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Somatosensory Modulation during Speech Planning

Description

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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Specificity of Auditory Modulation during Speech Planning

Description

Previous research has showed that auditory modulation may be affected by pure tone
stimuli played prior to the onset of speech production. In this experiment, we are examining the
specificity of the auditory stimulus by implementing congruent and incongruent speech

Previous research has showed that auditory modulation may be affected by pure tone
stimuli played prior to the onset of speech production. In this experiment, we are examining the
specificity of the auditory stimulus by implementing congruent and incongruent speech sounds in
addition to non-speech sound. Electroencephalography (EEG) data was recorded for eleven adult
subjects in both speaking (speech planning) and silent reading (no speech planning) conditions.
Data analysis was accomplished manually as well as via generation of a MATLAB code to
combine data sets and calculate auditory modulation (suppression). Results of the P200
modulation showed that modulation was larger for incongruent stimuli than congruent stimuli.
However, this was not the case for the N100 modulation. The data for pure tone could not be
analyzed because the intensity of this stimulus was substantially lower than that of the speech
stimuli. Overall, the results indicated that the P200 component plays a significant role in
processing stimuli and determining the relevance of stimuli; this result is consistent with role of
P200 component in high-level analysis of speech and perceptual processing. This experiment is
ongoing, and we hope to obtain data from more subjects to support the current findings.

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Date Created
2020-05

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Probing the Role of Auditory Feedback in Voice Pitch Control Using Vibrato Perturbation

Description

The objective of this study was to analyze the auditory feedback system and the pitch-shift reflex in relation to vibrato. 11 subjects (female n = 8, male n = 3) without speech, hearing, or neurological disorders were used. Compensation magnitude,

The objective of this study was to analyze the auditory feedback system and the pitch-shift reflex in relation to vibrato. 11 subjects (female n = 8, male n = 3) without speech, hearing, or neurological disorders were used. Compensation magnitude, adaptation magnitude, relative response phase, and passive and active perception were recorded when the subjects were subjected to auditory feedback perturbed by phasic amplitude and F0 modulation, or “vibrato”. “Tremolo,” or phasic amplitude modulation, was used as a control. Significant correlation was found between the ability to perceive vibrato and tremolo in active trials and the ability to perceive in passive trials (p=0.01). Passive perceptions were lower (more sensitive) than active perceptions (p< 0.01). Adaptation vibrato trials showed significant modulation magnitude (p=0.031), while tremolo did not. The two conditions were significantly different (p<0.01). There was significant phase change for both tremolo and vibrato, but vibrato phase change was greater, nearly 180° (p<0.01). In the compensation trials, the modulation change from control to vibrato trials was significantly greater than the change from control to tremolo (p=0.01). Vibrato and tremolo also had significantly different average phase change (p<0.01). It can be concluded that the auditory feedback system tries to cancel out dynamic pitch perturbations by cancelling them out out-of-phase. Similar systems must be used to adapt and to compensate to vibrato. Despite the auditory feedback system’s online monitoring, the passive perception was still better than active perception, possibly because it required only one task (perceiving) rather than two (perceiving and producing). The pitch-shift reflex compensates to the sensitivity of the auditory feedback system, as shown by the increased perception of vibrato over tremolo.

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Date Created
2018-05

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Vowel Normalization in Dysarthria

Description

In this study, the Bark transform and Lobanov method were used to normalize vowel formants in speech produced by persons with dysarthria. The computer classification accuracy of these normalized data were then compared to the results of human perceptual classification

In this study, the Bark transform and Lobanov method were used to normalize vowel formants in speech produced by persons with dysarthria. The computer classification accuracy of these normalized data were then compared to the results of human perceptual classification accuracy of the actual vowels. These results were then analyzed to determine if these techniques correlated with the human data.

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Date Created
2013-05

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

Description

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