Sequence skill learning in persons who stutter: implications for cortico-striato-thalamo-cortical dysfunction

The basal ganglia and cortico-striato-thalamo-cortical connections are known to play a critical role in sequence skill learning and increasing automaticity over practice. The current paper reviews four studies comparing the sequence skill learning and the transition to automaticity of persons who stutter (PWS) and fluent speakers (PNS) over practice. Studies One and Two found PWS to have poor finger tap sequencing skill and nonsense syllable sequencing skill after practice, and on retention and transfer tests relative to PNS. Studies Three and Four found PWS to be significantly less accurate and/or significantly slower after practice on dual tasks requiring concurrent sequencing and colour recognition over practice relative to PNS. Evidence of PWS’ deficits in sequence skill learning and automaticity development support the hypothesis that dysfunction in cortico-striato-thalamo-cortical connections may be one etiological component in the development and maintenance of stuttering.

Educational objectives: As a result of this activity, the reader will: (1) be able to articulate the research regarding the basal ganglia system relating to sequence skill learning; (2) be able to summarize the research on stuttering with indications of sequence skill learning deficits; and (3) be able to discuss basal ganglia mechanisms with relevance for theory of stuttering.     

Bimanual handedness in adults who stutter

25 adult stutterers and 29 nonstutterers who were right-handed as defined by a positive Laterality Quotient on the Edinburgh Handedness Inventory were compared with respect to their pattern of hand use in performing seven common tasks that involve bimanual cooperation. Among the stutterers was a higher proportion of participants who showed anomalies in how they carried out the two tasks that required synchronous manipulation by the two hands. On two other tasks that required speeded performance, the groups were similar in dealing playing cards with the right or left hands, but the stutterers were slower than nonstutterers and did not show a right-hand advantage on a task requiring removal of a nut from a bolt. The results were interpreted as indicating difficulty by stutterers in carrying out synchronously different response elements of motoric tasks.     

Phonological priming in adults who stutter

The purpose of this study was to compare the speed of phonological encoding between adults who stutter (AWS) and adults who do not stutter (ANS). Fifteen male AWS and 15 age- and gender-matched ANS participated in the study. Speech onset latency was obtained for both groups and stuttering frequency was calculated for AWS during three phonological priming tasks: (1) heterogeneous, during which the participants' single-word verbal responses differed phonemically; (2) C-homogeneous, during which the participants' response words shared the initial consonant; and (3) CV-homogeneous, during which the participants' response words shared the initial consonant and vowel. Response words containing the same C and CV patterns in the two homogeneous conditions served as phonological primes for one another, while the response words in the heterogeneous condition did not. During each task, the participants produced a verbal response after being visually presented with a semantically related cue word, with cue-response pairs being learned beforehand. The data showed that AWS had significantly longer speech onset latency when compared to ANS in all priming conditions, priming had a facilitating effect on word retrieval for both groups, and there was no significant change in stuttering frequency across the conditions for AWS. This suggests that phonological encoding may play no role, or only a minor role, in stuttering. EDUCATIONAL OBJECTIVES: The reader will be able to: (1) describe previous research paradigms that have been used to assess phonological encoding in adults and children who stutter; (2) explain performance similarities and differences between adults who do and do not stutter during various phonological priming conditions; (3) compare the present findings to past research that examined the relationship between phonological encoding and stuttering.     

The transition to increased automaticity during finger sequence learning in adult males who stutter

The present study compared the automaticity levels of persons who stutter (PWS) and persons who do not stutter (PNS) on a practiced finger sequencing task under dual task conditions. Automaticity was defined as the amount of attention required for task performance. Twelve PWS and 12 control subjects practiced finger tapping sequences under single and then dual task conditions. Control subjects performed the sequencing task significantly faster and less variably under single versus dual task conditions while PWS' performance was consistently slow and variable (comparable to the dual task performance of control subjects) under both conditions. Control subjects were significantly more accurate on a colour recognition distracter task than PWS under dual task conditions. These results suggested that control subjects transitioned to quick, accurate and increasingly automatic performance on the sequencing task after practice, while PWS did not. Because most stuttering treatment programs for adults include practice and automatization of new motor speech skills, findings of this finger sequencing study and future studies of speech sequence learning may have important implications for how to maximize stuttering treatment effectiveness. Educational objectives: As a result of this activity, the participant will be able to: (1) Define automaticity and explain the importance of dual task paradigms to investigate automaticity; (2) Relate the proposed relationship between motor learning and automaticity as stated by the authors; (3) Summarize the reviewed literature concerning the performance of PWS on dual tasks; and (4) Explain why the ability to transition to automaticity during motor learning may have important clinical implications for stuttering treatment effectiveness.     

Self-efficacy and quality of life in adults who stutter

PurposeSelf-efficacy has emerged as a potential predictor of quality of life for adults who stutter. Research has focused primarily on the positive relationship self-efficacy has to treatment outcomes, but little is known about the relationship between self-efficacy and quality of life for adults who stutter. The purpose of this mixed- methods study is to determine the predictive value of self-efficacy and its relationship to quality of life for adults who stutter.MethodThe Self-Efficacy Scale for Adult Stutterers and the Overall Assessment of the Speaker’s Experience with Stuttering were administered to 39 adults who stutter, aged 18– 77. Percentage of syllables stuttered was calculated from a conversational speech sample as a measure of stuttered speech frequency. Qualitative interviews with semi-structured probes were conducted with 10 adults and analyzed using thematic analysis to explore the lived experience of adults who stutter.ResultsSelf-efficacy emerged as a strong positive predictor of quality of life for adults living with a stuttered speech disorder. Stuttered speech frequency was a moderate negative predictor of self-efficacy. Major qualitative themes identified from the interviews with the participants were: encumbrance, self-concept, confidence, acceptance, life-long journey, treatment, and support.ConclusionResults provide clarity on the predictive value of self-efficacy and its relationship to quality of life and stuttered speech frequency. Findings highlight that the unique life experiences of adults who stutter require a multidimensional approach to the assessment and treatment of stuttered speech disorders.     

Auditory‐motor adaptation is reduced in adults who stutter but not in children who stutter

Previous studies have shown that adults who stutter produce smaller corrective motor responses to compensate for unexpected auditory perturbations in comparison to adults who do not stutter, suggesting that stuttering may be associated with deficits in integration of auditory feedback for online speech monitoring. In this study, we examined whether stuttering is also associated with deficiencies in integrating and using discrepancies between expected and received auditory feedback to adaptively update motor programs for accurate speech production. Using a sensorimotor adaptation paradigm, we measured adaptive speech responses to auditory formant frequency perturbations in adults and children who stutter and their matched nonstuttering controls. We found that the magnitude of the speech adaptive response for children who stutter did not differ from that of fluent children. However, the adaptation magnitude of adults who stutter in response to auditory perturbation was significantly smaller than the adaptation magnitude of adults who do not stutter. Together these results indicate that stuttering is associated with deficits in integrating discrepancies between predicted and received auditory feedback to calibrate the speech production system in adults but not children. This auditory‐motor integration deficit thus appears to be a compensatory effect that develops over years of stuttering.     

Speech sound articulation abilities of preschool-age children who stutter

Purpose

The purpose of this study was to assess the association between speech sound articulation and childhood stuttering in a relatively large sample of preschool-age children who do and do not stutter, using the Goldman–Fristoe Test of Articulation-2 (GFTA-2; Goldman & Fristoe, 2000).

Method

Participants included 277 preschool-age children who do (CWS; n = 128, 101 males) and do not stutter (CWNS; n = 149, 76 males). Generalized estimating equations (GEE) were performed to assess between-group (CWS versus CWNS) differences on the GFTA-2. Additionally, within-group correlations were performed to explore the relation between CWS’ speech sound articulation abilities and their stuttering frequency and severity, as well as their sound prolongation index (SPI; Schwartz & Conture, 1988).

Results

No significant differences were found between the articulation scores of preschool-age CWS and CWNS. However, there was a small gender effect for the 5-year-old age group, with girls generally exhibiting better articulation scores than boys. Additional findings indicated no relation between CWS’ speech sound articulation abilities and their stuttering frequency, severity, or SPI.

Conclusions

Findings suggest no apparent association between speech sound articulation—as measured by one standardized assessment (GFTA-2)—and childhood stuttering for this sample of preschool-age children (N = 277).Educational objectives: After reading this article, the reader will be able to: (1) discuss salient issues in the articulation literature relative to children who stutter; (2) compare/contrast the present study's methodologies and main findings to those of previous studies that investigated the association between childhood stuttering and speech sound articulation; (3) identify future research needs relative to the association between childhood stuttering and speech sound development; (4) replicate the present study's methodology to expand this body of knowledge.     

Avoidance of eye gaze by adults who stutter

PurposeAdults who stutter are at significant risk of developing social phobia. Cognitive theorists argue that a critical factor maintaining social anxiety is avoidance of social information. This avoidance may impair access to positive feedback from social encounters that could disconfirm fears and negative beliefs. Adults who stutter are known to engage in avoidance behaviours, and may neglect positive social information. This study investigated the gaze behaviour of adults who stutter whilst giving a speech.Method16 adults who stutter and 16 matched controls delivered a 3-min speech to a television display of a pre-recorded lecture theatre audience. Participants were told the audience was watching them live from another room. Audience members were trained to display positive, negative and neutral expressions. Participant eye movement was recorded with an eye-tracker.ResultsThere was a significant difference between the stuttering and control participants for fixation duration and fixation count towards an audience display. In particular, the stuttering participants, compared to controls, looked for shorter time at positive audience members than at negative and neutral audience members and the background.ConclusionsAdults who stutter may neglect positive social cues within social situations that could serve to disconfirm negative beliefs and fears.Educational objectives: The reader will be able to: (a) describe the nature of anxiety experienced by adults who stutter; (b) identify the most common anxiety condition among adults who stutter; (c) understand how information processing biases and the use of safety behaviours contribute to the maintenance of social anxiety; (d) describe how avoiding social information may contribute to the maintenance of social anxiety in people who stutter; and (e) describe the clinical implications of avoidance of social information in people who stutter.     

Cognitive control of action naming in adults who stutter

PurposeBased on previous evidence that cognitive control of lexical selection in object (noun) naming operates differently in adults who stutter (AWS) versus typically-fluent adults (TFA), the aim was to investigate cognitive control of lexical selection in action (verb) naming in AWS.Method12 AWS and 12 TFA named line drawings depicting actions using verbs. Half of the pictures had high-agreement action names and the other half low-agreement action names. Naming accuracy and reaction times (RT), and event-related potentials (ERPs) time-locked to picture onset, were compared between groups.ResultsNaming RTs were slower for low- versus high-agreement trials, and the magnitude of this effect was larger in AWS versus TFA. Delta-plot analysis of naming RTs revealed that individual differences in selective inhibition were associated with the agreement effect on naming RTs in AWS but not TFA. Action naming elicited frontal-central N2 activity in both agreement conditions in TFA but not AWS. Additionally, a later, posterior P3b component was affected by agreement in TFA only. In AWS, low-agreement action naming elicited frontal P3a activation.ConclusionsResults suggest that cognitive control of action name selection was qualitatively different between groups. In TFA, cognitive control of lexical selection in action naming involved nonselective inhibition, as well as more efficient working memory updating on high- versus low-agreement trials. In AWS, cognitive control of low-agreement action naming involved increased focal attention. Individual differences in selective inhibition may have moderated cognitive control of action naming in AWS.     

Investigating speech motor practice and learning in people who stutter

In this exploratory study, we investigated whether or not people who stutter (PWS) show motor practice and learning changes similar to those of people who do not stutter (PNS). To this end, five PWS and five PNS repeated a set of non-words at two different rates (normal and fast) across three test sessions (T1, T2 on the same day and T3 on a separate day, at least 1 week apart). The results indicated that PWS and PNS may resemble each other on a number of performance variables (such as movement amplitude and duration), but they differ in terms of practice and learning on variables that relate to movement stability and strength of coordination patterns. These findings are interpreted in support of recent claims about speech motor skill limitations in PWS.

Educational objectives: The reader will be able to: (1) define oral articulatory changes associated with motor practice and learning and their measurement; (2) summarize findings from previous studies examining motor practice and learning in PWS; and (3) discuss hypotheses that could account for the present findings that suggest PWS and PNS differ in their speech motor learning abilities.     

Self-efficacy beliefs: Experiences of adults who stutter

PurposeChildhood-onset stuttering is a complex and multifaceted disorder. Intervention for adults who stutter has historically addressed speech fluency more so than psychosocial aspects of the disorder, including the nature of the individual’s self-efficacy beliefs concerning their confidence in their capacity to enact change. Self-efficacy is an important construct related to quality of life, resilience, and maintenance of treatment gains for adults who stutter. The purpose of this qualitative study is to explore the nature of the self-efficacy beliefs expressed by adults who stutter in order to inform efficacious and holistic intervention for these individuals.MethodSemi-structured interviews were conducted with 29 adults who stutter to describe their experiences as a person who stutters and elucidate the nature of their self-efficacy beliefs.ResultsThematic analysis identified several major themes that provided novel insight into the complex nature of the self-efficacy beliefs experienced by adults who stutter: speaker experiences shaped communicative confidence, there was a conflict between communication and fluency, stuttering was viewed as more than fluency, and individual perspectives shaped communicative confidence, as did the pervading influence of self. The notion that fluency and confidence are inextricably linked was evident within and across each major theme.ConclusionThese preliminary findings provide further support for a multidimensional approach to the treatment of adults who stutter. Findings will be used to inform a novel integrated fluency and psychosocial intervention for adults who stutter that addresses fluency and self-efficacy concurrently, with a view of engendering durable improvements in speech fluency and communicative confidence.     

Phoneme monitoring in silent naming and perception in adults who stutter

The present study investigated phonological encoding skills in persons who stutter (PWS). Participants were 10 PWS (M = 31.8 years, S.D. = 5.9) matched for age, gender, and handedness with 12 persons who do not stutter (PNS) (M = 24.3 years, S.D. = 4.3). The groups were compared in a phoneme monitoring task performed during silent picture naming. The phonological complexity of the target items in the task was varied such that participants monitored either compound words or noun phrases. Performance in this task was compared to phoneme monitoring performed on aurally presented target words to investigate whether any differences observed in silent naming were also evident in perception. Analysis of the response time data, in milliseconds, indicated that PWS were significantly slower as compared to PNS in phoneme monitoring during silent naming; group differences were not obtained in the perception task. The groups were also comparable in the response time to phoneme monitoring within compound words and noun phrases in both silent naming and perception. The findings suggested that PWS were slower in the encoding of segmental, phonological units during silent naming. Furthermore, absence of such differences in perception ruled out a general monitoring deficit in PWS. Findings are interpreted within the context of the psycholinguistic theories of stuttering that postulate phonological encoding and/or monitoring as a causal variable in stuttering.

Educational objectives: As a result of this activity, the participant should: (1) describe relevant literature on phonological encoding skills in children and adults who stutter, (2) identify paradigms that can be used to investigate phonological processing in PWS, and (3) discuss the role of phonological encoding in speech production.     

A systematic review of interventions for adults who stutter

PurposeTo examine the effectiveness of (i) face to face interventions (ii) models of service delivery and (iii) psychological treatments combined with speech-focused interventions for adults who stutter.MethodsFive electronic databases and three clinical trial registries were searched. Systematic reviews, randomised controlled trials (RCTs) and studies that applied an intervention with adults who stutter were included. Pharmaceutical interventions were excluded. Primary outcomes included a measure of stuttering severity. Risk of bias assessment was conducted on included studies and overall quality of the evidence was graded.ResultsFive RCTS, four registered trials and three systematic reviews met inclusion criteria. Intervention approaches included speech restructuring programs (e.g. Camperdown Program) and transcranial direct current stimulation (tDCS). One study investigated cognitive behaviour therapy (CBT) alongside speech restructuring. Overall, studies were classified low risk of bias and good quality. Speech restructuring was included in all but one study (tDCS study) and had the most evidence i.e. supported by the greatest number of RCTs. On average, stuttering frequency was reduced by 50–57 % using speech restructuring approaches. No study reduced stuttering to the same level as community controls who don’t stutter. The study on tDCS reduced stuttering frequency by 22–27 %. Speech restructuring delivered via telehealth was non-inferior to face-to-face intervention. One study reported CBT was an effective adjunct to speech restructuring interventions.ConclusionSpeech restructuring interventions were found to reduce stuttering in adults, however degree and maintenance of fluency varied. The body of evidence surrounding tDCS and psychological interventions is limited. Replication studies should be considered.     

Working memory in adults who stutter using a visual N-back task

PurposeThe purpose of this study was to investigate working memory in adults who do (AWS) and do not (AWNS) stutter using a visual N-back task. Processes involved in an N-back task include encoding, storing, rehearsing, inhibition, temporal ordering, and matching.MethodsFifteen AWS (11 males, 4 females; M = 23.27 years, SD = 5.68 years) and 15 AWNS (M = 23.47 years, SD = 6.21 years) were asked to monitor series of images and respond by pressing a “yes” button if the image they viewed was the same as the image one, two, or three trials back. Stimuli included images with phonologically similar (i.e., phonological condition) or phonologically dissimilar (i.e., neutral condition) names. Accuracy and manual reaction time (mRT) were analyzed.ResultsNo difference was found between AWS and AWNS in accuracy. Furthermore, both groups were more accurate and significantly faster in 1- followed by 2- followed by 3-back trials. Finally, AWNS demonstrated faster mRT in the phonological compared to neutral condition, whereas AWS did not.ConclusionResults from this study suggest different processing mechanisms between AWS and AWNS for visually presented phonologically similar stimuli. Specifically, a phonological priming effect occurred in AWNS but not in AWS, potentially due to reduced spreading activation and organization in the mental lexicon of AWS. However, the lack of differences between AWS and AWNS across all N-back levels does not support deficits in AWS in aspects of working memory targeted through a visual N-back task; but, these results are preliminary and additional research is warranted.     

Results of intensive stuttering therapy with adults who clutter and stutter

The purpose of this investigation was to report on the identification of adult clients who clutter and stutter, evaluate their response to a stuttering therapy program, and determine if speech measures typically used in evaluating therapy outcome are sufficiently sensitive indicators of change for clients who clutter and stutter. Results suggest that cluttering-stuttering subjects had a very positive response to stuttering therapy, but greater improvements may have been achieved with additional therapy time and expanded therapy goals. Results also indicate that pretreatment and posttreatment measures of articulatory rate may be a more sensitive measure of change for cluttering-stuttering clients.     

Recurrent involuntary imagery in people who stutter and people who do not stutter

Objective

To compare intrusive memories in groups of people who do (PWS), and who do not (PWNS), stutter.

Method

Twenty-one participants who stuttered and 21 matched controls were given a semi-structured interview which explored imagery in speaking situations. The data were analyzed using a Content Analysis approach. Other outcome measures were the Beck Anxiety Inventory, the Beck Depression Inventory, the Post Traumatic Stress Disorder, PTSD, Symptom Scale: Self-Report Version.

Results

Significantly more stuttering participants than control participants indicated both recurrent imagery and associated memories. Content Analysis revealed themes of disfluency, anxiety, negative social evaluation, self-focus and pressure to speak that were common to both groups’ reports. Additional themes of helplessness, shame, sadness and frustration were found only in the images and memories of the stuttering group. No group differences were evident for the number of sensory modalities involved in images and memories, or for ratings of their vividness or strength of associated emotions, or on self-reports of depression, anxiety and trauma.

Conclusions

Recurrent imagery about events in childhood is a potent factor in the memories of PWS. It is worth modifying interventions that have been successfully applied for treating social anxiety for use with people who stutter.Educational objectives: After reading this article, participants will be able to: (a) identify the role of intrusive memories in psychiatric disorders and stuttering; (b) investigate how DSM criteria can be employed with people who stutter; (c) employ anxiety instruments used for assessing psychiatric disorders for stuttering; (d) distinguish between the intrusive memories experienced by people who stutter, and people who do not stutter; (e) apply treatments for intrusive memories in psychiatric disorders to work with people who stutter.     

Exogenous verbal response inhibition in adults who do and do not stutter

IntroductionBehavioral and questionnaire-based studies suggest that children who stutter (CWS) exhibit poorer response inhibition than children who do not stutter (CWNS). However, the behavioral findings in adults who stutter (AWS) are less unequivocal and mainly based on manual response inhibition. Further study is therefore needed, especially given the lack of studies on verbal response inhibition among these groups.MethodsThirteen AWS and 14 adults who do not stutter (AWNS) participated in a verbal stop signal task (SST) in which they were asked to read aloud six Chinese characters as fast as possible during the go-signal and ignore-signal trials and refrain from naming them during the stop-signal trials.ResultsThe two groups showed a comparable response reaction time in the go-signal and ignore-signal trial conditions. Furthermore, there were no significant differences in terms of the stop-signal reaction time (SSRT) and accuracy. However, a significant positive correlation was found between SSRT and the frequency of stuttering in conversation but not in reading.ConclusionCurrent findings seem to provide additional support that exogenously triggered response inhibition among AWS does not differ from AWNS. The association between stuttering frequency and SSRT seems to suggest that individuals with more severe stuttering in conversational speech have reduced exogenous response inhibition. However, this finding needs to be further explored in future studies using different measures of stuttering severity.     

A novel approach for measuring social participation in adults who stutter

This paper reports a preliminary study which trialled a novel approach for measuring speech output and social participation. The amount of phonation was accumulated via an objective measure called an Ambulatory Phonation Monitor (APM).Purpose(1) To establish whether adults who stutter will tolerate wearing an APM for an extended period of time (three days), (2) to test whether the APM can accumulate useful data about the amount of phonation adults who stutter produce in the course of a normal day and (3) to examine a possible relationship between stuttering severity and amount of phonation.MethodThree adults who stutter wore an APM for three consecutive days during their waking hours. Each completed a questionnaire regarding the device and kept a speech diary outlining daily speaking activities and self-reported stuttering severity. APM data regarding amount of phonation was collected, analysed and compared with the participants’ speech diaries.ResultsEach adult tolerated wearing the APM and while they felt comfortable speaking wearing the device, it was somewhat cumbersome. Variations in the amount of speaking across each day and in different speaking situations were evident. For two participants there was a positive correlation between phonation time and severity rating.ConclusionsPreliminary data suggests that the APM can provide valuable information about the amount adults who stutter speak. The APM is sufficiently sensitive to differentiate variations in the amount of phonation during different speaking situations. These favourable preliminary results suggest the value of a larger scale study.Educational Objectives: The reader will be able to: (a) describe the different aspects of stuttering currently routinely measured in clinical practice; (b) discuss the limitations of current measurement procedures; (c) discuss the advantages of speech measures obtained by an Ambulatory Phonation Monitor APM); (d) describe the perspectives of adults who stutter who have worn an APM to measure phonation time.     

Oral kinesthetic deficit in adults who stutter: a target-accuracy study

The current study was based on the hypothesis that chronic developmental stuttering in adults involves a deficiency in oral kinesthesia. The authors used a target-accuracy task to compare oral kinesthesia in adults who stutter (n = 17) and in normal speakers (n = 17). During the task, participants were instructed to make accurate jaw-opening movements in visual and nonvisual feedback conditions. The authors further contrasted oral movement control in a normal response time condition with that in a reaction time condition. Overall, the adults who stutter consistently made significantly less accurate and more variable movements than the control participants in the nonvisual condition, but particularly in the reaction time condition. In general, the present findings suggest that chronic developmental stuttering involves an oral kinesthetic deficiency, although without direct measures of somatosensory function, one cannot exclude a motor deficit interpretation.