Contemporary clinical conversations about stuttering: What does brain imaging research mean to clinicians?

PURPOSE

To discuss among neuroscientists and community speech-language pathologists what brain imaging research means to clinicians.

METHOD

Two university neuroscientists and two speech-language pathologists in private practice discussed the matter. Written conversational turns in an exchange were limited to 100 words each. When that written dialogue was concluded, each participant provided 200 words of final reflection about the matter.

RESULT

For now, neuroscience treatments are not available for clinicians to use. But sometime in the future, a critical mass of neuroscientists will likely produce such treatments. The neuroscientists expressed diverse views about the methods that might be used for that to occur.

CONCLUSION

Neuroscience does have practical clinical application at present and, in a way, that does not exclude a concurrent influence of the social model of disability. As such, the current practices of the clinicians are supported by basic neuroscience research.

Linguistic features of stuttering during spontaneous speech

PURPOSE

Previous work shows that linguistic features (e.g., word length, word frequency) impact the predictability of stuttering events. Most of this work has been conducted using reading tasks. Our study examined how linguistic features impact the predictability of stuttering events during spontaneous speech.

METHODS

The data were sourced from the FluencyBank database and consisted of interviews with 35 adult stutterers (27,009 words). Three logistic regression mixed models were fit as the primary analyses: one model with four features (i.e., initial phoneme, grammatical function, word length, and word position within a sentence), a second model with six features (i.e., the features from the previous model plus word frequency and neighborhood density), and a third model with nine features (i.e., the features from the previous model plus bigram frequency, word concreteness, and typical age of word acquisition). We compared our models using the Area Under the Curve statistic.

RESULTS

The four-feature model revealed that initial phoneme, grammatical function, and word length were predictive of stuttering events. The six-feature model revealed that initial phoneme, word length, word frequency, and neighborhood density were predictive of stuttering events. The nine-feature model was not more predictive than the six-feature model.

CONCLUSION

Linguistic features that were previously found to be predictive of stuttering during reading were predictive of stuttering during spontaneous speech. The results indicate the influence of linguistic processes on the predictability of stuttering events such that words associated with increased planning demands (e.g., longer words, low frequency words) were more likely to be stuttered.

Eliciting Stuttering in School-Age and Adolescent Stutterers in Experimental Settings

PURPOSE

Most neural and physiological research on stuttering focuses on the fluent speech of speakers who stutter due to the difficulty associated with eliciting stuttering reliably in the laboratory. We previously introduced an approach to elicit stuttered speech in the laboratory in adults who stutter. The purpose of this study was to determine whether that approach reliably elicits stuttering in school-age children and teenagers who stutter (CWS/TWS).

METHOD

Twenty-three CWS/TWS participated. A clinical interview was used to identify participant-specific anticipated and unanticipated words in CWS and TWS. Two tasks were administered: (a) a delayed word reading task in which participants read words and produced them after a 5-s delay and (b) a delayed response question task in which participants responded to examiner questions after a 5-s delay. Two CWS and eight TWS completed the reading task; six CWS and seven TWS completed the question task. Trials were coded as unambiguously fluent, ambiguous, and unambiguously stuttered.

RESULTS

The method yielded, at a group level, a near-equal distribution of unambiguously stuttered and fluent utterances: 42.5% and 45.1%, respectively, in the reading task and 40.5% and 51.4%, respectively, in the question task.

CONCLUSIONS

The method presented in this article elicited a comparable amount of unambiguously stuttered and fluent trials in CWS and TWS, at a group level, during two different word production tasks. The inclusion of different tasks supports the generalizability of our approach, which can be used to elicit stuttering in studies that aim to unravel the neural and physiological bases that underlie stuttered speech.

Activation in Right Dorsolateral Prefrontal Cortex Underlies Stuttering Anticipation

People who stutter learn to anticipate many of their overt stuttering events. Despite the critical role of anticipation, particularly how responses to anticipation shape stuttering behaviors, the neural bases associated with anticipation are unknown. We used a novel approach to identify anticipated and unanticipated words, which were produced by 22 adult stutterers in a delayed-response task while hemodynamic activity was measured using functional near infrared spectroscopy (fNIRS). Twenty-two control participants were included such that each individualized set of anticipated and unanticipated words was produced by one stutterer and one control participant. We conducted an analysis on the right dorsolateral prefrontal cortex (R-DLPFC) based on converging lines of evidence from the stuttering and cognitive control literatures. We also assessed connectivity between the R-DLPFC and right supramarginal gyrus (R-SMG), two key nodes of the frontoparietal network (FPN), to assess the role of cognitive control, and particularly error-likelihood monitoring, in stuttering anticipation. All analyses focused on the five-second anticipation phase preceding the go signal to produce speech. The results indicate that anticipated words are associated with elevated activation in the R-DLPFC, and that compared to non-stutterers, stutterers exhibit greater activity in the R-DLPFC, irrespective of anticipation. Further, anticipated words are associated with reduced connectivity between the R-DLPFC and R-SMG. These findings highlight the potential roles of the R-DLPFC and the greater FPN as a neural substrate of stuttering anticipation. The results also support previous accounts of error-likelihood monitoring and action-stopping in stuttering anticipation. Overall, this work offers numerous directions for future research with clinical implications for targeted neuromodulation.

The Relationship Between Auditory-Motor Integration, Interoceptive Awareness, and Self-Reported Stuttering Severity

Stuttering is a neurodevelopmental speech disorder associated with motor timing that differs from non-stutterers. While neurodevelopmental disorders impacted by timing are associated with compromised auditory-motor integration and interoception, the interplay between those abilities and stuttering remains unexplored. Here, we studied the relationships between speech auditory-motor synchronization (a proxy for auditory-motor integration), interoceptive awareness, and self-reported stuttering severity using remotely delivered assessments. Results indicate that in general, stutterers and non-stutterers exhibit similar auditory-motor integration and interoceptive abilities. However, while speech auditory-motor synchrony (i.e., integration) and interoceptive awareness were not related, speech synchrony was inversely related to the speaker’s perception of stuttering severity as perceived by others, and interoceptive awareness was inversely related to self-reported stuttering impact. These findings support claims that stuttering is a heterogeneous, multi-faceted disorder such that uncorrelated auditory-motor integration and interoception measurements predicted different aspects of stuttering, suggesting two unrelated sources of timing differences associated with the disorder.

The effect of gap duration on the perception of fluent versus disfluent speech

PURPOSE

Gap duration contributes to the perception of utterances as fluent or disfluent, but few studies have systematically investigated the impact of gap duration on fluency judgments. The purposes of this study were to determine how gaps impact disfluency perception, and how listener background and experience impact these judgments.

METHODS

Sixty participants (20 adults who stutter [AWS], 20 speech-language pathologists [SLPs], and 20 naïve listeners) listened to four tokens of the utterance, "Buy Bobby a puppy," produced at typical speech rates. The gap duration between "Buy" and "Bobby" was systematically manipulated with gaps ranging from 23.59 ms to 325.44 ms. Participants identified stimuli as fluent or disfluent.

RESULTS

The disfluency threshold - the point at which 50 % of trials were categorized as disfluent - occurred at a gap duration of 126.46 ms, across all participants and tokens. The SLPs exhibited higher disfluency thresholds than the AWS and the naïve listeners.

CONCLUSION

This study determined, based on the specific set of stimuli used, when the perception of utterances tends to shift from fluent to disfluent. Group differences indicated that SLPs are less inclined to identify disfluencies in speech potentially because they aim to be less critical of speech that deviates from "typical".

Adults who stutter do not stutter during private speech

PURPOSE

Adults who stutter tend not to stutter when they are alone. This phenomenon is difficult to study because it is difficult to know whether participants perceive that they are truly alone and not being heard or observed. This may explain the presence of stuttering during previous studies in which stutterers spoke while they were alone. We addressed this issue by developing a paradigm that elicited private speech, or overt speech meant only for the speaker. We tested the hypothesis that adults do not stutter during private speech.

METHOD

Twenty-four participants were audio-/video-recorded while speaking in several conditions: 1) conversational speech; 2) reading; 3) private speech, in which deception was used to increase the probability that participants produced speech intended for only themselves; 4) private speech+, for which real-time transcription was used so that participants produced the same words as in the private speech condition but while addressing two listeners; and 5) a second conversational speech condition.

RESULTS

Stuttering was not observed in more than 10,000 syllables produced during the private speech condition, except for seven possible, mild stuttering events exhibited by 3 of 24 participants. Stuttering frequency was similar for the remaining conditions.

CONCLUSIONS

Adults appear not to stutter during private speech, indicating that speakers' perceptions of listeners, whether real or imagined, play a critical and likely necessary role in the manifestation of stuttering events. Future work should disentangle whether this is due to the removal of concerns about social evaluation or judgment, self-monitoring, or other communicative processes.

Temperament is Linked to Avoidant Responses to Stuttering Anticipation

PURPOSE

The purpose of the present study was to examine the degree to which certain temperament constructs predict individual differences in three types of behavioral responses to anticipation among children and adults who stutter (CWS and AWS, respectively): avoidance, physical change, and approach.

METHODS

Participants included 64 CWS (9- to 17-years-old) and 54 AWS (18- to 50-years-old) who completed an online survey package including a temperament questionnaire (Early Adolescent Temperament Questionnaire-Revised for the CWS; Adult Temperament Questionnaire for the AWS) and the Stuttering Anticipation Scale. The data were analyzed separately for CWS and AWS using multivariate multiple regressions to assess how each temperament construct predicted avoidance, physical change, and approach responses to anticipation.

RESULTS

CWS who reported higher levels of shyness were more likely to engage in avoidant behavioral responses when they anticipate an upcoming moment of stuttering. AWS who reported higher levels of orienting sensitivity were more likely to engage in avoidant behavioral responses when they anticipate an upcoming moment of stuttering. No temperament constructs predicted physical change or approach responses to anticipation among either age group.

CONCLUSION

Specific aspects of temperament appear to be linked to the degree that CWS and AWS engage in avoidant behavioral responses to stuttering anticipation. These findings support the continued study of how individual differences impact the internal experience and outward manifestation of stuttering behaviors.

Deficit or Difference? Effects of Altered Auditory Feedback on Speech Fluency and Kinematic Variability in Adults Who Stutter

Purpose The purpose of this study was to test whether adults who stutter (AWS) display a different range of sensitivity to delayed auditory feedback (DAF). Two experiments were conducted to assess the fluency of AWS under long-latency DAF and to test the effect of short-latency DAF on speech kinematic variability in AWS. Method In Experiment 1, 15 AWS performed a conversational speaking task under nonaltered auditory feedback and 250-ms DAF. The rates of stuttering-like disfluencies, other disfluencies, and speech errors and articulation rate were compared. In Experiment 2, 13 AWS and 15 adults who do not stutter (AWNS) read three utterances under four auditory feedback conditions: nonaltered auditory feedback, amplified auditory feedback, 25-ms DAF, and 50-ms DAF. Across-utterance kinematic variability (spatiotemporal index) and within-utterance variability (percent determinism and stability) were compared between groups. Results In Experiment 1, under 250-ms DAF, the rate of stuttering-like disfluencies and speech errors increased significantly, while articulation rate decreased significantly in AWS. In Experiment 2, AWS exhibited higher kinematic variability than AWNS across the feedback conditions. Under 25-ms DAF, the spatiotemporal index of AWS decreased significantly compared to the other feedback conditions. AWS showed lower overall percent determinism than AWNS, but their percent determinism increased under 50-ms DAF to approximate that of AWNS. Conclusions Auditory feedback manipulations can alter speech fluency and kinematic variability in AWS. Longer latency auditory feedback delays induce speech disruptions, while subtle auditory feedback manipulations potentially benefit speech motor control. Both AWS and AWNS are susceptible to auditory feedback during speech production, but AWS appear to exhibit a distinct continuum of sensitivity.

Speech planning and execution in children who stutter: Preliminary findings from a fNIRS investigation

Few studies have investigated the neural mechanisms underlying speech production in children who stutter (CWS), despite the critical importance of understanding these mechanisms closer to the time of stuttering onset. The relative contributions of speech planning and execution in CWS therefore are also unknown. Using functional near-infrared spectroscopy, the current study investigated neural mechanisms of planning and execution in a small sample of 9-12 year-old CWS and controls (N = 12) by implementing two tasks that manipulated speech planning and execution loads. Planning was associated with atypical activation in bilateral inferior frontal gyrus and right supramarginal gyrus. Execution was associated with atypical activation in bilateral precentral gyrus and inferior frontal gyrus, as well as right supramarginal gyrus and superior temporal gyrus. The CWS exhibited some activation patterns that were similar to the adults who stutter (AWS) as reported in our previous study: atypical planning in frontal areas including left inferior frontal gyrus and atypical execution in fronto-temporo-parietal regions including left precentral gyrus, and right inferior frontal, superior temporal, and supramarginal gyri. However, differences also emerged. Whereas CWS and AWS both appear to exhibit atypical activation in right inferior and supramarginal gyri during execution, only CWS appear to exhibit this same pattern during planning. In addition, the CWS appear to exhibit atypical activation in left inferior frontal and right precentral gyri related to execution, whereas AWS do not. These preliminary results are discussed in the context of possible impairments in sensorimotor integration and inhibitory control for CWS.

A rapid and sensitive lateral flow immunoassay (LFIA) for the detection of gluten in foods

The gluten protein found in a variety of cereal grains is a food allergen that can elicit a spectrum of immuno-inflammatory responses in people. Consumer awareness has prompted changes in food labeling requirements, expanded gluten-free food product availability and increased demand for effective gluten testing methodologies. To meet the challenges associated with gluten testing from diverse and complex foods we developed a lateral flow immunoassay (LFIA) using a pair of novel gliadin monoclonal antibodies (MAbs). Using a visual gold reporter, we show sensitive gluten detection (150 ng/mL) from complex food substrates using a fast (<5 min) and easy testing methodology. In this report we characterize the binding properties of a cohort of newly generated gliadin monoclonal antibodies suitable for gluten detection using multiple assay formats and introduce a novel plug-n-play test strip platform with integrated test components in a single-use format.

Eliciting Stuttering in Laboratory Contexts

Purpose The contextual variability of stuttering events makes it difficult to reliably elicit stuttered speech in laboratory settings. As a result, studies that compare stuttered versus fluent speech are difficult to conduct and, thus, are limited in the literature. The purpose of the current study is to describe a novel approach to elicit stuttering during laboratory testing. Method A semistructured clinical interview leveraging the phenomenon of stuttering anticipation was administered to 22 adults who stutter (1st visit). The interview was used to generate participant-specific anticipated and unanticipated word lists, which were used as stimuli during a 2nd visit so that the validity of the method could be tested. Results The method yielded a near-equal distribution of unambiguously stuttered and fluent utterances (43.6% and 43.5%, respectively). Moreover, 12.9% of the utterances were judged to be ambiguous, that is, not unambiguously stuttered or fluent. Conclusion This approach outperformed previous attempts to elicit stuttering during laboratory testing. It could be implemented in future studies that compare neural, physiological, or behavioral correlates of fluent versus stuttered speech.

An exploratory factor analysis of action responses to stuttering anticipation

PURPOSE

We previously introduced theStuttering Anticipation Scale (SAS; Jackson, E. S., Gerlach, H., Rodgers, N. H., & Zebrowski, P. M. (2018). My Client Knows That He's About to Stutter: How Can We Address Stuttering Anticipation during Therapy with Young People Who Stutter? Seminars in Speech and Language, 39, 356-370) - a non-standardized self-report measure for children, teens, and adults who stutter (CWS, TWS, AWS) that quantifies how often they engage in 25 commonly reported action responses to anticipation. The purpose of this study was to leverage the SAS to explore the factor structure of action responses to stuttering anticipation.

METHODS

A total of 121 people who stutter completed the SAS online (27 CWS, 40 TWS, 54 AWS). We used exploratory factor analysis (EFA) to determine the underlying latent variables within the 25 SAS items that characterize how people who stutter respond to anticipation.

RESULTS

A three-factor model was most appropriate for the data with regard to factor loadings and other model fit indices. The three factors were named: avoidance (17 items), physical change (4 items), and approach (4 items).

CONCLUSION

Understanding these three types of action responses to anticipation can help guide clinical decision-making by providing a novel framework for clinicians and their clients who stutter to discuss how the client tends to respond to anticipation, and explore ways to facilitate productive responses to anticipation.

The Impact of Social-Cognitive Stress on Speech Variability, Determinism, and Stability in Adults Who Do and Do Not Stutter

Purpose

This study examined the impact of social-cognitive stress on sentence-level speech variability, determinism, and stability in adults who stutter (AWS) and adults who do not stutter (AWNS). We demonstrated that complementing the spatiotemporal index (STI) with recurrence quantification analysis (RQA) provides a novel approach to both assessing and interpreting speech variability in stuttering.

Method

Twenty AWS and 21 AWNS repeated sentences in audience and nonaudience conditions while their lip movements were tracked. Across-sentence variability was assessed via the STI; within-sentence determinism and stability were assessed via RQA.

Results

Compared with the AWNS, the AWS produced speech that was more variable across sentences and more deterministic and stable within sentences. Audience presence contributed to greater within-sentence determinism and stability in the AWS. A subset of AWS who were more susceptible to experiencing anxiety exhibited reduced across-sentence variability in the audience condition compared with the nonaudience condition.

Conclusions

This study extends the assessment of speech variability in AWS and AWNS into the social-cognitive domain and demonstrates that the characterization of speech within sentences using RQA is complementary to the across-sentence STI measure. AWS seem to adopt a more restrictive, less flexible speaking approach in response to social-cognitive stress, which is presumably a strategy for maintaining observably fluent speech.

Recurrence Quantification Analysis of Sentence-Level Speech Kinematics

PURPOSE

Current approaches to assessing sentence-level speech variability rely on measures that quantify variability across utterances and use normalization procedures that alter raw trajectory data. The current work tests the feasibility of a less restrictive nonlinear approach-recurrence quantification analysis (RQA)-via a procedural example and subsequent analysis of kinematic data.

METHOD

To test the feasibility of RQA, lip aperture (i.e., the Euclidean distance between lip-tracking sensors) was recorded for 21 typically developing adult speakers during production of a simple utterance. The utterance was produced in isolation and in carrier structures differing just in length or in length and complexity. Four RQA indices were calculated: percent recurrence (%REC), percent determinism (%DET), stability (MAXLINE), and stationarity (TREND).

RESULTS

Percent determinism (%DET) decreased only for the most linguistically complex sentence; MAXLINE decreased as a function of linguistic complexity but increased for the longer-only sentence; TREND decreased as a function of both length and linguistic complexity.

CONCLUSIONS

This research note demonstrates the feasibility of using RQA as a tool to compare speech variability across speakers and groups. RQA offers promise as a technique to assess effects of potential stressors (e.g., linguistic or cognitive factors) on the speech production system.

Effects of X-Ray Irradiation on Male Navel Orangeworm Moths (Lepidoptera: Pyralidae) on Mating, Fecundity, Fertility, and Inherited Sterility

Male adult navel orangeworm, Amyelois transitella (Walker), were irradiated using a laboratory scale x-ray irradiation unit to determine the required dose for complete egg sterility of mated female moths and inherited sterility of F1 and F2 generations. Adult male A. transitella were irradiated in two separate experiments at 100-300 Gy and 50-175 Gy. Mating frequency, fecundity, and fertility of normal females crossed with irradiated parental males was compared with the mating of nonirradiated moths. Mating frequency was 100% for females crossed with nonirradiated control males. At male treatment doses of ≥150 Gy the percentage of females found unmated increased, while multiple-mated females decreased. Female fecundity was not affected while fertility was affected in a dose-dependent relationship to exposure of parental males to x-ray irradiation. Embryonic development of eggs to the prehatch stage and egg eclosion did not occur at radiation doses ≥125 Gy. Emergence of F1 adults was low and occurred only for progeny of parental males exposed to doses ≤100 Gy, with no emergence at ≥125 Gy. Though fecundity appeared similar for control and irradiated F1 females, no F2 eggs hatched for the test exposures of 50-100 Gy. Based on our results, a dose of ≥125 Gy had efficacy in inducing both primary parental sterility in treated male moths and inherited sterility in F1 male and female moths. Results suggest that A. transitella might be considered a candidate for the sterile insect technique using adults irradiated at these relatively low x-ray exposure doses.

Responses of adults who stutter to the anticipation of stuttering

PURPOSE

Many people who stutter experience the phenomenon of anticipation-the sense that stuttering will occur before it is physically and overtly realized. A systematic investigation of how people who stutter respond to anticipation has not been previously reported. The purposes of this study were to provide self-report evidence of what people do in response to anticipation of stuttering and to determine the extent to which this anticipation occurs.

METHODS

Thirty adults who stutter indicated on a Likert rating scale the extent to which they anticipate stuttering and answered three open-ended (written) questions regarding how they respond to anticipation.

RESULTS

All participants reported experiencing anticipation at least "sometimes," and 77% of the participants reported experiencing anticipation "often" or "always." The extent to which participants reported experiencing anticipation was not related to stuttering severity, impact, or treatment history. Analysis of written responses revealed 24 major categories, which were heuristically divided into action or non-action responses. Categories representing avoidance and self-management strategies were further divided into 14 and 19 subcategories, respectively. Participants were just as likely to view anticipation as helpful as they were to view it as harmful.

CONCLUSION

Findings demonstrate that most, if not all, adults who stutter experience anticipation, and the majority of adults who stutter report doing so at least often. Adults who stutter respond to this anticipation by altering the speech production process in various ways. Results highlight the importance of the role that anticipation plays in how stuttering behaviors manifest themselves.

EDUCATIONAL OBJECTIVES

The reader will be able to: (a) summarize existing literature on the anticipation of stuttering; (b) describe the role and extent of anticipation of stuttering in adults; (c) describe the various ways that adults who stutter respond to anticipation; (d) describe the importance of measuring anticipation in clinical and research domains.

Cockroach allatostatin-immunoreactive neurons and effects of cockroach allatostatin in earwigs

A monoclonal antibody to allatostatin I of the cockroach Diploptera punctata was used to demonstrate the presence of allatostatin-immunoreactive cells and fiber tracts in the neuroendocrine system of the earwig Euborellia annulipes. The corpora cardiaca cells were not immunoreactive, nor were the neurosecretory endings of fiber tracts from the brain to the corpora cardiaca. No immunoreactive material was detected in the corpus allatum, although the corpus allatum contained neurosecretory endings, and some cells of the brain, including medial and lateral protocerebral cells, showed immunoreactivity. In addition, the recurrent and esophageal nerves were allatostatin-positive. The last abdominal ganglion contained immunoreactive somata, and immunoreactive axons of the proctodeal nerve innervated the rectum, anterior intestine, and posterior midgut. We did not detect reactive endocrine cells in the midgut. Allatostatin I at concentrations of 10(-5) and 10(-7) M did not inhibit juvenile hormone biosynthesis by E. annulipes corpora allata in vitro. This was true for glands of low activity from 2-day females and brooding females, as well as for relatively high activity glands from 10-day females. In contrast, 10(-7) M allatostatin I significantly and reversibly decreased hindgut motility. Motility was decreased in hindguts of high endogenous motility from 2-day females and in those of relatively low activity from brooding females. These results support the notion that a primary function of allatostatin might be to reduce gut motility.