Zhaocong Chen

ERP Correlates of Language-Specific Processing of Auditory Pitch Feedback during Self-Vocalization.

The present study investigated whether the neural correlates for auditory feedback control of vocal pitch can be shaped by tone language experience. Event-related potentials (P2/N1) were recorded from adult native speakers of Mandarin and Cantonese who heard their voice auditory feedback shifted in pitch by -50, -100, -200, or -500 cents when they sustained the vowel sound /u/. Cantonese speakers produced larger P2 amplitudes to -200 or -500 cents stimuli than Mandarin speakers, but this language effect failed to reach significance in the case of -50 or -100 cents. Moreover, Mandarin speakers produced shorter N1 latencies over the left hemisphere than the right hemisphere, whereas Cantonese speakers did not. These findings demonstrate that neural processing of auditory pitch feedback in vocal motor control is subject to language-dependent neural plasticity, suggesting that cortical mechanisms of auditory-vocal integration can be shaped by tone language experience.

Effect of temporal predictability on the neural processing of self-triggered auditory stimulation during vocalization

BackgroundSensory consequences of our own actions are perceived differently from the sensory stimuli that are generated externally. The present event-related potential (ERP) study examined the neural responses to self-triggered stimulation relative to externally-triggered stimulation as a function of delays between the motor act and the stimulus onset. While sustaining a vowel phonation, subjects clicked a mouse and heard pitch-shift stimuli (PSS) in voice auditory feedback at delays of either 0 ms (predictable) or 500–1000 ms (unpredictable). The motor effect resulting from the mouse click was corrected in the data analyses. For the externally-triggered condition, PSS were delivered by a computer with a delay of 500–1000 ms after the vocal onset.ResultsAs compared to unpredictable externally-triggered PSS, P2 responses to predictable self-triggered PSS were significantly suppressed, whereas an enhancement effect for P2 responses was observed when the timing of self-triggered PSS was unpredictable.ConclusionsThese findings demonstrate the effect of the temporal predictability of stimulus delivery with respect to the motor act on the neural responses to self-triggered stimulation. Responses to self-triggered stimulation were suppressed or enhanced compared with the externally-triggered stimulation when the timing of stimulus delivery was predictable or unpredictable. Enhancement effect of unpredictable self-triggered stimulation in the present study supports the idea that sensory suppression of self-produced action may be primarily caused by an accurate prediction of stimulus timing, rather than a movement-related non-specific suppression.

Auditory Feedback Control of Vocal Pitch during Sustained Vocalization: A Cross-Sectional Study of Adult Aging

Background Auditory feedback has been demonstrated to play an important role in the control of voice fundamental frequency (F0), but the mechanisms underlying the processing of auditory feedback remain poorly understood. It has been well documented that young adults can use auditory feedback to stabilize their voice F0 by making compensatory responses to perturbations they hear in their vocal pitch feedback. However, little is known about the effects of aging on the processing of audio-vocal feedback during vocalization. Methodology/Principal Findings In the present study, we recruited adults who were between 19 and 75 years of age and divided them into five age groups. Using a pitch-shift paradigm, the pitch of their vocal feedback was unexpectedly shifted ±50 or ±100 cents during sustained vocalization of the vowel sound/u/. Compensatory vocal F0 response magnitudes and latencies to pitch feedback perturbations were examined. A significant effect of age was found such that response magnitudes increased with increasing age until maximal values were reached for adults 51–60 years of age and then decreased for adults 61–75 years of age. Adults 51–60 years of age were also more sensitive to the direction and magnitude of the pitch feedback perturbations compared to younger adults. Conclusion These findings demonstrate that the pitch-shift reflex systematically changes across the adult lifespan. Understanding aging-related changes to the role of auditory feedback is critically important for our theoretical understanding of speech production and the clinical applications of that knowledge.

Sensorimotor control of vocal pitch production in Parkinson's disease

The present study was designed to investigate the sensorimotor control of voice fundamental frequency (F0) in individuals with Parkinsons diseases (PD). Fifteen Cantonese individuals with PD, and fifteen age- and sex-matched healthy Cantonese individuals participated in the experiment. Participants were asked to vocalize a vowel sound while hearing their voice auditory feedback unexpectedly pitch-shifted upwards or downwards through headphones. The size of pitch shifts varied from 50, 100, to 200 cents. One novel averaging method was used to categorize the individual trials such that only those trials that opposed the perturbation direction were averaged to generate an overall response. The results showed that Cantonese individuals with PD produced significantly larger magnitudes of vocal compensation for pitch perturbations than healthy participants. Both groups showed systematic changes in compensation magnitude as a function of perturbation size and direction: larger perturbation size or upward direction elicited greater compensation magnitude. Moreover, pitch variability indexed by the standard deviations of the baseline F0 was significantly correlated with the magnitude of vocal compensation in individuals with PD, whereas this correlation failed to reach significance for healthy participants. This study presents the first data demonstrating the abnormal processing of auditory feedback in the sensorimotor control of voice F0 for Cantonese individuals with PD. It is suggested that the abnormal sensorimotor integration of voice F0 control in PD may be caused by the increased weighting of auditory feedback control resulting from dysfunction of feedforward control and somatosensory feedback caused by the impairment of the basal ganglia.

Effect of tonal native language on voice fundamental frequency responses to pitch feedback perturbations during sustained vocalizations

The purpose of this cross-language study was to examine whether the online control of voice fundamental frequency (F(0)) during vowel phonation is influenced by language experience. Native speakers of Cantonese and Mandarin, both tonal languages spoken in China, participated in the experiments. Subjects were asked to vocalize a vowel sound /u/at their comfortable habitual F(0), during which their voice pitch was unexpectedly shifted (± 50, ± 100, ± 200, or ± 500 cents, 200 ms duration) and fed back instantaneously to them over headphones. The results showed that Cantonese speakers produced significantly smaller responses than Mandarin speakers when the stimulus magnitude varied from 200 to 500 cents. Further, response magnitudes decreased along with the increase in stimulus magnitude in Cantonese speakers, which was not observed in Mandarin speakers. These findings suggest that online control of voice F(0) during vocalization is sensitive to language experience. Further, systematic modulations of vocal responses across stimulus magnitude were observed in Cantonese speakers but not in Mandarin speakers, which indicates that this highly automatic feedback mechanism is sensitive to the specific tonal system of each language.

Sex-related differences in vocal responses to pitch feedback perturbations during sustained vocalization

The present study assessed the effect of sex on voice fundamental frequency (F(0)) responses to pitch feedback perturbations during sustained vocalization. Sixty-four native-Mandarin speakers heard their voice pitch feedback shifted at ± 50, ± 100, or ± 200 cents for 200 ms, five times during each vocalization. The results showed that, as compared to female speakers, male speakers produced significantly larger but slower vocal responses to the pitch-shifted stimuli. These findings reveal a modulation of vocal response as a function of sex, and suggest that there may be a differential processing of vocal pitch feedback perturbations between men and women.

Neurophysiological evidence of differential mechanisms involved in producing opposing and following responses to altered auditory feedback.

OBJECTIVE When hearing perturbations in voice auditory feedback, people produce responses that mostly oppose the perturbation direction, whereas a few responses follow the direction of feedback perturbation. The causes of opposing and following responses, however, remain poorly understood. The present event-related potential (ERP) study sought to examine the neurophysiological processing of opposing and following responses to pitch feedback perturbations during self-monitoring of vocal production. METHOD Twelve Mandarin-native speakers participated in the experiment. Vocal and neurophysiological responses to pitch perturbations (± 50 and ± 200 cents) in voice auditory feedback were measured. Individual-trial responses were categorized according to the response direction and then separately averaged in groups of opposing and following responses. ERPs indexed by the P1-N1-P2 complex corresponding to two types of vocal responses were also obtained. RESULTS Opposing and following vocal responses did not differ in the magnitude, but there were greater proportions of opposing to following responses to 50 cents stimuli. The amplitude and latency of the P1 and N1 components showed none of significance across conditions, whereas there was a direction × magnitude effect on the P2 response. Following responses elicited greater P2 amplitudes than opposing responses only when pitch feedback was perturbed for downward 200 cents, and upward pitch perturbation elicited greater P2 amplitudes than those with downward direction only in the production of opposing responses. CONCLUSION These findings demonstrate that cortical processing of opposing responses is different from that of following responses, which can be modulated by the physical properties of feedback perturbation. SIGNIFICANCE Different neural mechanisms are involved in the production of opposing and following responses to feedback perturbations during self-monitoring of vocal production.

Dynamics of Vocalization-Induced Modulation of Auditory Cortical Activity at Mid-utterance

Background Recent research has addressed the suppression of cortical sensory responses to altered auditory feedback that occurs at utterance onset regarding speech. However, there is reason to assume that the mechanisms underlying sensorimotor processing at mid-utterance are different than those involved in sensorimotor control at utterance onset. The present study attempted to examine the dynamics of event-related potentials (ERPs) to different acoustic versions of auditory feedback at mid-utterance. Methodology/Principal findings Subjects produced a vowel sound while hearing their pitch-shifted voice (100 cents), a sum of their vocalization and pure tones, or a sum of their vocalization and white noise at mid-utterance via headphones. Subjects also passively listened to playback of what they heard during active vocalization. Cortical ERPs were recorded in response to different acoustic versions of feedback changes during both active vocalization and passive listening. The results showed that, relative to passive listening, active vocalization yielded enhanced P2 responses to the 100 cents pitch shifts, whereas suppression effects of P2 responses were observed when voice auditory feedback was distorted by pure tones or white noise. Conclusion/Significance The present findings, for the first time, demonstrate a dynamic modulation of cortical activity as a function of the quality of acoustic feedback at mid-utterance, suggesting that auditory cortical responses can be enhanced or suppressed to distinguish self-produced speech from externally-produced sounds.

Developmental sex-specific change in auditory–vocal integration: ERP evidence in children

OBJECTIVE The present event-related potential (ERP) study examined the developmental mechanisms of auditory-vocal integration in normally developing children. Neurophysiological responses to altered auditory feedback were recorded to determine whether they are affected by age and sex. METHOD Forty-two children were pairwise matched for sex and were divided into a group of younger (10-12years) and a group of older (13-15years) children. Twenty healthy young adults (20-25years) also participated in the experiment. ERPs were recorded from the participants who heard their voice pitch feedback unexpectedly shifted -50, -100, or -200 cents during sustained vocalization. RESULTS P1 amplitudes became smaller as subjects increased in age from childhood to adulthood, and males produced larger N1 amplitudes than females. An age-related decrease in the P1-N1 latencies was also found: latencies were shorter in young adults than in school children. A complex age-by-sex interaction was found for the P2 component, where an age-related increase in P2 amplitudes existed only in girls, and boys produced longer P2 latencies than girls but only in the older children. CONCLUSIONS These findings demonstrate that neurophysiological responses to pitch errors in voice auditory feedback depend on age and sex in normally developing children. SIGNIFICANCE The present study provides evidence that there is a sex-specific development of the neural mechanisms involved in auditory-vocal integration.

Transfer Effect of Speech-sound Learning on Auditory-motor Processing of Perceived Vocal Pitch Errors

Speech perception and production are intimately linked. There is evidence that speech motor learning results in changes to auditory processing of speech. Whether speech motor control benefits from perceptual learning in speech, however, remains unclear. This event-related potential study investigated whether speech-sound learning can modulate the processing of feedback errors during vocal pitch regulation. Mandarin speakers were trained to perceive five Thai lexical tones while learning to associate pictures with spoken words over 5 days. Before and after training, participants produced sustained vowel sounds while they heard their vocal pitch feedback unexpectedly perturbed. As compared to the pre-training session, the magnitude of vocal compensation significantly decreased for the control group, but remained consistent for the trained group at the post-training session. However, the trained group had smaller and faster N1 responses to pitch perturbations and exhibited enhanced P2 responses that correlated significantly with their learning performance. These findings indicate that the cortical processing of vocal pitch regulation can be shaped by learning new speech-sound associations, suggesting that perceptual learning in speech can produce transfer effects to facilitating the neural mechanisms underlying the online monitoring of auditory feedback regarding vocal production.