Speech error rates after a sports-related concussion.

Background: Alterations in speech have long been identified as indicators of various neurologic conditions including traumatic brain injury, neurodegenerative diseases, and stroke. The extent to which speech errors occur in milder brain injuries, such as sports-related concussions, is unknown. The present study examined speech error rates in student athletes after a sports-related concussion compared to pre-injury speech performance in order to determine the presence and relevant characteristics of changes in speech production in this less easily detected neurologic condition. Methods: A within-subjects pre/post-injury design was used. A total of 359 Division I student athletes participated in pre-season baseline speech testing. Of these, 27 athletes (18-22 years) who sustained a concussion also participated in speech testing in the days immediately following diagnosis of concussion. Picture description tasks were utilized to prompt connected speech samples. These samples were recorded and then transcribed for identification of errors and disfluencies. These were coded by two trained raters using a 6-category system that included 14 types of error metrics. Results: Repeated measures analysis of variance was used to compare the difference in error rates at baseline and post-concussion. Results revealed significant increases in the speech error categories of pauses and time fillers (interjections/fillers). Additionally, regression analysis showed that a different pattern of errors and disfluencies occur after a sports-related concussion (primarily time fillers) compared to pre-injury (primarily pauses). Conclusion: Results demonstrate that speech error rates increase following even mild head injuries, in particular, sports-related concussion. Furthermore, the speech error patterns driving this increase in speech errors, rate of pauses and interjections, are distinct features of this neurological injury, which is in contrast with more severe injuries that are marked by articulation errors and an overall reduction in verbal output. Future studies should consider speech as a diagnostic tool for concussion.

Effects of sensorimotor voice training on event-related potentials to pitch-shifted auditory feedback.

The pitch perturbation technique is a validated technique that has been used for over 30 years to understand how people control their voice. This technique involves altering a person's voice pitch in real-time while they produce a vowel (commonly, a prolonged /a/ sound). Although post-task changes in the voice have been observed in several studies (e.g., a change in mean fo across the duration of the experiment), the potential for using the pitch perturbation technique as a training tool for voice pitch regulation and/or modification has not been explored. The present study examined changes in event related potentials (ERPs) and voice pitch in three groups of subjects due to altered voice auditory feedback following a brief, four-day training period. Participants in the opposing group were trained to change their voice fo in the opposite direction of a pitch perturbation stimulus. Participants in the following group were trained to change their voice fo in the same direction as the pitch perturbation stimulus. Participants in the non-varying group did not voluntarily change their pitch, but instead were asked to hold their voice constant when they heard pitch perturbations. Results showed that all three types of training affected the ERPs and the voice pitch-shift response from pre-training to post-training (i.e., "hold your voice pitch steady" task; an indicator of voice pitch regulation). Across all training tasks, the N1 and P2 components of the ERPs occurred earlier, and the P2 component of the ERPs occurred with larger amplitude post-training. The voice responses also occurred earlier but with a smaller amplitude following training. These results demonstrate that participation in pitch-shifted auditory feedback tasks even for brief periods of time can modulate the automatic tendency to compensate for alterations in voice pitch feedback and has therapeutic potential.

Comparison of volitional opposing and following responses across speakers with different vocal histories.

Research has shown that people who are instructed to volitionally respond to pitch-shifted feedback either produce responses that follow the shift direction with a short latency of 100-200 ms or oppose the shift direction with longer latencies of 300-400 ms. This difference in response latencies prompted a comparison of three groups of vocalists with differing abilities, non-trained English-speaking subjects, non-trained Mandarin-speaking subjects, and trained English-speaking singers. All subjects produced short latency following responses and long latency opposing responses, and in most cases the opposing responses were preceded by a shorter latency following response. Across groups, the magnitudes of the opposing and following responses were largest for the Mandarin speakers. Singers produced the smallest opposing response magnitudes, suggesting differences in the pitch goals of the two groups. Opposing response latencies were longest for the English and Mandarin speaking subjects and shortest for the trained singers, demonstrating that musical training increases the speed of producing the opposing responses. The presence of similar latencies of small following responses preceding larger opposing responses in all groups suggests that the tendency to mimic changes in sounds to which a person is attending are not influenced by vocal training or experience.

Right Hemisphere Regions Critical for Expression of Emotion Through Prosody.

Impaired expression of emotion through pitch, loudness, rate, and rhythm of speech (affective prosody) is common and disabling after right hemisphere (RH) stroke. These deficits impede all social interactions. Previous studies have identified cortical areas associated with impairments of expression, recognition, or repetition of affective prosody, but have not identified critical white matter tracts. We hypothesized that: (1) differences across patients in specific acoustic features correlate with listener judgment of affective prosody and (2) these differences are associated with infarcts of specific RH gray and white matter regions. To test these hypotheses, 41 acute ischemic RH stroke patients had MRI diffusion weighted imaging and described a picture. Affective prosody of picture descriptions was rated by 21 healthy volunteers. We identified percent damage (lesion load) to each of seven regions of interest previously associated with expression of affective prosody and two control areas that have been associated with recognition but not expression of prosody. We identified acoustic features that correlated with listener ratings of prosody (hereafter "prosody acoustic measures") with Spearman correlations and linear regression. We then identified demographic variables and brain regions where lesion load independently predicted the lowest quartile of each of the "prosody acoustic measures" using logistic regression. We found that listener ratings of prosody positively correlated with four acoustic measures. Furthermore, the lowest quartile of each of these four "prosody acoustic measures" was predicted by sex, age, lesion volume, and percent damage to the seven regions of interest. Lesion load in pars opercularis, supramarginal gyrus, or associated white matter tracts (and not control regions) predicted lowest quartile of the four "prosody acoustic measures" in logistic regression. Results indicate that listener perception of reduced affective prosody after RH stroke is due to reduction in specific acoustic features caused by infarct in right pars opercularis or supramarginal gyrus, or associated white matter tracts.

Bioelectrical brain effects of one's own voice identification in pitch of voice auditory feedback.

Control of voice fundamental frequency (F0) relies in part on comparison of the intended F0 level and auditory feedback. This comparison impacts "sense of agency", or SoA, commonly defined as being the agent of one's own actions and plays a key role for self-awareness and social interactions. SoA is aberrant in several psychiatric disorders. Knowledge about brain activity reflecting SoA can be used in clinical practice for these disorders. It was shown that perception of voice feedback as one's own voice, reflecting the recognition of SoA, alters auditory sensory processing. Using a voice perturbation paradigm we contrasted vocal and bioelectrical brain responses to auditory stimuli that differed in magnitude: 100 and 400 cents. Results suggest the different magnitudes were perceived as a pitch error in self-vocalization (100 cents) or as a pitch shift generated externally (400 cents). Vocalizations and neural responses to changes in pitch of self-vocalization were defined as those made to small magnitude pitch-shifts (100 cents) and which did not show differential neural responses to upward versus downward changes in voice pitch auditory feedback. Vocal responses to large magnitude pitch shifts (400 cents) were smaller than those made to small pitch shifts, and neural responses differed according to upwards versus downward changes in pitch. Our results suggest that the presence of SoA for self-produced sounds may modify bioelectrical brain responses reflecting differences in auditory processing of the direction of a pitch shift. We suggest that this modification of bioelectrical response can be used as a biological index of SoA. Possible neuronal mechanisms of this modification of bioelectrical brain response are discussed.

A Randomized Comparison of the Biomechanical Effect of Two Commercially Available Rocker Bottom Shoes to a Conventional Athletic Shoe During Walking in Healthy Individuals.

Rocker bottom shoes have recently gained considerable popularity, likely in part because of the many purported benefits, including reducing joint loading and toning muscles. Scientific inquiry about these benefits has not kept pace with the increased usage of this shoe type. A fundamental premise of rocker bottom shoes is that they transform hard, flat, level surfaces into more uneven ones. Published studies have described a variety of such shoes-all having a somewhat rounded bottom and a cut heel region or a cut forefoot region, or both (double rocker). Despite the fundamentally similar shoe geometries, the reported effects of rocker bottom shoes on gait biomechanics have varied considerably. Ten healthy subjects agreed to participate in the present study and were given appropriately sized Masai Barefoot Technology (St. Louis, MO), Skechers(™) (Manhattan Beach, CA), and New Balance (Boston, MA) conventional walking shoes. After a 12-day accommodation period, the subjects walked wearing each shoe while 3-dimensional motion and force data were collected in the gait laboratory. The key findings included (1) increased trunk flexion, decreased ankle plantarflexion range, and reduced plantarflexion moment in the early stance; (2) increased ankle dorsiflexion and knee flexor moment in the midstance; (3) decreased peak ankle plantarflexion in the late stance; and (4) decreased ankle plantarflexion and decreased hip flexor and knee extensor moments in the pre-swing and into swing phase. The walking speed was unconstrained and was maintained across all shoe types. A biomechanical explanation is suggested for the observed changes. Suggestions for cautions are provided for using rocker bottom shoes in patients with neuromuscular insufficiency.

Vocal and Neural Responses to Unexpected Changes in Voice Pitch Auditory Feedback During Register Transitions.

OBJECTIVE/HYPOTHESIS: It is known that singers are able to control their voice to maintain a relatively constant vocal quality while transitioning between vocal registers; however, the neural mechanisms underlying this effect are not understood. It was hypothesized that greater attention to the acoustical feedback of the voice and increased control of the vocal musculature during register transitions compared with singing within a register would be represented as neurological differences in event-related potentials. STUDY DESIGN/METHODS: Nine singers sang musical notes at the high end of the modal register (the boundary between the modal and the head/falsetto registers) and at the low end (the boundary between the modal and the fry/pulse registers). While singing, the pitch of the voice auditory feedback was unexpectedly shifted either into the adjacent register ("toward" the register boundary) or within the modal register ("away from" the boundary). Singers were instructed to maintain a constant pitch and ignore any changes to their voice feedback. RESULTS: Vocal response latencies and magnitude of the accompanying N1 and P2 event-related potentials were greatest at the lower (modal-to-fry) boundary when the pitch shift carried the subjects' voices into the fry register as opposed to remaining within the modal register. CONCLUSIONS: These findings suggest that when a singer lowers the pitch of his or her voice such that it enters the fry register from the modal register, there is increased sensory-motor control of the voice, reflected as increased magnitude of the neural potentials to help minimize qualitative changes in the voice.

Sensory contribution to vocal emotion deficit in Parkinson's disease after subthalamic stimulation.

Subthalamic nucleus (STN) deep brain stimulation in Parkinson's disease induces modifications in the recognition of emotion from voices (or emotional prosody). Nevertheless, the underlying mechanisms are still only poorly understood, and the role of acoustic features in these deficits has yet to be elucidated. Our aim was to identify the influence of acoustic features on changes in emotional prosody recognition following STN stimulation in Parkinson's disease. To this end, we analysed the performances of patients on vocal emotion recognition in pre-versus post-operative groups, as well as of matched controls, entering the acoustic features of the stimuli into our statistical models. Analyses revealed that the post-operative biased ratings on the Fear scale when patients listened to happy stimuli were correlated with loudness, while the biased ratings on the Sadness scale when they listened to happiness were correlated with fundamental frequency (F0). Furthermore, disturbed ratings on the Happiness scale when the post-operative patients listened to sadness were found to be correlated with F0. These results suggest that inadequate use of acoustic features following subthalamic stimulation has a significant impact on emotional prosody recognition in patients with Parkinson's disease, affecting the extraction and integration of acoustic cues during emotion perception.

Event related potentials study of aberrations in voice control mechanisms in adults with attention deficit hyperactivity disorder.

OBJECTIVE: The present study was designed to test for neural signs of impulsivity related to voice motor control in young adults with ADHD using EEG recordings in a voice pitch perturbation paradigm. METHODS: Two age-matched groups of young adults were presented with brief pitch shifts of auditory feedback during vocalization. Compensatory behavioral and corresponding bioelectrical brain responses were elicited by the pitch-shifted voice feedback. RESULTS: The analysis of bioelectrical responses showed that the ADHD group had shorter peak latency and onset time of motor-related bioelectrical brain responses as compared to the controls. CONCLUSIONS: These results were interpreted to suggest differences in executive functions between ADHD and control participants. SIGNIFICANCE: We hypothesize that more rapid motor-related bioelectrical responses found in the present study may be a manifestation of impulsiveness in adults with ADHD at the involuntary level of voice control.

Talking in Fury: The Cortico-Subcortical Network Underlying Angry Vocalizations.

Although the neural basis for the perception of vocal emotions has been described extensively, the neural basis for the expression of vocal emotions is almost unknown. Here, we asked participants both to repeat and to express high-arousing angry vocalizations to command (i.e., evoked expressions). First, repeated expressions elicited activity in the left middle superior temporal gyrus (STG), pointing to a short auditory memory trace for the repetition of vocal expressions. Evoked expressions activated the left hippocampus, suggesting the retrieval of long-term stored scripts. Secondly, angry compared with neutral expressions elicited activity in the inferior frontal cortex IFC and the dorsal basal ganglia (BG), specifically during evoked expressions. Angry expressions also activated the amygdala and anterior cingulate cortex (ACC), and the latter correlated with pupil size as an indicator of bodily arousal during emotional output behavior. Though uncorrelated, both ACC activity and pupil diameter were also increased during repetition trials indicating increased control demands during the more constraint production type of precisely repeating prosodic intonations. Finally, different acoustic measures of angry expressions were associated with activity in the left STG, bilateral inferior frontal gyrus, and dorsal BG.

Understanding the mechanisms underlying voluntary responses to pitch-shifted auditory feedback.

Previous research has shown that vocal errors can be simulated using a pitch perturbation technique. Two types of responses are observed when subjects are asked to ignore changes in pitch during a steady vowel production, a compensatory response countering the direction of the perceived change in pitch and a following response in the same direction as the pitch perturbation. The present study investigated the nature of these responses by asking subjects to volitionally change their voice fundamental frequency either in the opposite direction ("opposing" group) or the same direction ("following" group) as the pitch shifts (±100 cents, 1000 ms) presented during the speaker's production of an /a/ vowel. Results showed that voluntary responses that followed the stimulus directions had significantly shorter latencies (150 ms) than opposing responses (360 ms). In addition, prior to the slower voluntary opposing responses, there were short latency involuntary responses that followed the stimulus direction. These following responses may involve mechanisms of imitation or vocal shadowing of acoustical stimuli when subjects are predisposed to respond to a change in frequency of a sound. The slower opposing responses may represent a control strategy that requires monitoring and correcting for errors between the feedback signal and the intended vocal goal.

Identifying a comparison for matching rough voice quality.

PURPOSE: Perceptual estimates of voice quality obtained using rating scales are subject to contextual biases that influence how individuals assign numbers to estimate the magnitude of vocal quality. Because rating scales are commonly used in clinical settings, assessments of voice quality are also subject to the limitations of these scales. Instead, a matching task can be used to obtain objective measures of voice quality, thereby facilitating model development and tools for clinical use. METHOD: Twenty-seven individuals participated in a rating task or at least 1 of 3 matching tests (named after their modulation functions: SINE, SQUARE, POWER) to quantify the degree of roughness in dysphonic voice stimuli. Participants evaluated the roughness of 34 voice samples using an amplitude-modulated complex carrier. RESULTS: The matching thresholds were highly correlated with the ratings estimates. Reliability of thresholds did not significantly differ across tasks, but linear regressions showed that the POWER test resulted in larger perceptual distances. CONCLUSIONS: A matching task can be used to obtain reliable estimates of roughness in dysphonic voices. The POWER comparison is recommended because the variability in matching thresholds across the range of roughness was evenly distributed, and the perceptual distances between stimuli were maximized.

Developing a single comparison stimulus for matching breathy voice quality.

PURPOSE: In this experiment, a single comparison stimulus was developed as a reference in a perceptual matching task for the quantification of breathy voice quality. Perceptual judgments of a set of synthetic voice samples were compared to previous data obtained using multiple comparison stimuli "customized" for different voices (Patel, Shrivastav, & Eddins, 2010). METHOD: Five male and 5 female samples of the vowel /a/ were selected from the Kay Elemetrics Disordered Voice Database and resynthesized using a Klatt synthesizer. Eleven samples were created for each base voice by manipulating the aspiration noise level. Five samples from each continuum were evaluated in a perceptual matching task in which a single sawtooth and noise comparison stimulus was used to obtain breathiness judgments. Linear regression was used to compare measurements obtained using the new comparison stimulus against the customized comparison stimuli. RESULTS: Results indicated that the noncustomized sawtooth comparison provides reliability and perceptual distances between stimuli similar to those obtained using customized comparison stimuli. CONCLUSION: A single-variable matching task using a single comparison stimulus can be used to obtain perceptual estimates of breathiness across voices and experiments in a laboratory setting. This technique will help develop models of voice-quality perception.

Mapping emotions into acoustic space: the role of voice production.

Research on the vocal expression of emotion has long since used a "fishing expedition" approach to find acoustic markers for emotion categories and dimensions. Although partially successful, the underlying mechanisms have not yet been elucidated. To illustrate that this research can profit from considering the underlying voice production mechanism, we specifically analyzed short affect bursts (sustained/a/vowels produced by 10 professional actors for five emotions) according to physiological variations in phonation (using acoustic parameters derived from the acoustic signal and the inverse filter estimated voice source waveform). Results show significant emotion main effects for 11 of 12 parameters. Subsequent principal components analysis revealed three components that explain acoustic variations due to emotion, including "tension," "perturbation," and "voicing frequency." These results suggest that future work may benefit from theory-guided development of parameters to assess differences in physiological voice production mechanisms in the vocal expression of different emotions.

A model for the prediction of breathiness in vowels.

The perception of breathiness in vowels is cued by multiple acoustic cues, including changes in aspiration noise (AH) and the open quotient (OQ) [Klatt and Klatt, J. Acoust. Soc. Am. 87(2), 820-857 (1990)]. A loudness model can be used to determine the extent to which AH masks the harmonic components in voice. The resulting "partial loudness" (PL) and loudness of AH ["noise loudness" (NL)] have been shown to be good predictors of perceived breathiness [Shrivastav and Sapienza, J. Acoust. Soc. Am. 114(1), 2217-2224 (2003)]. The levels of AH and OQ were systematically manipulated for ten synthetic vowels. Perceptual judgments of breathiness were obtained and regression functions to predict breathiness from the ratio of NL to PL (η) were derived. Results show that breathiness can be modeled as a power function of η. The power parameter of this function appears to be affected by the fundamental frequency of the vowel. A second experiment was conducted to determine if the resulting power function could estimate breathiness in a different set of voices. The breathiness of these stimuli, both natural and synthetic, was determined in a listening test. The model estimates of breathiness were highly correlated with perceptual data but the absolute predicted values showed some discrepancies.

Perceptual distances of breathy voice quality: a comparison of psychophysical methods.

Experiments to study voice quality have typically used rating scales or direct magnitude estimation to obtain listener judgments. Unfortunately, the data obtained using these tasks are context dependent, which makes it difficult to compare perceptual judgments of voice quality across experiments. The present experiment describes a simple matching task to quantify voice quality. The data obtained through this task were compared to perceptual judgments obtained using rating scale and direct magnitude estimation tasks to determine whether the three tasks provide equivalent perceptual distances across stimuli. Ten synthetic vowel continua that varied in terms of their aspiration noise were evaluated for breathiness using each of the three tasks. Linear and nonlinear regressions were used to compare the perceptual distances between stimuli obtained through each technique. Results show that the perceptual distances estimated from matching and direct magnitude estimation task are similar, but both differ from the rating scale task, suggesting that the matching task provides perceptual distances with ratio-level measurement properties. The matching task is advantageous for measurement of vocal quality because it provides reliable measurement with ratio-level scale properties. It allows the use of a fixed reference signal for all comparisons, thus allowing researchers to directly compare findings across different experiments.