Magnetoencephalography in stroke: a 1-year follow-up study

Pathological changes of brain oscillations following ischemic stroke

Brain oscillations recorded in the extracellular space are among the most important aspects of neurophysiology data reflecting the activity and function of neurons in a population or a network. The signal strength and patterns of brain oscillations can be powerful biomarkers used for disease detection and prediction of the recovery of function. Electrophysiological signals can also serve as an index for many cutting-edge technologies aiming to interface between the nervous system and neuroprosthetic devices and to monitor the efficacy of boosting neural activity. In this review, we provided an overview of the basic knowledge regarding local field potential, electro- or magneto- encephalography signals, and their biological relevance, followed by a summary of the findings reported in various clinical and experimental stroke studies. We reviewed evidence of stroke-induced changes in hippocampal oscillations and disruption of communication between brain networks as potential mechanisms underlying post-stroke cognitive dysfunction. We also discussed the promise of brain stimulation in promoting post stroke functional recovery via restoring neural activity and enhancing brain plasticity.

Effects of Training for Finger Perception on Functional Recovery of Hemiplegic Upper Limbs in Acute Stroke Patients

Background

Stroke causes severe disability, including motor and sensory impairments. We hypothesized that upper limb functional recovery after stroke may be augmented by combining treatments for motor and sensory functions. In order to examine this hypothesis, we conducted a controlled trial on rehabilitation for sensory function to the plegic hand.

Methods

The sensory training program consisted of several types of discrimination tasks performed under blind conditions. The sensory training program was performed for 20 min per day, 5 days a week. An experimental group of 31 patients followed this sensory program, while a control group of 25 patients underwent standard rehabilitation. The efficacy of the intervention was evaluated by the tactile-pressure threshold, handgrip strength, and the completion time of manipulating objects. A two-way repeated measures analysis of variance was used to assess interactions between group and time. Moreover, to provide a meaningful analysis for comparisons, effect sizes were calculated using Cohen's d.

Results

The mean change in the tactile pressure threshold was significantly larger in the experimental group than in the control group (p < 0.05, d = 0.59). Moreover, the completion times to manipulate a middle-sized ball (d = 0.53) and small ball (d = 0.80) and a small metal disc (d = 0.81) in the experimental group were significantly different from those in the control group (p < 0.05).

Conclusion

The present results suggest that the sensory training program to enhance finger discrimination ability contributes to improvements in not only sensory function but also manual function in stroke patients. The trial is registered with the UMIN Clinical Trials Registry (UMIN000032025).

IFCN-endorsed practical guidelines for clinical magnetoencephalography (MEG)

Magnetoencephalography (MEG) records weak magnetic fields outside the human head and thereby provides millisecond-accurate information about neuronal currents supporting human brain function. MEG and electroencephalography (EEG) are closely related complementary methods and should be interpreted together whenever possible. This manuscript covers the basic physical and physiological principles of MEG and discusses the main aspects of state-of-the-art MEG data analysis. We provide guidelines for best practices of patient preparation, stimulus presentation, MEG data collection and analysis, as well as for MEG interpretation in routine clinical examinations. In 2017, about 200 whole-scalp MEG devices were in operation worldwide, many of them located in clinical environments. Yet, the established clinical indications for MEG examinations remain few, mainly restricted to the diagnostics of epilepsy and to preoperative functional evaluation of neurosurgical patients. We are confident that the extensive ongoing basic MEG research indicates potential for the evaluation of neurological and psychiatric syndromes, developmental disorders, and the integrity of cortical brain networks after stroke. Basic and clinical research is, thus, paving way for new clinical applications to be identified by an increasing number of practitioners of MEG.

Mapping the topological organisation of beta oscillations in motor cortex using MEG

The spatial topology of the human motor cortex has been well studied, particularly using functional Magnetic Resonance Imaging (fMRI) which allows spatial separation of haemodynamic responses arising from stimulation of different body parts, individual digits and even spatially separate areas of the same digit. However, the spatial organisation of electrophysiological responses, particularly neural oscillations (rhythmic changes in electrical potential across cellular assemblies) has been less well studied. Mapping the spatial signature of neural oscillations is possible using magnetoencephalography (MEG), however spatial differentiation of responses induced by movement of separate digits is a challenge, because the brain regions involved are separated by only a few millimetres. In this paper we first show, in simulation, how to optimise experimental design and beamformer spatial filtering techniques to increase the spatial specificity of MEG derived functional images. Combining this result with experimental data, we then capture the organisation of the post-movement beta band (13–30 Hz) oscillatory response to movement of digits 2 and 5 of the dominant hand, in individual subjects. By comparing these MEG results to ultra-high field (7T) fMRI, we also show significant spatial agreement between beta modulation and the blood oxygenation level dependent (BOLD) response. Our results show that, when using an optimised inverse solution and controlling subject movement (using custom fitted foam padding) the spatial resolution of MEG can be of order 3–5 mm. The method described offers exciting potential to understand better the cortical organisation of oscillations, and to probe such organisation in patient populations where those oscillations are known to be abnormal.

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Aim is to map the topological organisation of neural oscillations in motor cortex.

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MEG spatial resolution optimised by temporal separation of sources.

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Subject motion controlled using foam headcasts.

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Cortical representation of Digit 2 and Digit 5 separated spatially.

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Post movement beta rebound maps motortopically in agreement with BOLD responses.

The sensory side of post-stroke motor rehabilitation

Contemporary strategies to promote motor recovery following stroke focus on repetitive voluntary movements. Although successful movement relies on efficient sensorimotor integration, functional outcomes often bias motor therapy toward motor-related impairments such as weakness, spasticity and synergies; sensory therapy and reintegration is implied, but seldom targeted. However, the planning and execution of voluntary movement requires that the brain extracts sensory information regarding body position and predicts future positions, by integrating a variety of sensory inputs with ongoing and planned motor activity. Neurological patients who have lost one or more of their senses may show profoundly affected motor functions, even if muscle strength remains unaffected. Following stroke, motor recovery can be dictated by the degree of sensory disruption. Consequently, a thorough account of sensory function might be both prognostic and prescriptive in neurorehabilitation. This review outlines the key sensory components of human voluntary movement, describes how sensory disruption can influence prognosis and expected outcomes in stroke patients, reports on current sensory-based approaches in post-stroke motor rehabilitation, and makes recommendations for optimizing rehabilitation programs based on sensory stimulation.

Quantitative EEG Evaluation During Robot-Assisted Foot Movement

Passiveand imagined limbmovements induce changes in cerebral oscillatory activity. Central modulatory effects play a role in plastic changes, and are of uttermost importance in rehabilitation. This has extensively been studied for upper limb, but less is known for lower limb. The aim of this study is to investigate the topographical distribution of event-related desynchronization/synchronization(ERD/ERS) and task-relatedcoherence during a robot-assisted and a motor imagery task of lower limb in healthy subjects to inform rehabilitation paradigms. 32-channels electroencephalogram (EEG) was recorded in twenty-one healthy right footed and handed subjects during a robot-assisted single-joint cyclic right ankle movement performed by the BTS ANYMOV robotic hospital bed. Data were acquired with a block protocol for passive and imagined movement at a frequency of 0.2 Hz. ERD/ERS and task related coherence were calculated in alpha1 (8-10 Hz), alpha2 (10.5-12.5 Hz) and beta (13-30 Hz) frequency ranges. During passive movement, alpha2 rhythm desynchronized overC3 and ipsilateral frontal areas (F4, FC2, FC6); betaERD was detected over the bilateral motor areas (Cz, C3, C4). During motor imagery, a significant desynchronization was evident for alpha1 over contralateral sensorimotor cortex (C3), for alpha2 over bilateral motor areas (C3 and C4), and for beta over central scalp areas. Task-related coherence decreased during passive movement in alpha2 band between contralateral central area (C3, CP5, CP1, P3) and ipsilateral frontal area (F8, FC6, T8); beta band coherence decreased between C3-C4 electrodes, and increased between C3-Cz. These data contribute to the understanding of oscillatory activity and functional neuronal interactions during lower limb robot-assisted motor performance. The final output of this line of research is to inform the design and development of neurorehabilitation protocols.

Wireless simultaneous stimulation-and-recording device to train cortical circuits in somatosensory cortex

We describe for the first time the design, implementation, and testing of a telemetry controlled simultaneous stimulation and recording device (SRD) to deliver chronic intercortical microstimulation (ICMS) to physiologically identified sites in rat somatosensory cortex (SI) and test hypotheses that chronic ICMS strengthens interhemispheric pathways and leads to functional reorganization in the enhanced cortex. The SRD is a custom embedded device that uses the Cypress Semiconductor's programmable system on a chip (PSoC) that is remotely controlled via Bluetooth. The SRC can record single or multiunit responses from any two of 12 available inputs at 1-15 ksps per channel and simultaneously deliver stimulus pulses (0-255 μA; 10 V compliance) to two user selectable electrodes using monophasic, biphasic, or pseudophasic stimulation waveforms (duration: 0-5 ms, inter-phase interval: 0-5 ms, frequency: 0.1-5 s, delay: 0-10 ms). The SRD was bench tested and validated in vivo in a rat animal model.

Neuromagnetic beta and gamma oscillations in the somatosensory cortex after music training in healthy older adults and a chronic stroke patient

OBJECTIVE

Extensive rehabilitation training can lead to functional improvement even years after a stroke. Although neuronal plasticity is considered as a main origin of such ameliorations, specific subtending mechanisms need further investigation. Our aim was to obtain objective neuromagnetic measures sensitive to brain reorganizations induced by a music-supported training.

METHODS

We applied 20-Hz vibrotactile stimuli to the index finger and the ring finger, recorded somatosensory steady-state responses with magnetoencephalography, and analyzed the cortical sources displaying oscillations synchronized with the external stimuli in two groups of healthy older adults before and after musical training or without training. In addition, we applied the same analysis for an anecdotic report of a single chronic stroke patient with hemiparetic arm and hand problems, who received music-supported therapy (MST).

RESULTS

Healthy older adults showed significant finger separation within the primary somatotopic map. Beta dipole sources were more anterior located compared to gamma sources. An anterior shift of sources and increases in synchrony between the stimuli and beta and gamma oscillations were observed selectively after music training. In the stroke patient a normalization of somatotopic organization was observed after MST, with digit separation recovered after training and stimulus induced gamma synchrony increased.

CONCLUSIONS

The proposed stimulation paradigm captures the integrity of primary somatosensory hand representation. Source position and synchronization between the stimuli and gamma activity are indices, sensitive to music-supported training. Responsiveness was also observed in a chronic stroke patient, encouraging for the music-supported therapy. Notably, changes in somatosensory responses were observed, even though the therapy did not involve specific sensory discrimination training.

SIGNIFICANCE

The proposed protocol can be used for monitoring changes in neuronal organization during training and will improve the understanding of the brain mechanisms underlying rehabilitation.

Somatotopic finger mapping using MEG: toward an optimal stimulation paradigm

OBJECTIVE

In non-invasive somatotopic mapping based on neuromagnetic source analysis, the recording time can be shortened and accuracy improved by applying simultaneously vibrotactile stimuli at different frequencies to multiple body sites and recording multiple steady-state responses. This study compared the reliability of sensory evoked responses, source localization performance, and reproducibility of digit maps for three different stimulation paradigms.

METHODS

Vibrotactile stimuli were applied to the fingertip and neuromagnetic steady-state responses were recorded. Index and middle fingers were stimulated either sequentially in separate blocks, simultaneously at different frequencies, or in alternating temporal order within a block.

RESULTS

Response amplitudes were largest and source localization was most accurate between 21 and 23 Hz. Separation of adjacent digits was significant for all paradigms in all participants. Suppressive interactions occurred between simultaneously applied stimuli. However, when frequently alternating between stimulus sites, the higher stimulus novelty resulted in increased amplitudes and superior localization performance.

CONCLUSIONS

When receptive fields are strongly overlapping, the alternating stimulation is preferable over recording multiple steady state responses.

SIGNIFICANCE

The new paradigm improved the measurement of the distance of somatotopic finger representation in human primary somatosensory cortex, which is an important metric for neuroplastic reorganization after learning and rehabilitation training.

Modulation of event-related desynchronization in robot-assisted hand performance: brain oscillatory changes in active, passive and imagined movements

Background

Robot-assisted therapy in patients with neurological disease is an attempt to improve function in a moderate to severe hemiparetic arm. A better understanding of cortical modifications after robot-assisted training could aid in refining rehabilitation therapy protocols for stroke patients. Modifications of cortical activity in healthy subjects were evaluated during voluntary active movement, passive robot-assisted motor movement, and motor imagery tasks performed under unimanual and bimanual protocols.

Methods

Twenty-one channel electroencephalography (EEG) was recorded with a video EEG system in 8 subjects. The subjects performed robot-assisted tasks using the Bi-Manu Track robot-assisted arm trainer. The motor paradigm was executed during one-day experimental sessions under eleven unimanual and bimanual protocols of active, passive and imaged movements. The event-related-synchronization/desynchronization (ERS/ERD) approach to the EEG data was applied to investigate where movement-related decreases in alpha and beta power were localized.

Results

Voluntary active unilateral hand movement was observed to significantly activate the contralateral side; however, bilateral activation was noted in all subjects on both the unilateral and bilateral active tasks, as well as desynchronization of alpha and beta brain oscillations during the passive robot-assisted motor tasks. During active-passive movement when the right hand drove the left one, there was predominant activation in the contralateral side. Conversely, when the left hand drove the right one, activation was bilateral, especially in the alpha range. Finally, significant contralateral EEG desynchronization was observed during the unilateral task and bilateral ERD during the bimanual task.

Conclusions

This study suggests new perspectives for the assessment of patients with neurological disease. The findings may be relevant for defining a baseline for future studies investigating the neural correlates of behavioral changes after robot-assisted training in stroke patients.

Precise mapping of the somatotopic hand area using neuromagnetic steady-state responses

The body surface is represented in somatotopically organized maps in the primary somatosensory cortex. Estimating the size of the hand area with neuromagnetic source analysis has been used as a metric for monitoring neuroplastic changes related to training, learning, and brain injury. Commonly, results were significant as group statistics only because source localization accuracy was limited by factors such as residual noise and head motion. In this study we aimed to develop a robust method for obtaining the somatotopic map of the hand area in individuals using the bootstrap framework. Furthermore, a comprehensive analysis of the different factors affecting the accuracy of the obtained maps was provided. We applied vibrotactile touch stimuli to the tip of the index finger or the ring finger of the right hand and recorded the 22-Hz steady-state response using MEG. Single equivalent dipole sources were localized in contralateral left somatosensory cortex. Bootstrap resampling revealed the confidence intervals for the source coordinates using a single block of 5 min MEG recording. Residual noise in the averaged evoked response predominantly affected source localization, and the related confidence interval was reciprocally related to the signal-to-noise ratio. Apparently, head movements within a block of MEG recording contributed less to the variability of source localization in cooperative volunteers. The results of the current study indicate that significant separations of index finger and ring finger representations along the somatotopic map can be revealed in an individual using bootstrap framework.

Activation in parietal operculum parallels motor recovery in stroke

Motor recovery after stroke requires continuous interaction of motor and somatosensory systems. Integration of somatosensory feedback with motor programs is needed for the automatic adjustment of the speed, range, and strength of the movement. We recorded somatosensory evoked fields (SEFs) to tactile finger stimulation with whole-scalp magnetoencephalography in 23 acute stroke patients at 1 week, 1 month, and 3 months after stroke to investigate how deficits in the somatosensory cortical network affect motor recovery. SEFs were generated in the contralateral primary somatosensory cortex (SI) and in the bilateral parietal opercula (PO) in controls and patients. In the patients, SI amplitude or latency did not correlate with any of the functional outcome measures used. In contrast, the contralateral PO (cPO) amplitude to the affected hand stimuli correlated significantly with hand function in the acute phase and during recovery; the weaker the PO activation, the clumsier the hand was. At 1 and 3 months, enhancement of the cPO activation paralleled the improvement of the hand function. Whole-scalp magnetoencephalography measurements revealed that dysfunction of somatosensory cortical areas distant from the ischemic lesion may affect the motor recovery. Activation strength of the PO paralleled motor recovery after stroke, suggesting that the PO area is an important hub in mediating modulatory afferent input to motor cortex.

Review: Functional Neuroimaging Studies of Early Upper Limb Recovery After Stroke: A Systematic Review of the Literature

Background. Understanding mechanisms of recovery may result in new treatment strategies to improve motor outcome after stroke. Imaging techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) allow changes in brain activity after stroke recovery to be identified. Objective. To systematically review serial imaging studies on recovery within 6 months poststroke, assess their methodological quality, and identify trends in the association between task-related brain activation patterns and functional upper limb recovery. Methods. A literature search was performed using Medline, PICARTA, and EMBASE databases. Studies were appraised using binary weighted methodological criteria for internal, statistical, and external validity. Results. Twenty-two of the 869 identified studies met the inclusion criteria. Studies showed methodological weaknesses with respect to controlling for task performance, selecting appropriate outcome measures, and adequate presentation and execution of statistical analysis. After stroke, motor task performance shows unilateral overactivation of motor and nonmotor areas, a posterior shift in activity in the primary motor cortex, and bilateral recruitment of associated motor and nonmotor areas. Concomitant with neurological recovery, overactivation appears to diminish longitudinally, but not in all patients. Conclusion . Despite methodological shortcomings and heterogeneity, trends can be discerned. However, statistically sound associations with recovery are not consistent. The challenges in future research will be, controlling for confounding factors, finding outcomes that specifically measure dexterity of the paretic limb, to control for the extent of white matter damage and changes in perfusion in order to establish the longitudinal construct validity of fMRI and PET with regard to upper limb recovery after stroke.

Interhemispheric asymmetry of primary hand representation and recovery after stroke: A MEG study

In patients affected by monohemispheric stroke in the middle cerebral artery territory, who do not regain a normal neurological function, a positive contribution to the clinical recovery seems to be made by the involvement of primary hand representation areas in the affected hemisphere (AH), excessively asymmetric to its homologous in the unaffected hemisphere (UH). We investigated primary sensory hand areas in 41 chronic patients who had improved their clinical status without reaching complete recovery. The location and strength of the first cerebral sources activated by a contralateral galvanic median nerve stimulation (M20 and M30) were evaluated in both hemispheres, together with their interhemispheric differences. The source displacement in the AH with respect to the UH was positively correlated with clinical recovery (Spearman's rho=0.584, p=0.003). The excessive interhemispheric asymmetry - as defined on the basis of reference ranges in the healthy population - could be interpreted as the involvement of neuronal pools in the AH outside the hand 'omega zone' of the Rolandic sulcus, revealing the presence of plasticity phenomena. The present data provide support to a positive role of cerebral plasticity phenomena, partially contributing to post-stroke recovery in patients unable to achieve normal neurological function.

Recovery in a patient with locked-in syndrome

BACKGROUND AND PURPOSE

Sildenafil citrate has been shown to enhance neurogenesis, angiogenesis, synaptogenesis, and neurological outcome by augmentation of cyclic guanosine monophosphate (cGMP) levels in animal models of ischemic stroke. Whether sildenafil citrate may be helpful for recovery in human stroke is unknown at this time.

METHODS

A 41-year-old woman with locked-in syndrome due to pontine infarction began receiving 150 mg of oral sildenafil citrate daily on a compassionate use basis in August 2003 and continues treatment at this time. Magneto-encephalography (MEG) was performed at 12 and 17 months after stroke.

RESULTS

No serious adverse events have occurred. Significant milestone recoveries including standing, use of both arms, talking, and full return of swallowing have occurred, particularly after nine months of treatment. The MEG showed a significantly increased amplitude in the somatosensory cortex.

CONCLUSION

Daily use of high dose sildenafil citrate appears to be safe in this patient with stroke resulting in locked-in syndrome. Further studies will be required to establish safety and efficacy.

Brain plasticity in recovery from stroke: an MEG assessment

The aim of this paper was to deepen understanding about the role played by brain plasticity in obtaining clinical recovery. Eighteen patients, who had recovered partially or totally from dysfunctions due to a monohemispheric infarction within the middle cerebral artery territory, underwent magnetoencephalographic (MEG) recordings of rolandic areas cerebral activity both in rest state (spectral power properties) and in response to the electrical stimulation of the contralateral median nerve (M20 and M30 cortical sources). MEG evaluation was performed in acute (T0: mean 5 days from ischemic attach) and post-acute phase (T1: median 6 months). At T1, all the inter-hemispheric asymmetries were reduced for both spontaneous and evoked activity parameters with respect to T0. In post-acute phase, lower cortical excitability, higher delta and theta power and lower spectral entropy were associated to a worse clinical state. An unusual recruitment-as revealed by an excessive inter-hemispheric asymmetry of M20 cortical source position-correlated with higher level of clinical amelioration in the patients who showed a partial recovery. In addition to confirmative evidence that "normalization" of neural activity in both the affected and unaffected hemispheres subtends best clinical recovery, present data provide support to the positive role of cerebral plasticity phenomena--i.e. unusual neural recruitments--to regain lost functions in those patients unable to achieve total recovery.

Brain sensorimotor hand area functionality in acute stroke: insights from magnetoencephalography

An understanding of the functional readjustments that the brain undergoes during the early days after a stroke would give us a major insight into how and how much neurons are capable to react to an insult. Thirty-two patients affected by an acute monohemispheric ischemic stroke were enrolled in the study. Magnetoencephalography was used to record the somatosensory-evoked fields (SEF) generated in response to median nerve stimulation. Latency, strength, and position of the related early cortical components (M20 and M30) were studied both separately within each hemisphere, and in terms of interhemispheric differences. Interhemispheric cross-correlations among SEF waveshapes in the two hemispheres were also investigated. Overall, except for some source displacement possibly induced by the perilesional edema, results did not demonstrate any unusual neural recruitment. The severity of the clinical picture was found related to the sources' strengths (both as absolute values and as interhemispheric differences), to excessive interhemispheric differences in SEF waveshapes and in the M30 latencies. Signs of an enhanced excitability were present in the affected hemisphere (AH) following a cortical lesion, usually in combination with preserved hand functionality. An enhanced excitability of the unaffected hemisphere (UH) was paired with larger lesions with cortical involvement; signs compatible with an abnormal transcallosal transmission and intracortical function of inhibitory GABAergic interneurons in the AH were found subtending UH enhancement. Spared responsiveness from Brodmann's area (BA) 2 and posterior parietal areas despite an altered response from BA 3b was found in six patients, combined to high hand functionality. Present results in acute phase increase the knowledge of the mechanisms governing brain adaptation/reaction capabilities, for future efforts to establish therapeutic and rehabilitative procedures.

Neural plasticity and recovery of function

Recovery of the function after stroke is a consequence of many factors including resolution of oedema and survival of the ischaemic penumbra. In addition there is a growing interest in the role of central nervous system (CNS) reorganization. Much of the evidence supporting this comes from animal models of focal brain injury, but non-invasive techniques such as functional magnetic resonance imaging, transcranial magnetic stimulation, electroencephalography and magnetoencephalography now allow the study of the working human brain. Using these techniques it is apparent that the motor system of the brain adapts to damage in a way that attempts to preserve motor function. This has been demonstrated after stroke, as part of the ageing process, and even after disruption of normal motor cortex with repetitive transcranial magnetic stimulation. The result of this reorganization is a new functional architecture, one which will vary from patient to patient depending on the anatomy of the damage, the biological age of the patient and lastly the chronicity of the lesion. The success of any given therapeutic intervention will depend on how well it interacts with this new functional architecture. Thus it is crucial that the study of novel therapeutic strategies for treating motor impairment after stroke take account of this. This review maps out the attempts to describe functionally relevant adaptive changes in the human brain following focal damage. A greater understanding of how these changes are related to the recovery process will allow not only the development of novel therapeutic techniques that are based on neurobiological principles and designed to minimize impairment in patients suffering from stroke, but also to target these therapies at the appropriate patients.

Functional reorganization of the cerebral motor system after stroke

PURPOSE OF REVIEW

Recovery of function after stroke is now widely considered to be a consequence of central nervous system reorganization. Non-invasive techniques such as functional magnetic resonance imaging, transcranial magnetic stimulation, electroencephalography and magnetoencephalography now allow the study of the working human brain. Studies in stroke patients can now address how cerebral networks in the human brain respond to focal injury and whether these changes are related to functional recovery. This understanding may in turn lead to the development of techniques that will drive cerebral reorganization in a way that promotes functional improvement.

RECENT FINDINGS

The relationship between cerebral reorganization and functional recovery has been examined in both cross-sectional and longitudinal studies. It appears that the motor system reacts to damage in a way that attempts to generate motor output through surviving brain regions and networks. There are changes in cortical excitability after stroke that may provide the substrate whereby the effects of motor practice or experience can be more effective in driving long lasting changes in motor networks. This will be particularly important in intact portions of neural networks subserving motor skills learning.

SUMMARY

Functionally relevant adaptive changes occur in the human brain following focal damage. A greater understanding of how these changes are related to the recovery process will allow the development of novel therapeutic techniques that are based on neurobiological principles and which are designed to minimize impairment in appropriately targeted patients suffering from stroke.