Ipsilesional Hand Research Articles

Pantomime versus actual tool use: alterations of movement kinematics with the mode of execution and with brain damage

Apraxic stroke patients demonstrate impaired miming of the use of common tools. A subset of these patients may show a deficit in the actual use of these tools as well. As movement goals and task mechanics differ substantially between actual tool use and corresponding pantomimes, we aimed to understand whether this interpersonal variability in apraxia is due to a general deficit affecting both modes of action execution or whether some patients show an association of two distinct functional impairments. In the present study, we assessed repetitive ladle scooping movements in brain damaged patients with and without apraxia using their ipsilesional hand and healthy control subjects and compared their movement kinematics between three execution modes: pantomime, demonstration with the tool only, and actual use in the normal context. Analysis of the wrist trajectory during the ladle transport revealed clear differences between the execution modes, such as slower actual use, and moderate deficits in patients with left brain damage (LBD). LBD patients were impaired in the scooping component: especially, LBD patients with apraxia yielded reduced hand rotation at the bowl and the plate. This deficit was most obvious during pantomime but actual use was also affected and reduced hand rotation was consistent across conditions as indicated by pair-wise correlations between the execution modes. In contrast in healthy control subjects, correlations of movement parameters were most evident between the pantomime and demonstration modes but weak in pairs including actual use. We conclude from our findings that for a specific tool use action, common motor schemas are activated but are adjusted according to the constraints of the task and its demands. Therefore, an apraxic LBD individual can show a common deficit across all action conditions but the severity of which can differ substantially.

Tool use without a tool: kinematic characteristics of pantomiming as compared to actual use and the effect of brain damage

Movement goals and task mechanics differ substantially between actual tool use and corresponding pantomimes. In addition, apraxia seems to be more severe during pantomime than during actual tool use. Comparisons of these two modes of action execution using quantitative methods of movement analyses are rare. In the present study, repetitive scooping movements with a ladle from a bowl into a plate were recorded and movement kinematics was analyzed. Brain-damaged patients using their ipsilesional hand and healthy control subjects were tested in three conditions: pantomime, demonstration with the tool only, and actual use in the normal context. Analysis of the hand trajectories during the transport component revealed clear differences between the tasks, such as slower actual use and moderate deficits in patients with left brain damage (LBD). LBD patients were particularly impaired in the scooping component: LBD patients with apraxia exhibited reduced hand rotation at the bowl and the plate. The deficit was most obvious during pantomime but actual use was also affected, and reduced hand rotation was consistent across conditions as indicated by strong pair-wise correlations between task conditions. In healthy control subjects, correlations between movement parameters were most evident between the pantomime and demonstration conditions but weak in correlation pairs involving actual use. From these findings and published neuroimaging evidence, we conclude that for a specific tool-use action, common motor schemas are activated but are adjusted and modified according to the actual task constraints and demands. An apraxic LBD individual can show a deficit across all three action conditions, but the severity can differ substantially between conditions.

Contralesional Motor Cortex Activation Depends on Ipsilesional Corticospinal Tract Integrity in Well-Recovered Subcortical Stroke Patients

Background. The relationship between structural and functional integrity of descending motor pathways can predict the potential for motor recovery after stroke. The authors examine the relationship between brain imaging biomarkers within contralesional and ipsilesional hemispheres and hand function in well-recovered patients after subcortical stroke at the level of the internal capsule. Objective. Measures of functional activation and integrity of the ipsilesional corticospinal tract might predict paretic hand function. Methods. A total of 14 patients in the chronic stable phase of motor recovery after subcortical stroke and 24 healthy age-matched individuals participated in the study. Functional MRI was used to examine BOLD contrast during passive wrist flexion–extension and paced or maximum-velocity active fist clenching. Functional integrity of the corticospinal pathway was assessed by transcranial magnetic stimulation to obtain motor-evoked potentials (MEPs) in the first dorsal interosseus muscle of the paretic and nonparetic hands. Fractional anisotropy and the proportion of traces between hemispheres in the posterior limb of both internal capsules were quantified using diffusion-weighted MRI. Results. Patients with smaller MEPs had a weaker paretic hand and more primary motor cortex activation in their affected hemisphere. Asymmetry between white matter tracts of either hemisphere was associated with reduced precision grip strength and increased BOLD activation within the contralesional dorsal premotor cortex for demanding hand tasks. Conclusion. There may be beneficial reorganization in contralesional secondary motor areas with increasing damage to the corticospinal tract after subcortical stroke. Associations between clinical, functional, and structural integrity measures in chronic stroke may lead to a better understanding of motor recovery processes.

Bilateral hand representations in human primary proprioceptive areas

Sensory representations in the postcentral gyrus are supposed to be strictly lateralised and to provide spatially unbiased representations of limb positions. However, electrophysiological and behavioural measurements in humans and non-human primates tentatively suggested some degree of bilateral processing even in early somatosensory areas. We report a patient who suffered a small and confined lesion of the hand area in the postcentral gyrus that resulted in a proprioceptive deficit without any concomitant primary motor impairment. We performed a finger position-matching task with target locations being defined proprioceptively. Without visual feedback of either hand, the patient demonstrated a significant leftward shift of perceived locations when reaching with the ipsilesional right hand to her contralesional left hand and an opposite rightward shift when reaching with the left hand to the position of the right hand. Although these directional errors improved when vision of the active hand was allowed, errors were still significantly larger than those of age-matched healthy controls with unconstrained view of the active contralesional hand. Reaching to visual targets without visual online feedback the patient revealed comparable errors with both hands. Reaching to visual targets with full visual feedback, she was as accurate as controls with either hand. In summary, our data demonstrate an effect of the right postcentral lesion on proprioceptive information processing for both hands. The results suggest an integration of contralateral and ipsilateral proprioceptive information already at this early processing stage possibly mediated by callosal connections.

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.

Frequency of discriminative sensory loss in the hand after stroke in a rehabilitation setting

Somatosensory loss following stroke is common, with negative consequences for functional outcome. However, existing studies typically do not include quantitative measures of discriminative sensibility. The aim of this study was to quantify the proportion of stroke patients presenting with discriminative sensory loss of the hand in the post-acute rehabilitation phase. Prospective cohort study of stroke survivors presenting for rehabilitation. Fifty-one consecutive patients admitted to a metropolitan rehabilitation centre over a continuous 12-month period who met selection criteria. Quantitative measures of touch discrimination and limb position sense, with high re-test reliability, good discriminative test properties and objective criteria of abnormality, were employed. Both upper limbs were tested, in counterbalanced order. Impaired touch discrimination was identified in the hand contralateral to the lesion in 47% of patients, and in the ipsilesional hand in 16%. Forty-nine percent showed impaired limb position sense in the contralesional limb and 20% in the ipsilesional limb. Sixty-seven percent demonstrated impairment of at least one modality in the contralesional limb. Ipsilesional impairment was less severe. Discriminative sensory impairment was quantified in the contralesional hand in approximately half of stroke patients presenting for rehabilitation. A clinically significant number also experienced impairment in the ipsilesional "unaffected" hand.

Stroke and Action Slowing: Mechanisms, Determinants and Prognosis Value

Aim: The present study aimed to determine the mechanisms and determinants of stroke-related action slowing. Methods: Thirty-six stroke patients not presenting any clinical motor deficit of the preferred hand (mean post-stroke delay 11 months) were compared to matched controls on Finger Tapping test (motor speed), Visual Inspection Time test (visual perceptual speed) and Simple and Choice Reaction Time tests. Results: Patients were slower on all tests except Choice Reaction Time: Visual Inspection (p = 0.003), Finger Tapping test (p = 0.001), Simple Reaction Time (p = 0.002) tests were impaired including performance measured with the ipsi-lesional hand. This pattern and the uniform lengthening across the entire reaction time distribution both suggest that psychomotor slowing was due to slowing of perceptual and motor processes. The main determinant of action slowing was lesion location: (1) Visual Inspection Time = right inferior parietal lobulus (OR 18, 95% CI 2.9–108); (2) Finger Tapping = left frontal middle gyrus (OR 18, 95% CI 2.9–108) and lenticular nucleus (OR 59, 95% CI 1.9–1,775), and (3) Simple Reaction Time = right lenticular nucleus (OR 110, 95% CI 8–1,490) and posterior fossa (OR 55, 95% CI 3.4–890). Finally poor outcome depended on Tapping Frequency measured with the contra-lesional index (OR 0.1, 95% CI 0.02–0.5; p = 0.0005) and impairment on the Token test (OR 151, 95% CI 2.24–1136; p = 0.02). Conclusions: This study shows that stroke-related action slowing is mainly due to slowing of perceptual and motor processes. Action slowing was related to lesions of the large network. Finally Tapping Frequency is an independent predictor of outcome. This supports that action slowing is an important consequence of stroke and that it is a promising prognosis index.

Effects of Unilateral Motor Cortex Lesion on Ipsilesional Hand's Reach and Grasp Performance in Monkeys: Relationship With Recovery in the Contralesional Hand

Manual dexterity, a prerogative of primates, is under the control of the corticospinal (CS) tract. Because 90-95% of CS axons decussate, it is assumed that this control is exerted essentially on the contralateral hand. Consistently, unilateral lesion of the hand representation in the motor cortex is followed by a complete loss of dexterity of the contralesional hand. During the months following lesion, spontaneous recovery of manual dexterity takes place to a highly variable extent across subjects, although largely incomplete. In the present study, we tested the hypothesis that after a significant postlesion period, manual performance in the ipsilesional hand is correlated with the extent of functional recovery in the contralesional hand. To this aim, ten adult macaque monkeys were subjected to permanent unilateral motor cortex lesion. Monkeys' manual performance was assessed for each hand during several months postlesion, using our standard behavioral test (modified Brinkman board task) that provides a quantitative measure of reach and grasp ability. The ipsilesional hand's performance was found to be significantly enhanced over the long term (100-300 days postlesion) in six of ten monkeys, with the six exhibiting the best, though incomplete, recovery of the contralesional hand. There was a statistically significant correlation (r = 0.932; P < 0.001) between performance in the ipsilesional hand after significant postlesion period and the extent of recovery of the contralesional hand. This observation is interpreted in terms of different possible mechanisms of recovery, dependent on the recruitment of motor areas in the lesioned and/or intact hemispheres.

Visuomotor Training Improves Stroke-Related Ipsilesional Upper Extremity Impairments

Background. Unilateral middle cerebral artery infarction has been reported to impair bilateral hand grasp. Methods. Individuals (5 males and 5 females; age 33-86 years) with chronic unilateral middle cerebral artery stroke (4 right lesions and 6 left lesions) repeatedly lifted a 260-g object. Participants were then trained to lift the object using visuomotor feedback via an oscilloscope that displayed their actual grip force (GF) and a target GF, which roughly matched the physical properties of the object. Results.The subjects failed to accurately modulate the predictive GF when relying on somatosensory information from the previous lifts. Instead, for all the lifts, they programmed excessive GF equivalent to the force used for the first lift. The predictive GF was lowered for lifts following the removal of the visual feedback. The mean difference in predictive GF between the lifts before and after visual training was significant (4.35 ± 0.027 N; P ≤ .001; 95% confidence interval [CI] = 3.80-4.88). After removal of visual feedback, there was also a significant mean difference in the applied predictive GF between the “early” and “late” lifts (0.78 ± 0.029 N; P ≤ .006; 95% CI = 0.22-1.35), demonstrating continued increase in predictive GF accuracy. Conclusion. Predictive or feedforward fingertip force generation is impaired in the ipsilesional hand when lifting a novel object with precision grip. Reacquisition of the motor forces for the grasp of objects is possible after stroke. Potentially, retraining grasp control for the ipsilesional hand may translate to improved function and motor learning within the contralesional hand.

Safety and Behavioral Effects of High-Frequency Repetitive Transcranial Magnetic Stimulation in Stroke

Electromagnetic brain stimulation might have value to reduce motor deficits after stroke. Safety and behavioral effects of higher frequencies of repetitive transcranial magnetic stimulation (rTMS) require detailed assessment. Using an active treatment-only, unblinded, 2-center study design, patients with chronic stroke received 20 minutes of 20 Hz rTMS to the ipsilesional primary motor cortex hand area. Patients were assessed before, during the hour after, and 1 week after rTMS. The 12 patients were 4.7+/-4.9 years poststroke (mean+/-SD) with moderate-severe arm motor deficits. In terms of safety, rTMS was well tolerated and did not cause new symptoms; systolic blood pressure increased from pre- to immediately post-rTMS by 7 mm Hg (P=0.043); and none of the behavioral measures showed a decrement. In terms of behavioral effects, modest improvements were seen, for example, in grip strength, range of motion, and pegboard performance, up to 1 week after rTMS. The strongest predictor of these motor gains was lower patient age. A single session of high-frequency rTMS to the motor cortex was safe. These results require verification with addition of a placebo group and thus blinded assessments across a wide spectrum of poststroke deficits and with larger doses of 20 Hz rTMS.

Spatial perception errors do not predict pointing errors by individuals with brain lesions

We examined the relationship between errors in sensorimotor transformations (SMT) for reaching to external targets and visual and kinesthetic spatial perception of those targets by participants with damage to the posterior parietal lobule (PPL) and adjacent areas. A total of 12 participants had focal PPL lesions, 7 had with brain lesions outside the PPL, and 10 had no brain lesions. Brain lesions were due to stroke (12) or surgical resection (7). Participants made visually and kinesthetically guided pointing movements to 16 targets with the ipsilesional hand (to minimize effects of motor deficits). Head and eye movements were unrestricted. When full vision was allowed, all participants pointed accurately to visually specified targets. However, participants with PPL lesions made larger vertical plane errors than did neurologically intact control participants in visual and kinesthetic perceptual tasks and in SMT tasks (in which participants reached without vision to targets that had been visually presented). However, across all 29 participants, the size and direction of SMT errors showed low correlation with visual and kinesthetic perceptual errors. Moreover, participants with PPL lesions who made large visual and/or kinesthetic perceptual errors to individual targets also showed weak correlations with SMT errors to those targets. The results are compatible with theories that different neural pathways support perception and action for both the visual and the kinesthetic systems.

Grip forces isolated from knowledge about object properties following a left parietal lesion

When lifting two objects with equal weight but different size, we judge the smaller object to be heavier. This size-weight illusion has been intensively tested by the recruitment of fingertip grip forces during precision lifting. Previous findings have suggested that perceptual (object size) prediction can influence sensorimotor prediction (anticipatory grip force scaling to the object size) but these predictions could be processed independently. This study investigates whether the anticipatory scaling of the grip forces according to object properties critically depends on the integrity of the posterior parietal cortex (PPC) and how a deficit may affect the perceptual size-weight illusion. Here, we report the case of a patient, F.S., with a large left temporal parietal lesion intruding into the temporal cortex and limb apraxia, who did not show anticipatory scaling of fingertip grip force to object size whereas matched controls did. However, the patient's perception of the size-weight illusion was only impaired during his ipsi-lesional hand lifting. Our findings suggest that left parietal cortex may be particularly responsible for the anticipatory grip force scaling of both hands and the perceptual process of size-weight illusion involving ipsi-lesional hand motion.

Residual haptic sensation following stroke using ipsilateral stimulation

In 1987, Weiskrantz and Zhang described a stroke patient with severe somatosensory loss who, nevertheless, demonstrated impressive residual sensory performance when required to touch the affected limb with her ipsilesional...

Dexterity is impaired at both hands following unilateral subcortical middle cerebral artery stroke

Dexterity was investigated in right-handed subjects in the subacute phase of a first unilateral subcortical middle cerebral artery stroke affecting the left or right hemisphere and right-handed healthy subjects. Dexterity was quantified at both hands by kinematic recordings of finger and hand tapping, a reach-to-grasp movement, quantitative analysis of grip forces in a grasp-lift task and clinical rating scales. Stroke subjects exhibited significant deficits in timing and coordination of tapping movements at both the contralesional and ipsilesional hands, irrespective of the hemisphere affected. Likely for the reach-to-grasp and grasp-lift movements a bilateral impairment was found in stroke subjects. In particular, slowing of hand transport towards the object, deficient timing and scaling of grasp formation, discoordination between grip and lift forces and inefficient scaling of grip forces were observed. The severity of impairment was independent of the hemisphere affected and evident for both the reach (involving more proximal muscles of the arm) and grasp (involving more distal muscles of the arm and hand) components of the task. Strong correlations were found between clinical scores of hand function and loss of sensibility with the deficits in timing, coordination and efficiency of movement of the contralesional and ipsilesional hand. These data provide evidence that dexterity is impaired at both hands after subcortical middle cerebral artery stroke.

Mirror writing and reversing single letters in stroke patients and normal elderly

Mirror writing (MW) refers to the production of individual letters or whole word strings in reversed direction. When held to a mirror, these letters or words can be read normally. We observed MW in a considerable number of stroke patients. Of the 86 patients screened 15 (17.5%) showed at least one instance of mirror writing in any of the tasks. Both right (14% of 36 patients) and left (20% of 50 patients) hemisphere damaged patients produced reversed letters only when writing with their left hand, respectively the contralesional and ipsilesional hand. The dissociated performance between the two hands in brain damaged patients is relevant to the interpretation of MW because, unlike all other peripheral dysgraphias, MW affects the non-dominant hand only. Importantly, healthy elderly also showed MW solely when writing with their left hand (6.9% of 86 participants). MW in controls was less frequent but qualitatively similar to that observed in brain damaged patients. This finding is consistent with the motor interpretation of MW that assumes an inability to transform the stored letter forming programmes for left hand writing. However, several cases have been reported in the literature of a more pervasive form of MW whereby patients mirror reverse entire words or sentences. This pattern has been observed in children learning to write but it has never been observed in healthy adult volunteers. We propose that the diagnosis of MW should be limited to the reversal of whole words, multi-digit numbers and full sentences, which reveal a disorder in coding the correct direction of writing rather than an inability to accomplish the correct spatial orientation of single letters.

Optic ataxia is not only ‘optic’: Impaired spatial integration of proprioceptive information

Optic ataxia is considered to be a specific visuo-manual guidance deficit, which combines pointing errors due to the use of the contralesional hand (“hand effect”) and to the presentation of the visual target in the contralesional field (“field effect”). The nature of the hand effect has not been identified. The field effect is acknowledged as an impaired spatial integration of visual target location. However, spatial integration of proprioceptive information from the arm has never been experimentally tested in these patients. Here, we specifically investigated the capacity of two patients with unilateral optic ataxia in tasks requiring different levels of proprioceptive integration from primary information processing to proprioceptivo-motor integration. In a first experiment -proprioceptive pointing with the ipsilesional hand toward the index finger of the contralesional hand- revealed a large mislocalisation of the ataxic hand accounting for the hand effect. In a second experiment -proprioceptive pointing with the ataxic arm toward the finger of the ipsilesional hand- revealed reaching errors for non-visual targets, i.e. optic ataxia is not specific to ‘optic’ targets. Altogether, the present results call for a redefinition of this neurological condition in the framework of parietal functions.

Abnormalities in skilled reaching movements are improved by peripheral anesthetization of the less-affected forelimb after sensorimotor cortical infarcts in rats

Unilateral damage to sensorimotor cortical (SMC) regions can profoundly impair skilled reaching function in the contralesional forelimb. Such damage also results in impairments and compensatory changes in the less-affected/ipsilesional forelimb, but these effects remain poorly understood. Furthermore, anesthetization of the ipsilesional hand in humans with cerebral infarcts has been reported to produce transient functional improvements in the paretic hand [Floel A, Nagorsen U, Werhahn KJ, Ravindran S, Birbaumer N, Knecht S, et al. Influence of somatosensory input on motor function in patients with chronic stroke. Ann Neurol 2004;56:206–12; Voller B, Floel A, Werhahn KJ, Ravindran S, Wu CW, Cohen LG. Contralateral hand anesthesia transiently improves poststroke sensory deficits. Ann Neurol 2006;59:385–8]. One aim of this study was to sensitively assay the bilateral effects of unilateral ischemic SMC damage on performance of a unimanual skilled reaching task (the single pellet retrieval task) that rats had acquired pre-operatively with each forelimb. The second aim was to determine whether partially recovered contralesional reaching function is influenced by anesthetization of the ipsilesional forelimb. Unilateral SMC lesions were found to result in transient ipsilesional impairments in reaching success and significant ipsilesional abnormalities in reaching movements compared with sham-operates. There were major contralesional reaching impairments which improved during a 4 week training period, but movements remained significantly abnormal. Anesthetization of the ipsilesional forelimb with lidocaine at this time attenuated the contralesional movement abnormalities. These findings indicate that unilateral ischemic SMC lesions impair skilled reaching behavior in both forelimbs. Furthermore, after partial recovery in the contralesional forelimb, additional improvements can be induced by transient anesthetization of the ipsilesional forelimb. This is consistent with the effects of unilateral anesthetization in humans which have been attributed to the modulation of competitive interhemispheric interactions. The present findings suggest that such interactions are also likely to influence skilled reaching function in rats.

Impaired Grip Force Modulation in the Ipsilesional Hand after Unilateral Middle Cerebral Artery Stroke

Understanding grasping control after stroke is important for relearning motor skills. The authors examined 10 individuals (5 males; 5 females; ages 32-86) with chronic unilateral middle cerebral artery (MCA) stroke (4 right lesions; 6 left lesions) when lifting a novel test object using skilled precision grip with their ipsilesional (“unaffected”) hand compared to healthy controls (n = 14; 6 males; 8 females; ages 19-86). All subjects possessed normal range of motion, cutaneous sensation, and proprioception in the hand tested and had no apraxia or cognitive deficits. Subjects lifted the object 10 times at each object weight (260 g, 500 g, 780 g) using a moderately paced self-selected lifting speed. The normal horizontal (“grip”) force and vertical tangential (“lift”) force were separately measured at the thumb and index finger. Regardless of the object weight or stroke location, the stroke group generated greater grip forces at liftoff of the object (≥39%; P ≤ 0.05) and across the dynamic (P ≤ 0.05) and static portions (P ≤ 0.05) of the lifts compared to the healthy group. Peak lift forces were equivalent between groups, suggesting accurate load force information processing occurred. These results warrant further investigation of altered sensorimotor processing or compensatory biomechanical strategies that may lead to inaccurate grip force execution after strokes.

REPRESENTATION OF IMAGINED and EXECUTED SEQUENTIAL FINGER MOVEMENTS OF ADULTS POST STROKE and HEALTHY CONTROLS.

Purpose/Hypothesis: The purpose of this study was to describe the effects of brain injury on imagery ability and representation by examining executed and imagined complex finger movement sequences with each hand. We hypothesized that individuals post-stroke would exhibit similar patterns of brain activation for executed and imagined movements to healthy controls (HC) when using their ipsilesional hand but not their contra-lesional hand. Number of Subjects: Five individuals post stroke (at least one year post-stroke, right CVA with preserved motor function in the contralesional hand) and five age matched HC. Materials/Methods: Subjects were tested in two sessions with one week interval. In the first session imagery ability was examined using the Motor Imagery Questionnaire (MIQ) and chronometric break tests. Subjects practiced executed and imagined paced sequential finger movement sequences with each hand. Audio taped instructions were provided for practice of the tasks at home. During the second session prior to brain scanning accuracy of finger movements was confirmed. Data were acquired with a 3T Allegra MR scanner (Siemens) using an echo-planar imaging (EPI) gradient system. Functional studies (fMRI) were acquired using a 32 slice gradient echo EPI (TR=4000, TE=30, 64x64 matrix, FOV=22 cm); and a blocked paradigm, each consisting of 4 epochs of task performance alternating with visual attention. The four trials of hand movements were: executed ipsi-lesional, imagined ipsi-lesional, exe-cuted contra-lesional, imagined contra-lesional. MRI data were analyzed using SPM 99, with a corrected height (p=.05) threshold. Group analyses were performed to determine the volume of activation in pre-determined regions of interest. Results: MIQ scores did not differ significantly between groups. HC's pattern of activation during executed tasks by either hand included the contralateral primary sensory (1, 2, 3) motor (4) parietal (5, 7) and premotor (PMC) and supplementary motor areas (SMA) (6). Individuals post stroke pattern of brain activation when using their ipsilesional hand was similar to that of HC. For the stroke affected hand executed movements were bilaterally represented while imagined movements were lateralized to the brains' primary lesioned side. For all tasks performed by the individuals post-stroke there was greater activation (50–500%) of area six on the con-tralesional side of the brain. Conclusions: The pattern of activation observed for tasks by the stroke affected hand suggest that it was easier for individuals post-stroke to imagine rather than execute the movements. The increased activity of the pre-motor and supplementary motor areas of the contra-lesional side during all tasks for the stroke affected subjects suggests that there may be a compensatory shift in the tasks of planning and sequencing both imagined and executed sequential finger movements. Clinical Relevance: Mental imagery by individuals post-stroke may serve as a stimulus for plasticity of stroke affected side of the brain and possibly be a good tool for rehabilitation of motor function.