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Compensatory Responses During Unexpected Vowel Perturbations

Description

During speech, the brain is constantly processing and monitoring speech output through the auditory feedback loop to ensure correct and accurate speech. If the speech signal is experimentally altered/perturbed while speaking, the brain compensates for the perturbations by changing speech

During speech, the brain is constantly processing and monitoring speech output through the auditory feedback loop to ensure correct and accurate speech. If the speech signal is experimentally altered/perturbed while speaking, the brain compensates for the perturbations by changing speech output in the opposite direction of the perturbations. In this study, we designed an experiment that examined the compensatory responses in response to unexpected vowel perturbations during speech. We applied two types of perturbations. In one condition, the vowel /ɛ/ was perturbed toward the vowel /æ/ by simultaneously shifting both the first formant (F1) and the second formant (F2) at 3 different levels (.5=small, 1=medium, and 1.5=large shifts). In another condition, the vowel /ɛ/ was perturbed by shifting F1 at 3 different levels (small, medium, and large shifts). Our results showed that there was a significant perturbation-type effect, with participants compensating more in response to perturbation that shifted /ɛ/ toward /æ/. In addition, we found that there was a significant level effect, with the compensatory responses to level .5 being significantly smaller than the compensatory responses to levels 1 and 1.5, regardless of the perturbation pathway. We also found that responses to shift level 1 and shift level 1.5 did not differ. Overall, our results highlighted the importance of the auditory feedback loop during speech production and how the brain is more sensitive to auditory errors that change a vowel category (e.g., /ɛ/ to /æ/).

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2019-05

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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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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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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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2018-05

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Utilizing functional MRI to Analyze Differences in the Brain in Response to Speech and Music Stimuli in Persons with Aphasia

Description

The distinctions between the neural resources supporting speech and music comprehension have long been studied using contexts like aphasia and amusia, and neuroimaging in control subjects. While many models have emerged to describe the different networks uniquely recruited in response

The distinctions between the neural resources supporting speech and music comprehension have long been studied using contexts like aphasia and amusia, and neuroimaging in control subjects. While many models have emerged to describe the different networks uniquely recruited in response to speech and music stimuli, there are still many questions, especially regarding left-hemispheric strokes that disrupt typical speech-processing brain networks, and how musical training might affect the brain networks recruited for speech after a stroke. Thus, our study aims to explore some questions related to the above topics. We collected task-based functional MRI data from 12 subjects who previously experienced a left-hemispheric stroke. Subjects listened to blocks of spoken sentences and novel piano melodies during scanning to examine the differences in brain activations in response to speech and music. We hypothesized that speech stimuli would activate right frontal regions, and music stimuli would activate the right superior temporal regions more than speech (both findings not seen in previous studies of control subjects), as a result of functional changes in the brain, following the left-hemispheric stroke and particularly the loss of functionality in the left temporal lobe. We also hypothesized that the music stimuli would cause a stronger activation in right temporal cortex for participants who have had musical training than those who have not. Our results indicate that speech stimuli compared to rest activated the anterior superior temporal gyrus bilaterally and activated the right inferior frontal lobe. Music stimuli compared to rest did not activate the brain bilaterally, but rather only activated the right middle temporal gyrus. When the group analysis was performed with music experience as a covariate, we found that musical training did not affect activations to music stimuli specifically, but there was greater right hemisphere activation in several regions in response to speech stimuli as a function of more years of musical training. The results of the study agree with our hypotheses regarding the functional changes in the brain, but they conflict with our hypothesis about musical expertise. Overall, the study has generated interesting starting points for further explorations of how musical neural resources may be recruited for speech processing after damage to typical language networks.

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Date Created
2021-05

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Predicting /r/ Acquisition: A Longitudinal Analysis Using Signal Processing

Description

The purpose of this longitudinal study was to predict /r/ acquisition using acoustic signal processing. 19 children, aged 5-7 with inaccurate /r/, were followed until they turned 8 or acquired /r/, whichever came first. Acoustic and descriptive data from 14

The purpose of this longitudinal study was to predict /r/ acquisition using acoustic signal processing. 19 children, aged 5-7 with inaccurate /r/, were followed until they turned 8 or acquired /r/, whichever came first. Acoustic and descriptive data from 14 participants were analyzed. The remaining 5 children continued to be followed. The study analyzed differences in spectral energy at the baseline acoustic signals of participants who eventually acquired /r/ compared to that of those who did not acquire /r/. Results indicated significant differences between groups in the baseline signals for vocalic and postvocalic /r/, suggesting that the acquisition of certain allophones may be predictable. Participants’ articulatory changes made during the progression of acquisition were also analyzed spectrally. A retrospective analysis described the pattern in which /r/ allophones were acquired, proposing that vocalic /r/ and the postvocalic variant of consonantal /r/ may be acquired prior to prevocalic /r/, and /r/ followed by low vowels may be acquired before /r/ followed by high vowels, although individual variations exist.

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Date Created
2021-05

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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

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Effects of Error-Detection Training on Speech Motor Learning

Description

When we produce speech movements, we expect a specific auditory consequence, but an error occurs when the predicted outcomes do not match the actual speech outcome. The brain notes these discrepancies, learns from the errors, and works to lower these

When we produce speech movements, we expect a specific auditory consequence, but an error occurs when the predicted outcomes do not match the actual speech outcome. The brain notes these discrepancies, learns from the errors, and works to lower these errors. Previous studies have shown a relationship between speech motor learning and auditory targets. Subjects with smaller auditory targets were more sensitive to errors. These subjects estimated larger perturbations and generated larger responses. However, these responses were often ineffective, and the changes were usually minimal. The current study examined whether subjects’ auditory targets can be manipulated in an experimental setting. We recruited 10 healthy young adults to complete a perceptual vowel categorization task. We developed a novel procedure where subjects heard different auditory stimuli and reported the stimuli by locating the stimuli relative to adjacent vowels. We found that when stimuli are closer to vowel boundary, subjects are less accurate. Importantly, by providing visual feedback to subjects, subjects were able to improve their accuracy of locating the stimuli. These results indicated that we might be able to improve subjects’ auditory targets and thus may improve their speech motor learning ability.

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2022-05