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Somatosensory Modulation during Speech Planning

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Previous studies have found that the detection of near-threshold stimuli is decreased immediately before movement and throughout movement production. This has been suggested to occur through the use of the internal forward model processing an efferent copy of the motor

Previous studies have found that the detection of near-threshold stimuli is decreased immediately before movement and throughout movement production. This has been suggested to occur through the use of the internal forward model processing an efferent copy of the motor command and creating a prediction that is used to cancel out the resulting sensory feedback. Currently, there are no published accounts of the perception of tactile signals for motor tasks and contexts related to the lips during both speech planning and production. In this study, we measured the responsiveness of the somatosensory system during speech planning using light electrical stimulation below the lower lip by comparing perception during mixed speaking and silent reading conditions. Participants were asked to judge whether a constant near-threshold electrical stimulation (subject-specific intensity, 85% detected at rest) was present during different time points relative to an initial visual cue. In the speaking condition, participants overtly produced target words shown on a computer monitor. In the reading condition, participants read the same target words silently to themselves without any movement or sound. We found that detection of the stimulus was attenuated during speaking conditions while remaining at a constant level close to the perceptual threshold throughout the silent reading condition. Perceptual modulation was most intense during speech production and showed some attenuation just prior to speech production during the planning period of speech. This demonstrates that there is a significant decrease in the responsiveness of the somatosensory system during speech production as well as milliseconds before speech is even produced which has implications for speech disorders such as stuttering and schizophrenia with pronounced deficits in the somatosensory system.

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2019-05

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StartReact and its Effect on Functional Upper Extremity Motor Tasks

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The phenomenon known as startReact is the fast, involuntary execution of a planned movement triggered by a startling acoustic stimulus. StartReact has previously been analyzed in simple motor movements such as finger abduction tasks, hand grasp tasks, and elbow extension

The phenomenon known as startReact is the fast, involuntary execution of a planned movement triggered by a startling acoustic stimulus. StartReact has previously been analyzed in simple motor movements such as finger abduction tasks, hand grasp tasks, and elbow extension tasks. More complex movements have also been analyzed, but there have been limited studies that look into functional complex tasks that require end-point accuracy. The objective of this project was to assess the ability to elicit startReact in tasks that simulate activities of daily living like feeding or picking up a glass of water. We hypothesized that a startReact response would be present in complex functional tasks, but the response would not be as accurate due to the increase in speed. Five subjects performed a simulated feeding task by moving kidney beans from one target to another where the end target changed in diameter as well as, a simulated drinking task where the subject moved a cup full of beads from one target to another. The hypothesis was supported due to a significant difference between no stimulus and stimulus trials for tricep muscle onset time, duration time, and the accuracy parameters of amount of beans dropped and weight in beads dropped. The results coincided with previous studies where subjects compensated for the change in diameter by increasing reaction time as the target diameter size decreased. The data obtained contradicted a previous study in relation to the duration time between the tasks due to our smallest diameter size having a faster duration time in comparison to the other diameter sizes. This study provides preliminary data that could assist researchers and clinicians in improving physical therapy methods for patients with impaired upper extremity motor movements.

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2020-12

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Startle-evoked movement in multi-jointed, two-dimensional reaching tasks

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Previous research has shown that a loud acoustic stimulus can trigger an individual's prepared movement plan. This movement response is referred to as a startle-evoked movement (SEM). SEM has been observed in the stroke survivor population where results have shown

Previous research has shown that a loud acoustic stimulus can trigger an individual's prepared movement plan. This movement response is referred to as a startle-evoked movement (SEM). SEM has been observed in the stroke survivor population where results have shown that SEM enhances single joint movements that are usually performed with difficulty. While the presence of SEM in the stroke survivor population advances scientific understanding of movement capabilities following a stroke, published studies using the SEM phenomenon only examined one joint. The ability of SEM to generate multi-jointed movements is understudied and consequently limits SEM as a potential therapy tool. In order to apply SEM as a therapy tool however, the biomechanics of the arm in multi-jointed movement planning and execution must be better understood. Thus, the objective of our study was to evaluate if SEM could elicit multi-joint reaching movements that were accurate in an unrestrained, two-dimensional workspace. Data was collected from ten subjects with no previous neck, arm, or brain injury. Each subject performed a reaching task to five Targets that were equally spaced in a semi-circle to create a two-dimensional workspace. The subject reached to each Target following a sequence of two non-startling acoustic stimuli cues: "Get Ready" and "Go". A loud acoustic stimuli was randomly substituted for the "Go" cue. We hypothesized that SEM is accessible and accurate for unrestricted multi-jointed reaching tasks in a functional workspace and is therefore independent of movement direction. Our results found that SEM is possible in all five Target directions. The probability of evoking SEM and the movement kinematics (i.e. total movement time, linear deviation, average velocity) to each Target are not statistically different. Thus, we conclude that SEM is possible in a functional workspace and is not dependent on where arm stability is maximized. Moreover, coordinated preparation and storage of a multi-jointed movement is indeed possible.

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2016-12