arm for specifying initial trajectory features, such as movement direction and peak acceleration. The purpose of this study was to determine whether different features of control could characterize ipsilesional motor deficits following stroke. Healthy control subjects and patients with either left- or right-hemisphere damage performed targeted single-joint elbow movements of different amplitudes in their ipsilateral hemispace. We predicted that left-hemisphere damage would produce deficits in specification of initial trajectory features, while right-hemisphere damage would produce deficits in final position accuracy. Consistent with our predictions, patients with left, but not right, hemisphere damage showed reduced modulation of acceleration amplitude. However, patients with right, but not left, hemisphere damage showed significantly larger errors in final position, which corresponded to reduced modulation of acceleration duration. Neither patient group differed from controls in terms of movement speed. Instead, the mechanisms by which speed was specified, through modulation of acceleration amplitude and modulation of acceleration duration, appeared to be differentially affected by left- and right-hemisphere damage. These findings support the idea that each hemisphere contributes differentially to the control of initial trajectory and final position, and that ipsilesional deficits following stroke reflect this lateralization in control.

Left Hemisphere Dominance for Movement

Clinical neuropsychology's dependence upon a core scientific background in clinical neuropsychology, and clinical psychology, neurology, and neuroanatomy, as well as biopsychology, cognitive neuroscience, and cognitive science is the basis of its designation as an APA-approved clinical specialty. This dependence highlights the importance of these scientific underpinnings and the scientist-practitioner model of training, detailed in the Houston Guidelines. This presentation is meant to demonstrate that cognitive neuroscience research should influence our conception of brain behavior relationships, which, in turn, should influence our clinical work. In addition, I want to illustrate how the utilization of converging methods, which is an increasingly popular approach to research, can ensure more valid conclusions about the neuroanatomical substrates for complex skills. Limb apraxia will be used as an example of a deficit that has functional implications and whose cognitive mechanisms and neuroanatomical correlates are better understood as a result of research that combines neuroanatomical imaging of brain damaged patients, functional imaging, and cognitive paradigms. This work demonstrates that left frontoparietal circuits control limb praxis and motor sequencing, suggesting that these complex motor skills should be examined in patients with such damage.

Deviations in upper-limb function of the less-affected side in congenital hemiparesis

In the present study we examined upper-limb function of the less-affected side in young adolescents with congenital hemiparesis (cerebral palsy: CP). Five participants with hemiparetic CP and five control participants performed a cyclical reach-and-grasp task with the less-affected hand towards targets placed at 60%, 100%, and 140% of the participant's arm-length. Trunk involvement, end-effector kinematics and activation of the biceps and triceps were examined together with several clinical measures. Movements at the less-affected side were slower and peak velocity was reached later in the experimental group. Even though total trunk involvement was identical in both groups, it was selectively limited to forward bending in participants with CP. Elbow amplitudes of these participants were smaller for the 60% and 100% arm-length target distances. Additionally, participants with CP showed weak positive correlations between agonist (triceps) activity and elbow amplitude, suggesting that deficient agonist rather than antagonist innervation was responsible for the decreased elbow involvement. Especially the more severely affected participants with CP proved to compensate their relatively small elbow amplitudes by increased forward bending. Collectively, the findings demonstrate deviations in upper-limb control of the less-affected body side in congenital hemiparesis.