Cortical dynamics of disfluency in adults who stutter

Citation: Sengupta, R., Shah, S., Loucks, T. M. J., Pelczarski, K., Scott Yaruss, J., Gore, K., & Nasir, S. M. (2017). Cortical dynamics of disfluency in adults who stutter. Physiological Reports, 5(9). doi:10.14814/phy2.13194Stuttering is a disorder of speech production whose origins have been traced to the central nervous system. One of the factors that may underlie stuttering is aberrant neural miscommunication within the speech motor network. It is thus argued that disfluency (any interruption in the forward flow of speech) in adults who stutter (AWS) could be associated with anomalous cortical dynamics. Aberrant brain activity has been demonstrated in AWS in the absence of overt disfluency, but recording neural activity during disfluency is more challenging. The paradigm adopted here took an important step that involved overt reading of long and complex speech tokens under continuous EEG recording. Anomalies in cortical dynamics preceding disfluency were assessed by subtracting out neural activity for fluent utterances from their disfluent counterparts. Differences in EEG spectral power involving alpha, beta, and gamma bands, as well as anomalies in phase-coherence involving the gamma band, were observed prior to the production of the disfluent utterances. These findings provide novel evidence for compromised cortical dynamics that directly precede disfluency in AWS. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society

Automatic determination of pauses in speech for classification of stuttering disorder

An algorithm to automatically identify segments of silence or speech is presented. The algorithm was developed to measure the silence periods in spontaneous and read speech. These silence periods are one of the parameters used to know the degree of severity of stuttered speech. For this purpose the three longer disfluent events (pauses or other disfluent events) and also the percentage of silence are useful. The algorithm is based on the evaluation of the energy and the zero crossing rate of the signal compared to the threshold values previously determined in silence. One experiment with eight subjects is described using the Stuttering Severity Instrument for Children and Adults – SSI and the percentage of silence in speech. It was concluded that the percentage of silence is good enough to separate stuttered from the normal speech but alone is not capable of measuring the degree of severity of the stuttered speech.info:eu-repo/semantics/publishedVersio

Classification of Types of Stuttering Symptoms Based on Brain Activity

Among the non-fluencies seen in speech, some are more typical (MT) of stuttering speakers, whereas others are less typical (LT) and are common to both stuttering and fluent speakers. No neuroimaging work has evaluated the neural basis for grouping these symptom types. Another long-debated issue is which type (LT, MT) whole-word repetitions (WWR) should be placed in. In this study, a sentence completion task was performed by twenty stuttering patients who were scanned using an event-related design. This task elicited stuttering in these patients. Each stuttered trial from each patient was sorted into the MT or LT types with WWR put aside. Pattern classification was employed to train a patient-specific single trial model to automatically classify each trial as MT or LT using the corresponding fMRI data. This model was then validated by using test data that were independent of the training data. In a subsequent analysis, the classification model, just established, was used to determine which type the WWR should be placed in. The results showed that the LT and the MT could be separated with high accuracy based on their brain activity. The brain regions that made most contribution to the separation of the types were: the left inferior frontal cortex and bilateral precuneus, both of which showed higher activity in the MT than in the LT; and the left putamen and right cerebellum which showed the opposite activity pattern. The results also showed that the brain activity for WWR was more similar to that of the LT and fluent speech than to that of the MT. These findings provide a neurological basis for separating the MT and the LT types, and support the widely-used MT/LT symptom grouping scheme. In addition, WWR play a similar role as the LT, and thus should be placed in the LT type

Arabic Fluency Assessment: Procedures for Assessing Stuttering in Arabic Preschool Children

The primary aim of this thesis was to screen school-aged (4+) children for two separate types of fluency issues and to distinguish both groups from fluent children. The two fluency issues are Word-Finding Difficulty (WFD) and other speech disfluencies (primarily stuttering). The cohort examined consisted of children who spoke Arabic and English. We first designed a phonological assessment procedure that can equitably test Arabic and English children, called the Arabic English non-word repetition task (AEN_NWR). Riley’s Stuttering Severity Instrument (SSI) is the standard way of assessing fluency for speakers of English. There is no standardized version of SSI for Arabic speakers. Hence, we designed a scheme to measure disfluency symptoms in Arabic speech (Arabic fluency assessment). The scheme recognizes that Arabic and English differ at all language levels (lexically, phonologically and syntactically). After the children with WFD had been separated from those with stuttering, our second aim was to develop and deliver appropriate interventions for the different cohorts. Specifically, we aimed to develop treatments for the children with WFD using short procedures that are suitable for conducting in schools. Children who stutter are referred to SLTs to receive the appropriate type of intervention. To treat WFD, another set of non-word materials was designed to include phonemic patterns not used in the speaker’s native language that are required if that speaker uses another targeted language (e.g. phonemic patterns that occur in English, but not Arabic). The goal was to use these materials in an intervention to train phonemic sequences that are not used in the child’s additional language such as the phonemic patterns that occur in English, but not Arabic. The hypothesis is that a native Arabic speaker learning English would be expected to struggle on those phonotactic patterns not used in Arabic that are required for English. In addition to the screening and intervention protocols designed, self-report procedures are desirable to assess speech fluency when time for testing is limited. To that end, the last chapter discussed the importance of designing a fluency questionnaire that can assess fluency in the entire population of speakers. Together with the AEN_NWR, the brief self-report instrument forms a package of assessment procedures that facilitate screening of speech disfluencies in Arabic children (aged 4+) when they first enter school. The seven chapters, described in more detail below, together constitute a package that achieves the aims of identifying speech problems in children using Arabic and/or English and offering intervention to treat WFD

Variability, Stability, and Flexibility in the Speech Kinematics and Acoustics of Adults Who Do and Do Not Stutter

It is well known that people who do and do not stutter produce speech differently, at least some of the time, even when perceived as fluent. One way that investigators have assessed these differences is by measuring variability, or the inconsistency of repeated speech movements. Variability in speech has typically been quantified using linear analysis techniques (e.g., measures of central tendency), and results have indicated that people who stutter produce speech that is (sometimes) characterized by increased variability. However, variability is a complex phenomenon, one that cannot be assessed by linear methods alone. This dissertation employs linear and nonlinear analysis techniques to examine the nature of variability, stability, and flexibility in stuttering and non-stuttering speakers. Two experiments are reported in this dissertation. The first is a pilot study in which 11 participants judged short utterances that were manipulated in gap (or pause) duration to be fluent or disfluent. This preliminary study facilitated the selection of \u27fluent\u27 utterances for the primary experiment, which measured lip aperture kinematics and acoustics for 20 speakers who stutter and 21 speakers who do not stutter, under two manipulations: 1) audience and non-audience; 2) increasing linguistic complexity. Results from the primary experiment corroborated results from prior studies that used linear techniques to show that 1) adults who stutter exhibit more effector variability than adults who do not stutter when target utterances are embedded in sentences of increased linguistic complexity, and 2) linear acoustic measures are as effective as linear kinematic measures for quantifying variability. Nonlinear analysis techniques demonstrated that adults who stutter exhibit more deterministic structure in lip aperture dynamics. Furthermore, cognitive-emotional stress (i.e., the presence of an audience) resulted in decreased surface variability, increased deterministic structure, decreased stationarity, and decreased signal complexity in speakers who stutter, but not in those who do not stutter. Thus, adults who stutter appear to exhibit less overall stability, which leads to a more rigid, less flexible approach to speech production, especially when cognitive-emotional stressors are placed on their speech motor systems. These findings highlight the benefits of using nonlinear analysis techniques to examine variability in speech production. Specifically, the results demonstrated that speech movements that appear to be less variable on the surface, may in fact be overly deterministic and nonstationary\u27two attributes that indicate system instability in complex biological systems. Thus, a combination of linear and nonlinear approaches is warranted in future investigations of speech production

Perceptions, Thoughts, And Feelings, Of Women Who Stutter In Four Life Domains

I explored how stuttering affects adult women in aspects of their life in 4 domains: social, occupational, academic, and financial. The literature contains few studies on adult women who stutter, and this research addressed these women regarding the kinds of problems they have encountered in their lives. The results of this phenomenological study identified the perceptions, thoughts, and feelings of adult women who stutter regarding how their speech disorder affected them in the 4 domains. The theoretical orientation used for this study was positive psychology. Positive psychology reflects how women who stutter used positive coping strategies to move forward, despite being confronted by harsh conditions in 4 life domains. I explored the positive coping strategies these adult women used in each of these areas of their lives. The participants ranged in age from 26 to 66. The recruitment for the participants took place through the Stuttering Foundation website. The interviews were conducted via Skype and focused on lived experiences of women who stutter in 4 life domains and what positive coping strategies they use. I audio recorded interviews for 10 participants. I transcribed the interviews, and identified, and analyzed the meaning units. I assigned the meaning units ideographic themes. I renamed reoccurring idiographic themes to nomothetic themes. The key findings indicated that stuttering consistently interfered with women in 4 life domains: social, financial, academic, and occupational. This phenomenological study might lead to positive social change through education about stuttering that comes from a personal level of lived experiences. This work contributes to the advancement of science for future studies to research other aspects of stuttering

AN ARTICULATORY-ACOUSTIC INVESTIGATION OF TIMING AND COORDINATION IN THE FLUENT SPEECH OF PEOPLE WHO STAMMER

This thesis investigates Wingate’s Fault-Line hypothesis (1988) which suggests that disfluencies in people who stammer (PWS) result from a deficit in transition from consonant to vowel (CV) thereby implying that stammering as a motor-control disorder would affect transitions even when not perceptually salient. To test this proposal, we explored the perceptually fluent speech of PWS using instrumental analysis (ultrasound and acoustic) to determine the underlying pervasiveness of disfluencies in this group as compared to people who do not stammer (PNS). Following fluency screening of recorded utterances, we applied acoustic and articulatory analysis techniques to perceptually fluent utterances of 9 PWS and 9 typical speakers in order to identify indicators of disfluency in the transition from syllable onsets to the following vowel. Measures of acoustic duration, locus equation and formant slope offer insights into timing and degree of coarticulation. The articulatory ultrasound tongue imaging technique moreover provides kinematic information of the tongue. A novel technique was applied to dynamically analyse and quantify the tongue kinematics in transition. This allowed us to treat the perceptually fluent speech of PWS as an ongoing time-situated process. Both acoustic and articulatory findings indicate by-group differences in timing, whereby PWS are overall slower and more variable in the execution of CV transitions when compared to typical speakers (PNS). The findings from both instrumental approaches also indicate differences in coordination, suggesting that PWS coarticulate to a lesser extent than PNS. Overall, these findings suggest that PWS exhibit a global deficit in CV transition that can be observed in perceptually fluent as well as stammered speech. This is in keeping with the predictions of Wingate’s Fault-Line hypothesis. iv The fact that the conclusions from the acoustic and articulatory measures are coherent, shows that acoustic measures may be sufficient to act as a proxy for articulatory measures