Changes in reliance on auditory feedback cues as a function of oral practice.

A role for auditory feedback in maintaining fluency appears less specific than for pitch control, as one example, but delayed auditory feedback (DAF) clearly provides a potent manipulation of fluency. As most speakers are susceptible to DAF, we predicted DAF is particularly suited to identifying individual differences in auditory-motor integration. We conducted a series of studies to probe susceptibility to DAF-induced disfluency in 60 normally fluent speakers during conversation and oral reading. We further contrasted DAF effects on fluency with dual-task effects on fluency. During conversation and reading under DAF (250 ms delay), multivariate cluster classification indicated speakers show high, low, or intermediate susceptibility to disfluency. In contrast, dual-task effects on fluency appeared bimodal with individuals showing high or low susceptibility. DAF susceptibility was not related to dual-task disfluency in 41/60 speakers, but the remaining speakers were disfluent under DAF and dual-task conditions. When the DAF paradigm was extended to adults who stutter, most were classified as highly susceptible. The findings provide compelling evidence that individual differences need to be considered in auditory-motor integration research. Fluency is influenced by both auditory feedback and cognitive factors related to attention, which can inform theories of normal and disordered speech.

The complementary view of strategy combinations points to the fact that a combination of strategies that promote memory encoding and retrieval practice strategies can be effective in improving memory retention. This study examines the effectiveness of the combination of oral reading and retrieval practice strategies and the effect of the development of reading patterns on their effectiveness. This study designed a mixed experimental design of 3 (grades: Grade three, Grade five, college students) × 2 (reading mode: oral reading and silent reading) × 2 (learning strategies: re-learning and retrieval practice). Among them, reading mode is the within-subject variable, and learning strategy and grade are the between-subjects variables. The dependent variable is the ratio of specific words recalled in the final test. The results show that the oral and retrieval practice is a significant and effective combination of memory strategies for primary school students who are mainly oral reading or in the transition from oral reading to silent reading. It is significantly better than the three strategy combinations of oral reading combined with re-leaning, silent reading combined with re-learning, and silent reading combined with retrieval practice. For adult students who dominated silent reading, silent reading combined with retrieval practice is the best memory strategy.

Electromyographic changes with delayed auditory feedback of speech

39 3- to 6-yr.-old children counted to 10 or recited the alphabet with normal auditory feedback, and delays of 150, 350, and 550 msec. There were no age differences. In addition to affecting rate of speech, delay differentially influenced the prosody, intelligibility, and content of utterances. For both tasks and all delay intervals, delay slowed speaking and produced more prosodic disturbances than no delay. More disturbances of intelligibility occurred at the 350- and 550-msec. delays than under no or 150-msec. delay. Disturbances in the content of counting were greater than in the no-delay condition but did not differ across delays. For alphabet recitation, disturbances in content under delay were greater than under no delay and were greater at 350 and 550 msec. than at 150 msec. Thirty-four children lost track of what they were doing; 10 articulated confusion. Children as young as 3 years of age concurrently self-monitor their speech for content.

Vocal control plays a critical role in smooth social communication. Speakers constantly monitor auditory feedback (AF) and make adjustments when their voices deviate from their intentions. Previous studies have shown that when certain acoustic features of the AF are artificially altered, speakers compensate for this alteration in the opposite direction. However, little is known about how the vocal control system implements compensations for alterations of different acoustic features, and associates them with subjective consciousness. The present study investigated whether compensations for the fundamental frequency (F0), which corresponds to perceived pitch, and formants, which contribute to perceived timbre, can be performed unconsciously and independently. Forty native Japanese speakers received two types of altered AF during vowel production that involved shifts of either only the formant frequencies (formant modification; Fm) or both the pitch and formant frequencies (pitch + formant modification; PFm). For each type, three levels of shift (slight, medium, and severe) in both directions (increase or decrease) were used. After the experiment, participants were tested for whether they had perceived a change in the F0 and/or formants. The results showed that (i) only formants were compensated for in the Fm condition, while both the F0 and formants were compensated for in the PFm condition; (ii) the F0 compensation exhibited greater precision than the formant compensation in PFm; and (iii) compensation occurred even when participants misperceived or could not explicitly perceive the alteration in AF. These findings indicate that non-experts can compensate for both formant and F0 modifications in the AF during vocal production, even when the modifications are not explicitly or correctly perceived, which provides further evidence for a dissociation between conscious perception and action in vocal control. We propose that such unconscious control of voice production may enhance rapid adaptation to changing speech environments and facilitate mutual communication.

Neurobiology of speaking and stuttering

Zebra finches memorize a tutor song as juveniles, and then faithfully reproduce this song for the remainder of their lives. This thesis investigates how the intricate and concerted activity of ensembles of neurons in the zebra finch brain gives rise to this complex behavior. The first section of the thesis demonstrates how neurons in RA, a pre-motor song control nucleus, coordinate their activity to generate the instantaneous spectral and temporal structure seen in the song. Similar sounds are produced by entirely different ensembles of RA neurons. Additionally, rapidly changing patterns of RA neural activity are capable of generating constant acoustic outputs. This is a new form of neural coding, previously unobserved in any other system. This unusual neural representation provides a concise account of an unexplained aspect of song learning. The second part of the thesis develops a new, noninvasive method of altering the auditory feedback heard by singing zebra finches. This type of feedback perturbation causes the normally stable songs of adult birds to deteriorate, indicating that auditory feedback is essential to song control throughout life. Restoration of the normal auditory feedback heard by these birds enables the gradual recovery of their original songs, demonstrating that a memory of the original song persists in the song control system despite the destabilization of the behavior. The song is thus maintained by an active feedback control process. The final project investigates the role of nucleus LMAN in real-time song control via auditory feedback. Neurons in nucleus LMAN were previously believed to compare auditory feedback to a memorized song template. The result of this comparison was thought to be used as an error-correction signal to update the motor control program. By recording from individual LMAN neurons while simultaneously manipulating the auditory feedback heard by the singing bird, it is shown that during singing, rather than auditory feedback, LMAN processes an efference copy of the motor commands used to generate the bird's song. This suggests a different model of the system, in which the efference copy is the basis of the real-time error-correction signal. Taken together, these three projects significantly expand our knowledge of the neural mechanisms responsible for the generation of birdsong.

Effects of auditory feedback on movements with two-segment sequence and eye-hand coordination: Using a short auditory contact cue

Two auditory feedback perturbation experiments were conducted to examine the nature of control of the first two formants in vowels. In the first experiment, talkers heard their auditory feedback with either F1 or F2 shifted in frequency. Talkers altered production of the perturbed formant by changing its frequency in the opposite direction to the perturbation but did not produce a correlated alteration of the unperturbed formant. Thus, the motor control system is capable of fine-grained independent control of F1 and F2. In the second experiment, a large meta-analysis was conducted on data from talkers who received feedback where both F1 and F2 had been perturbed. A moderate correlation was found between individual compensations in F1 and F2 suggesting that the control of F1 and F2 is processed in a common manner at some level. While a wide range of individual compensation magnitudes were observed, no significant correlations were found between individuals' compensations and vowel space differences. Similarly, no significant correlations were found between individuals' compensations and variability in normal vowel production. Further, when receiving normal auditory feedback, most of the population exhibited no significant correlation between the natural variation in production of F1 and F2.

Speech production involves a combination of feedforward and sensory feedback-based control mechanisms. The latter have been characterized in experiments involving real-time perturbations during speech. Unexpected perturbations of auditory feedback result in corrective motor responses with a minimum latency of approximately 100 ms after perturbation onset. These responses have been shown for both pitch and formant frequency perturbations, and the responsible neural circuitry includes portions of the superior temporal gyrus and ventral premotor cortex (vPMC). Corrective responses to somatosensory perturbations (such as a downward force applied to the jaw) occur approximately 50 ms after perturbation onset and are mediated by ventral somatosensory cortex and vPMC. The degree to which an individual weights auditory versus somatosensory feedback varies substantially. Such differences rely in part on differences in sensory acuity, e.g., a speaker with relatively poor hearing is likely to rely more heavily on somatosensory feedback control mechanisms than auditory feedback control mechanisms. Additionally, reliance on feedback control may be modulated to compensate for impairments in the feedforward system for speech, e.g., adults who stutter show a reduced reliance on auditory feedback control compared to fluent speakers, perhaps because auditory feedback can have a deleterious effect on speech initiation in stuttering.

Visual and auditory feedback cues have been shown to improve gait and balance in patients with movement disorders, such as Parkinson's disease and multiple sclerosis. Subsequently, closed-loop virtual reality was used to enhance the gait improvement effect of such cues. Objectives: To study the effects of gait training with visual and auditory feedback cues on the walking abilities of patients with gait disorders due to cerebral palsy. Methods: Visual and auditory feedback cues were generated by a wearable accelerometry-driven device. Ten randomly selected patients with gait disorders due to cerebral palsy trained with visual feedback cues while ten such patients trained with auditory feedback cues. Baseline performance (walking speed and stride length along a 10 m straight track) was measured before device use. Following 20 min training with the device, performance without the device was measured again and compared to the baseline performance. Results: For patients training with visual feedback, the average improvement in walking speed was 21.70%+/-36.06% and in stride length 8.72%plusmn9.47%. For patients training with auditory feedback, average improvement in walking speed was 25.43%plusmn28.65% and in stride length 13.58%plusmn13.10%. Conclusion: Visual and auditory feedback cues can improve gait parameters in patients with gait disorders due to cerebral palsy.

The neural responses to sensory consequences of a self-produced motor act are suppressed compared with those in response to a similar but externally generated stimulus. Previous studies in the somatosensory and auditory systems have shown that the motor-induced suppression of the sensory mechanisms is sensitive to delays between the motor act and the onset of the stimulus. The present study investigated time-dependent neural processing of auditory feedback in response to self-produced vocalizations. ERPs were recorded in response to normal and pitch-shifted voice auditory feedback during active vocalization and passive listening to the playback of the same vocalizations. The pitch-shifted stimulus was delivered to the subjects' auditory feedback after a randomly chosen time delay between the vocal onset and the stimulus presentation. Results showed that the neural responses to delayed feedback perturbations were significantly larger than those in response to the pitch-shifted stimulus occurring at vocal onset. Active vocalization was shown to enhance neural responsiveness to feedback alterations only for nonzero delays compared with passive listening to the playback. These findings indicated that the neural mechanisms of auditory feedback processing are sensitive to timing between the vocal motor commands and the incoming auditory feedback. Time-dependent neural processing of auditory feedback may be an important feature of the audio-vocal integration system that helps to improve the feedback-based monitoring and control of voice structure through vocal error detection and correction.

Human-machine interface (HMI) designs offer the possibility of improving quality of life for patient populations as well as augmenting normal user function. Despite pragmatic benefits, utilizing auditory feedback for HMI control remains underutilized, in part due to observed limitations in effectiveness. The goal of this study was to determine the extent to which categorical speech perception could be used to improve an auditory HMI. Using surface electromyography, 24 healthy speakers of American English participated in 4 sessions to learn to control an HMI using auditory feedback (provided via vowel synthesis). Participants trained on 3 targets in sessions 1–3 and were tested on 3 novel targets in session 4. An “established categories with text cues” group of eight participants were trained and tested on auditory targets corresponding to standard American English vowels using auditory and text target cues. An “established categories without text cues” group of eight participants were trained and tested on the same targets using only auditory cuing of target vowel identity. A “new categories” group of eight participants were trained and tested on targets that corresponded to vowel-like sounds not part of American English. Analyses of user performance revealed significant effects of session and group (established categories groups and the new categories group), and a trend for an interaction between session and group. Results suggest that auditory feedback can be effectively used for HMI operation when paired with established categorical (native vowel) targets with an unambiguous cue.

ABSTRACTThe history of reading is a comparatively recent field. Work to date has been diverse both in period and methodology, ranging from case studies of individuals to statistical analyses of populations. This diversity means that it can be hard to discern either a broadly agreed narrative of reading practices or a clear set of debates. However, a range of scholars have emphasized contrasts between intensive and extensive reading, oral and silent reading, utilitarian and recreational reading, and public and private reading. These contrasts have been aligned with historical periods, with oral reading, for example, being associated with early modern reading in contrast to later periods. This article analyses the reading practices of Samuel Pepys and concludes that his example supports a contrast between a more intensive, oral, utilitarian, and public reading in the seventeenth century and that of later periods. Pepys's reading practices are also shown to have profound effects on his interpretation of texts. He sees texts of all genres as scripts to be performed by particular individuals, and judges them according to their suitability for this performance in a specific context.

Speakers change the level of their voice when they listen to noise or hear their own speech amplified: When noise level is increased the voice becomes louder, whilst the response to speech amplification is a reduction of voice level. The question posed here is whether, when the level of various sounds concurrent with vocalisation is raised, the direction of the vocal level response is like that to the speaker's speech or like that to noise. Voice level was measured in response to speech, white noise, delayed auditory feedback, frequency-shifted speech, and noise created by an "Edinburgh masker". Selection of these sounds was governed by the role they have played in the explanation and treatment of stuttering. Fluent speakers and stutterers increased voice level when played delayed auditory feedback, the Edinburgh masker, or white noise; they reduced the level slightly in the remaining conditions. These results are used to assess auditory feedback monitoring accounts of the speech behavior of fluent speakers and stutterers, and some implications for the treatment of stuttering are pointed out.