Velar-vowel coarticulation in a virtual target model of stop production.

Velar-vowel coarticulation in English, resulting in so-called velar fronting in front vowel contexts, was studied using ultrasound imaging of the tongue during /k/ onsets of monosyllabic words with no coda or a labial coda. Ten native English speakers were recorded and analyzed. A variety of coarticulation patterns that often appear to contain small differences in typical closure location for similar vowels was found. An account of the coarticulation pattern is provided using a virtual target model of stop consonant production where there are two /k/ allophones in English, one for front vowels and one for non-front vowels. Small differences in closure location along the palate between productions within each context are the result of the trajectory of movement of the tongue from the vowel to vowel through the virtual target beyond the limit of the palate. The overall pattern is thus seen as a combination of a large planned allophonic difference between consonant closure targets and smaller phonetic differences for each particular vowel quality that are the result of coarticulation.

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.

Anticipatory coarticulation and stability of speech in typically fluent speakers and people who stutter.

This project replicates and extends previous work on coarticulation in velar-vowel sequences in English. Coarticulatory data for 46 young adult speakers, 23 who stutter and 23 who do not stutter show coarticulatory patterns in young adults who stutter that are no different from typical young adults. Additionally, the stability of velar-vowel production is analysed in token-to-token variability found in multiple repetitions of the same velar-vowel sequence. Across participants, identical patterns of coarticulation were found between people who do and do not stutter, but decreased stability was found in velar closure production in a significant subset of people who stutter. Other people who stutter appeared no different than typical speakers. Outcomes of this study suggest that articulatory maturation in young adults who stutter is, on average, no different from typical young adults, but that some young adults who stutter could be viewed as having less stably activated articulatory sub-systems.

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.

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.

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.

Multi-site diagnosis and management of 260 patients with auditory neuropathy/dys-synchrony (auditory neuropathy spectrum disorder).

Test results and management data are summarized for 260 patients with diagnoses of Auditory Neuropathy Spectrum Disorder (ANSD). Hearing aids were tried in 85 of these patients, and 49 patients tried cochlear implants. Approximately 15% reported some benefit from hearing aids for language learning, while improvement in speech comprehension and language acquisition was reported in 85% of patients who were implanted. Approximately 5% (13/260) of the total population developed normal speech and language without intervention. Patients were diagnosed at our laboratory (n=66) or referred from other sites (n=194), and all showed absent/grossly abnormal auditory brainstem responses (ABR), often 'ringing' cochlear microphonics, and the presence or history of otoacoustic emissions. Etiologies and co-existing conditions included genetic (n=41), peripheral neuropathies (n=20), perinatal jaundice and/or anoxia and/or prematurity (n=74). These patients comprise 10% or more of hearing impaired patients; their language acquisition trajectories are generally unpredictable from their audiograms.

Preattentive cortical-evoked responses to pure tones, harmonic tones, and speech: influence of music training.

OBJECTIVE: Cortical auditory evoked potentials, including mismatch negativity (MMN) and P3a to pure tones, harmonic complexes, and speech syllables, were examined across groups of trained musicians and nonmusicians. Because of the extensive formal and informal auditory training received by musicians throughout their lifespan, it was predicted that these electrophysiological indicators of preattentive pitch discrimination and involuntary attention change would distinguish musicians from nonmusicians and provide insight regarding the influence of auditory training and experience on central auditory function. DESIGN: A total of 102 (67 trained musicians, 35 nonmusicians) right-handed young women with normal hearing participated in three auditory stimulus conditions: pure tones (25 musicians/15 nonmusicians), harmonic tones (42 musicians/20 nonmusicians), and speech syllables (26 musicians/15 nonmusicians). Pure tone and harmonic tone stimuli were presented in multideviant oddball paradigms designed to elicit MMN and P3a. Each paradigm included one standard and two infrequently occurring deviants. For the pure tone condition, the standard pure tone was 1000 Hz, and the two deviant tones differed in frequency from the standard by either 1.5% (1015 Hz) or 6% (1060 Hz). The harmonic tone complexes were digitally created and contained a fundamental frequency (F0) and three harmonics. The amplitude of each harmonic was divided by its harmonic number to create a natural amplitude contour in the frequency spectrum. The standard tone was G4 (F0 = 392 Hz), and the two deviant tones differed in fundamental frequency from the standard by 1.5% (F0 = 386 Hz) or 6% (F0 = 370 Hz). The fundamental frequencies of the harmonic tones occur within the average female vocal range. The third condition to elicit MMN and P3a was designed for the presentation of speech syllables (/ba/ and /da/) and was structured as a traditional oddball paradigm (one standard/one infrequent deviant). Each speech stimulus was presented as a standard and a deviant in separate blocks. P1-N1-P2 was elicited before each oddball task by presenting each auditory stimulus alone in single blocks. All cortical auditory evoked potentials were recorded in a passive listening condition. RESULTS: Incidental findings revealed that musicians had longer P1 latencies for pure tones and smaller P1 amplitudes for harmonic tones than nonmusicians. There were no P1 group differences for speech stimuli. Musicians compared with nonmusicians had shorter MMN latencies for all deviances (harmonic tones, pure tones, and speech). Musicians had shorter P3a latencies to harmonic tones and speech but not to pure tones. MMN and P3a amplitude were modulated by deviant frequency but not by group membership. CONCLUSIONS: Formally trained musicians compared with nonmusicians showed more efficient neural detection of pure tones and harmonic tones; demonstrated superior auditory sensory-memory traces for acoustic features of pure tones, harmonic tones, and speech; and revealed enhanced sensitivity to acoustic changes of spectrally rich stimuli (i.e., harmonic tones and speech). Findings support a general influence of music training on central auditory function and illustrate experience-facilitated modulation of the auditory neural system.

The relationship between pitch discrimination and vocal production: comparison of vocal and instrumental musicians.

Auditory pitch discrimination and vocal pitch accuracy are fundamental abilities and essential skills of a professional singer; yet, the relationship between these abilities, particularly in trained vocal musicians, has not been the subject of much research. Difference limens for frequency (DLFs) and pitch production accuracy (PPA) were examined among 20 vocalists, 21 instrumentalists, and 21 nonmusicians. All were right-handed young adult females with normal hearing. Stimuli were harmonic tone complexes simulating piano tones and represented the mid-frequency of the untrained female vocal range, F0=261.63-392 Hz (C4-G4). DLFs were obtained by an adaptive psychophysical paradigm. Vocal pitch recordings were analyzed to determine PPA. Musicians demonstrated superior pitch discrimination and production accuracy compared to nonmusicians. These abilities did not distinguish instrumentalists and vocalists. DLF and PPA were significantly correlated with each other only for musicians with instrumental training; however, PPA was most consistent with minimal variance for vocalists. It would appear that a relationship between DLF and PPA develops with musical training, and these abilities can be differentially influenced by the type of specialty training.

Hearing of note: an electrophysiologic and psychoacoustic comparison of pitch discrimination between vocal and instrumental musicians.

Cortical auditory evoked potentials of instrumental musicians suggest that music expertise modifies pitch processing, yet less is known about vocal musicians. Mismatch negativity (MMN) to pitch deviances and difference limen for frequency (DLF) were examined among 61 young adult women, including 20 vocalists, 21 instrumentalists, and 20 nonmusicians. Stimuli were harmonic tone complexes from the mid-female vocal range (C4-G4). MMN was elicited by multideviant paradigm. DLF was obtained by an adaptive psychophysical paradigm. Musicians detected pitch changes earlier and DLFs were 50% smaller than nonmusicians. Both vocal and instrumental musicians possess superior sensory-memory representations for acoustic parameters. Vocal musicians with instrumental training appear to have an auditory neural advantage over instrumental or vocal only musicians. An incidental finding reveals P3a as a sensitive index of music expertise.

Modeling open-set spoken word recognition in postlingually deafened adults after cochlear implantation: some preliminary results with the neighborhood activation model.

HYPOTHESES: Do cochlear implants provide enough information to allow adult cochlear implant users to understand words in ways that are similar to listeners with acoustic hearing? Can we use a computational model to gain insight into the underlying mechanisms used by cochlear implant users to recognize spoken words? BACKGROUND: The Neighborhood Activation Model has been shown to be a reasonable model of word recognition for listeners with normal hearing. The Neighborhood Activation Model assumes that words are recognized in relation to other similar-sounding words in a listener's lexicon. The probability of correctly identifying a word is based on the phoneme perception probabilities from a listener's closed-set consonant and vowel confusion matrices modified by the relative frequency of occurrence of the target word compared with similar-sounding words (neighbors). Common words with few similar-sounding neighbors are more likely to be selected as responses than less common words with many similar-sounding neighbors. Recent studies have shown that several of the assumptions of the Neighborhood Activation Model also hold true for cochlear implant users. METHODS: Closed-set consonant and vowel confusion matrices were obtained from 26 postlingually deafened adults who use cochlear implants. Confusion matrices were used to represent input errors to the Neighborhood Activation Model. Responses to the different stimuli were then generated by the Neighborhood Activation Model after incorporating the frequency of occurrence counts of the stimuli and their neighbors. Model outputs were compared with obtained performance measures on the Consonant-Vowel Nucleus-Consonant word test. Information transmission analysis was used to assess whether the Neighborhood Activation Model was able to successfully generate and predict word and individual phoneme recognition by cochlear implant users. RESULTS: The Neighborhood Activation Model predicted Consonant-Vowel Nucleus-Consonant test words at levels similar to those correctly identified by the cochlear implant users. The Neighborhood Activation Model also predicted phoneme feature information well. CONCLUSION: The results obtained suggest that the Neighborhood Activation Model provides a reasonable explanation of word recognition by postlingually deafened adults after cochlear implantation. It appears that multichannel cochlear implants give cochlear implant users access to their mental lexicons in a manner that is similar to listeners with acoustic hearing. The lexical properties of the test stimuli used to assess performance are important to spoken-word recognition and should be included in further models of the word recognition process.

Perception of Wordlikeness: Effects of Segment Probability and Length on the Processing of Nonwords.

A probabilistic phonotactic grammar based on the probabilities of the constituents contained in a dictionary of English was used to generate multisyllabic nonwords. English-speaking listeners evaluated the wordlikeness of these patterns. Wordlikeness ratings were higher for nonwords containing high-probability constituents and were also higher for nonwords with fewer syllables. Differences in the processing of these same nonwords that partially reflected their perceived wordlikeness were also found in a recognition memory task. Nonwords with higher probability constituents yielded better recognition memory performance, suggesting that participants were able to use their knowledge of frequently occurring lexical patterns to improve recognition. These results suggest that lexical patterns provide the foundation of an emergent phonological competence used to process nonwords in both linguistic and metalinguistic tasks.