66 research outputs found

    A computational model based on corticospinal functional MRI revealed asymmetrically organized motor corticospinal networks in humans

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    新規MRI技術で利き手の神経制御メカニズムを解明 --手指運動中の脳・脊髄機能結合パターンの左右差を世界で初めて計測--. 京都大学プレスリリース. 2022-08-08.Evolution of the direct, monosynaptic connection from the primary motor cortex to the spinal cord parallels acquisition of hand dexterity and lateralization of hand preference. In non-human mammals, the indirect, multi-synaptic connections between the bilateral primary motor cortices and the spinal cord also participates in controlling dexterous hand movement. However, it remains unknown how the direct and indirect corticospinal pathways work in concert to control unilateral hand movement with lateralized preference in humans. Here we demonstrated the asymmetric functional organization of the two corticospinal networks, by combining network modelling and simultaneous functional magnetic resonance imaging techniques of the brain and the spinal cord. Moreover, we also found that the degree of the involvement of the two corticospinal networks paralleled lateralization of hand preference. The present results pointed to the functionally lateralized motor nervous system that underlies the behavioral asymmetry of handedness in humans

    Motor Imagery for Neurorehabilitation: The F-Wave Study

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    The immediate enrollment in rehabilitation program and facilitation of the excitability of spinal motor neurons are very important for post-stroke patients. We previously suggested that persistence and the F/M amplitude ratio, indicator of the excitability of spinal motor neurons, were significantly increased during MI. Thus, MI has a greater effect on the excitability of spinal motor neurons. We also indicated that the imagined muscle contraction strength may not affect the excitability of spinal motor neurons. Further, kinesthetic imagery can more facilitate the excitability of spinal motor neurons. However, longer duration of MI may not affect the excitability of spinal motor neurons. Therefore, slight imagined muscle contraction strength may be sufficient to facilitate the excitability of spinal motor neurons, and duration and strategy of imagery should be considered in neurorehabilitation

    Neuroplastic Changes Following Brain Ischemia and their Contribution to Stroke Recovery: Novel Approaches in Neurorehabilitation

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    Ischemic damage to the brain triggers substantial reorganization of spared areas and pathways, which is associated with limited, spontaneous restoration of function. A better understanding of this plastic remodeling is crucial to develop more effective strategies for stroke rehabilitation. In this review article, we discuss advances in the comprehension of post-stroke network reorganization in patients and animal models. We first focus on rodent studies that have shed light on the mechanisms underlying neuronal remodeling in the perilesional area and contralesional hemisphere after motor cortex infarcts. Analysis of electrophysiological data has demonstrated brain-wide alterations in functional connectivity in both hemispheres, well beyond the infarcted area. We then illustrate the potential use of non-invasive brain stimulation (NIBS) techniques to boost recovery. We finally discuss rehabilitative protocols based on robotic devices as a tool to promote endogenous plasticity and functional restoration

    Fusion, 2009

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    https://hsrc.himmelfarb.gwu.edu/smhs_fusion/1002/thumbnail.jp

    Investigating the Cortical, Metabolic and Behavioral Effects of Transcranial Direct Current Stimulation in Preparation for Combined Rehabilitation

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    The goal of this thesis was to determine the cortical reorganization that occurs in patients with cervical spondylotic myelopathy (CSM) after surgical decompression and to implement this knowledge into a new rehabilitation strategy. Transcranial direct current stimulation (tDCS) is a non-invasive technique to modulate human behavior. Due to the novel electrode montage used, it was first pertinent that we determine how tDCS would modulate cortical, metabolic and motor behavior in healthy individuals. We observed the longitudinal functional adaptations that occur in patients with CSM using functional MRI. Enhanced excitation of supplementary motor area (SMA) was observed following surgical decompression and associated with increased function following surgery. This novel finding of enhanced excitation of motivated us to use a bihemispheric tDCS protocol, exciting bilateral motor areas to provide optimal motor enhancement. This novel tDCS electrode montage, targeting the SMA and primary motor cortex (M1) was implemented in healthy older adults to determine its effects on enhancing manual dexterity. Furthermore, to determine the frequency with which to apply tDCS, a single and tri session protocol was used. We observed a differential pattern of action with anti-phase and in-phase motor tasks during multisession tDCS. We used ultra-high field (7T) MRI to examined the metabolic changes that occur following tDCS. After the stimulation period we observed no significant metabolite modulation. A trend towards an increase in the NAA/tCr ratio, with a concomitant decrease in the absolute concentration of tCr was observed. Finally, we examined the functional connectivity before, during and after tDCS with the use of resting-state fMRI at 7T. We observed enhanced connectivity within right sensorimotor area after stimulation compared to during stimulation. This result confirmed that cortical modulations differ during versus after tDCS, signifying that optimal modulation of behaviour may be after the stimulation period. Furthermore, we observed an enhanced correlation between motor regions and the caudate, both during and after stimulation. In conclusion, we observed novel cortical adaptations in CSM patients after surgical decompression, which led us to believe that bihemispheric tDCS of M1-SMA network would result in optimal motor enhancement and warrants further investigation in CSM and other neurological disorders

    EEG Characterization of Sensorimotor Networks: Implications in Stroke

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    The purpose of this dissertation was to use electroencephalography (EEG) to characterize sensorimotor networks and examine the effects of stroke on sensorimotor networks. Sensorimotor networks play an essential role in completion of everyday tasks, and when damaged, as in stroke survivors, the successful completion of seemingly simple motor tasks becomes fantasy. When sensorimotor networks are impaired as a result of stroke, varying degrees of sensorimotor deficits emerge, most often including loss of sensation and difficulty generating upper extremity movements. Although sensory therapies, such as the application of tendon vibration, have been shown to reduce the sensorimotor deficits after stroke, the underlying sensorimotor mechanisms associated with such improvements are unknown. While sensorimotor networks have been studied extensively, unanswered questions still surround their role in basic control paradigms and how their role changes after stroke. EEG provides a way to probe the high-speed temporal dynamics of sensorimotor networks that other more common imaging modalities lack. Sensorimotor network function was examined in controls during a task designed to differentiate potential mechanisms of arm stabilization and determine to what degree the sensorimotor network is involved. After sensorimotor network function was characterized in controls, we examined the effect of stroke on the sensorimotor network during rest and described the reorganization that occurs. Lastly, we explored tendon vibration as a sensory therapy for stroke survivors and determined if sensorimotor network mechanisms underlie improvements in arm tracking performance due to wrist tendon vibration. We observed cortical activity and connectivity that suggests sensorimotor networks are involved in the control of arm stability, cortical networks reorganize to more asymmetric, local networks after stroke, and tendon vibration normalizes sensorimotor network activity and connectivity during motor control after stroke. This dissertation was among the first studies using EEG to characterize the high-speed temporal dynamics of sensorimotor networks following stroke. This new knowledge has led to a better understanding of how sensorimotor networks function under ordinary circumstances as well as extreme situations such as stroke and revealed previously unknown mechanisms by which tendon vibration improves motor control in stroke survivors, which will lead to better therapeutic approaches
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