Cognitive control of action naming in adults who stutter.

PURPOSE: Based 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. METHOD: 12 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. RESULTS: Naming 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. CONCLUSIONS: Results 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.

Processing of Self-Repairs in Stuttered and Non-Stuttered Speech.

Previous research suggests that listeners can use the presence of speech disfluencies to predict upcoming linguistic input. But how is the processing of typical disfluencies affected when the speaker also produces atypical disfluencies, as in the case of stuttering? We addressed this question in a visual-world eye-tracking experiment in which participants heard self-repair disfluencies while viewing displays that contained a predictable target entity. Half the participants heard the sentences spoken by a speaker who stuttered, and half heard the sentences spoken by the same speaker who produced the sentences without stuttering. Results replicated previous work in demonstrating that listeners engage in robust predictive processing when hearing self-repair disfluencies. Crucially, the magnitude of the prediction effect was reduced when the speaker stuttered compared to when the speaker did not stutter. Overall, the results suggest that listeners' ability to model the production system of a speaker is disrupted when the speaker stutters.

Inhibitory Control of Lexical Selection in Adults who Stutter.

PURPOSE: Based on previous evidence that lexical selection may operate differently in adults who stutter (AWS) versus typically-fluent adults (TFA), and that atypical attentional processing may be a contributing factor, the purpose of this study was to investigate inhibitory control of lexical selection in AWS. METHOD: 12 AWS and 12 TFA completed two tasks. One was a picture naming task featuring High and Low Agreement object naming. Naming accuracy and reaction times (RT), and event-related potentials (ERPs) time-locked to picture onset, were recorded. Second was a flanker task featuring Congruent and Incongruent arrow arrays. Push-button accuracy and RTs, and ERPs time-locked to arrow array onset, were recorded. RESULTS: Low Agreement pictures were named less accurately and slower than High Agreement pictures in both Groups. The magnitude of the Agreement effect on naming RTs was larger in AWS versus TFA. Delta-plot analysis revealed that the Agreement effect was positively correlated with individual differences in inhibition in TFA but not in AWS. Moreover, Low Agreement pictures elicited negative-going ERP activity relative to High Agreement pictures in both Groups. However, the scalp topography of this effect was markedly reduced in AWS versus TFA. For the Flanker task, Congruency affected push-button accuracy and RTs, and N2 amplitudes, similarly between groups. CONCLUSIONS: Results point to a selective deficit in inhibitory control of lexical selection in AWS. Potential pathways between diminished inhibitory control of lexical selection, speech motor control and stuttering are discussed.

Temperament in Adults Who Stutter and Its Association With Stuttering Frequency and Quality-of-Life Impacts.

Purpose The study aim was to determine whether self-reported temperament traits differentiate adults who stutter (AWS) from adults who do not stutter (AWNS). Additionally, associations between temperament and stuttering frequency, and between temperament and quality of life impacts of stuttering, were investigated in AWS. Method Self-reported temperament traits were documented for 33 AWS and 43 AWNS using the Adult Temperament Questionnaire (ATQ; Evans & Rothbart, 2007). Quality-of-life impacts of stuttering were assessed using the Overall Assessment of the Speaker's Experience with Stuttering (Yaruss & Quesal, 2010). Stuttering frequency was calculated from 100-word monologue and reading samples. Results A between-groups difference in scores on the ATQ Positive Affect subscale was nominally significant (i.e., before correcting for multiple tests) and also approached statistical significance after Bonferroni correction. Positive Affect scores were lower for AWS, and the size of this trending effect was moderate. Within AWS, a statistically significant positive correlation was found between impact scores on the General Information section of the Overall Assessment of the Speaker's Experience with Stuttering and ATQ Frustration subscale scores after Bonferroni correction. No associations were detected between temperament traits and stuttering frequency. Conclusions Results reveal a nontrivial tendency for AWS to experience decreased positive affect compared to AWNS. In addition, increased frustration was found to be associated with reduced general knowledge about stuttering in AWS. Neither effect has been previously reported for adults or children who stutter. Finally, self-reported temperament traits were not found to vary with stuttering frequency in adults, consistent with previous results for AWS.

Backward-Looking Sentence Processing in Typically Disfluent versus Stuttered Speech: ERP Evidence.

The aim was to determine how backward-looking sentence processing is affected by typically-disfluent versus stuttered speech. Two listener groups heard Garden Path (GP) and control sentences. GP sentences contained no disfluency, a silent pause, or a filled pause before the disambiguating verb. For one group, the sentence preambles additionally contained stuttering-like disfluencies. Comprehension accuracy, event-related potentials (ERPs) time-locked to disambiguating verbs, and perceptual speaker ratings, were compared between groups. The With Stuttering group perceived the speaker as less competent but had better comprehension accuracy for GP sentences. ERPs to disambiguating verbs in GP sentences included a P600 component, indexing backward-looking sentence processing, but only for the No Stuttering group. Other ERP components, elicited to GP sentences with silent/filled pauses, did not differ between groups. Results suggest that listeners abandon prior expectations when processing sentences containing stuttering-like disfluencies, possibly because they lack a speaker model defined by the presence of stuttering.

Semantic and Phonological Encoding Times in Adults Who Stutter: Brain Electrophysiological Evidence.

Purpose: Some psycholinguistic theories of stuttering propose that language production operates along a different time course in adults who stutter (AWS) versus typically fluent adults (TFA). However, behavioral evidence for such a difference has been mixed. Here, the time course of semantic and phonological encoding in picture naming was compared in AWS (n = 16) versus TFA (n = 16) by measuring 2 event-related potential (ERP) components: NoGo N200, an ERP index of response inhibition, and lateralized readiness potential, an ERP index of response preparation. Method: Each trial required a semantic judgment about a picture in addition to a phonemic judgment about the target label of the picture. Judgments were mapped onto a dual-choice (Go-NoGo/left-right) push-button response paradigm. On each trial, ERP activity time-locked to picture onset was recorded at 32 scalp electrodes. Results: NoGo N200 was detected earlier to semantic NoGo trials than to phonemic NoGo trials in both groups, replicating previous evidence that semantic encoding generally precedes phonological encoding in language production. Moreover, N200 onset was earlier to semantic NoGo trials in TFA than in AWS, indicating that semantic information triggering response inhibition became available earlier in TFA versus AWS. In contrast, the time course of N200 activity to phonemic NoGo trials did not differ between groups. Lateralized readiness potential activity was influenced by strategic response preparation and, thus, could not be used to index real-time semantic and phonological encoding. Conclusion: NoGo N200 results point to slowed semantic encoding in AWS versus TFA. Discussion considers possible factors in slowed semantic encoding in AWS and how fluency might be impacted by slowed semantic encoding.

Attention demands of language production in adults who stutter.

OBJECTIVE: We investigated whether language production is atypically resource-demanding in adults who stutter (AWS) versus typically-fluent adults (TFA). METHODS: Fifteen TFA and 15 AWS named pictures overlaid with printed Semantic, Phonological or Unrelated Distractor words while monitoring frequent low tones versus rare high tones. Tones were presented at a short or long Stimulus Onset Asynchrony (SOA) relative to picture onset. Group, Tone Type, Tone SOA and Distractor Type effects on P3 amplitudes were the main focus. P3 amplitude was also investigated separately in a simple tone oddball task. RESULTS: P3 morphology was similar between groups in the simple task. In the dual task, a P3 effect was detected in TFA in all three distractor conditions at each Tone SOA. In AWS, a P3 effect was attenuated or undetectable at the Short Tone SOA depending on Distractor Type. CONCLUSIONS: In TFA, attentional resources were available for P3-indexed processes in tone perception and categorization in all distractor conditions at both Tone SOAs. For AWS, availability of attentional resources for secondary task processing was reduced as competition in word retrieval was resolved. SIGNIFICANCE: Results suggest that language production can be atypically resource-demanding in AWS. Theoretical and clinical implications of the findings are discussed.

Real-time processing in picture naming in adults who stutter: ERP evidence.

OBJECTIVE: The aim was to compare real-time language/cognitive processing in picture naming in adults who stutter (AWS) versus typically-fluent adults (TFA). METHODS: Participants named pictures preceded by masked prime words. Primes and target picture labels were identical or mismatched. Priming effects on naming and picture-elicited ERP activity were analyzed. Vocabulary knowledge correlations with these measures were assessed. RESULTS: Priming improved naming RTs and accuracy in both groups. RTs were longer for AWS, and correlated positively with receptive vocabulary in TFA. Electrophysiologically, posterior-P1 amplitude negatively correlated with expressive vocabulary in TFA versus receptive vocabulary in AWS. Frontal/temporal-P1 amplitude correlated positively with expressive vocabulary in AWS. Identity priming enhanced frontal/posterior-N2 amplitude in both groups, and attenuated P280 amplitude in AWS. N400 priming was topographically-restricted in AWS. CONCLUSIONS: Results suggest that conceptual knowledge was perceptually-grounded in expressive vocabulary in TFA versus receptive vocabulary in AWS. Poorer expressive vocabulary in AWS was potentially associated with greater suppression of irrelevant conceptual information. Priming enhanced N2-indexed cognitive control and visual attention in both groups. P280-indexed focal attention attenuated with priming in AWS only. Topographically-restricted N400 priming suggests that lemma/word form connections were weaker in AWS. SIGNIFICANCE: Real-time language/cognitive processing in picture naming operates differently in AWS.

Cognitive training and selective attention in the aging brain: an electrophysiological study.

OBJECTIVE: Age-related deficits in selective attention are hypothesized to result from decrements in inhibition of task-irrelevant information. Speed of processing (SOP) training is an adaptive cognitive intervention designed to enhance processing speed for attention tasks. The effectiveness of SOP training to improve cognitive and everyday functional performance is well documented. However, underlying mechanisms of these training benefits are unknown. METHODS: Participants completed a visual search task evaluated using event-related potentials (ERPs) before and after 10 weeks of SOP training or no contact. N2pc and P3b components were evaluated to determine SOP training effects on attentional resource allocation and capacity. RESULTS: Selective attention to a target was enhanced after SOP training compared to no training. N2pc and P3b amplitudes increased after training, reflecting attentional allocation and capacity enhancement, consistent with previous studies demonstrating behavioral improvements in selective attention following SOP training. CONCLUSIONS: Changes in ERPs related to attention allocation and capacity following SOP training support the idea that training leads to cognitive enhancement. Specifically, we provide electrophysiological evidence that SOP training may be successful in counteracting age-related declines in selective attention. SIGNIFICANCE: This study provides important evidence of the underlying mechanisms by which SOP training improves cognitive function in older adults.

Nicotine deprivation influences P300 markers of cognitive control.

Studies suggest that reduced cognitive control due to nicotine withdrawal may have a critical role in promoting tobacco use. The P3 family of event-related brain potential (ERP) components is thought to serve as markers of cognitive control processes. Unfortunately, existing research that examines the effects of nicotine deprivation on P3 amplitude has been marred by small sample sizes and other design limitations. The present study sought to determine the effects of nicotine deprivation on P3b and P3a amplitudes, which index task relevant target detection and orienting responses to novelty, respectively. A secondary aim was to examine self-reported trait cognitive control as a moderator of nicotine deprivation-induced reductions in P3b and P3a amplitudes. In all, 121 nicotine-dependent smokers attended two experimental sessions following 12-h smoking/nicotine deprivation. In a counterbalanced manner, participants smoked nicotine cigarettes during one session and placebo cigarettes during the other session. Findings indicated that nicotine deprivation reduced P3b amplitude (p<0.00001) during a three-stimulus oddball task independent of trait cognitive control. In contrast, nicotine deprivation reduced P3a only among participants who scored lower on measures of trait cognitive control. Implications for conceptualizing risk for nicotine dependence, and its treatment, are discussed.

Exploring semantic and phonological picture-word priming in adults who stutter using event-related potentials.

OBJECTIVE: Our aim was to investigate how semantic and phonological information is processed in adults who stutter (AWS) preparing to name pictures, following-up a report that event-related potentials (ERPs) in AWS evidenced atypical semantic picture-word priming (Maxfield et al., 2010). METHODS: Fourteen AWS and 14 typically-fluent adults (TFA) participated. Pictures, named at a delay, were followed by probe words. Design elements not used in Maxfield et al. (2010) let us evaluate both phonological and semantic picture-word priming. RESULTS: TFA evidenced typical priming effects in probe-elicited ERPs. AWS evidenced diminished semantic priming, and reverse phonological N400 priming. CONCLUSIONS: Results point to atypical processing of semantic and phonological information in AWS. Discussion considers whether AWS ERP effects reflect unstable activation of target label semantic and phonological representations, strategic inhibition of target label phonological neighbors, and/or phonological label-probe competition. SIGNIFICANCE: Results raise questions about how mechanisms that regulate activation spreading operate in AWS.

Auditory evoked response to gaps in noise: older adults.

OBJECTIVE: The objective of this study was to describe the auditory evoked response to silent gaps for a group of older adults using stimulus conditions identical to those used in psychophysical studies of gap detection. DESIGN: The P1-N1-P2 response to the onsets of stimuli (markers) defining a silent gap for within-channel (spectrally identical markers) and across-channel (spectrally different markers) conditions was examined using four perceptually-equated gap durations. STUDY SAMPLE: A group of 24 older adults (mean age = 63 years) with normal hearing or minimal hearing loss participated. RESULTS: Older adults exhibited neural activation patterns that were qualitatively different and more frontally oriented than those observed in a previous study (Lister et al., 2007) of younger listeners. Older adults showed longer P2 latencies and larger P1 amplitudes than younger adults, suggesting relatively slower neural travel time and altered auditory inhibition/arousal by irrelevant stimuli. CONCLUSION: Older adults appeared to recruit later-occurring T-complex-like generators for gap processing, compared to earlier-occurring T-complex-like generators by the younger group. Early and continued processing of channel cues with later processing of gap cues may represent the inefficiency of the aging auditory system and may contribute to poor speech understanding in noisy, real-world listening environments.

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

OBJECTIVE: On 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). METHODS: Fourteen 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. RESULTS: Posterior 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. CONCLUSIONS: The 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. SIGNIFICANCE: This study contributes to a growing body of research describing linguistic performance in AWS.

Disfluencies along the garden path: brain electrophysiological evidence of disrupted sentence processing.

Bailey and Ferreira (2003) hypothesized and reported behavioral evidence that disfluencies (filled and silent pauses) undesirably affect sentence processing when they appear before disambiguating verbs in Garden Path (GP) sentences. Disfluencies here cause the parser to "linger" on, and apparently accept as correct, an erroneous parse. Critically, the revision process usually associated with GP-disambiguating verbs does not appear to be triggered. In order to verify this effect, we recorded event-related potentials (ERPs) time-locked to disambiguating verbs in spoken GP sentences from 15 adults. A filled pause, silent pause, or no disfluency appeared before the GP-disambiguating verbs. Principal component analysis (PCA) revealed that fluent GP sentences elicited P600, an ERP index that revision of the initial parse was attempted. Crucially, P600 was attenuated for sentences containing a filled or silent pause before the GP-disambiguating verb. However, PCA detected an N400-like activation for these items, suggesting that listeners accepted the original (erroneous) parse and continued integrating at the verb; a conclusion that is tentative and requires further study. A left anterior positivity was also detected at GP-disambiguating verbs flanked by a filled pause. Discussion focuses on what these preliminary findings tell us about how oral comprehension proceeds when the time-course of sentence processing is disrupted.

Cortical evoked response to gaps in noise: within-channel and across-channel conditions.

OBJECTIVES: The objective of this study was to describe the cortical evoked response to silent gaps in a group of young adults with normal hearing using stimulus conditions identical to those used in psychophysical studies of gap detection. Specifically, we sought to examine the P1-N1-P2 auditory evoked response to the onsets of stimuli (markers) defining a silent gap for within-channel (spectrally identical markers) and across-channel (spectrally different markers) conditions using four perceptually-equated gap durations. It was hypothesized that (1) P1, N1, and P2 would be present and consistent for 1st marker (before the gap) onsets; (2) for within-channel markers, P1, N1, and P2 would be present for 2nd marker (after the gap) onsets only when the gap was of a duration equal to or larger than the behaviorally measured gap detection threshold; and (3) for the across-channel conditions, P1, N1, and P2 would be present for 2nd marker onsets regardless of gap duration. This is expected due to the additional cue of frequency change following the gap. DESIGN: Twelve young adults (mean age 26 years) with normal hearing participated. Within-channel and across-channel gap detection thresholds were determined using an adaptive psychophysical procedure. Next, cortical auditory evoked potentials (P1-N1-P2) were recorded with a 32-channel Neuroscan electroencephalogram system using within-channel and across-channel markers identical to those used for the psychophysical task and four perceptually weighted gap durations: (1) individual listener's gap detection threshold; (2) above gap detection threshold; (3) below gap detection threshold; and (4) a 1-ms gap identical to the gap in the standard interval of the psychophysical task. P1-N1-P2 peak latencies and amplitudes were analyzed using repeated-measures analyses of variance. A temporal-spatial principal component analysis was also conducted. RESULTS: The latency of P2 and the amplitude of P1, N1, and P2 were significantly affected by the acoustic characteristics of the 2nd marker as well as the duration of the gap. Larger amplitudes and shorter latencies were generally found for the conditions in which the acoustic cues were most salient (e.g., across-channel markers, 1st markers, large gap durations). Interestingly, the temporal-spatial principal component analysis revealed activity elicited by gap durations equal to gap detection threshold in the latency regions of 167 and 183 ms for temporal-parietal and right-frontal spatial locations. CONCLUSIONS: The cortical response to a silent gap is unique to specific marker characteristics and gap durations among young adults with normal hearing. Specifically, when the onset of the 2nd marker is perceptually salient, the amplitude of the P1-N1-P2 response is relatively larger and the P2 latency is relatively shorter than for nonsalient 2nd marker onsets, providing noninvasive, nonbehavioral indicators of the neural coding of this important temporal cue in the thalamic-cortical region of the central auditory system. Gap duration appears to be most clearly indicated by P1 and T-complex amplitude.