Motor skill training, but not voluntary exercise, improves skilled reaching after unilateral ischemic lesions of the sensorimotor cortex in rats

Activity-based therapies to promote forelimb use after a cervical spinal cord injury

Significant interest exists in strategies for improving forelimb function following spinal cord injury. We investigated the effect of enriched housing combined with skilled training on the recovery of skilled and automatic forelimb function after a cervical spinal cord injury in adult rats. All animals were pretrained in skilled reaching, gridwalk crossing, and overground locomotion. Some received a cervical over-hemisection lesion at C4-5, interrupting the right side of the spinal cord and dorsal columns bilaterally, and were housed in standard housing alone or enriched environments with daily training. A subset of animals received rolipram to promote neuronal plasticity. Animals were tested weekly for 4 weeks to measure reaching, errors on the gridwalk, locomotion, and vertical exploration. Biotinylated dextran amine was injected into the cortex to label the corticospinal tract. Enriched environments/daily training significantly increased the number and success of left reaches compared to standard housing. Animals also made fewer errors on the gridwalk, a measure of coordinated forelimb function. However, there were no significant improvements in forelimb use during vertical exploration or locomotion. Likewise, rolipram did not improve any of the behaviors tested. Both enriched housing and rolipram increased plasticity of the corticospinal tract rostral to the lesion. These studies indicate that skilled training after a cervical spinal cord injury improves recovery of skilled forelimb use (reaching) and coordinated limb function (gridwalk) but does not improve automatic forelimb function (locomotion and vertical exploration). These studies suggest that rehabilitating forelimb function after spinal cord injury will require separate strategies for descending and segmental pathways.

The effects of repeated rehabilitation "tune-ups" on functional recovery after focal ischemia in rats

BACKGROUND

For most stroke survivors, rehabilitation therapy is the only treatment option available. The beneficial effects of early rehabilitation on neuroplasticity and functional recovery have been modeled in experimental stroke using a combination of enriched environment and rehabilitation. However, the impact of a secondary intervention, such as a periodic return to therapy, remains unclear.

OBJECTIVE

This study examines whether a return to enriched rehabilitation (ie, "tune-up") can further promote functional recovery or produce beneficial changes in brain plasticity in the chronic phase of stroke recovery.

METHODS

Rats were exposed to focal ischemia (endothelin-1 applied to forelimb sensorimotor cortex and dorsolateral striatum) and allowed to recover either in standard housing or in a combination of enriched environment and rehabilitative reaching for 9 weeks. Animals were then exposed to rotating periods of standard housing (5 weeks) and intensive "tune-up" therapy consisting of various sensorimotor/cognitive activities (2 weeks). Functional recovery was assessed using the Montoya staircase, beam-traversing, and cylinder tests, and Golgi-Cox analysis was used to examine dendritic complexity in the contralesional forelimb motor cortex.

RESULTS

Although early enriched rehabilitation significantly improved sensorimotor function in both the beam and staircase tests, "tune-up" therapy had no effect on recovery. Golgi-Cox analysis revealed no effect of treatment on dendritic complexity.

CONCLUSIONS

This study reaffirms the benefits of early rehabilitation for functional recovery after stroke. However, "tune-up" therapy provided no benefit in ischemic animals regardless of earlier rehabilitation experience. It is possible that alternative approaches in the chronic phase may prove more effective.

Progressive Staging of Pilot Studies to Improve Phase III Trials for Motor Interventions

Based on the suboptimal research pathways that finally led to multicenter randomized clinical trials (MRCTs) of treadmill training with partial body weight support and of robotic assistive devices, strategically planned successive stages are proposed for pilot studies of novel rehabilitation interventions. Stage 1, consideration-of-concept studies, drawn from animal experiments, theories, and observations, delineate the experimental intervention in a small convenience sample of participants, so the results must be interpreted with caution. Stage 2, development-of-concept pilots, should optimize the components of the intervention, settle on most appropriate outcome measures, and examine dose-response effects. A well-designed study that reveals no efficacy should be published to counterweight the confirmation bias of positive trials. Stage 3, demonstration-of-concept pilots, can build out from what has been learned to test at least 15 participants in each arm, using random assignment and blinded outcome measures. A control group should receive an active practice intervention aimed at the same primary outcome. A third arm could receive a substantially larger dose of the experimental therapy or a combinational intervention. If only 1 site performed this trial, a different investigative group should aim to reproduce positive outcomes based on the optimal dose of motor training. Stage 3 studies ought to suggest an effect size of 0.4 or higher, so that approximately 50 participants in each arm will be the number required to test for efficacy in a stage 4, proof-of-concept MRCT. By developing a consensus around acceptable and necessary practices for each stage, similar to CONSORT recommendations for the publication of phase III clinical trials, better quality pilot studies may move quickly into better designed and more successful MRCTs of experimental interventions.

Interhemispheric competition after stroke: brain stimulation to enhance recovery of function of the affected hand

BACKGROUND AND PURPOSE

Within the concept of interhemispheric competition, technical modulation of the excitability of motor areas in the contralesional and ipsilesional hemisphere has been applied in an attempt to enhance recovery of hand function following stroke. This review critically summarizes the data supporting the use of novel electrophysiological concepts in the rehabilitation of hand function after stroke.

SUMMARY OF REVIEW

Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are powerful tools to inhibit or facilitate cortical excitability. Modulation of cortical excitability may instantaneously induce plastic changes within the cortical network of sensorimotor areas, thereby improving motor function of the affected hand after stroke. No significant adverse effects have been noted when applying brain stimulation in stroke patients. To date, however, the clinical effects are small to moderate and short lived. Future work should elucidate whether repetitive administration of rTMS or tDCS over several days and the combination of these techniques with behavioral training (ie, physiotherapy) could result in an enhanced effectiveness.

CONCLUSION

Brain stimulation is a safe and promising tool to induce plastic changes in the cortical sensorimotor network to improve motor behavior after stroke. However, several methodological issues remain to be answered to further improve the effectiveness of these new approaches.

Sensorimotor behavioral effects of endothelin-1 induced small cortical infarcts in C57BL/6 mice

Mouse models have not paralleled rat models of stroke in advances in sensitive, species appropriate measures of neurological and behavioral recovery. Most available tests of mouse sensorimotor function are adaptations of those originally developed in rats and may not be as sensitive in detecting behavioral deficits after small cortical lesions in mice. Our purpose was to test the use of a vasoconstricting peptide, endothelin-1 (ET-1), to produce focal infarcts of the mouse sensorimotor cortex and to establish a behavioral test battery sensitive to resulting sensorimotor deficits. Young adult (3-5-month-old) male C57BL/6 mice received intracortical infusions of ET-1 that produced unilateral lesions of the forelimb region of the sensorimotor cortex, intracortical infusions of sterile saline, or sham surgeries. Pre-operatively and at various time points over 3 weeks post-surgery, they were administered a test battery that included measures of sensorimotor asymmetry (Corner and Bilateral Tactile Stimulation Tests), coordinated forepaw use (Cylinder and Ladder Rung Tests), and dexterous forepaw function (Pasta Matrix Reaching Test). ET-1 infusions resulted in consistently placed, focal cortical infarcts and forelimb impairments as measured with the Ladder Rung, Bilateral Tactile Stimulation, and Pasta Matrix Reaching Tests. On the Bilateral Tactile Stimulation and Pasta Matrix Reaching Tests, impairments persisted throughout the time span of observation (26 days). These results support ET-1 as a viable option for creating small, reproducible lesions of anatomical subregions in the mouse neocortex that result in lasting functional impairments in the forelimb, as observed with sufficiently sensitive measures.

Cortical Excitability in Chronic Stroke and Modulation by Training: A TMS Study

Background. A possible role for GABA in regulating cortical plasticity after stroke has been proposed. Objective. To investigate changes in intracortical inhibitory and facilitatory circuits in the affected hemisphere more than 6 months after stroke, as well as modulation of excitability by a single training session. Methods. A total of 22 patients >6 months after stroke were compared to age- and gender-matched healthy participants. Cortical excitability was assessed by transcranial magnetic stimulation (TMS), including paired-pulse stimulation, before and up to 30 minutes after a single 15-minute session of 1 Hz thumb abduction-adduction movements. Results. At baseline, TMS showed decreased intracortical inhibition in the affected hemisphere of patients ( P = .004) compared to healthy participants. After training a short-lasting decline in motor evoked potentials was observed in both patients ( P = .002) and healthy participants ( P = .06). Moreover, in healthy participants, inhibitory activity decreased up to 30 minutes after training whereas no significant change was seen in the patients. Conclusions. The findings indicate that inhibitory intracortical circuits are less active after stroke, and no change in inhibitory activity is evident after a single training session. This may indicate that intracortical disinhibition is beneficial during recovery and that an impaired capacity for modulation remains in the chronic stage of stroke.

The future of restorative neurosciences in stroke: driving the translational research pipeline from basic science to rehabilitation of people after stroke

BACKGROUND

Major advances during the past 50 years highlight the immense potential for restoration of function after neural injury, even in the damaged adult human brain. Yet, the translation of these advances into clinically useful treatments is painstakingly slow.

OBJECTIVE

Here, we consider why the traditional model of a "translational research pipeline" that transforms basic science into novel clinical practice has failed to improve rehabilitation practice for people after stroke.

RESULTS

We find that (1) most treatments trialed in vitro and in animal models have not yet resulted in obviously useful functional gains in patients; (2) most clinical trials of restorative treatments after stroke have been limited to small-scale studies; (3) patient recruitment for larger clinical trials is difficult; (4) the determinants of patient outcomes and what patients want remain complex and ill-defined, so that basic scientists have no clear view of the clinical importance of the problems that they are addressing; (5) research in academic neuroscience centers is poorly integrated with practice in front-line hospitals and the community, where the majority of patients are treated; and (6) partnership with both industry stakeholders and patient pressure groups is poorly developed, at least in the United Kingdom where research in the translational restorative neurosciences in stroke depends on public sector research funds and private charities.

CONCLUSIONS

We argue that interaction between patients, front-line clinicians, and clinical and basic scientists is essential so that they can explore their different priorities, skills, and concerns. These interactions can be facilitated by funding research consortia that include basic and clinical scientists, clinicians and patient/carer representatives with funds targeted at those impairments that are major determinants of patient and carer outcomes. Consortia would be instrumental in developing a lexicon of common methods, standardized outcome measures, data sharing and long-term goals. Interactions of this sort would create a research-friendly, rather than only target-led, culture in front-line stroke rehabilitation services.

Cortical plasticity following motor skill learning during mental practice in stroke

BACKGROUND

and purpose. Mental practice (MP), which involves cognitive rehearsal of physical movements, is a noninvasive, inexpensive method of enabling repetitive, task-specific practice (RTP). Recent, randomized controlled data suggest that MP, when combined with an RTP therapy program, increases affected arm use and function significantly more than RTP only. As a next step, this 10-subject case series examined the possibility that cortical plasticity is a mechanism underlying the treatment effect of MP when combined with RTP.

METHOD

Ten chronic stroke patients (mean = 36.7 months) exhibiting stable, moderate motor deficits received 30-minute therapy sessions for their affected arms, occurring 3 days/week for 10 weeks, and emphasizing valued activities of daily living (ADLs). Directly after therapy, subjects received 30-minute MP sessions, which required MP of the ADLs performed during therapy. Behavioral outcomes were blindly evaluated using the Action Research Arm Test (ARAT) and the Fugl-Meyer Assessment (FM). Functional magnetic resonance imaging (fMRI) was administered before and after intervention to assess cortical changes.

RESULTS

Before intervention, subjects exhibited stable motor deficits. After intervention, subjects exhibited ARAT and FM score increases (+5.3 and +4.2, respectively) and clinically significant gains in ADLs. Postintervention fMRI revealed significant increases in activation to wrist flexion and extension of the affected hand in the premotor area and primary motor cortex ipsilateral and contralateral to the affected hand, as well as in superior parietal cortex ipsilateral to the affected hand. Decreased activation was noted in parietal cortex of the hemisphere ipsilateral to the affected hand. These changes correlated with anatomical regions in which behavioral changes were observed in the ARAT and FM.

CONCLUSIONS

MP is an easy to use, cost-effective strategy that was again shown to improve affected arm outcomes after stroke. This is the first study to demonstrate alteration in the cortical map in response to MP training.

Botulinum toxin-a in children with congenital spastic hemiplegia does not improve upper extremity motor-related function over rehabilitation alone: a randomized controlled trial

BACKGROUND

Rehabilitation of the upper extremity in children with hemiplegic cerebral palsy has not been compared to the same intensity of therapy combined with injected botulinum toxin (BTX).

OBJECTIVE

To measure the short-term (2 weeks) and long-term (6 and 9 months) effects of a standardized functional training program versus without the addition of chemodenervation of forearm and hand muscles.

METHODS

Twenty children with spastic hemiplegia, aged 4 to 16 years, were matched for baseline characteristics and then randomized to standardized functional physical and occupational therapies for 6 months (PT/OT group) or to the same therapies plus multimuscle BTX-A (BTX+ group).

MAIN OUTCOME MEASURES

were isometric generated force, overshoot and undershoot (force production error), active and passive range of motion by goniometry (ROM), stretch restricted angle (SRA) of joints, Ashworth scores at the elbow and wrist, and the Melbourne assessment of unilateral upper limb function. All measures were performed at baseline, 2 weeks after BTX-A, 6 months (end of therapy), and then 3 months after termination of the therapy.

RESULTS

Clinical measures (muscle tone, active ROM of wrist and elbow) showed improvement in both groups. However, no significant differences emerged between groups on functional measures. Generated force decreased directly after the BTX-A injection but increased during the therapy period. The PT/OT group, however, showed a significantly higher increase in force and accuracy with therapy compared with the BTX+ therapy group.

CONCLUSIONS

Functional rehabilitation therapies for the upper extremity increase manual isometric flexor force at the wrist and ROM, but BTX injections cause weakness and do not lead to better outcomes than therapy alone.

Delayed rehabilitation lessens brain injury and improves recovery after intracerebral hemorrhage in rats

Rehabilitation improves recovery after intracerebral hemorrhage (ICH) in rats. In some cases, brain damage is attenuated. In this study, we tested whether environmental enrichment (EE) combined with skilled reach training improves recovery and lessens brain injury after ICH in rats. Collagenase was injected stereotaxically to produce a moderate-sized striatal ICH. One week after ICH rats were either placed into a rehabilitation (REHAB) or control (CONT) condition. The REHAB rats received 15 h of EE and four 15-minute reach-training sessions daily over 5 days a week for 2 weeks. The CONT rats stayed in standard group cages. Skilled reaching (staircase test), walking (horizontal ladder) and forelimb use bias (cylinder test) were assessed at 4 and 6 weeks after ICH. Lesion volume, corpus callosum volume and cortical thickness were calculated 46 days after ICH. The REHAB treatment reduced lesion volume by 28% (p=0.019) without affecting the corpus callosum volume (p=0.405) or cortical thickness (p=0.300), thus indicating that protection was due to lessening striatal injury. As well, REHAB significantly improved skilled reaching ability in the staircase apparatus at 4 (p=0.002) and 6 weeks (p<0.001) post-ICH. Transient benefit was obtained in the ladder test at 4 weeks (p=0.021). Unexpectedly, REHAB treatment lessened spontaneous use of the contralateral-to-ICH limb at 4 (p=0.045) and 6 weeks (p=0.041). In summary, the combination of EE and reach training significantly attenuates lesion volume (striatal injury) while improving skilled reaching and walking ability. These findings encourage the use of early rehabilitation therapies in patients suffering from basal ganglia hemorrhaging.

Motor network changes associated with successful motor skill relearning after acute ischemic stroke: a longitudinal functional magnetic resonance imaging study

BACKGROUND

. Motor learning mechanisms may be operative in stroke recovery and possibly reinforced by rehabilitative training.

OBJECTIVES

. To assess early motor network changes after acute ischemic stroke in patients treated with very early mobilization and task-oriented physical therapy in a comprehensive stroke unit, to investigate the association between neuronal activity and improvements in hand function, and to qualitatively explore the changes in neuronal activity in relation to motor learning.

METHODS

. Patients were assessed by functional magnetic resonance imaging and by clinical tests within the first week after stroke and 3 months later. After discharge, all participants were offered functional training of the affected arm according to individual needs.

RESULTS

. A total of 359 patients were screened, with 12 patients experiencing first-ever stroke, excluding primary sensorimotor cortex (MISI), with severe to moderately impaired hand function fulfilling the inclusion criteria. Laterality indexes (LIs) for MISI increase significantly during follow-up. There is increased cerebellar and striatal activation acutely, replaced by increased activation of ipsilesional MISI in the chronic phase. Bilateral somatosensory association areas and contralesional secondary somatosensory cortex (SII) area are also more active in the chronic phase. Activation of the latter region also correlates positively with improved hand function.

CONCLUSIONS

. Restoration of hand function is associated with highly lateralized MISI. Activity in bilateral somatosensory association area and contralesional SII may represent cortical plasticity involved in successful motor recovery. The changes in motor activity between acute and chronic phases seem to correspond to a motor learning process.

Experience--a double edged sword for restorative neural plasticity after brain damage

During the time period following damage, the brain undergoes widespread reorganizational processes. Manipulations of behavioral experience can be potent therapeutic interventions for shaping this reorganization and enhancing long-term functional outcome. Recovery of function is a major concern for survivors of central nervous system damage and management of post-injury rehabilitation is increasingly becoming a topic of chief importance. Animal research, the focus of this review, suggests that, in the absence of behavioral manipulations, the brain is unlikely to realize its full potential for supporting function. However, experiences also have the capacity to be maladaptive for brain and behavioral function. From a treatment perspective, it may be unwise to adopt the canon of "first, do no harm" because maladaptive experiences include behaviors that individuals learn to do on their own. A better understanding of how behavioral experience interacts with brain reorganization could result in rehabilitative therapies, individually tailored and optimized for functional outcome.

Maladaptive effects of learning with the less-affected forelimb after focal cortical infarcts in rats

It is common following stroke to focus early rehabilitation efforts on developing compensatory use of the less-affected body side. Here we used a rat model of focal cortical infarct to examine how motor skill acquisition with the less-affected ("intact") forelimb influences sensorimotor function of the infarct-impaired forelimb and neural activity in peri-infarct cortex. Rats proficient in skilled reaching with one forelimb were given focal ischemic lesions in the contralateral sensorimotor cortex (SMC). Recovery in this forelimb was tested following a period of reach training focused on the intact forelimb or control procedures. Quantitative measures of the cumulatively expressed transcription factor, FosB/DeltaFosB, were used to assay intact forelimb training effects on neuronal activity in remaining SMC of the infarcted hemisphere. Intact forelimb training worsened behavioral recovery in the impaired forelimb following unilateral focal ischemia. Furthermore, it decreased neuronal FosB/DeltaFosB expression in layer II/III of peri-infarct SMC. These effects were not found in sham-operated rats trained sequentially with both forelimbs or in animals receiving bilateral forelimb training after unilateral infarcts. Thus, focused use of the intact forelimb has detrimental effects on recovery of impaired forelimb function following a focal ischemic injury and this is linked to reduced neuronal activation in remaining cortex. These results suggest that peri-infarct cortex becomes vulnerable to early post-stroke experience with the less-affected forelimb and that this experience may drive neural plasticity here in a direction that is maladaptive for functional outcome.

The vermicelli handling test: a simple quantitative measure of dexterous forepaw function in rats

Loss of function in the hands occurs with many brain disorders, but there are few measures of skillful forepaw use in rats available to model these impairments that are both sensitive and simple to administer. Whishaw and Coles previously described the dexterous manner in which rats manipulate food items with their paws, including thin pieces of pasta [Whishaw IQ, Coles BL. Varieties of paw and digit movement during spontaneous food handling in rats: postures, bimanual coordination, preferences, and the effect of forelimb cortex lesions. Behav Brain Res 1996;77:135-48]. We set out to develop a measure of this food handling behavior that would be quantitative, easy to administer, sensitive to the effects of damage to sensory and motor systems of the CNS and useful for identifying the side of lateralized impairments. When rats handle 7 cm lengths of vermicelli, they manipulate the pasta by repeatedly adjusting the forepaw hold on the pasta piece. As operationally defined, these adjustments can be easily identified and counted by an experimenter without specialized equipment. After unilateral sensorimotor cortex (SMC) lesions, transient middle cerebral artery occlusion (MCAO) and striatal dopamine depleting (6-hydroxydopamine, 6-OHDA) lesions in adult rats, there were enduring reductions in adjustments made with the contralateral forepaw. Additional pasta handling characteristics distinguished between the lesion types. MCAO and 6-OHDA lesions increased the frequency of several identified atypical handling patterns. Severe dopamine depletion increased eating time and adjustments made with the ipsilateral forepaw. However, contralateral forepaw adjustment number most sensitively detected enduring impairments across lesion types. Because of its ease of administration and sensitivity to lateralized impairments in skilled forepaw use, this measure may be useful in rat models of upper extremity impairment.