Use it and/or lose it-experience effects on brain remodeling across time after stroke

Experience-driven competition in neural reorganization after stroke

Behavioural experiences interact with regenerative responses to shape patterns of neural reorganization after stroke. This review is focused on the competitive nature of these behavioural experience effects. Interactions between learning-related plasticity and regenerative reactions have been found to underlie the establishment of new compensatory behaviours and the efficacy of motor rehabilitative training in rodent stroke models. Learning in intact brains depends on competitive and cooperative mechanisms of synaptic plasticity. Synapses are added in response to learning and selectively maintained and strengthened via activity-dependent competition. Long-term memories for experiences that occur closely in time can be weakened or enhanced by competitive or cooperative interactions in the time-dependent process of stabilizing synaptic changes. Rodent stroke model findings suggest that compensatory reliance on the non-paretic hand after stroke can shape and stabilize synaptic reorganization patterns in both hemispheres, to compete with the capacity for experiences of the paretic side to do so. However, the competitive edge of the non-paretic side can be countered by overlapping experiences of the paretic hand, and might even be shifted in a cooperative direction with skilfully coordinated bimanual experience. Advances in the basic understanding of learning-related synaptic competition are helping to inform the basis of experience-dependent variations in stroke outcome.

Ankle joint position sense acuity differences among stroke survivors at three walking ability levels: a cross-sectional study

Background

Despite the importance of lower limb sensation in walking highlighted in systematic reviews, there is limited research investigating the effect of proprioceptive deficits after stroke and any relationship with walking ability.

Objectives

With stroke survivors of different walking ability, this study aimed to (1) explore side (affected/unaffected) and movement direction (inversion/plantar flexion) effects in ankle joint position sense (JPS) acuity, and (2) compare ankle JPS acuity between groups of stroke survivors with different walking ability.

Methods

Seventy subacute stroke survivors were recruited and divided into three groups based on walking ability, as determined by their gait speed on the 10-Meter Walking Test: household (<0.4 m/s), limited community (0.4-0.8 m/s) and community (>0.8 m/s). Ankle JPS acuity was measured by the active movement extent discrimination apparatus (AMEDA).

Results

A significant difference was found between sides, with the AMEDA scores for the unaffected side significantly higher than for the affected side (F1.67 = 22.508, p < 0.001). The mean AMEDA scores for plantar flexion were significantly higher than for inversion (F1.67 = 21.366, p < 0.001). There was a significant linear increase in ankle JPS acuity with increasing walking ability among stroke survivors (F1.67 = 17.802, p < 0.001).

Conclusion

After stroke, ankle JPS acuity on the affected side was lower than the unaffected side. Stroke survivors had higher ankle JPS acuity in plantar-flexion movements, compared with inversion movements. Overall, stroke survivors with higher ankle JPS acuity tended to have higher walking ability, highlighting the importance of ankle JPS acuity in walking ability after stroke. These findings provide new insights into proprioceptive deficits after stroke and their relevance in neurorehabilitation.

The effect of exercise on balance function in stroke patients: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

A growing body of studies has examined the effect of exercise on balance function in stroke patients, with conflicting findings. This study aimed to investigate the effect of exercise on balance function in stroke patients and to determine the optimal exercise prescription for stroke patients.

METHODS

We conducted an extensive search across various databases, including PubMed, Web of Science, EBSCO, Cochrane, and Scopus. The search was conducted until March 11th, 2024. Data were pooled using the weighted mean difference (WMD) and 95% confidence interval.

RESULTS

Twenty-nine studies fulfilled the inclusion criteria. Exercise significantly improved Berg balance scale (BBS, WMD, 5.24, P < 0.00001) and timed up and go test (TUG, WMD, - 2.91, P < 0.00001) in stroke patients. Subgroup analyses showed that aerobic exercise (WMD, 6.71, P = 0.003), exercise conducted ≥ 8 weeks (WMD, 6.43, P < 0.00001), > 3 times per week (WMD, 6.18, P < 0.00001), ≥ 60 min per session (WMD, 6.40, P < 0.0001), and ≥ 180 min per week (WMD, 7.49, P < 0.00001) were more effective in improving BBS.

CONCLUSIONS

Exercise improved balance function in stroke patients, and aerobic exercise might be the most effective intervention. To improve balance function, this meta-analysis provides clinicians with evidence to recommend that stroke patients participate in a minimum of 8 weeks of exercise at least 3 times per week for more than 60 min per session, with a goal of 180 min per week being achieved by increasing the frequency of exercise.

Suppression of DAPK1 reduces ischemic brain injury through inhibiting cell death signaling and promoting neural remodeling

The role of death-associated protein kinase1 (DAPK1) in post-stroke functional recovery is controversial, as is its mechanism of action and any neural remodeling effect after ischemia. To assess the debatable role of DAPK1, we established the middle cerebral artery occlusion (MCAo) model in DAPK1 knockout mice and Sprague-Dawley (SD) rats. We identified that the genetic deletion of the DAPK1 as well as pharmacological inhibition of DAPK1 showed reduced brain infarct volume and neurological deficit. We report that DAPK1 inhibition (DI) reduces post-stroke neuronal death by inhibiting BAX/BCL2 and LC3/Beclin1 mediated apoptosis and autophagy, respectively. Histological analysis displayed a reduction in nuclear condensation, neuronal dissociation, and degraded cytoplasm in the DI group. The DI treatment showed enhanced dendrite spine density and neurite outgrowth, upregulated neural proliferation marker proteins like brain-derived neurotrophic factor, and reduced structural abnormalities of the cortical pyramidal neurons. This research shows that DAPK1 drives cell death, its activation exacerbates functional recovery after cerebral ischemia and shows that oxazolone-based DI could be an excellent candidate for stroke and ischemic injury intervention.

Enhancing upper-limb neurorehabilitation in chronic stroke survivors using combined action observation and motor imagery therapy

Introduction

For people who have had a stroke, recovering upper-limb function is a barrier to independence. When movement is difficult, mental practice can be used to complement physical therapy. In this within-participants study we investigated the effects of combined action observation and motor imagery (AO + MI) therapy on upper-limb recovery in chronic stroke survivors.

Methods

A Graeco-Latin Square design was used to counterbalance four mental practice conditions (AO + MI, AO, MI, Control) across four cup-stacking tasks of increasing complexity. Once a week, for five consecutive weeks, participants (n = 10) performed 16 mental practice trials under each condition. Each trial displayed a 1st person perspective of a cup-stacking task performed by an experienced model. For AO, participants watched each video and responded to an occasional color cue. For MI, participants imagined the effort and sensation of performing the action; cued by a series of still-images. For combined AO + MI, participants observed a video of the action while they simultaneously imagined performing the same action in real-time. At three time points (baseline; post-test; two-week retention test) participants physically executed the three mentally practiced cup-stacking tasks, plus a fourth unpractised sequence (Control), as quickly and accurately as possible.

Results

Mean movement execution times were significantly reduced overall in the post-test and the retention test compared to baseline. At retention, movement execution times were significantly shorter for combined AO + MI compared to both MI and the Control. Individual participants reported clinically important changes in quality of life (Stroke Impact Scale) and positive qualitative experiences of AO + MI (social validation).

Discussion

These results indicate that when physical practice is unsuitable, combined AO + MI therapy could offer an effective adjunct for neurorehabilitation in chronic stroke survivors.

Effects of Gaze Stabilization Exercises on Gait, Plantar Pressure, and Balance Function in Post-Stroke Patients: A Randomized Controlled Trial

This study aims to explore the effects of gaze stabilization exercises (GSEs) on gait, plantar pressure, and balance function in post-stroke patients (≤6 months). Forty post-stroke patients were randomly divided into an experimental group (n = 20) and a control group (n = 20). The experimental group performed GSEs combined with physical therapy, while the control group only performed physical therapy, once a day, 5 days a week, for 4 weeks. The Berg Balance Scale (BBS) was used to test the balance function and the risk of falling, which was the primary outcome. The Timed Up and Go test (TUGT) evaluated the walking ability and the fall risk. The envelope ellipse area and the plantar pressure proportion of the affected side were used to measure the patient’s supporting capacity and stability in static standing. The anterior−posterior center of pressure displacement velocity was used to test the weight-shifting capacity. Compared to the control group, the swing phase of the affected side, swing phase’s absolute symmetric index, envelope ellipse area when eyes closed, and TUGT of the experimental group had significantly decreased after GSEs (p < 0.05); the BBS scores, TUGT, the anterior−posterior COP displacement velocity, and the plantar pressure proportion of the affected side had significantly increased after 4 weeks of training (p < 0.05). In conclusion, GSEs combined with physical therapy can improve the gait and balance function of people following stroke. Furthermore, it can enhance the weight-shifting and one-leg standing capacity of the affected side, thus reducing the risk of falling.

Changes in upper limb capacity and performance in the early and late subacute phase after stroke

BACKGROUND

The course of spontaneous biological recovery indicates that no essential improvements in upper limb (UL) capacity should be expected 3 months after stroke. Likewise, UL performance as assessed with accelerometers does not seem to increase. However, this plateau may not apply to all patients with stroke.

OBJECTIVES

This study aimed to investigate the changes in UL capacity and performance from 3 to 6 months post-stroke, and the association between patients' UL capacity and actual UL performance.

METHODS

This study was a secondary analysis of a prospective longitudinal cohort study. Patients with UL impairment and first or recurrent stroke were included. Their UL capacity was assessed at 3 and 6 months with the Action Research Arm Test (ARAT) and UL performance was examined with accelerometry and expressed as a use ratio. The association between ARAT and use ratio was examined with multiple regression analyses.

RESULTS

Data from 67 patients were analyzed. It was shown that UL capacity as assessed with ARAT still improved from 3 to 6 months. A clinically meaningful improvement (≥ 6 points on ARAT) was found in 16 (46%) of the 35 patients whose scores allowed for such an increase. Improvements were mainly observed for patients with ARAT scores in the range of 15-51 at 3 months. Conversely, UL performance did not change. Three and 6 months after stroke respectively 69% and 64% of the variation in use ratio was explained by ARAT.

CONCLUSION

While a substantial part of patients improved their UL capacity, UL performance did not change from 3 to 6 months post-stroke. Strategies to remind patients of including their affected UL may encourage the transfer from better capacity to increased performance.

Prolonged release of VEGF and Ang1 from intralesionally implanted hydrogel promotes perilesional vascularization and functional recovery after experimental ischemic stroke

Injectable hydrogels can generate and support pro-repair environments in injured tissue. Here we used a slow-releasing drug carrying in situ-forming hydrogel to promote post-stroke recovery in a rat model. Release kinetics were measured in vitro and in vivo with MRI, using gadolinium-labeled albumin (Galbumin), which demonstrated prolonged release over multiple weeks. Subsequently, this hydrogel was used for long-term delivery of vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang1) (Gel VEGF + Ang1, n = 14), in a photothrombotically induced cortical stroke lesion in rats. Control stroke animals were intralesionally injected with saline (Saline, n = 10), non-loaded gel (Gel, n = 10), or a single bolus of VEGF + Ang1 in saline (Saline VEGF + Ang1, n = 10). MRI was executed to guide hydrogel injection. Functional recovery was assessed with sensorimotor function tests, while tissue status and vascularization were monitored by serial in vivo MRI. Significant recovery from sensorimotor deficits from day 28 onwards was only measured in the Gel VEGF + Ang1 group. This was accompanied by significantly increased vascularization in the perilesional cortex. Histology confirmed (re)vascularization and neuronal sparing in perilesional areas. In conclusion, intralesional injection of in situ-forming hydrogel loaded with pro-angiogenic factors can support prolonged brain tissue regeneration and promote functional recovery in the chronic phase post-stroke.

Short-term arm immobilization modulates excitability of inhibitory circuits within, and between, primary motor cortices

Previous research has suggested that short-term immobilization of the arm may be a low-cost, non-invasive strategy to enhance the capacity for long-term potentiation (LTP)-like plasticity in primary motor cortex (M1). Short-term immobilization reduces corticospinal excitability (CSE) in the contralateral M1, and interhemispheric inhibition (IHI) from ipsi- onto contralateral M1 is increased. However, it is unclear whether reduced CSE and increased IHI are associated with changes in intracortical inhibition, which has been shown to be important for regulating neuroplasticity in M1. The current study used transcranial magnetic stimulation to evaluate the effects of short-term (6 h) arm immobilization on CSE, IHI, and intracortical inhibition measured bilaterally in 43 neurotypical young adults (23 immobilized). We replicated previous findings demonstrating that immobilization decreased CSE in, and increased IHI onto, the immobilized hemisphere, but a significant change in intracortical inhibition was not observed at the group level. Across individuals, decreased CSE was associated with a decreased short-interval intracortical inhibition, an index of GABAA -ergic inhibition, within the immobilized hemisphere only in the immobilization group. Previous research has demonstrated that decreases in GABAA -ergic inhibition are necessary for the induction of LTP-like plasticity in M1; therefore, decreased intracortical inhibition after short-term arm immobilization may provide a novel mechanism to enhance the capacity for LTP-like plasticity within M1 and may be a potential target for strategies to augment plasticity capacity to enhance motor learning in health and disease.

Functional connectivity drives stroke recovery: shifting the paradigm from correlation to causation

Stroke is a leading cause of disability, with deficits encompassing multiple functional domains. The heterogeneity underlying stroke poses significant challenges in the prediction of post-stroke recovery, prompting the development of neuroimaging-based biomarkers. Structural neuroimaging measurements, particularly those reflecting corticospinal tract injury, are well-documented in the literature as potential biomarker candidates of post-stroke motor recovery. Consistent with the view of stroke as a 'circuitopathy', functional neuroimaging measures probing functional connectivity may also prove informative in post-stroke recovery. An important step in the development of biomarkers based on functional neural network connectivity is the establishment of causality between connectivity and post-stroke recovery. Current evidence predominantly involves statistical correlations between connectivity measures and post-stroke behavioural status, either cross-sectionally or serially over time. However, the advancement of functional connectivity application in stroke depends on devising experiments that infer causality. In 1965, Sir Austin Bradford Hill introduced nine viewpoints to consider when determining the causality of an association: (i) strength; (ii) consistency; (iii) specificity; (iv) temporality; (v) biological gradient; (vi) plausibility; (vii) coherence; (viii) experiment; and (ix) analogy. Collectively referred to as the Bradford Hill Criteria, these points have been widely adopted in epidemiology. In this review, we assert the value of implementing Bradford Hill's framework to stroke rehabilitation and neuroimaging. We focus on the role of neural network connectivity measurements acquired from task-oriented and resting-state functional MRI, EEG, magnetoencephalography and functional near-infrared spectroscopy in describing and predicting post-stroke behavioural status and recovery. We also identify research opportunities within each Bradford Hill tenet to shift the experimental paradigm from correlation to causation.

Posture Deficits and Recovery After Unilateral Vestibular Loss: Early Rehabilitation and Degree of Hypofunction Matter

Postural instability and balance impairment are disabling symptoms in patients with acute unilateral peripheral vestibular hypofunction (UVH). Vestibular rehabilitation (VR) is known to improve the vestibular compensation process, but (1) its effect on posture recovery remains poorly understood, (2) little is known about when VR must be done, and (3) whether the degree of vestibular loss matters is uncertain. We analyzed posture control under static (stable support) and dynamic (unstable support) postural tasks performed in different visual conditions [eye open (EO); eyes closed (EC); and optokinetic stimulation] using dynamic posturography. Non-linear analyses of the postural performance (wavelet transform, diffusion analysis, and fractal analysis) were performed in two groups of patients with UVH subjected to the same VR program based on the unidirectional rotation paradigm and performed either early (first 2 weeks) or later (fifth to the sixth week) after vertigo attack. Distribution of the angular horizontal vestibulo-ocular reflex (aVOR) gain values recorded on the hypofunction side before rehabilitation differentiated two distinct sub-groups (cluster analysis) with aVOR gains below or above 0.20. The postural performance of the four sub-groups of patients with UVH (early rehabilitation with aVOR gain <0.20: n = 25 or gain >0.20: n = 19; late rehabilitation with aVOR gain <0.20: n = 15 or gain >0.20: n = 10) tested before VR showed significantly altered postural parameters compared with healthy controls. Greater instability, higher energy to control posture, larger sway without feedback corrections, and lower time of automatic control of posture were observed in static conditions. The four sub-groups recovered near-normal postural performance after VR in the EO and EC conditions, but still exhibited altered postural performance with optokinetic stimulation. In dynamic posturography conditions and before VR, the percentage of patients able to perform the postural tasks with EC and optokinetic stimulation was significantly lower in the two sub-groups with aVOR gain <0.20. After VR, the improvement of the postural parameters depended on the stage of rehabilitation and the degree of vestibular hypofunction. The best balance function recovery was found in the sub-group with early VR and pre-rehabilitation aVOR gain above 0.20, the worst in the sub-group with late rehabilitation and aVOR gain below 0.20. These differences were seen when the vestibular input remains the main sensory cue to control balance, that is, on unstable support without vision or altered visual motion cues. These findings extend to dynamic balance recovery the crucial roles of early rehabilitation and degree of vestibular hypofunction which we have already highlighted for vestibulo-ocular reflex recovery.

Brain-Computer Interface Training Based on Brain Activity Can Induce Motor Recovery in Patients With Stroke: A Meta-Analysis

BACKGROUND

Brain-computer interface (BCI) is a procedure involving brain activity in which neural status is provided to the participants for self-regulation. The current review aims to evaluate the effect sizes of clinical studies investigating the use of BCI-based rehabilitation interventions in restoring upper extremity function and effective methods to detect brain activity for motor recovery.

METHODS

A computerized search of MEDLINE, CENTRAL, Web of Science, and PEDro was performed to identify relevant articles. We selected clinical trials that used BCI-based training for post-stroke patients and provided motor assessment scores before and after the intervention. The pooled standardized mean differences of BCI-based training were calculated using the random-effects model.

RESULTS

We initially identified 655 potentially relevant articles; finally, 16 articles fulfilled the inclusion criteria, involving 382 participants. A significant effect of neurofeedback intervention for the paretic upper limb was observed (standardized mean difference = .48, [.16-.80], P = .006). However, the effect estimates were moderately heterogeneous among the studies (I² = 45%, P = .03). Subgroup analysis of the method of measurement of brain activity indicated the effectiveness of the algorithm focusing on sensorimotor rhythm.

CONCLUSION

This meta-analysis suggested that BCI-based training was superior to conventional interventions for motor recovery of the upper limbs in patients with stroke. However, the results are not conclusive because of a high risk of bias and a large degree of heterogeneity due to the differences in the BCI interventions and the participants; therefore, further studies involving larger cohorts are required to confirm these results.

When Spinal Neuromodulation Meets Sensorimotor Rehabilitation: Lessons Learned From Animal Models to Regain Manual Dexterity After a Spinal Cord Injury

Electrical neuromodulation has strongly hit the foundations of spinal cord injury and repair. Clinical and experimental studies have demonstrated the ability to neuromodulate and engage spinal cord circuits to recover volitional motor functions lost after the injury. Although the science and technology behind electrical neuromodulation has attracted much of the attention, it cannot be obviated that electrical stimulation must be applied concomitantly to sensorimotor rehabilitation, and one would be very difficult to understand without the other, as both need to be finely tuned to efficiently execute movements. The present review explores the difficulties faced by experimental and clinical neuroscientists when attempting to neuromodulate and rehabilitate manual dexterity in spinal cord injured subjects. From a translational point of view, we will describe the major rehabilitation interventions employed in animal research to promote recovery of forelimb motor function. On the other hand, we will outline some of the state-of-the-art findings when applying electrical neuromodulation to the spinal cord in animal models and human patients, highlighting how evidences from lumbar stimulation are paving the path to cervical neuromodulation.

Motor learning in neurological rehabilitation

While most upper limb training interventions in neurological rehabilitation are based on established principles of motor learning and neural plasticity, recovery potential may be improved if the focus includes remediating an individual's specific motor impairment within the framework of a motor control theory. This paper reviews current theories of motor control and motor learning and describes how they can be incorporated into training programs to enhance sensorimotor recovery in patients with neurological lesions. An emphasis is placed on dynamical systems theory and the use of new technologies such as virtual, augmented and mixed reality applications for rehabilitation to facilitate learning.Implications for RehabilitationKinematic abundance allows the healthy nervous system to produce different combinations of joint rotations to perform a desired task.The structure of practice to improve the movement repertoire in rehabilitation should take into account the kinematic abundance of the system.Learning can be enhanced by varied practice with feedback about key movement elements.Virtual reality environments provide opportunities to manipulate the structure and schedule of practice and feedback.

Non-invasive, non-pharmacological/bio-technological interventions towards neurorestoration upshot after ischemic stroke, in adults-systematic, synthetic, literature review

Considering its marked life-threatening and (not seldom: severe and/or permanent) disabling, potential, plus the overall medico-psycho-socio-economic tough burden it represents for the affected persons, their families and the community, the cerebrovascular accident (CVA)-including with the, by far more frequent, ischemic type-is subject to considerable scientific research efforts that aim (if possible) at eliminating the stroke induced lesions, and consist, as well, in ambitious-but still poorly transferable into medical practice-goals such as brain neuroregeneration and/or repair, within related corollary/upshot of neurorestoration. We have conducted, in this respect, a systematic and synthetic literature review, following the "Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)" concept. Accordingly, we have interrogated five internationally renowned medical data bases: Elsevier, NCBI/PubMed, NCBI/PMC, PEDro, and ISI Web of Knowledge/Science (the last one to check whether the initially identified articles are published in ISI indexed journals), based on a large (details in the body text) number of most appropriate, to our knowledge, key word combinations/"syntaxes"-used contextually-and subsequently fulfilling the related, on five steps, filtering/selection methodology. We have thereby selected 114 fully eligible (of which contributive: 83-see further) papers; at the same time, additionally, we have enhanced our documentation-basically, but not exclusively, for the introductive part of this work (see further)-with bibliographic resources, overall connected to our subject, identified in the literature within a non-standardized search. It appears that the opportunity window for morph-functional recovery after stroke is larger than previously thought, actually being considered that brain neurorestoration/repair could occur, and therefore be expected, in later stages than in earlier ones, although, in this context, the number of cases possibly benefitting (for instance after physical and/or cognitive rehabilitation-including with magnetic or direct current transcranial stimulation) is quite small and with more or less conflicting, related outcomes, in the literature. Moreover, applying especially high intense, solicitating, rehabilitation interventions, in early stages post (including ischemic) stroke could even worsen the functional evolution. Accordingly, for clarifications and validation of more unitary points of view, continuing and boosting research efforts in this complex, interdisciplinary domain, is necessary. Until finding (if ever) effective modalities to cure the lesions of the central nervous system (CNS)-including post ischemic stroke-it is reasonable and recommendable-based on rigorous methodologies-the avail of combined ways: physiatric, pharmacologic, possibly also bio-technologic. On a different note, but however connected to our subject: periodic related systematic, synthetic literature reviews reappraisals are warranted and welcome.

Advancing motor rehabilitation for adults with chronic neurological conditions through increased involvement of kinesiologists: a perspective review

Many people with neurological conditions experience challenges with movement. Although rehabilitation is often provided acutely and sub-acutely following the onset of a condition, motor deficits commonly persist in the long-term and are exacerbated by disuse and inactivity. Notably, motor rehabilitation approaches that incorporate exercise and physical activity can support gains in motor function even in the chronic stages of many neurological conditions. However, delivering motor rehabilitation on a long-term basis to people with chronic neurological conditions is a challenge within health care systems, and the onus is often placed on patients to find and pay for services. While neurological motor rehabilitation is largely the domain of physical and occupational therapists, kinesiologists may be able to complement existing care and support delivery of long-term neurological motor rehabilitation, specifically through provision of supported exercise and physical activity programs. In this perspective style review article, we discuss potential contributions of kinesiologists to advancing the field through exercise programming, focusing on community-based interventions that increase physical activity levels. We conclude with recommendations on how kinesiologists' role might be further optimized towards improving long-term outcomes for people with chronic neurological conditions, considering issues related to professional regulation and models of care.

Remote Corticospinal Tract Degeneration After Cortical Stroke in Rats May Not Preclude Spontaneous Sensorimotor Recovery

Background. Recovery of motor function after stroke appears to be related to the integrity of axonal connections in the corticospinal tract (CST) and corpus callosum, which may both be affected after cortical stroke. Objective. In the present study, we aimed to elucidate the relationship of changes in measures of the CST and transcallosal tract integrity, with the interhemispheric functional connectivity and sensorimotor performance after experimental cortical stroke. Methods. We conducted in vivo diffusion magnetic resonance imaging (MRI), resting-state functional MRI, and behavior testing in twenty-five male Sprague Dawley rats recovering from unilateral photothrombotic stroke in the sensorimotor cortex. Twenty-three healthy rats served as controls. Results. A reduction in the number of reconstructed fibers, a lower fractional anisotropy, and higher radial diffusivity in the ipsilesional but intact CST, reflected remote white matter degeneration. In contrast, transcallosal tract integrity remained preserved. Functional connectivity between the ipsi- and contralesional forelimb regions of the primary somatosensory cortex significantly reduced at week 8 post-stroke. Comparably, usage of the stroke-affected forelimb was normal at week 28, following significant initial impairment between day 1 and week 8 post-stroke. Conclusions. Our study shows that post-stroke motor recovery is possible despite degeneration in the CST and may be supported by intact neuronal communication between hemispheres.

Longitudinal fMRI measures of cortical reactivation and hand use with and without training after sensory loss in primates

In a series of previous studies, we demonstrated that damage to the dorsal column in the cervical spinal cord deactivates the contralateral somatosensory hand cortex and impairs hand use in a reach-to-grasp task in squirrel monkeys. Nevertheless, considerable cortical reactivation and behavioral recovery occurs over the following weeks to months after lesion. This timeframe may also be a window for targeted therapies to promote cortical reactivation and functional reorganization, aiding in the recovery process. Here we asked if and how task specific training of an impaired hand would improve behavioral recovery and cortical reorganization in predictable ways, and if recovery related cortical changes would be detectable using noninvasive functional magnetic resonance imaging (fMRI). We further asked if invasive neurophysiological mapping reflected fMRI results. A reach-to-grasp task was used to test impairment and recovery of hand use before and after dorsal column lesions (DC-lesion). The activation and organization of the affected primary somatosensory cortex (area 3b) was evaluated with two types of fMRI - either blood oxygenation level dependent (BOLD) or cerebral blood volume (CBV) with a contrast agent of monocrystalline iron oxide nanocolloid (MION) - before and after DC-lesion. At the end of the behavioral and fMRI studies, microelectrode recordings in the somatosensory areas 3a, 3b and 1 were used to characterize neuronal responses and verify the somatotopy of cortical reactivations. Our results indicate that even after nearly complete DC lesions, monkeys had both considerable post-lesion behavioral recovery, as well as cortical reactivation assessed with fMRI followed by extracellular recordings. Generalized linear regression analyses indicate that lesion extent is correlated with the behavioral outcome, as well as with the difference in the percent signal change from pre-lesion peak activation in fMRI. Monkeys showed behavioral recovery and nearly complete cortical reactivation by 9-12 weeks post-lesion (particularly when the DC-lesion was incomplete). Importantly, the specific training group revealed trends for earlier behavioral recovery and had higher magnitude of fMRI responses to digit stimulation by 5-8 weeks post-lesion. Specific kinematic measures of hand movements in the selected retrieval task predicted recovery time and related to lesion characteristics better than overall task performance success. For measures of cortical reactivation, we found that CBV scans provided stronger signals to vibrotactile digit stimulation as compared to BOLD scans, and thereby may be the preferred non-invasive way to study the cortical reactivation process after sensory deprivations from digits. When the reactivation of cortex for each of the digits was considered, the reactivation by digit 2 stimulation as measured with microelectrode maps and fMRI maps was best correlated with overall behavioral recovery.

Two conditions to fully recover dynamic canal function in unilateral peripheral vestibular hypofunction patients

BACKGROUND

The crucial role of early vestibular rehabilitation (VR) to recover a dynamic semicircular canal function was recently highlighted in patients with unilateral vestibular hypofunction (UVH). However, wide inter-individual differences were observed, suggesting that parameters other than early rehabilitation are involved.

OBJECTIVE

The aim of the study was to determine to what extent the degree of vestibular loss assessed by the angular vestibulo-ocular reflex (aVOR) gain could be an additional parameter interfering with rehabilitation in the recovery process. And to examine whether different VR protocols have the same effectiveness with regard to the aVOR recovery.

METHODS

The aVOR gain and the percentage of compensatory saccades were recorded in 81 UVH patients with the passive head impulse test before and after early VR (first two weeks after vertigo onset: N = 43) or late VR (third to sixth week after onset: N = 38) performed twice a week for four weeks. VR was performed either with the unidirectional rotation paradigm or gaze stability exercises. Supplementary outcomes were the dizziness handicap inventory (DHI) score, and the static and dynamic subjective visual vertical.

RESULTS

The cluster analysis differentiated two distinct populations of UVH patients with pre-rehab aVOR gain values on the hypofunction side below 0.20 (N = 42) or above 0.20 (N = 39). The mean gain values were respectively 0.07±0.05 and 0.34±0.12 for the lateral canal (p < 0.0001), 0.09±0.06 and 0.44±0.19 for the anterior canal (p < 0.0001). Patients with aVOR gains above 0.20 and early rehab fully recovered dynamic horizontal canal function (0.84±0.14) and showed very few compensatory saccades (18.7% ±20.1%) while those with gains below 0.20 and late rehab did not improve their aVOR gain value (0.16±0.09) and showed compensatory saccades only (82.9% ±23.7%). Similar results were found for the anterior canal function. Recovery of the dynamic function of the lateral canal was found with both VR protocols while it was observed with the gaze stability exercises only for the anterior canal. All the patients reduced their DHI score, normalized their static SVV, and exhibited uncompensated dynamic SVV.

CONCLUSIONS

Early rehab is a necessary but not sufficient condition to fully recover dynamic canal function. The degree of vestibular loss plays a crucial role too, and to be effective rehabilitation protocols must be carried out in the plane of the semicircular canals.

A First Step Toward the Operationalization of the Learned Non-Use Phenomenon: A Delphi Study

BACKGROUND

The negative discrepancy between residual functional capacity and reduced use of the contralesional hand, frequently observed after a brain lesion, has been termed Learned Non-Use (LNU) and is thought to depend on the interaction of neuronal mechanisms during recovery and learning-dependent mechanisms.

OBJECTIVE

Albeit the LNU phenomenon is generally accepted to exist, currently, no transdisciplinary definition exists. Furthermore, although therapeutic approaches are implemented in clinical practice targeting LNU, no standardized diagnostic routine is described in the available literature. Our objective was to reach consensus regarding a definition as well as synthesize knowledge about the current diagnostic procedures.

METHODS

We used a structured group communication following the Delphi method among clinical and scientific experts in the field, knowledge from both, the work with patient populations and with animal models.

RESULTS

Consensus was reached regarding a transdisciplinary definition of the LNU phenomenon. Furthermore, the mode and strategy of the diagnostic process, as well as the sources of information and outcome parameters relevant for the clinical decision making, were described with a wide range showing the current lack of a consistent universal diagnostic approach.

CONCLUSIONS

The need for the development of a structured diagnostic procedure and its implementation into clinical practice is emphasized. Moreover, it exists a striking gap between the prevailing hypotheses regarding the mechanisms underlying the LNU phenomenon and the actual evidence. Therefore, basic research is needed to bridge between bedside and bench and eventually improve clinical decision making and further development of interventional strategies beyond the field of stroke rehabilitation.

Reorganization of Higher-Order Somatosensory Cortex After Sensory Loss from Hand in Squirrel Monkeys

Unilateral dorsal column lesions (DCL) at the cervical spinal cord deprive the hand regions of somatosensory cortex of tactile activation. However, considerable cortical reactivation occurs over weeks to months of recovery. While most studies focused on the reactivation of primary somatosensory area 3b, here, for the first time, we address how the higher-order somatosensory cortex reactivates in the same monkeys after DCL that vary across cases in completeness, post-lesion recovery times, and types of treatments. We recorded neural responses to tactile stimulation in areas 3a, 3b, 1, secondary somatosensory cortex (S2), parietal ventral (PV), and occasionally areas 2/5. Our analysis emphasized comparisons of the responsiveness, somatotopy, and receptive field size between areas 3b, 1, and S2/PV across DCL conditions and recovery times. The results indicate that the extents of the reactivation in higher-order somatosensory areas 1 and S2/PV closely reflect the reactivation in primary somatosensory cortex. Responses in higher-order areas S2 and PV can be stronger than those in area 3b, thus suggesting converging or alternative sources of inputs. The results also provide evidence that both primary and higher-order fields are effectively activated after long recovery times as well as after behavioral and electrocutaneous stimulation interventions.

Brain Functional Networks Study of Subacute Stroke Patients With Upper Limb Dysfunction After Comprehensive Rehabilitation Including BCI Training

Brain computer interface (BCI)-based training is promising for the treatment of stroke patients with upper limb (UL) paralysis. However, most stroke patients receive comprehensive treatment that not only includes BCI, but also routine training. The purpose of this study was to investigate the topological alterations in brain functional networks following comprehensive treatment, including BCI training, in the subacute stage of stroke. Twenty-five hospitalized subacute stroke patients with moderate to severe UL paralysis were assigned to one of two groups: 4-week comprehensive treatment, including routine and BCI training (BCI group, BG, n = 14) and 4-week routine training without BCI support (control group, CG, n = 11). Functional UL assessments were performed before and after training, including, Fugl-Meyer Assessment-UL (FMA-UL), Action Research Arm Test (ARAT), and Wolf Motor Function Test (WMFT). Neuroimaging assessment of functional connectivity (FC) in the BG was performed by resting state functional magnetic resonance imaging. After training, as compared with baseline, all clinical assessments (FMA-UL, ARAT, and WMFT) improved significantly (p < 0.05) in both groups. Meanwhile, better functional improvements were observed in FMA-UL (p < 0.05), ARAT (p < 0.05), and WMFT (p < 0.05) in the BG. Meanwhile, FC of the BG increased across the whole brain, including the temporal, parietal, and occipital lobes and subcortical regions. More importantly, increased inter-hemispheric FC between the somatosensory association cortex and putamen was strongly positively associated with UL motor function after training. Our findings demonstrate that comprehensive rehabilitation, including BCI training, can enhance UL motor function better than routine training for subacute stroke patients. The reorganization of brain functional networks topology in subacute stroke patients allows for increased coordination between the multi-sensory and motor-related cortex and the extrapyramidal system. Future long-term, longitudinal, controlled neuroimaging studies are needed to assess the effectiveness of BCI training as an approach to promote brain plasticity during the subacute stage of stroke.

Rehabilitation of dynamic visual acuity in patients with unilateral vestibular hypofunction: earlier is better

PURPOSE

Patients with acute peripheral unilateral hypofunction (UVH) complain of vertigo and dizziness and show posture imbalance and gaze instability. Vestibular rehabilitation therapy (VR) enhances the functional recovery and it has been shown that gaze stabilization exercises improved the dynamic visual acuity (DVA). Whether the effects of VR depend or not on the moment when it is applied remains however unknown, and investigation on how the recovery mechanisms could depend or not on the timing of VR has not yet been tested.

METHODS

Our study investigated the recovery of DVA in 28 UVH patients whose unilateral deficit was attested by clinical history and video head impulse test (vHIT). Patients were tested under passive conditions before (pre-tests) and after (post-tests) being subjected to an active DVA rehabilitation protocol. The DVA protocol consisted in active gaze stabilization exercises with two training sessions per week, each lasting 30 min, during four weeks. Patients were sub-divided into three groups depending on the time delay between onset of acute UVH and beginning of VR. The early DVA group (N = 10) was composed of patients receiving the DVA protocol during the first 2 weeks after onset (mean = 8.9 days), the late group 1 (N = 9) between the 3rd and the 4th week (mean = 27.5 days after) and the late group 2 (N = 9) after the 1st month (mean: 82.5 days). We evaluated the DVA score, the angular aVOR gain, the directional preponderance and the percentage of compensatory saccades during the HIT, and the subjective perception of dizziness with the Dizziness Handicap Inventory (DHI). The pre- and post-VR tests were performed with passive head rotations done by the physiotherapist in the plane of the horizontal and vertical canals.

RESULTS

The results showed that patients submitted to an early DVA rehab improved significantly their DVA score by increasing their passive aVOR gain and decreasing the percentage of compensatory saccades, while the late 1 and late 2 DVA groups 1 and 2 showed less DVA improvement and an inverse pattern, with no change in the aVOR gain and an increase in the percentage of compensatory saccades. All groups of patients exhibited significant reductions of the DHI score, with higher improvement in subjective perception of dizziness handicap in the patients receiving the DVA rehab protocol in the first month.

CONCLUSION

Our data provide the first demonstration in UVH patients that earlier is better to improve DVA and passive aVOR gain. Gaze stabilization exercises would benefit from the plastic events occurring in brain structures during a sensitive period or opportunity time window to elaborate optimal functional reorganizations. This result is potentially very important for the VR programs to restore the aVOR gain instead of recruiting compensatory saccades assisting gaze stability.

Rehabilitative Training Interacts with Ischemia-Instigated Spine Dynamics to Promote a Lasting Population of New Synapses in Peri-Infarct Motor Cortex

After subtotal infarcts of primary motor cortex (M1), motor rehabilitative training (RT) promotes improvements in paretic forelimb function that have been linked with its promotion of structural and functional reorganization of peri-infarct cortex, but how the reorganization unfolds is scantly understood. Cortical infarcts also instigate a prolonged period of dendritic spine turnover in peri-infarct cortex. Here we investigated the possibility that synaptic structural responses to RT in peri-infarct cortex reflect, in part, interactions with ischemia-instigated spine turnover. This was tested after artery-targeted photothrombotic M1 infarcts or Sham procedures in adult (4 months) C57BL/6 male and female GFP-M line (n = 24) and male yellow fluorescent protein-H line (n = 5) mice undergoing RT in skilled reaching or no-training control procedures. Regardless of training condition, spine turnover was increased out to 5 weeks postinfarct relative to Sham, as was the persistence of new spines formed within a week postinfarct. However, compared with no-training controls, new spines formed during postinfarct weeks 2-4 in mice undergoing RT persisted in much greater proportions to later time points, by a magnitude that predicted behavioral improvements in the RT group. These results indicate that RT interacts with ischemia-instigated spine turnover to promote preferential stabilization of newly formed spines, which is likely to yield a new population of mature synapses in peri-infarct cortex that could contribute to cortical functional reorganization and behavioral improvement. The findings newly implicate ischemia-instigated spine turnover as a mediator of cortical synaptic structural responses to RT and newly establish the experience dependency of new spine fates in the postischemic turnover context.SIGNIFICANCE STATEMENT Motor rehabilitation, the main treatment for motor impairments after stroke, is far from sufficient to normalize function. A better understanding of neural substrates of rehabilitation-induced behavioral improvements could be useful for understanding how to optimize it. Here, we investigated the nature and time course of synaptic responses to motor rehabilitative training in vivo Focal ischemia instigated a period of synapse turnover in peri-infarct motor cortex of mice. Rehabilitative training increased the stability of new synapses formed during the initial weeks after the infarct, the magnitude of which was correlated with improvements in skilled motor performance. Therefore, the maintenance of new synapses formed after ischemia could represent a structural mechanism of rehabilitative training efficacy.

Passive accessory joint mobilization in the multimodal management of chronic dysesthesia following thalamic stroke

Study design: Case Report. Purpose: Stroke is the most common cause of long-term disability. Dysesthesia, an unpleasant sensory disturbance, is common following thalamic stroke and evidence-based interventions for this impairment are limited. The purpose of this case report was to describe a decrease in dysesthesia following manual therapy intervention in a patient with history of right lacunar thalamic stroke. Case description: A 66-year-old female presented with tingling and dysesthesia in left hemisensory distribution including left trunk and upper/lower extremities, limiting function. Decreased left shoulder active range of motion, positive sensory symptoms but no sensory loss in light touch was found. She denied pain and moderate shoulder muscular weakness was demonstrated. Laterality testing revealed right/left limb discrimination deficits and neglect-like symptoms were reported. Passive accessory joint motion assessment of glenohumeral and thoracic spine revealed hypomobility and provoked dysesthesia. Interventions included passive oscillatory joint mobilization of glenohumeral joint, thoracic spine, ribs and shoulder strengthening. Results: After six sessions, shoulder function, active range of motion, strength improved and dysesthesia decreased. Global Rating of Change Scale was +5 and QuickDASH score decreased from 45% to 22% disability. Laterality testing was unchanged. Conclusion: Manual therapy may be a beneficial intervention in management of thalamic stroke-related dysesthesia. Implications for Rehabilitation While pain is common following thalamic stroke, patients may present with chronic paresthesia or dysesthesia, often in a hemisensory distribution. Passive movement may promote inhibition of hyperexcitable cortical pathways, which may diminish aberrant sensations. Passive oscillatory manual therapy may be an effective way to treat sensory disturbances such as paresthesias or dysesthesia.

Mild Contralesional Hypothermia Reduces Use of the Unimpaired Forelimb in a Skilled Reaching Task After Motor Cortex Injury in Rats

Therapeutic hypothermia (TH) mitigates neuronal injury in models of ischemic stroke. Although this therapy is meant for injured tissue, most protocols cool the whole body, including the contralesional hemisphere. Neuroplasticity responses within this hemisphere can affect functional outcome. Thus, cooling the contralesional hemisphere serves no clear neuroprotective function and may instead be detrimental. In this study, we cooled the contralesional hemisphere to determine whether this harms behavioral recovery after cortical injury in rats. All rats were trained on skilled reaching and walking tasks. Rats then received a motor cortex insult contralateral to their dominant paw after which they were randomly assigned to focal contralesional TH (∼33°C) for 1-48, 1-97, or 48-96 hours postinjury, or to a normothermic control group. Contralesional cooling did not impact lesion volume (p = 0.371) and had minimal impact on neurological outcome of the impaired limb. However, rats cooled early were significantly less likely to shift paw preference to the unimpaired paw (p ≤ 0.043), suggesting that cooling reduced learned nonuse. In a second experiment, we tested whether cooling impaired learning of the skilled reaching task in naive rats. Localized TH applied to the hemisphere contralateral or ipsilateral to the preferred paw did not impair learning (p ≥ 0.677) or dendritic branching/length in the motor cortex (p ≥ 0.105). In conclusion, localized TH did not impair learning or plasticity in the absence of neural injury, but contralesional TH may reduce unwanted shifts in limb preference after stroke.

Coordinated Plasticity of Synapses and Astrocytes Underlies Practice-Driven Functional Vicariation in Peri-Infarct Motor Cortex

Motor rehabilitative training after stroke can improve motor function and promote topographical reorganization of remaining motor cortical movement representations, but this reorganization follows behavioral improvements. A more detailed understanding of the neural bases of rehabilitation efficacy is needed to inform therapeutic efforts to improve it. Using a rat model of upper extremity impairments after ischemic stroke, we examined effects of motor rehabilitative training at the ultrastructural level in peri-infarct motor cortex. Extensive training in a skilled reaching task promoted improved performance and recovery of more normal movements. This was linked with greater axodendritic synapse density and ultrastructural characteristics of enhanced synaptic efficacy that were coordinated with changes in perisynaptic astrocytic processes in the border region between head and forelimb areas of peri-infarct motor cortex. Disrupting synapses and motor maps by infusions of anisomycin (ANI) into anatomically reorganized motor, but not posterior parietal, cortex eliminated behavioral gains from rehabilitative training. In contrast, ANI infusion in the equivalent cortical region of intact animals had no effect on reaching skills. These results suggest that rehabilitative training efficacy for improving manual skills is mediated by synaptic plasticity in a region of motor cortex that, before lesions, is not essential for manual skills, but becomes so as a result of the training. These findings support that experience-driven synaptic structural reorganization underlies functional vicariation in residual motor cortex after motor cortical infarcts.SIGNIFICANCE STATEMENT Stroke is a leading cause of long-term disability. Motor rehabilitation, the main treatment for physical disability, is of variable efficacy. A better understanding of neural mechanisms underlying effective motor rehabilitation would inform strategies for improving it. Here, we reveal synaptic underpinnings of effective motor rehabilitation. Rehabilitative training improved manual skill in the paretic forelimb and induced the formation of special synapse subtypes in coordination with structural changes in astrocytes, a glial cell that influences neural communication. These changes were found in a region that is nonessential for manual skill in intact animals, but came to mediate this skill due to training after stroke. Therefore, motor rehabilitation efficacy depends on synaptic changes that enable remaining brain regions to assume new functions.

Use of Electroencephalography Brain-Computer Interface Systems as a Rehabilitative Approach for Upper Limb Function After a Stroke: A Systematic Review

BACKGROUND

Brain-computer interface (BCI) systems have been suggested as a promising tool for neurorehabilitation. However, to date, there is a lack of homogeneous findings. Furthermore, no systematic reviews have analyzed the degree of validation of these interventions for upper limb (UL) motor rehabilitation poststroke.

OBJECTIVES

The study aims were to compile all available studies that assess an UL intervention based on an electroencephalography (EEG) BCI system in stroke; to analyze the methodological quality of the studies retrieved; and to determine the effects of these interventions on the improvement of motor abilities. TYPE: This was a systematic review.

LITERATURE SURVEY

Searches were conducted in PubMed, PEDro, Embase, Cumulative Index to Nursing and Allied Health, Web of Science, and Cochrane Central Register of Controlled Trial from inception to September 30, 2015.

METHODOLOGY

This systematic review compiles all available studies that assess UL intervention based on an EEG-BCI system in patients with stroke, analyzing their methodological quality using the Critical Review Form for Quantitative Studies, and determining the grade of recommendation of these interventions for improving motor abilities as established by the Oxford Centre for Evidence-based Medicine. The articles were selected according to the following criteria: studies evaluating an EEG-based BCI intervention; studies including patients with a stroke and hemiplegia, regardless of lesion origin or temporal evolution; interventions using an EEG-based BCI to restore functional abilities of the affected UL, regardless of the interface used or its combination with other therapies; and studies using validated tools to evaluate motor function.

SYNTHESIS

After the literature search, 13 articles were included in this review: 4 studies were randomized controlled trials; 1 study was a controlled study; 4 studies were case series studies; and 4 studies were case reports. The methodological quality of the included papers ranged from 6 to 15, and the level of evidence varied from 1b to 5. The articles included in this review involved a total of 141 stroke patients.

CONCLUSIONS

This systematic review suggests that BCI interventions may be a promising rehabilitation approach in subjects with stroke.

LEVEL OF EVIDENCE

II.

Motor compensation and its effects on neural reorganization after stroke

Stroke instigates a dynamic process of repair and remodelling of remaining neural circuits, and this process is shaped by behavioural experiences. The onset of motor disability simultaneously creates a powerful incentive to develop new, compensatory ways of performing daily activities. Compensatory movement strategies that are developed in response to motor impairments can be a dominant force in shaping post-stroke neural remodelling responses and can have mixed effects on functional outcome. The possibility of selectively harnessing the effects of compensatory behaviour on neural reorganization is still an insufficiently explored route for optimizing functional outcome after stroke.

Increased functional connectivity one week after motor learning and tDCS in stroke patients

Recent studies using resting-state functional magnetic resonance imaging (rs-fMRI) demonstrated that changes in functional connectivity (FC) after stroke correlate with recovery. The aim of this study was to explore whether combining motor learning to dual transcranial direct current stimulation (dual-tDCS, applied over both primary motor cortices (M1)) modulated FC in stroke patients. Twenty-two chronic hemiparetic stroke patients participated in a baseline rs-fMRI session. One week later, dual-tDCS/sham was applied during motor skill learning (intervention session); one week later, the retention session started with the acquisition of a run of rs-fMRI imaging. The intervention+retention sessions were performed once with dual-tDCS and once with sham in a randomized, cross-over, placebo-controlled, double-blind design. A whole-brain independent component analysis based analysis of variance (ANOVA) demonstrated no changes between baseline and sham sessions in the somatomotor network, whereas a FC increase was observed one week after dual-tDCS compared to baseline (qFDR <0.05, t₆₃=4.15). A seed-based analysis confirmed specific stimulation-driven changes within a network of motor and premotor regions in both hemispheres. At baseline and one week after sham, the strongest FC was observed between the M1 and dorsal premotor cortex (PMd) of the undamaged hemisphere. In contrast, one week after dual-tDCS, the strongest FC was found between the M1 and PMd of the damaged hemisphere. Thus, a single session of dual-tDCS combined with motor skill learning increases FC in the somatomotor network of chronic stroke patients for one week.

Rewiring neuronal microcircuits of the brain via spine head protrusions--a role for synaptopodin and intracellular calcium stores

Neurological diseases associated with neuronal death are also accompanied by axonal denervation of connected brain regions. In these areas, denervation leads to a decrease in afferent drive, which may in turn trigger active central nervous system (CNS) circuitry rearrangement. This rewiring process is important therapeutically, since it can partially recover functions and can be further enhanced using modern rehabilitation strategies. Nevertheless, the cellular mechanisms of brain rewiring are not fully understood. We recently reported a mechanism by which neurons remodel their local connectivity under conditions of network-perturbance: hippocampal pyramidal cells can extend spine head protrusions (SHPs), which reach out toward neighboring terminals and form new synapses. Since this form of activity-dependent rewiring is observed only on some spines, we investigated the required conditions. We speculated, that the actin-associated protein synaptopodin, which is involved in several synaptic plasticity mechanisms, could play a role in the formation and/or stabilization of SHPs. Using hippocampal slice cultures, we found that ~70 % of spines with protrusions in CA1 pyramidal neurons contained synaptopodin. Analysis of synaptopodin-deficient neurons revealed that synaptopodin is required for the stability but not the formation of SHPs. The effects of synaptopodin could be linked to its role in Ca²⁺ homeostasis, since spines with protrusions often contained ryanodine receptors and synaptopodin. Furthermore, disrupting Ca²⁺ signaling shortened protrusion lifetime. By transgenically reintroducing synaptopodin on a synaptopodin-deficient background, SHP stability could be rescued. Overall, we show that synaptopodin increases the stability of SHPs, and could potentially modulate the rewiring of microcircuitries by making synaptic reorganization more efficient.

Plasticity and Reorganization in the Rehabilitation of Stroke

Abstract. This paper outlines some actual developments in the behavioral treatment and rehabilitation of stroke and other brain injuries in post-acute and chronic conditions of brain lesion. It points to a number of processes that demonstrate the enormous plasticity and reorganization capacity of the human brain following brain lesion. It also highlights a series of behavioral and neuroscientific studies that indicate that successful behavioral rehabilitation is paralleled by plastic changes of brain structures and by cortical reorganization and that the amount of such plastic changes is obviously significantly determining the overall outcome of rehabilitation.

Combinatorial Motor Training Results in Functional Reorganization of Remaining Motor Cortex after Controlled Cortical Impact in Rats

Cortical reorganization subsequent to post-stroke motor rehabilitative training (RT) has been extensively examined in animal models and humans. However, similar studies focused on the effects of motor training after traumatic brain injury (TBI) are lacking. We previously reported that after a moderate/severe TBI in adult male rats, functional improvements in forelimb use were accomplished only with a combination of skilled forelimb reach training and aerobic exercise, with or without nonimpaired forelimb constraint. Thus, the current study was designed to examine the relationship between functional motor cortical map reorganization after experimental TBI and the behavioral improvements resulting from this combinatorial rehabilitative regime. Adult male rats were trained to proficiency on a skilled reaching task, received a unilateral controlled cortical impact (CCI) over the forelimb area of the caudal motor cortex (CMC). Three days post-CCI, animals began RT (n = 13) or no rehabilitative training (NoRT) control procedures (n = 13). The RT group participated in daily skilled reach training, voluntary aerobic exercise, and nonimpaired forelimb constraint. This RT regimen significantly improved impaired forelimb reaching success and normalized reaching strategies, consistent with previous findings. RT also enlarged the area of motor cortical wrist representation, derived by intracortical microstimulation, compared to NoRT. These findings indicate that sufficient RT can greatly improve motor function and improve the functional integrity of remaining motor cortex after a moderate/severe CCI. When compared with findings from stroke models, these findings also suggest that more intense RT may be needed to improve motor function and remodel the injured cortex after TBI.

Motor System Reorganization After Stroke: Stimulating and Training Toward Perfection

Stroke instigates regenerative responses that reorganize connectivity patterns among surviving neurons. The new connectivity patterns can be suboptimal for behavioral function. This review summarizes current knowledge on post-stroke motor system reorganization and emerging strategies for shaping it with manipulations of behavior and cortical activity to improve functional outcome.

Experience with the "good" limb induces aberrant synaptic plasticity in the perilesion cortex after stroke

Following unilateral stroke, the contralateral (paretic) body side is often severely impaired, and individuals naturally learn to rely more on the nonparetic body side, which involves learning new skills with it. Such compensatory hyper-reliance on the "good" body side, however, can limit functional improvements of the paretic side. In rats, motor skill training with the nonparetic forelimb (NPT) following a unilateral infarct lessens the efficacy of rehabilitative training, and reduces neuronal activation in perilesion motor cortex. However, the underlying mechanisms remain unclear. In the present study, we investigated how forelimb movement representations and synaptic restructuring in perilesion motor cortex respond to NPT and their relationship with behavioral outcomes. Forelimb representations were diminished as a result of NPT, as revealed with intracortical microstimulation mapping. Using transmission electron microscopy and stereological analyses, we found that densities of axodendritic synapses, especially axo-spinous synapses, as well as multiple synaptic boutons were increased in the perilesion cortex by NPT. The synaptic density was negatively correlated with the functional outcome of the paretic limb, as revealed in reaching performance. Furthermore, in animals with NPT, there was dissociation between astrocytic morphological features and axo-spinous synaptic density in perilesion motor cortex, compared with controls. These findings demonstrate that skill learning with the nonparetic limb following unilateral brain damage results in aberrant synaptogenesis, potentially of transcallosal projections, and this seems to hamper the functionality of the perilesion motor cortex and the paretic forelimb.

Proper housing conditions in experimental stroke studies-special emphasis on environmental enrichment

Environmental enrichment provides laboratory animals with novelty and extra space, allowing different forms of multisensory stimulation ranging from social grouping to enhanced motor activity. At the extreme end of the spectrum, one can have a super-enriched environment. Environmental enrichment is believed to result in improved cognitive and sensorimotor functions both in naïve rodents and in animals with brain lesions such as those occurring after a stroke. Robust behavioral effects in animals which have suffered a stroke are probably related not only to neuronal plasticity in the perilesional cortex but also in remote brain areas. There is emerging evidence to suggest that testing restorative therapies in an enriched environment can maximize treatment effects, e.g., the perilesional milieu seems to be more receptive to concomitant pharmacotherapy and/or cell therapy. This review provides an updated overview on the effect of an enriched environment in stroke animals from the practical points to be considered when planning experiments to the mechanisms explaining why combined therapies can contribute to behavioral improvement in a synergistic manner.

Interaction between Vestibular Compensation Mechanisms and Vestibular Rehabilitation Therapy: 10 Recommendations for Optimal Functional Recovery

This review questions the relationships between the plastic events responsible for the recovery of vestibular function after a unilateral vestibular loss (vestibular compensation), which has been well described in animal models in the last decades, and the vestibular rehabilitation (VR) therapy elaborated on a more empirical basis for vestibular loss patients. The main objective is not to propose a catalog of results but to provide clinicians with an understandable view on when and how to perform VR therapy, and why VR may benefit from basic knowledge and may influence the recovery process. With this perspective, 10 major recommendations are proposed as ways to identify an optimal functional recovery. Among them are the crucial role of active and early VR therapy, coincidental with a post-lesion sensitive period for neuronal network remodeling, the instructive role that VR therapy may play in this functional reorganization, the need for progression in the VR therapy protocol, which is based mainly on adaptation processes, the necessity to take into account the sensorimotor, cognitive, and emotional profile of the patient to propose individual or "à la carte" VR therapies, and the importance of motivational and ecologic contexts. More than 10 general principles are very likely, but these principles seem crucial for the fast recovery of vestibular loss patients to ensure good quality of life.