Past studies have documented that musical tones separated by an octave interval are perceived as highly similar (“octave equivalence”). A recent study of children showed that they downshifted their fundamental frequency (F0) during a nonword imitation task to match the target, which was below their vocal ranges, at an octave above the target. This was the case for stressed syllables in all children and for unstressed syllables as well in the children without speech sound disorder (SSD). This finding was interpreted as implying that children utilize the octave equivalence effect to enhance their imitations when the target is below their vocal ranges. Here, we expand on this finding by investigating the hypothesis that octave-shifted pitch matching can also be observed in adults. Specifically, we ask whether men match a target spoken by a female adult at an octave below the target, and whether women and children match targets spoken by a male adult an octave above the target. Participants were not asked to match the pitch of the target; they were simply instructed to imitate the nonwords as they heard them. For each participant, imitation/target ratios were calculated and averaged. As in the 2008 study, the role of lexical stress and speech sound disorder (SSD) is addressed as well. Initial results show octave shifting occurred most often with the adult male participants. One woman directly pitch-matched the male target. During the remainder of this project, we will evaluate the role of lexical stress in each participant group and the role of an SSD history in the adults. We will also compare conversational F0 for each participant, drawing on the results from a companion study. Evidence of pitch matching at an octave interval implies the presence of octave based perceptual similarity in speech sounds.

Traditionally, nonword imitations have been used as a measure of phonological awareness. In a recent study of nonword imitations by children where the targets were below the children’s vocal pitch ranges, it was surprising to find that the children matched the low vocal pitch one octave above the targets (Peter et al., 2008). This was interpreted as a covert awareness of the perceptual similarities between octave-shifted vocal pitches. It was unknown whether children and adults would match pitches directly when the target is within their vocal range. This question is addressed in my current project, which also evaluates the role of lexical stress and speech sound disorder (SSD). SSD occurs when articulation and phonological mistakes continue beyond the point when the child should have mastered the sound through normal development. In a dataset collected for a multigenerational family genetics study, men, women, and children imitated nonwords produced by men and women. Each family in the study had a history of SSD represented in several members of the family. Data analysis is complete for all participants in the study. This consisted of determining the fundamental frequency for each vowel in the non-word for two different imitation tasks (Syllable Repetition Task and Tennessee Test of Rhythm and Intonation Patterns). The participant’s fundamental frequency is compared to the fundamental frequency of the target. Results indicated that the participants showed strong evidence for direct pitch matching in these tasks. I am currently working on determining conversational pitch for each individual to show that the participant is changing his/her pitch to match that of the target voice. In addition, I am determining what effect SSD has on the direct pitch-matching task. Finally, I will also consider the role of stressed verses unstressed syllables has on the expected pitch matching.

This project was conducted as part of a larger research endeavor called the Triadic Eye Gaze (TEG) project, a 5-year study funded by the National Institutes of Health. The TEG study is an ongoing investigation into the efficacy of one type of communication intervention for children 10 to 25 months of age with moderate-to-severe motor impairments and delayed expressive communication. Our project's purpose was to compare the routine interventions these children received for early signals of communication to standard clinical practices as recommended in the literature. We specifically wanted to know how much treatment the children were receiving and from which professionals, how much of that early intervention focused on communication, and how parents were involved in the treatment sessions. The population for this study was a convenience sample from the larger TEG study, comprised of 15 children with a range of disorders including cerebral palsy, several genetic syndromes, and general developmental delay. Intervention documents, including Individualized Family Service Plans, daily notes, and attendance records, were obtained for each participant from the appropriate birth-to-three center. Quantitative data reduction methods were used to determine the average number of treatment sessions per month, average minutes of treatment per month, and the proportion of total treatment time that each professional provided. Qualitative methodology was used to determine how much of the intervention focused on early communication signals and how parents were involved in this intervention. Results will be compared to clinical practices recommended in the literature. If we find inconsistencies, it will suggest that the typical treatment these children receive is not sufficient. It will be imperative to conduct further research with a larger, more in-depth study to expand upon these findings.

Childhood apraxia of speech (CAS) is a proposed motor speech disorder. At present, there is no universally accepted catalogue of diagnostic criteria for CAS. Peter & Raskind described a motor-based familial speech disorder in two multigenerational families where one or more children had a diagnosis of CAS. The current study attempted a qualitative analysis of errors made by adult members of five multigenerational families (N = 22), including the two families with the previously described motor-based speech disorder subtype, on real word and nonword repetition tasks, rapid automatic naming tasks, and measures of reading. In one family, three biologically related individuals showed slowed alternating, but not repetitive, oral movements and deficits in sequencing during multisyllabic word and nonword repetition and reading, but unimpaired naming speeds. Results are consistent with a familial CAS subtype characterized by multimodal sequencing deficits, which has implications for future diagnosis and treatment of CAS.

Adults can hear a target sound better if competing sound is modulated, or changing in amplitude over time, because they can focus on times when the competing sound level is low. Infants can do this too. However, one highly modulated sound, infant- directed speech is very attractive to infants, and it is possible that this sort of sound would distract, rather than help, them to hear a target sound. In this experiment, infants discriminate between the vowels /a/ and /i/ in the presence of either a modulated speech spectrum noise or an unmodulated speech spectrum noise. In both conditions, the speech-spectrum noise is presented at 70 dB Sound Pressure Level (SPL). The modulation of the noise is based on the modulation in samples of infant-directed speech. Seven-to-nine-month-old infants are tested using an observer-based, or conditioned response, procedure in a sound attenuated booth while seated on the caregiver’s lap. One vowel is presented repeatedly throughout the experiment. Half of the infants learn to respond when they hear the vowel change from /a/ to /i/; half learn to respond when the vowel changes from /i/ to /a/. Only the infant can hear the vowels. After training to an 80% correct criterion at an easy amplitude, infants complete 36 trials at an amplitude of 44 dB SPL, previously shown to allow infants to discriminate the vowels correctly about 70% of the time. The vowel changes on half the trials, but does not change on the other trials. An observer, blind to trial type, decides on each trial whether a change occurred or not, based on the infant’s response. The dependent variable is an unbiased measure of accuracy, d'. In theory, if infants can make use of the modulation in infant-directed speech, then their auditory sensitivity to speech would improve in the modulated noise compared to the unmodulated noise.

Over the last decade, neurofeedback has become increasingly popular as a potential treatment option for various neurodevelopmental and neurological disorders. As a completely noninvasive procedure, electroencephalographic (EEG) neurofeedback uses auditory or visual methods to provide an individual with information derived from scalp-electrode recordings of his or her own brain activity. The feedback information may relate to the spatial distribution of activation across the brain or the energy distribution across specific frequency bands. To date, no studies have been undertaken to investigate the potential use of EEG neurofeedback in the clinical management of stuttering. Stuttering is a high-prevalence (1% of the population) speech disorder that often develops into a chronic, life-long problem with severe social implications. The ultimate causes are unknown, but recent studies have revealed structural and functional neural deficits that impact sensorimotor functioning. The present project therefore aims to test the feasibility of developing EEG neurofeedback procedures that may reduce the severity of stuttering in adult participants. Initial testing with 19 data channels and BCI2000 software focuses on reliably discriminating between rest and speech or nonspeech motor activity and designing conceptually relevant feedback displays that represent the spatial or energy distribution of the recorded brain signals.  If successful, this research could have important clinical implications in the treatment of stuttering.

Adductor spasmodic dysphonia (ADSD) is a rare neurological disorder characterized by the involuntary spasm of the vocal folds, which results in an effortful, strained voice quality. This altered voice quality may result in negative reactions from speakers with ADSD as well as their communication partners. One qualitative study reported that some ADSD speakers expressed feeling inadequate, as though their “capabilities” were called into question, when conversing with others. In reality, the way in which individuals perceive a person with a communication disorder may reveal inherent biases that extend beyond voice quality. For example, when researchers manipulated the rate and pitch of a normal voice sample, listeners similarly altered their assessment of that speaker’s characteristics, such as intelligence. Literature also indicates that the more severe an individual’s voice quality, the more negatively that individual’s traits will be perceived. Additional studies have examined how listeners’ perceptions of voice quality relate to a speaker’s voice handicap; neither topic has been investigated in ADSD. Therefore, the objectives of this study are: 1) to determine whether there is a relationship between listeners’ perceptions of severity of ADSD speech with perceived speaker’s confidence; and, 2) to determine whether listeners’ ratings of speaker confidence relate to speakers’ self-rated voice handicap. Twenty speakers with ADSD were previously recorded and completed validated questionnaires (Voice Handicap Index; VHI). Twenty inexperienced listeners are enrolled in this study. These participants will listen to and judge ADSD speech samples on overall vocal effort and speaker confidence using 100 mm visual analog scales. It is hypothesized that speakers with more severely effortful voices will receive lower ratings of speaker confidence. It is also expected that more negative assessments of confidence will correlate with a speaker’s higher VHI score. Results of this study have implications for understanding the role of potential biases in ADSD outcomes.

Previous studies have shown that neurologically healthy subjects learn to generate adaptive motor commands when either sensory feedback (e.g., visual or auditory information) or the movements themselves (e.g., arm movements for reaching or jaw movements for speech) are experimentally perturbed - a phenomenon known as sensorimotor adaptation. In parallel, a different line of research has shown that for both nonspeech and speech movements the central nervous system (CNS) differentiates between self-generated and externally-caused sensory input by comparing actual and predicted inputs - a detected mismatch causes the input to be attributed increasingly to external sources. Here, we investigate these two phenomena in combination by means of two experiments that examine whether sensorimotor adaptation in speech production is diminished, or even abolished, when an auditory feedback perturbation (shifted formant frequencies) is either delivered with increasing delays or made increasingly large. Based on our own pilot data and recent findings from other labs, we hypothesize that increasing either the delay or the extent of the formant perturbation will cause the CNS to increasingly interpret the perceived error as an external manipulation rather than a production error that requires adaptive corrections in future trials. For each experiment, acoustic analyses are used to determine adjustments in subjects’ produced formant frequencies from a baseline phase (unaltered feedback) to the perturbation phase (formant-shifted feedback) across conditions varying in delay and amount of shift in the auditory feedback signal.

Despite a surge in research efforts over the past two decades, scientific understanding of the mechanisms underlying motor learning remains limited. Although many procedures have been designed to assess an individual’s ability to update motor commands in an altered environment, few attempts have been made to design procedures that assess, and possibly improve, an individual’s ability to learn a completely novel mapping of motor commands and sensory consequences. This is unfortunate because the latter approach has potential clinical applications: various brain disorders cause sensorimotor deficits, and learning alternative movement strategies may aid recovery. Whereas the above studies focused on hand or arm movements, our own research focus is on the speech motor system. The present project aims to design protocols to test and quantify the ability of the speech motor system to learn neural representations of a novel link between motor commands and sensory results. We make use of 3D electromagnetic motion capture technology that tracks 3 position coordinates and 2 angles for up to 9 sensors on the tongue, lips, and jaw; thus for a maximum of 45 dimensions. These 45 dimensions are mapped onto 2 dimensions of movement for a cursor displayed on a computer monitor. As subjects are instructed to move the cursor, their performance (i.e., learning of the novel mapping) is quantified. We will also test individuals from a clinical population (such as those with motor speech disorders or stuttering) and analyze their performance over time to design the most optimal techniques and procedures for quantifying the speech sensorimotor system’s ability to learn the complex relationship between a high-dimensional movement space and a 2D visual space.

Despite major advancements in our understanding of the neural systems involved in persistent developmental stuttering (PDS), the causal mechanisms underlying acquired neurogenic stuttering (ANS) remain poorly understood. ANS typically occurs after stroke, and its primary symptoms resemble those of PDS (i.e., within-word dysfluencies). However, individuals with ANS often show no adaptation effect and no fluency-enhancement with altered auditory feedback. To date, little is known about differences and similarities between ANS and PDS in terms of the loci of stuttering—that is, the locations of stuttering moments within spoken utterances. Brown’s research on PDS has shown that stuttering is more likely to occur on (1) longer words, (2) words that occur early in the sentence, (3) content words, and (4) words that start with a consonant. In this study, we therefore compared ANS and PDS with regard to the distribution of stuttering moments as quantified by Brown’s word weights (for each stuttered or fluent word, 0-4 points are assigned based on the aforementioned four factors). As expected, adults with PDS showed greater word weights for stuttered versus fluent words. Individuals with ANS showed a highly similar pattern with greater word weights for stuttered versus fluent words. Calculating word weights for each factor separately (word length, sentence position, grammatical class, initial consonant) revealed that the ANS group also did not differ from the PDS group in the relative influence of each individual factor. Thus, although there are several known differences between acquired neurogenic and developmental stuttering, the loci of stuttering appear to be influenced by similar factors in both disorders. Of those factors, word length and grammatical class had the strongest influence on the occurrence of dysfluencies in both groups. These findings can be used to generate new hypotheses regarding the neural basis of fluent and dysfluent speech production.

The mechanism to direct auditory attention consciously is not well understood. For hearing impaired people, it is very hard to direct attention efficiently between conversations with background noise. My project investigated the differences between maintaining and switching attention prompted by visual cues. In the behavioral task, two streams were presented simultaneously, one with high pitch and the other, low. Each stream consisted two triplets of spoken letters and the two triplets were separated by a silent gap that varied in duration. In the beginning of each trial, subjects were prompted by two spoken letters which stream (high or low) to pay attention to initially. Simultaneously, a visual cue directed subjects to either stay or switch between two streams during the silent gap period. Subjects were asked to respond when they heard the second ‘E’ from one of two streams that they attended to as quickly and accurately as possible. Preliminary results suggest that subjects needed more time to respond when they had to switch between streams. As expected, there were no differences between subjects attending to the high or low pitch stream. We also hypothesized that the shorter the gap period, the longer the response time will be—I hope to test this hypothesis through more in-depth data analysis. The result from this project will be analyzed together with neural data obtained using magnetoencephalography where subjects will be performing a similar task. The findings of this project will provide insight into the underlying mechanism of switching of auditory attention—a task that hearing impaired people find difficult to perform in a noisy environment, even with the help of hearing aids or other augmentative devices.