Browsing by Subject "Dystonia"

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    Neurophysiology and Neuromodulation: Incorporating Task Training to Harness Cerebellar Neuroplasticity in Rehabilitation
    (2018-12) Summers, Rebekah
    Dystonia is a neurologic movement disorder characterized by involuntary muscular contractions that may be sustained or intermittent, resulting in abnormal movement and postures. The burden associated with dystonia is considerable as there is no cure or known pathophysiology. Despite the immediate need for innovative treatments, alternative interventions are barred by a lack of understanding of the pathology and mechanism of dystonia. To develop and refine effective rehabilitative interventions for patients with focal dystonia, the pathology must be better understood and methods to assess corticospinal excitability refined. There are emerging lines of evidence that suggest there is an altered balance of inhibition and excitation contributing to the cause of dystonia. This may be due to dysfunctional interplays between the cerebellum, basal ganglia and motor cortex that generate network dysfunction. One strategy to study the affected brain regions in people with dystonia is via the use of non-invasive brain stimulation to measure and modulate motor cortical excitability. The overall goal of this dissertation is to evaluate the use of non-invasive brain stimulation, using both transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), to assess and modulate aspects of neurophysiology and neuroplasticity in people with cervical dystonia (CD) and healthy controls. Four studies were designed to achieve this research goal. 1) The first study evaluated the validity of using fine-wire electrodes to record motor evoked responses. Fine-wire electrodes were found to be a valid means to record muscle responses, allowing the investigation of motor cortical excitability in small or intrinsic muscles that can be affected by dystonia. 2) The second study evaluated the use of cerebellar neuromodulation with simultaneous task training in healthy adults. This investigation revealed that cerebellar neuromodulation interfered with practice-related changes in corticospinal excitability. 3) The third study evaluated ipsilateral and contralateral motor evoked responses in the upper trapezius between people with CD and controls and provided evidence that inhibitory responses are asymmetrically regulated in people with CD. 4) The fourth study explored the use of cerebellar tDCS to modulate eye-blink classical conditioning and measures of motor cortical excitability. The results suggest poor conditioning responses in all participants, limiting the interpretation of the study; however, no differences between groups were detected in outcomes of motor cortical excitability. These studies add to our understanding of how non-invasive brain stimulation may be used to assess measures of excitation and inhibition in-vivo to probe aspects of neuroplasticity and the effects of neuromodulation.
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    Regional specificity in the hand area of the primary motor cortex for healthy individuals and individuals with focal hand dystonia.
    (2010-07) Pickett, Kristen Alexis
    Idiopathic focal hand dystonia is a movement disorder characterized by abnormal postures and loss of motor control of the affected limb. Currently, the underlying pathophysiology responsible for these motor manifestations is not fully understood. Recent empirical evidence suggests a link between deficits of cortical inhibition, maladaptive plasticity and abnormal sensory and motor processing in individuals with dystonia. These factors may contribute to an atypical organization of the hand knob area of the primary motor cortex. The current literature lacks a well designed method to clearly define and quantify healthy cortical activation. The purpose of this study was to first establish a definition of healthy cortical activation in the primary motor cortex during a finger tapping task and then use this baseline for comparison to a group of participants with focal hand dystonia. Methods. Functional magnetic resonance imaging was used to compare the cortical activation of six participants diagnosed with idiopathic focal hand dystonia to eight healthy individuals during a randomly ordered finger tapping task. Quantification of the cortical activation was performed with GLM beta weight analysis to examine for main effects and through a `Selectivity Index' that allowed for activation of a single digit (in the hemisphere contralateral to the moving digit) to be measured relative to the activation of the four other digits of the hand. Results. In the beta weight analysis differences in cortical activation was found at the group, finger and hemisphere levels (p < 0.05). Significant interaction effects were found in activation for group x finger x hemisphere (p = 0.02 ). The analysis demonstrated less selectivity of individual finger activation in both hemispheres for the dystonic group compared to the healthy group (right: p = 0.0017, left p = 0.0105). Discussion. This study is the first to define a method for determining the degree to which a cortical area is associated with the movement of one digit related to another. Importantly, it elucidates a potential neuropathophysiological substrate related to individual finger activation in the primary motor cortex in humans with focal dystonia.
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    Vibro tactile stimulation as a treatment for the voice disorder spasmodic dysphonia
    (2021-03) Mahnan, Arash
    Spasmodic dysphonia (SD) is rare focal dystonia affecting the laryngeal musculature. Patients with SD typically experience a strained or choked speech and report that it takes an exhausting effort for them to speak. The disorder develops spontaneously during midlife. Its progression is gradual in the first year and then becomes chronic for life. At present, there is no cure for SD and it is unresponsive to behavioral speech therapy. It is treated primarily with Botulinum toxin (Botox) injections for temporary symptom relief. Proprioceptive deficits are an underlying feature of SD - a finding that opens an avenue for a missing behavioral treatment for the disease. Specifically, vibro-tactile stimulation (VTS) could be the suitable tool, given that it alters afferent signals from the mechanoreceptors in the vibrated muscles and skin.This cumulative dissertation concerns a non-invasive neuromodulation approach using VTS for treating the voice symptoms in people with SD. It consists of three separate projects. The first project examined the short-term effect of vibro-tactile stimulation (VTS) on speech quality and cortical activity of 12 participants with adductor SD and one with abductor SD. The results showed that 9 participants (69%) exhibited a reduction of voice breaks and/or a meaningful increase in smoothed cepstral peak prominence, an acoustic measure of voice/speech quality. Symptom improvements persisted for 20 minutes past VTS. In addition, VTS induced a significant suppression of theta band power over the left somatosensory-motor cortex and a significant rise of gamma rhythm over the right somatosensory-motor cortex. Our results show convincingly that VTS represents a non-invasive form of neuromodulation that induces measurable short-term improvements in patients' speech with adductor SD. The second project represents a logical step to expand on the previous work to improve VTS technology and make it wearable. To that effect, I have designed and developed a wearable non-invasive collar-like device that applies VTS to the laryngeal muscles. The device provides two operational modes, continuous VTS and real-time VTS, using a developed speech detection technology. The speech detection algorithm allows for individualized system calibration providing flexibility in adjusting the device for users with different anatomy and/or disease severity. For the final project, I used the device that was developed in project 2 to examine the efficacy of VTS for treating voice symptoms in people with abductor SD. The results showed an improvement in at least one marker of voice quality for 3 out of 4 participants. The improvement lasted for 20 and 60 minutes after cessation of VTS for one participant. However, we require a larger sample to have a confident response rate to the laryngeal VTS in AB SD. The current analysis of electrocortical responses to VTS in people with AB SD did not closely mimic the event -elated cortical activity patterns seen in AD SD. More data are needed to delineate consistent patterns of cortical responses induced by laryngeal VTS in AB SD.