Estimates of functional cerebral hemispheric differences in monolingual and bilingual people who stutter: Dual-task paradigm

The inter-relationship of stuttering and bilingualism to functional cerebral hemispheric processing was examined on a dual-task paradigm. Eighty native German (L1) speakers, half of whom were sequential bilinguals (L2 = English), were recruited. The participants (mean age = 38.9 years) were organised into four different groups according to speech status and language ability: 20 bilinguals who stutter (BWS), 20 monolinguals who stutter (MWS), 20 bilinguals who do not stutter (BWNS), and 20 monolinguals who do not stutter (MWNS). All participants completed a dual-task paradigm involving simultaneous speaking and finger tapping. No performance differences between BWS and BWNS were found. In contrast, MWS showed greater dual-task interference compared to BWS and MWNS, as well as greater right- than left-hand disruption. A prevailing finding was that bilingualism seems to offset deficits in executive functioning associated with stuttering. Cognitive reserve may have been reflected in the present study, resulting in a bilingual advantage.     

Early-stage chunking of finger tapping sequences by persons who stutter and fluent speakers

This research note explored the hypothesis that chunking differences underlie the slow finger-tap sequencing performance reported in the literature for persons who stutter (PWS) relative to fluent speakers (PNS). Early-stage chunking was defined as an immediate and spontaneous tendency to organize a long sequence into pauses, for motor planning, and chunks of fluent motor performance. A previously published study in which 12 PWS and 12 matched PNS practised a 10-item finger tapping sequence 30 times was examined. Both groups significantly decreased the duration of between-chunk intervals (BCIs) and within-chunk intervals (WCIs) over practice. PNS had significantly shorter WCIs relative to PWS, but minimal differences between groups were found for the number of, or duration of, BCI. Results imply that sequencing differences found between PNS and PWS may be due to differences in automatizing movements within chunks or retrieving chunks from memory rather than chunking per se.     

Estimates of functional cerebral hemispheric differences in monolingual and bilingual people who stutter: Visual hemifield paradigm

The relationship between stuttering and bilingualism to functional cerebral hemispheric processing was examined using a visual hemifield paradigm. Eighty native German speakers, half of whom were also proficient speakers of English as a second language (L2), were recruited. The participants were organised into four different groups according to speech status and language ability: 20 monolinguals who stutter, 20 bilinguals who stutter, 20 monolinguals who do not stutter, and 20 bilinguals who do not stutter. All participants completed a task involving selective identification of common objects simultaneously presented to both visual fields. Overall, an LVF advantage was observed across all groups with no significant group differences in regard to hemispheric asymmetry. However, both bilingual groups showed faster reaction times and fewer identification errors than the two monolingual groups. A prevailing finding was that bilingualism seems to offset deficits in executive functioning associated with stuttering. Hence, the results lend support to previous findings implicating the benefits of bilingualism.     

Amino acids profiles of children who stutter compared to their fluent sibling

Abstract

Purpose: This study scrutinises the abundances of 9 neurological-related amino acids of the scalp hair of 35 (5 females, 30 males) children who stutter and 30 normally fluent children (age and sex matched).

Methods: Samples of hair from children who stutter aged (5–9?years) were collected from Speech Clinic at King Abdullah Hospital. The control subjects were selected from the same families of children who stutter to exclude the effect of nutritional, environmental, and biological factors. Amino Acid Analyser was used to measure the concentrations of amino acids in acid hydrolysed hair samples.

Results: results indicated that the concentrations of threonine, tyrosine, and isoleucine (p?=?0.001, 0.001, 0.02 respectively) are lower in hair samples of people who stutter compared with samples of normal fluent speakers.

Conclusion: The findings of this study could introduce a new treatment protocol including the supplementation of reduced nutritional elements.

• KEY POINTS

• Concentrations of amino acids (threonine, isoleucine, and tyrosine) in the hair samples of people who stutter were significantly lower than the concentrations in the hair samples of control group.

• Concentrations of amino acids (histidine and glutamate) in hair samples of people who stutter were lower than control group with low significant values.

• The concentrations of amino acids (phenylalanine, serine, glycine, aspartate, glutamate) were not significantly different between hair samples of stuttering group and control group.

• The findings of the current study will be helpful in designing a new treatment method based on the supplementation of deficient amino acids.

     

Phonological and language disorders in children who stutter: impact on treatment recommendations

In the profession of speech‐language pathology, it is commonly reported that children who stutter, as a group, are more likely to have phonological and language disorders than their non‐stuttering peers. Some support for this belief comes from survey studies that have questioned speech‐language pathologists about the children on their caseloads who stutter. Recently, one such study reported that 44% of children who stuttered had at least one additional communication disorder (Arndt & Healey, 2001). In the present investigation, speech‐language pathologists (n=127) who were treating children with speech and language disorders were questioned about their views on the treatment of stuttering. The results indicated that children who stutter and have at least one additional disorder are more likely to be recommended for treatment than those whose only disorder is stuttering. This suggests that caseload surveys may overestimate the rate of additional communication disorders in children who stutter. The results provide reason to question the widespread belief that children who stutter have a high rate of concomitant disorders, especially when it is based on caseload surveys. Suggestions are offered for ways to determine more precisely the frequency with which stuttering co‐occurs with other speech and language disorders in children through large‐scale epidemiological research.     

An exploration of dichotic listening among adults who stutter

Abstract

A pilot investigation of dichotic listening of CV stimuli was undertaken using seven adults who stutter (AWS) and a comparison group of seven adults who do not stutter (AWNS). The aim of this research was to investigate whether AWS show a difference in the strength of the right ear advantage (REA) in both undirected and directed attention tasks when compared to AWNS. The undirected attention task involved manipulating the interaural intensity difference (IID) of the CV stimuli presented to each ear. The CV stimuli were presented with equal intensity for the directed attention task. The undirected attention results indicated that both AWS and AWNS have a REA for processing speech information, with a primary difference observed between groups in regard to the IID point at which a REA shifts to a LEA. This crossing-over point occurred earlier for AWS, indicating a stronger right hemisphere involvement for the processing of speech compared to AWNS. No differences were found between groups in the directed attention task. The differences and similarities observed in dichotic listening between the two groups are discussed in regard to hemispheric specialization in the processing of speech.     

Speech skill learning of persons who stutter and fluent speakers under single and dual task conditions

Two studies compared the accuracy and efficiency of initiating oral reading of nonsense syllables by persons who stutter (PWS) and fluent speakers (PNS) over practise. Findings of Study One, comparing 12 PWS and 12 PNS, replicated previous findings of slow speech sequence initiation over practise by PWS relative to PNS. In Study Two, nine PWS and eight PNS practised reading syllable sequences under single, and then dual task conditions in which a colour recognition distracter task was introduced. The speech sequences of PWS were initiated significantly slower than those of PNS. Significant Group×Condition interactions for reaction time and accuracy were interpreted to suggest that PNS, but not PWS, demonstrated the ability to switch between an attention‐demanding movement strategy under dual task conditions and a relatively automatic (little attention required) movement strategy after practise under single task conditions.     

Social anxiety disorder in adults who stutter

Background: The nature and prevalence of social anxiety disorder (social phobia (SP)) in people who stutter is uncertain, and DSM‐IV differential diagnosis guidelines make it difficult to classify an adult who stutters (AWS) with SP as it is assumed any social anxiety symptoms will be a consequence of their stuttering. The aim of this study was to determine the spot prevalence of SP in AWS and to investigate differences in social anxiety between AWS and controls who do not stutter. Methods: The study involved a comprehensive assessment of 200 AWS and 200 adults who do not stutter similar in age and sex ratio. Measures included stuttering severity, health status, self‐report measures of social anxiety as well as a structured diagnostic interview for SP for randomly selected sub‐group of 50 from each group. Results: The AWS were found to have significantly raised trait and social anxiety, as well as significantly increased risk of SP in comparison to the controls. Findings indicated a SP spot prevalence of at least 40% in AWS, and for them to be at high risk of having Generalized SP. Conclusions: It is concluded that the DSM‐IV diagnostic guidelines for diagnosing SP in AWS could result in professional confusion and have possible negative mental health ramifications. Implications for the psychological and medical treatment of AWS are discussed. Depression and Anxiety, 2010. © 2010 Wiley‐Liss, Inc.     

The integrity of anticipatory coarticulation in fluent and non-fluent tokens of adults who stutter

This article analysed the acoustic structure of voiced stop + vowel sequences in a group of persons who stutter (PWS). This phonetic unit was chosen because successful production is highly dependent on the differential tweaking of right-to-left anticipatory coarticulation as a function of stop place. Thus, essential elements of both speech motor planning and execution can be parsimoniously assessed. Five adult PWS read three passages 3 times in a randomised order. These passages contained an overabundance of words beginning with initial [bV], [dV] and [gV] sequences. Digital audio and visual recordings were analysed to first identify fluent and stuttered target words, which were then spectrally analysed to yield locus equation (LE) regression plots. The slope of the LE regression function directly indexes the coarticulatory extent of the vowel's influence on the preceding stop consonant. The PWS revealed LE parameters falling within the normal ranges based on previously documented data obtained from fluent speakers. Theoretical considerations of possible underlying factors responsible for stuttering disfluencies are discussed relevant to these findings.     

Neural correlates of semantic activation spreading on the path to picture naming in adults who stutter

ObjectiveOn the path to picture naming, words that relate semantically to the pictured object become activated in the mental lexicon. We used a neuroscientific approach to investigate this semantic activation spreading process in adults who stutter (AWS).MethodsFourteen AWS and 14 adults who do not stutter (AWNS) completed a picture–word priming task. On each trial, a picture was named at a delay. On some trials, an unattended auditory probe word was presented after the picture, before naming commenced. Event-related potentials recorded to probe words Semantically-Related to the picture labels, and to probe words Semantically- and Phonologically-Unrelated to the picture labels, were compared using spatial–temporal principal component analysis.ResultsPosterior N400 amplitude was attenuated for Semantically-Related versus Unrelated probes in AWNS, while in AWS posterior N400 amplitude was enhanced for Semantically-Related versus Unrelated probes. Marginal albeit potentially relevant group differences in the morphology of other ERP components were also observed.ConclusionsThe posterior N400 results point to a strategic, inhibitory influence on semantic activation spreading in AWS on the path to naming. Group differences in the amplitude of other ERP components tentatively suggest that AWS allocated attentional resources differently than the AWNS during the task. Preliminary ERP evidence of intact conceptual (as opposed to lexical-semantic) priming in the AWS is also discussed.SignificanceThis study contributes to a growing body of research describing linguistic performance in AWS.     

The transition from the core vowels to the following segments in Japanese children who stutter: The second,third and fourth syllables

, Syllable weight and phonological encoding in Japanese children who stutter. Japanese Journal of Special Education, 44, 451–462; 2008, Syllable weight and frequency of stuttering: Comparison between children who stutter with and without a family history of stuttering. Japanese Journal of Special Education, 45, 437–445; 2009, Difference in frequency of stuttering between light and heavy syllables in the production of monosyllables: From the viewpoint of phonetic transition. The Japanese Journal of Logopedics and Phoniatrics, 50, 116–122 (in Japanese)) proposed the hypothesis that in Japanese the transition from the core vowels (CVs) to the following segments affected the occurrence of stuttering. However, the transition we investigated was in the first syllables only, and the effect of the transition in second, third and fourth syllables was not addressed. The purpose of this study was to investigate whether the transition from the CVs in the second, third and fourth syllables affected the occurrence of stuttering. The participants were 21 Japanese children. A non-word naming task and a non-word reading task were used. The frequency of stuttering was not significantly different where the number of transitions from the CVs differed on either task. These results suggest that the transition from the CVs in the second, third and fourth syllables does not have a significant effect on the occurrence of stuttering in Japanese.     

Decreased occipital alpha oscillation in children who stutter during a visual Go/Nogo task

Objective

Our goal was to discover attention- and inhibitory control-related differences in the main oscillations of the brain of children who stutter (CWS) compared to typically developed children (TDC).

Phonological and language disorders in children who stutter: impact on treatment recommendations

In the profession of speech-language pathology, it is commonly reported that children who stutter, as a group, are more likely to have phonological and language disorders than their non-stuttering peers. Some support for this belief comes from survey studies that have questioned speech-language pathologists about the children on their caseloads who stutter. Recently, one such study reported that 44% of children who stuttered had at least one additional communication disorder (Arndt & Healey, 2001). In the present investigation, speech-language pathologists (n = 127) who were treating children with speech and language disorders were questioned about their views on the treatment of stuttering. The results indicated that children who stutter and have at least one additional disorder are more likely to be recommended for treatment than those whose only disorder is stuttering. This suggests that caseload surveys may overestimate the rate of additional communication disorders in children who stutter. The results provide reason to question the widespread belief that children who stutter have a high rate of concomitant disorders, especially when it is based on caseload surveys. Suggestions are offered for ways to determine more precisely the frequency with which stuttering co-occurs with other speech and language disorders in children through large-scale epidemiological research.     

Comparison of alternative methods for obtaining severity scores of the speech of people who stutter

Riley's Stuttering Severity Instrument (SSI) is widely used. The manuals allow SSI assessments to be made in different ways (e.g. from digital recordings or whilst listening to speech live). Digital recordings allow segments to be selected and listened to, whereas the entire recording has to be judged when listened to live. Comparison was made between expert judges when they used these digital and live procedures to establish whether one method was more sensitive and reliable than the other.

Five expert judges assessed eight speakers four times each in two judgment conditions (digital vs. live). The eight speakers were chosen so that they spanned a wide range of stuttering severity. SSI version 3 (SSI-3) estimates were obtained on all occasions.

An ANOVA showed a three-way interaction between sessions, speakers and condition that indicated that digital and live judgments varied across speakers and across sessions.

The predictions that were upheld were (1) SSI-3 scores made from digital segments are more sensitive than SSI-3 scores made on the entire live signal; (2) digital and live judgments vary with respect to speaker's stuttering severity and across test sessions.     

Performance on the Test of Everyday Attention and Standard Tests of Attention following Severe Traumatic Brain Injury

The Test of Everyday Attention (TEA) was designed to address some of the limitations of established measures of attention. However, very few studies have examined its clinical utility. A group of 35 patients who had sustained a severe TBI were compared with 35 age- and education-matched controls on the TEA, Stroop, SDMT, WMS-R Digit Span, Ruff 2s and 7s Selective Attention Test, and PASAT. Of the TEA subtests, only the Map and Telephone Search subtests of the TEA produced significant differences between the two groups, suggesting a deficit in visual selective attention following TBI. Principal components analysis revealed a four-component/factor structure of attention, largely consistent with previous studies. A logistic regression found that the TEA Map Search and Modified Colour-Word subtest of the Stroop were best able to discriminate between the TBI and control groups. When the TBI group was divided into Early (< 1 year post injury) and Late (> 2 years post injury) groups, there was an additional deficit on the Lottery (sustained attention) subtest in the Early TBI group, indicating that there is some recovery in attentional function beyond 1 year post injury.     

Lexical category influences in Persian children who stutter

Abstract

This article explores the effect that words from different lexical categories have on disfluency in 12 Persian children, ten boys and two girls, who stutter. They were aged 7 years 5 months to 10 years 6 months. Words from the participants’ narrative and reading samples (sub-tests of the Reading and Dyslexia Test validated for Persian school-aged children) were categorized as content, function, or content–function, and stuttering-like disfluencies were coded in each speech sample. Content and content–function words were significantly more likely to show stuttering-like disfluencies than function words. The distribution of symptom types over content and content–function words was similar, and differed from the distribution seen in function words. The symptom type analysis also supported the view that whole-word repetitions should not be grouped with other stuttering-like disfluencies.     

Exchange of disfluency with age from function to content words in Brazilian Portuguese speakers who do and do not stutter

The purpose of this study was to investigate the exchange of disfluencies from function words to content words with age in Brazilian Portuguese speakers who do and do not stutter. Ninety stuttering individuals and 90 controls, native speakers of Brazilian Portuguese, were divided into three age groups (children, adolescents and adults). The study method involved analyzing the occurrence of stuttering on content and function words based on spontaneous speech samples. Results indicated that children tend to be more disfluent on function words. With the increase in age, teenagers and adults who stutter presented a higher number of disfluencies on content words. These findings support the current literature, indicating that with the aging process, there is an exchange of disfluencies from function to content words. This shift in the disfluency pattern may account for a more advanced type of stuttering. The study also demonstrated that disfluencies in Portuguese speakers follow the same pattern of shifting from function to content words with age as for English speakers.     

The transition from the core vowels to the following segments in Japanese children who stutter: the second, third and fourth syllables

Shimamori and Ito (2007 , Syllable weight and phonological encoding in Japanese children who stutter. Japanese Journal of Special Education, 44, 451-462; 2008, Syllable weight and frequency of stuttering: Comparison between children who stutter with and without a family history of stuttering. Japanese Journal of Special Education, 45, 437-445; 2009, Difference in frequency of stuttering between light and heavy syllables in the production of monosyllables: From the viewpoint of phonetic transition. The Japanese Journal of Logopedics and Phoniatrics, 50, 116-122 (in Japanese)) proposed the hypothesis that in Japanese the transition from the core vowels (CVs) to the following segments affected the occurrence of stuttering. However, the transition we investigated was in the first syllables only, and the effect of the transition in second, third and fourth syllables was not addressed. The purpose of this study was to investigate whether the transition from the CVs in the second, third and fourth syllables affected the occurrence of stuttering. The participants were 21 Japanese children. A non-word naming task and a non-word reading task were used. The frequency of stuttering was not significantly different where the number of transitions from the CVs differed on either task. These results suggest that the transition from the CVs in the second, third and fourth syllables does not have a significant effect on the occurrence of stuttering in Japanese.     

A voxel-based morphometry (VBM) analysis of regional grey and white matter volume abnormalities within the speech production network of children who stutter

It is well documented that neuroanatomical differences exist between adults who stutter and their fluently speaking peers. Specifically, adults who stutter have been found to have more grey matter volume (GMV) in speech relevant regions including inferior frontal gyrus, insula and superior temporal gyrus (Beal et al., 2007; Song et al., 2007). Despite stuttering having its onset in childhood only one study has investigated the neuroanatomical differences between children who do and do not stutter. Chang et al. (2008) reported children who stutter had less GMV in the bilateral inferior frontal gyri and middle temporal gyrus relative to fluently speaking children. Thus it appears that children who stutter present with unique neuroanatomical abnormalities as compared to those of adults who stutter. In order to better understand the neuroanatomical correlates of stuttering earlier in its development, near the time of onset, we used voxel-based morphometry to examine volumetric differences between 11 children who stutter and 11 fluent children. Children who stutter had less GMV in the bilateral inferior frontal gyri and left putamen but more GMV in right Rolandic operculum and superior temporal gyrus relative to fluent children. Children who stutter also had less white matter volume bilaterally in the forceps minor of the corpus callosum. We discuss our findings of widespread anatomic abnormalities throughout the cortical network for speech motor control within the context of the speech motor skill limitations identified in people who stutter (Namasivayam and van Lieshout, 2008; Smits-Bandstra et al., 2006).     

The role of the DRD2 C957T polymorphism in neuroticism in persons who stutter and healthy controls

The present study investigates for the first time the influence of the DRD2 C957T polymorphism on personality in persons who stutter. In a recent study, the CC genotype of this single nucleotide polymorphism has been associated with stuttering, which could not be replicated in a follow-up study. Here, we demonstrate, in N=105 persons who stutter, that carriers of the CC and the CT genotype significantly have the highest neuroticism scores. This shows that the inclusion of personality measures in the investigation of the biological underpinnings of stuttering represents an important new avenue. In healthy control persons, a sex by C+/- allele interaction effect could be demonstrated. Female but not male carriers of the C+ variant report the highest neuroticism scores. Because neuroticism has been reported to be associated with stuttering before, the present data support the idea that this personality trait acts as an endophenotype for stuttering, contributing towards bridging the gap from gene variation to the complex pathology. This idea is supported by an additional path model showing that the polymorphism DRD2 C957T influences the self-reported severity of stuttering mainly by its influence on neuroticism (independent of the variable sex).