[Dissertation] BRAIN CONNECTIVITY CHANGES AFTER STROKE AND REHABILITATION – Full Text PDF

ABSTRACT

Several cortical and subcortical areas of brain interact coherently during various tasks such as motor-imagery (MI) and motor-execution (ME) and even during resting-state (RS). How these interactions are affected following stroke and how the functional organization is regained from rehabilitative treatments as people begin to recover have not been systematically studied. Role of primary motor area during MI task and how this differs during ME task are still questions of interest.

To answer such questions, we recorded functional magnetic resonance imaging (fMRI) signals from 30 participants: 17 young healthy controls and 13 aged stroke survivors following stroke and following rehabilitation – either mental practice (MP) or combined session of mental practice and physical therapy (MP + PT). All the participants performed RS task whereas stroke survivors performed MI and ME tasks as well. We investigated the activity of motor network consisting of the left primary motor area (LM1), the right primary motor area (RM1), the left pre-motor cortex (LPMC), the right pre-motor cortex (RPMC) and the midline supplementary motor area (SMA).

In this dissertation, first, we report that during RS the causal information flow (i) between the regions was reduced significantly following stroke (ii) did not increase significantly after MP alone and (iii) among the regions after MP+PT increased significantly towards the causal flow values for young able-bodied people. Second, we found that there was suppressive influence of SMA on M1 during MI task where as the influence was unrestricted during ME task. We reported that following intervention the connection between PMC and M1 was stronger during MI task whereas along with connection from PMC to M1, SMA to M1 also dominated during ME task. Behavioral results showed significant improvement in sensation and motor scores and significant correlation between differences in Fugl-Meyer Assessment (FMA) scores and differences in causal flow values as well differences in endogenous connectivity measures before and after intervention.

We conclude that the spectra of causal information flow can be used as a reliable biomarker for evaluating rehabilitation in stroke survivors. These studies deepen our understanding of motor network activity during the recovery of motor behaviors in stroke. Understanding the stroke specific effective connectivity may be clinically beneficial in identifying effective treatments to maximize functional recovery in stroke survivors.

Full Text PDF

[Dissertation] BRAIN CONNECTIVITY CHANGES AFTER STROKE AND REHABILITATION – Full Text PDF

ABSTRACT

Several cortical and subcortical areas of brain interact coherently during various tasks such as motor-imagery (MI) and motor-execution (ME) and even during resting-state (RS). How these interactions are affected following stroke and how the functional organization is regained from rehabilitative treatments as people begin to recover have not been systematically studied. Role of primary motor area during MI task and how this differs during ME task are still questions of interest.

To answer such questions, we recorded functional magnetic resonance imaging (fMRI) signals from 30 participants: 17 young healthy controls and 13 aged stroke survivors following stroke and following rehabilitation – either mental practice (MP) or combined session of mental practice and physical therapy (MP + PT). All the participants performed RS task whereas stroke survivors performed MI and ME tasks as well. We investigated the activity of motor network consisting of the left primary motor area (LM1), the right primary motor area (RM1), the left pre-motor cortex (LPMC), the right pre-motor cortex (RPMC) and the midline supplementary motor area (SMA).

In this dissertation, first, we report that during RS the causal information flow (i) between the regions was reduced significantly following stroke (ii) did not increase significantly after MP alone and (iii) among the regions after MP+PT increased significantly towards the causal flow values for young able-bodied people. Second, we found that there was suppressive influence of SMA on M1 during MI task where as the influence was unrestricted during ME task. We reported that following intervention the connection between PMC and M1 was stronger during MI task whereas along with connection from PMC to M1, SMA to M1 also dominated during ME task.

Behavioral results showed significant improvement in sensation and motor scores and significant correlation between differences in Fugl-Meyer Assessment (FMA) scores and differences in causal flow values as well differences in endogenous connectivity measures before and after intervention.

We conclude that the spectra of causal information flow can be used as a reliable biomarker for evaluating rehabilitation in stroke survivors. These studies deepen our understanding of motor network activity during the recovery of motor behaviors in stroke. Understanding the stroke specific effective connectivity may be clinically beneficial in identifying effective treatments to maximize functional recovery in stroke survivors.

Full Text PDF

[ARTICLE] A longitudinal study of brain activation during stroke recovery using BOLD-fMRI

Stroke recovery involves a battery of plastic changes in the brain. Blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) provides brain activation information with exquisite spatial resolution as a powerful tool for investigating changes in brain plasticity.

In this paper, we performed a longitudinal study examining plasticity of functional activation by BOLD-fMRI following stroke. Data were collected from 11 patients with corticospinal tract (CST) damage at three stages of recovery, i.e., acute stage (3mons) post stroke. The evolution of cortical activations for both affected and unaffected hand motion tasks were studied. Quantitative activation measurements including the effective size and sum of t values were calculated and the correlations with patient Fugl-Meyer index were analyzed across all stages. Stroke patients showed a shift from bilateral activation in acute and early stage to the ipsilesional activation in chronic stage when performing a movement task with the affected hand, which suggests a compensation effect from the contralesional hemisphere during the recovery process. The correlation analysis showed a significantly negative correlation with cingulate cortex activity at early stage from both quantitative activation measurements, implying the special role of cingulate cortex in stroke recovery. Further investigations are in need to improve the understanding of brain plasticity in stroke patients.

via IEEE Xplore Abstract – A longitudinal study of brain activation during stroke recovery using BOLD-fMRI.

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[ARTICLE] Brain effective connectivity during motor-imagery and execution following stroke and rehabilitation – Full Text HTML

Abstract

Brain areas within the motor system interact directly or indirectly during motor-imagery and motor-execution tasks. These interactions and their functionality can change following stroke and recovery. How brain network interactions reorganize and recover their functionality during recovery and treatment following stroke are not well understood.

To contribute to answering these questions, we recorded blood oxygenation-level dependent (BOLD) functional magnetic resonance imaging (fMRI) signals from 10 stroke survivors and evaluated dynamical causal modeling (DCM)-based effective connectivity among three motor areas: primary motor cortex (M1), pre-motor cortex (PMC) and supplementary motor area (SMA), during motor-imagery and motor-execution tasks. We compared the connectivity between affected and unaffected hemispheres before and after mental practice and combined mental practice and physical therapy as treatments. The treatment (intervention) period varied in length between 14 to 51 days but all patients received the same dose of 60 h of treatment. Using Bayesian model selection (BMS) approach in the DCM approach, we found that, after intervention, the same network dominated during motor-imagery and motor-execution tasks but modulatory parameters suggested a suppressive influence of SM A on M1 during the motor-imagery task whereas the influence of SM A on M1 was unrestricted during the motor-execution task.

We found that the intervention caused a reorganization of the network during both tasks for unaffected as well as for the affected hemisphere. Using Bayesian model averaging (BMA) approach, we found that the intervention improved the regional connectivity among the motor areas during both the tasks. The connectivity between PMC and M1 was stronger in motor-imagery tasks whereas the connectivity from PMC to M1, SM A to M1 dominated in motor-execution tasks. There was significant behavioral improvement (p = 0.001) in sensation and motor movements because of the intervention as reflected by behavioral Fugl-Meyer (FMA) measures, which were significantly correlated (p = 0.05) with a subset of connectivity.

These findings suggest that PMC and M1 play a crucial role during motor-imagery as well as during motor-execution task. In addition, M1 causes more exchange of causal information among motor areas during a motor-execution task than during a motor-imagery task due to its interaction with SM A. This study expands our understanding of motor network involved during two different tasks, which are commonly used during rehabilitation following stroke. A clear understanding of the effective connectivity networks leads to a better treatment in helping stroke survivors regain motor ability.

Abbreviations

• DCM, dynamical causal modeling
• BMS, Bayesian model selection
• BMA, Bayesian model averaging; IU, imagine unaffected
• IA, imagine affected
• PU, pinch unaffected
• PA, pinch affected
• MI, motor imagery
• ME, motor-execution.

 

Continue —> Brain effective connectivity during motor-imagery and execution following stroke and rehabilitation.

[ARTICLE] Motor Recovery and Cortical Reorganization After Mirror Therapy in Chronic Stroke Patients

…This phase II trial showed some effectiveness for mirror therapy in chronic stroke patients and is the first to associate mirror therapy with cortical reorganization. Future research has to determine the optimum practice intensity and duration for improvements to persist and generalize to other functional domains…

via Motor Recovery and Cortical Reorganization After Mirror Therapy in Chronic Stroke Patients.