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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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Date Created
2019-05

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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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Date Created
2016-12

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Sensory-motor mechanisms unify psychology: motor effort and perceived distance to cultural out-groups

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ABSTRACT This thesis proposes that a focus on the bodily level of analysis can unify explanation of behavior in cognitive, social, and cultural psychology. To examine this unifying proposal, a sensorimotor mechanism with reliable explanatory power in cognitive and social

ABSTRACT This thesis proposes that a focus on the bodily level of analysis can unify explanation of behavior in cognitive, social, and cultural psychology. To examine this unifying proposal, a sensorimotor mechanism with reliable explanatory power in cognitive and social psychology was used to predict a novel pattern of behavior in cultural context, and these predictions were examined in three experiments. Specifically, the finding that people judge objects that require more motor effort to interact with as farther in visual space was adapted to predict that people with interdependent self-construal(SC) , relative to those with independent SC, would visually perceive their cultural outgroups as farther relative to their cultural in-groups. Justifying this cultural extension of what is primarily a cognitive mechanism is the assumption that, unlike independents, Interdependents interact almost exclusively with in-group members, and hence there sensorimotor system is less tuned to cross-cultural interactions. Thus, interdependents, more so than independents, expect looming cross-cultural interactions to be effortful, which may inflate their judgment of distance to the out-groups. Two experiments confirmed these predictions: a) interdependent Americans, compared to independent Americans, perceived American confederates (in-group) as visually closer; b) interdependent Arabs, compared to independent Arabs, perceived Arab confederates (in-group) as closer; and c) interdependent Americans, relative to independent Americans, perceived Arab confederates (out-group) as farther. A third study directly established the proposed relation between motor effort and distance to human targets: American men perceived other American men as closer after an easy interaction than after a more difficult interaction. Together, these results demonstrate that one and the same sensorimotor mechanism can explain/predict homologous behavioral patterns across the subdisciplines of psychology.

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Date Created
2013

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Movement kinematics and fractal properties in Fitts' law task

Description

Fractal analyses examine variability in a time series to look for temporal structure

or pattern that reveals the underlying processes of a complex system. Although fractal

property has been found in many signals in biological systems, how it relates to

behavioral performance and

Fractal analyses examine variability in a time series to look for temporal structure

or pattern that reveals the underlying processes of a complex system. Although fractal

property has been found in many signals in biological systems, how it relates to

behavioral performance and what it implies about the complex system under scrutiny are

still open questions. In this series of experiments, fractal property, movement kinematics,

and behavioral performance were measured on participants performing a reciprocal

tapping task. In Experiment 1, the results indicated that the alpha value from detrended

fluctuation analysis (DFA) reflected deteriorating performance when visual feedback

delay was introduced into the reciprocal tapping task. This finding suggests that this

fractal index is sensitive to performance level in a movement task. In Experiment 2, the

sensitivity of DFA alpha to the coupling strength between sub-processes within a system

was examined by manipulation of task space visibility. The results showed that DFA

alpha was not influenced by disruption of subsystems coupling strength. In Experiment 3,

the sensitivity of DFA alpha to the level of adaptivity in a system under constraints was

examined. Manipulation of the level of adaptivity was not successful, leading to

inconclusive results to this question.

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Created

Date Created
2019