Biology subjects

Tang, D.-l.

Publications and source records attributed to Tang, D.-l..

8 recordsLinked to original sources

bioRxiv2024

Theta-burst stimulation over primary somatosensory cortex modulates tactile acuity of tongue

BackgroundEmerging studies in humans have established the modulatory effects of repetitive transcranial magnetic stimulation (rTMS) over primary somatosensory cortex (S1) on somatosensory cortex activity and perception. However, to date, research in this area has primarily focused on the hand and fingers, leaving a gap in our understanding of the modulatory effects of rTMS on somatosensory perception of the orofacial system and speech articulators. ObjectiveThe present study aimed to examine the effects of different types of theta-burst stimulation--continuous TBS (cTBS), intermittent TBS (iTBS), or sham--over the tongue representation of left S1 on tactile acuity of the tongue. MethodsIn a repeated-measures design, fifteen volunteers participated in four separate sessions, where cTBS, iTBS, sham, or no stimulation was applied over the tongue representation of left S1. Effects of TBS were measured on both temporal and spatial perceptual acuity of tongue using a custom vibrotactile stimulator. ResultsCTBS significantly impaired spatial amplitude threshold at the time window of 16-30 minutes after stimulation, while iTBS improved it at the same time window. The effect of iTBS, however, was smaller than cTBS. In contrast, neither cTBS nor iTBS had any effect on the temporal discrimination threshold. ConclusionsThe current study establishes the validity of using TBS to modulate somatosensory perception of the orofacial system. Directly modifying somatosensation in the orofacial system has the potential to benefit clinical populations with abnormal tactile acuity, improve our understanding of the role of sensory systems in speech production, and enhance speech motor learning and rehabilitation. HighlightsO_LITheta-burst stimulation (TBS) can modulate somatosensation in the orofacial system C_LIO_LIcTBS over S1 impaired spatial acuity of tongue C_LIO_LIiTBS over S1 improved spatial acuity of tongue C_LI

neuroscience↗

bioRxiv2023

Pars opercularis underlies efferent predictions and successful auditory feedback processing in speech: Evidence from left-hemisphere stroke

Hearing ones own speech allows for acoustic self-monitoring in real time. Left-hemisphere motor planning regions are thought to give rise to efferent predictions that can be compared to true feedback in sensory cortices, resulting in neural suppression commensurate with the degree of overlap between predicted and actual sensations. Sensory prediction errors thus serve as a possible mechanism of detection of deviant speech sounds, which can then feed back into corrective action, allowing for online control of speech acoustics. The goal of this study was to assess the integrity of this detection-correction circuit in persons with aphasia (PWA) whose left-hemisphere lesions may limit their ability to control variability in speech output. We recorded magnetoencephalography (MEG) while 15 PWA and age-matched controls spoke monosyllabic words and listened to playback of their utterances. From this, we measured speaking-induced suppression of the M100 neural response and related it to lesion profiles and speech behavior. Both speaking-induced suppression and cortical sensitivity to deviance were preserved at the group level in PWA. PWA with more spared tissue in pars opercularis had greater left-hemisphere neural suppression and greater behavioral correction of acoustically deviant pronunciations, whereas sparing of superior temporal gyrus was not related to neural suppression or acoustic behavior. In turn, PWA who made greater corrections had fewer overt speech errors in the MEG task. Thus, the motor planning regions that generate the efferent prediction are integral to performing corrections when that prediction is violated.

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bioRxiv2023

The brain's sensitivity to sensory error can be modulated by altering perceived variability

When individuals make a movement that produces an unexpected outcome, they learn from the resulting error. This process, essential in both acquiring new motor skills and adapting to changing environments, critically relies on error sensitivity, which governs how much behavioral change results from a given error. Although behavioral and computational evidence suggests error sensitivity can change in response to task demands, neural evidence regarding the flexibility of error sensitivity in the human brain is lacking. Critically, the sensitivity of the nervous system to auditory errors during speech production, a complex and well-practiced motor behavior, has been extensively studied by examining the prediction-driven suppression of auditory cortical activity. Here, we tested whether the nervous systems sensitivity to errors, as measured by this suppression, can be modulated by altering speakers perceived variability. Our results showed that error sensitivity was increased after exposure to an auditory perturbation that increased participants perceived variability, consistent with predictions generated from previous behavioral data and state-space modeling. Conversely, we observed no significant changes in error sensitivity when perceived variability was unaltered or artificially reduced. The current study establishes the validity of behaviorally modulating the nervous systems sensitivity to errors. As sensitivity to sensory errors plays a critical role in sensorimotor adaptation, modifying error sensitivity has the potential to enhance motor learning and rehabilitation in speech and, potentially, more broadly across motor domains. Significance StatementThe process of learning from error is essential for both the acquisition of new skills and successful adaptation to changing environments. Such error-based learning critically relies on error sensitivity, which determines how much we learn from a given error. Although evidence from behavioral studies suggests error sensitivity is malleable, neural evidence regarding the flexibility of error sensitivity in the human brain is lacking. Here, we showed that the nervous systems sensitivity to errors can be modulated by altering perceived variability. The present study establishes the validity of behaviorally modulating neural sensitivity to sensory errors. Improving our ability to learn from error can play a critical role in applied settings such as rehabilitation.

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bioRxiv2021

Variability is actively regulated in speech

Although movement variability is often attributed to unwanted noise in the motor system, recent work has demonstrated that variability may be actively controlled. To date, research on regulation of motor variability has relied on relatively simple, laboratory-specific reaching tasks. It is not clear how these results translate to complex, well-practiced and real-world tasks. Here, we test how variability is regulated during speech production, a complex, highly over-practiced and natural motor behavior that relies on auditory and somatosensory feedback. Specifically, in a series of four experiments, we assessed the effects of auditory feedback manipulations that modulate perceived speech variability, shifting every production either towards (inward-pushing) or away from (outward-pushing) the center of the distribution for each vowel. Participants exposed to the inward-pushing perturbation (Experiment 1) increased produced variability while the perturbation was applied as well as after it was removed. Unexpectedly, the outward-pushing perturbation (Experiment 2) also increased produced variability during exposure, but variability returned to near baseline levels when the perturbation was removed. Outward-pushing perturbations failed to reduce participants produced variability both with larger perturbation magnitude (Experiment 3) or after their variability had increased above baseline levels as a result of the inward-pushing perturbation (Experiment 4). Simulations of the applied perturbations using a state space model of motor behavior suggest that the increases in produced variability in response to the two types of perturbations may arise through distinct mechanisms: an increase in controlled variability in response to the inward-pushing perturbation, and an increase in sensitivity to auditory errors in response to the outward-pushing perturbation. Together, these results suggest that motor variability is actively regulated even in complex and well-practiced behaviors, such as speech.

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bioRxiv2021

Dopamine enhanced auditory perceptual learning in humans via long-term memory consolidation

Dopamine is known to modulate sensory plasticity in animal brain, but how it impacts perceptual learning in humans remains largely unknown. In a placebo-controlled, double-blinded training experiment with young healthy adults (both male and female), oral administration of Madopar, a dopamine precursor, during each of multiple training sessions was shown to enhance auditory perceptual learning, particularly in late training sessions. Madopar also enhanced learning and transfer to working memory when tested outside the time widow of drug effect, which appeared to retain for at least 20 days. To test whether such learning modulation was mediated by the dopaminergic working memory network, the same dopamine manipulation was applied to working memory training, but to little influence on learning or transfer. Further, a neural network model of auditory perceptual learning revealed distinctive behavioural modulation patterns for proposed dopaminergic functions in the auditory cortex: trial-by-trial reinforcement signals (reward/reward prediction error and expected reward) and across-session memory consolidation. Only the memory consolidation simulations matched experimental observations. The results thus demonstrate that dopamine modulates human perceptual learning, mostly likely via enhancing memory consolidation over extended time scales.

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bioRxiv2020

Asymmetry of auditory-motor speech processing is determined by language experience

Speech processing relies on interactions between auditory and motor systems and is asymmetrically organized in the human brain. The left auditory system is specialized for processing of phonemes, whereas the right is specialized for processing of pitch changes in speech that affect prosody. In speakers of tonal languages, however, processing of pitch (i.e., tone) changes that alter word meaning is left-lateralized. This indicates that linguistic function and language experience shape auditory speech processing asymmetries; their effect on auditory-motor speech processing remains unknown, however. Here, we investigated the asymmetry of motor contributions to auditory speech processing in speakers of tonal and non-tonal languages. We temporarily disrupted the left or right speech motor cortex using repetitive transcranial magnetic stimulation (rTMS) and measured the impact of these disruptions on auditory processing of phoneme and tone changes in sequences of syllables using electroencephalography (EEG). We found that disruption of the speech motor cortex in the left, but not the right hemisphere, impaired processing of phoneme changes in both language groups equally. In contrast, the effect of motor disruptions on processing of tone changes differed in tonal and non-tonal language groups: disruption of the left speech motor cortex significantly impaired processing of tone changes in tonal language speakers, whereas disruption of the right speech motor cortex modulated processing of tone changes in non-tonal speakers. We conclude that the contribution of the left and right speech motor cortex to auditory speech processing is determined by the functional role of the acoustic cues in the listeners native language. Significance StatementThe principles underlying hemispheric asymmetries of auditory speech processing remain debated. The asymmetry of auditory speech processing is affected by the low-level acoustic cues, but also by their linguistic function. By combining TMS and EEG, we investigated the asymmetry of motor contributions to auditory speech processing in tonal and non-tonal language speakers. For the first time, we provide causal evidence that auditory-motor speech processing asymmetries are shaped by the functional role of the acoustic cues in the listeners native language. The lateralised top-down motor influences are likely to affect asymmetry of speech processing in the auditory system.

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bioRxiv2019

Altered auditory feedback induces coupled changes in formant frequencies during speech production

Speaking is one of the most complicated motor behaviours, involving a large number of articulatory muscles which can move independently to command precise changes in speech acoustics. Here, we used real-time manipulations of speech feedback to test whether the acoustics of speech production (e.g. the formants) reflect independently controlled articulatory movements or combinations of movements. During repetitive productions of \"head, bed, dead\", either the first (F1) or the second formant (F2) of vowels was shifted and fed back to participants. We then examined whether changes in production in response to these alterations occurred for only the perturbed formant or both formants. In Experiment 1, our results showed that participants who received increased F1 feedback significantly decreased their F1 productions in compensation, but also significantly increased the frequency of their F2 productions. The combined F1-F2 change moved the utterances closer to a known pattern of speech production (i.e. the vowel category \"hid, bid, did\"). In Experiment 2, we further showed that a downshift in frequency of F2 feedback also induced significant compensatory changes in both the perturbed (F2) and the unperturbed formant (F1) that were in opposite directions. Taken together, the results demonstrate that a shift in auditory feedback of a single formant drives combined changes in related formants. The results suggest that, although formants can be controlled independently, the speech motor system may favour a strategy in which changes in formant production are coupled to maintain speech production within specific regions of the vowel space corresponding to existing speech-sound categories.\n\nNew & NoteworthyFindings from previous studies examining responses to altered auditory feedback are inconsistent with respect to the changes speakers make to their production. Speakers can compensate by specifically altering their production to offset the acoustic error in feedback. Alternatively, they may compensate by changing their speech production more globally to produce a speech sound closer to an existing category in their repertoire. Our study shows support for the latter strategy.

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bioRxiv2019

Does deliberation really need more effort than intuition? A test using event-related brain potential

Intuition and deliberation are two strategies for problem-solving and decision-making. It is commonly believed that deliberation requires more effort than intuition. However, to date, neural evidence approving or disapproving this point is scarce. To explore this issue, we asked participants to play two well-matched games requiring either deliberation or intuition. Using event-related brain potential (ERP) technique, we found: (1) Deliberation elicited more deflective ERP than intuition during -1000 ~ -500 ms before the response, which is consistent with the common belief. (2) More importantly, intuition evoked more deflective ERP than deliberation during 550 ~ 650 ms after the onset of the stimulus, which suggests that intuition may need more effort than deliberation at early stage, contradicting the common belief.

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