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PubMed2000

The effect of sequence repeat time on auditory cortex stimulation during phonetic discrimination.

Acoustic noise generated by the MR scanner gradient system during fMRI studies of auditory function is a very significant potential confound. Despite these deleterious effects, fMRI of the auditory cortex has been successful and numerous practitioners have circumvented the problem of acoustic masking noise. In the context of auditory cortex fMRI, the sequence repeat time (TR) has the effect of altering the length of time during which the scanner is quiet. Indeed, the move to whole-brain fMRI makes the problem of acoustic noise more acute and points to the need to examine the role of TR and its influence on the BOLD signal. The aim of this study was to examine the effect of varying the TR time on activation of auditory cortex during presentation and performance of a phonetic discrimination task. The results presented here demonstrate that the influence of sequence repeat time is considerable. For a short repeat time it is likely that the noise from the scanner is a significant mask and hinders accurate task performance. At the other extreme, a repeat time of 9 s is also suboptimal, probably due to attentional effects and lack of concentration and not least because of the longer overall measurement times. The results of this study point to a complicated interplay between psychophysical factors as well as physical parameters; attention, acoustic noise, total duration of the experiment, consideration of the volume of acquisition, and overall difficulty of the task have to be assessed and balanced. For the paradigm used here, the results suggest an optimal TR of around 6 s for a 16-slice acquisition.

Artifacts↗
PubMed1981

Listener agreement on phonetic segments in early infant vocalizations.

Noncry, nonlanguage vocalizations were sampled from four female babies between the ages of 7 and 21 months. Three trained listeners' phonetic transcriptions of more than 1,000 vocalizations were compared for interjudge and intrajudge agreement. The amount of agreement varied with the child's age and the criterion of agreement. The tendency toward somewhat greater interjudge agreement in the older than in the younger sampled months was attributed to the possibility that the child's vocal output becomes more speechlike with increasing age. Using an identical segment match criterion, interjudge and intrajudge agreement rarely exceeded 60% of the total number of segment comparisons made at any age. A feature-match criterion applied just to oral stops yielded higher agreement than did the identical segment match criterion. The results underscore the importance of considering listener reliability in assessing the validity of auditory descriptions of early vocal behavior and have implications for the methods used to describe auditory impressions.

Child Language↗
PubMed1987

Sound-meaning relationships in speakers of Urdu and English: evidence for a cross-cultural phonetic symbolism.

Twelve English- and 12 Urdu-speaking males, ranging in age from 18 to 30 years, were asked to assign pure-tone frequencies as a "best fit" to visually presented shapes. Six basic figures were employed (circle, ellipse, right triangle, isosceles triangle, along with two historical psycholinguistic forms--uloomu and takete) and varied on three dimensions of size, complexity, and density. The results of the study indicate that there was consistency in the assignment of pure-tone frequencies to the dimensions of the figures and that the pattern of assignment was generally similar for both English- and Urdu-speaking subjects alike. Specifically, for both language groups, round figures (circles and ellipses) were assigned significantly lower frequencies than other stimuli. Also, complex and dense figures (i.e., those designed to simulate "visual depth" and "visual texture," respectively) received significantly higher frequency settings than those stimuli not possessing these dimensions. Additional analyses revealed several factors that may have contributed to the observed pattern. For example, Urdu subjects of the English proficiency produced frequency assignments that closely resembled those of the English-speaking subjects, while subjects of low English proficiency produced a pattern that was somewhat different, particularly with regard to round, complex figures. Length of residency in the United States (6 months, 1 year, or 2 years), however, did not significantly influence frequency assignments for the Urdu subjects. These results are discussed in terms of "cross-cultural" versus "language-specific" phonetic symbolism.

Adolescent↗
PubMedDate not supplied

Patterns of covert speech behavior and phonetic coding.

In previous research a discriminative relationship has been established between patterns of covert speech behavior and the phonemic system when processing continuous linguistic material. The goal of the present research was to be more analytic and pinpoint covert neuromuscular speech patterns when one processes specific instances of phonemes. Electromyographic (EMG) recording indicated that the lips are significantly active when visually processing the letter "P"(an instance of bilabial material), but not when processing the letter "T" or a nonlinguistic control (C) stimulus. Similarly, the tongue is significantly active when processing the letter "T" (an instance of lingual-alveolar material), but not when processing the letters "P" or "C". It is concluded that the speech musculature covertly responds systematically as a function of class of phoneme being processed. These results accord with our model that semantic processing ("understanding") occurs when the speech (and other) musculature interacts with linguistic regions of the brain. In the interactions phonetic coding is generated and transmitted through neuromuscular circuits that have cybernetic characteristics.

Afferent Pathways↗
PubMed1984

Phonetic reduction of names.

The University of Alberta Hospitals, Edmonton, required an efficient phonetic reduction of names for accessing up to one-million patient records. The familiar Soundex methodology was enhanced, to provide some equating of beginning letters but somewhat greater discrimination beyond. The result was a potent 16-bit representation; an appropriate algorithm is provided.

Computers↗
PubMed1982

The effects of phonetic context and linguistic complexity on /s/ misarticulation in children.

The present investigation was designed to examine the effects of phonetic context and linguistic complexity level on /s/ misarticulations in children. The subjects were normal children who misarticulated the /s/ phoneme interdentally in all positions of words. The stimuli were 48 sound-in-context initiative sequences which contained one /s/ phoneme embedded in a C1SC2 frame with all permutations of the phonemes /k,t,n,p/ in the C1 and C2 positions. The 48 sequences were composed of two basic linguistic complexity levels. The simple level consisted of the C1SC2 frame occurring in 16 noun phrases and in the more complex linguistic level seven-word sentences contained the C1SC2 frames in the subject-noun-phrase and object-noun-phrase positions. All presentations of complexity levels were counterbalanced over the three trials for a total of 144 /s/ productions for each child. Results demonstrated that certain phonemes were more facilitory for correct /s/ production than other phonemes. The analysis revealed no position effect. The mean percent correct /s/ productions over three trials did not differ significantly; however, the mean percent correct /s/ productions did vary significantly with linguistic complexity levels by position.

Articulation Disorders↗
PubMed1983

Phonetic influences on stuttering in monolingual and bilingual stutterers.

The difficulty stutterers might have with individual sounds was investigated with respect to two modes of speaking (oral reading versus spontaneous speech) and two languages (English versus Kannada). Ten monolingual and ten bilingual stutterers read 16 lists of words (8 in each language). Analysis of stuttering was made with respect to a three-way classification of sounds (vowels, voiceless consonants, and voiced consonants) as well as an eight-way classification (short vowels, long vowels, voiceless stops, voiceless fricatives, voiced stops, voiced fricatives, nasals, and semivowels). Analysis was made with respect to both word-initial and total stuttering. The results indicated that both monolingual and bilingual stutterers were more dysfluent on voiceless consonants and especially on voiceless fricatives, when total stuttering was considered. Results of the analysis of word-initial stuttering on an eight-way classification of sounds showed that the bilingual stutterers stuttered more on the nasal sounds. The results of the bilingual comparison indicated the possibility that the phonetic influences on stuttering might be dependent on the number of languages spoken by the subjects as well as the specific language in which the effects were observed.

Adolescent↗
PubMed1975

Phonetic considerations of chromium alloy palates for complete dentures.

Two useful approaches for the construction of dentures with a chromium alloy palate have been described. The phonetic considerations were recognized, and allowances were made for their vital role when determining the palatal contours of both the metal and plastic portions of the denture base.

Chromium Alloys↗
PubMed1989

Resolving esthetic and phonetic problems associated with maxillary implant-supported prostheses. A clinical report.

A technique has been presented for placement of an implant prosthesis without a visually detectable space between the prosthesis and soft tissue or visibility of the metal abutments. The prosthesis permits better phonetics and greatly improved esthetics including better lip support. Proper presurgical planning and careful assessment of the potential level of home care are especially important when this technique is used.

Adult↗
PubMed1983

Phonetic disintegration in aphasia: acoustic analysis of spectral characteristics for place of articulation.

In this study, we attempted to determine whether phonetic disintegration of speech in Broca's aphasia affects the spectral characteristics of speech sounds as has been shown for the temporal characteristics of speech. To this end, we investigated the production of place of articulation in Broca's aphasics. Acoustic analysis of the spectral characteristics for stop consonants were conducted. Results indicated that the static aspects of speech production were preserved, as Broca's aphasics seemed to be able to reach the articulatory configuration for the appropriate place of articulation. However, the dynamic aspects of speech production seemed to be impaired, as their productions reflected problems with the source characteristics of speech sounds and with the integration of articulatory movements in the vocal tract. Listener perceptions of the aphasics' productions were compared with acoustic analyses for these same productions. The two measures were related; that is, the spectral characteristics of the utterances provided salient cues for place of articulation perception. An analysis of the occurrences of errors along the dimensions of voicing and place showed that aphasics rarely produce utterances containing both voice and place substitutions.

Adult↗
PubMed1985

Is there parallel and independent hemispheric processing of intonational and phonetic components of dichotic speech stimuli?

The possibility of hemisphere interaction in the processing of spoken language was studied in two dichotic listening experiments. The stimulus material consisted of six CV syllable triplets each spoken with each one of six intonation contours. In Experiment I, 15 aphasic patients, 8 patients with unilateral right hemisphere lesions, and 10 normal controls were asked to identify the four components of a dichotic item from a multiple-choice (MC) set comprising all possible CV triplets and intonation contours. In Experiment II, 30 normal subjects were required to identify either the right or left ear stimulus alone from an MC set comprising the right and left ear stimulus together with the two wrong combinations of right ear CV triplet with left ear intonation and vice versa. It is concluded from the results that the left hemisphere is capable of processing both phonetic and intonational information and that there is neither the necessity nor the tendency for right hemisphere participation in the perception of spoken language.

Adult↗
PubMed1990

Cerebral hemispheric involvement in the acquisition of new phonetic categories.

This study was concerned with the involvement of the cerebral hemispheres in the acquisition of perceptual skill with novel speech sounds. Two groups of eight subjects rated on three occasions the dissimilarity of pairs of Mandarin Chinese speech sounds varying on voicing and aspiration, presented to the left or right ear with contralateral noise. The experimental group received listening experience with long passages of Mandarin containing the target sounds. Multidimensional scaling analysis of dissimilarity ratings indicated that listening experience leads to increased perceptual differentiation of phonetic categories drawn from a language unfamiliar to the listener. This improvement occurred sooner with presentation of the target sounds to the right hemisphere than to the left if the phonological contrast was along the voicing dimension. Improvement in the perception of stimuli varying on aspiration occurred in right ear presentations only. This finding supports the position that speech perception mechanisms at the feature level may be distributed asymmetrically across the hemispheres.

Adult↗
PubMedDate not supplied

Acoustic versus phonetic representation of speech as reflected by the mismatch negativity event-related potential.

The concept of categorical perception of speech and speech-like sounds has been central to models of speech perception for decades. Event-related potentials (ERPs) provide a neurophysiologic perspective of this important phenomenon. In the present experiment the mismatch negativity (MMN) event-related potential, which is sensitive to fine acoustic differences, was recorded in adults. Of interest was whether the MMN reflects the acoustic or categorical perception of speech. The MMN was elicited by stimulus pairs (along a continuum varying in place of articulation from /da/ to /ga/) which had been identified as the same phoneme /da/ (within category condition) and as different phonemes /da/ and /ga/ (across categories condition). The acoustic differences between these two pairs of stimuli were equivalent. The MMN was observed in all subjects both in the within and across category conditions. Furthermore, the MMN did not differ in latency, amplitude or area within and across categories. That is, the MMN indicated equal discrimination both across and within categories. These results suggest that the MMN appears to reflect the processing of acoustic aspects of the speech stimulus, but not phonetic processing into categories. The MMN appears to be an extremely sensitive electrophysiologic index of minimal acoustic differences in speech stimuli.

Acoustic Stimulation↗
PubMed2005

The role of lexical competition and acoustic-phonetic structure in lexical processing: evidence from normal subjects and aphasic patients.

This study examined the effects that the acoustic-phonetic structure of a stimulus exerts on the processes by which lexical candidates compete for activation. An auditory lexical decision paradigm was used to investigate whether shortening the VOT of an initial voiceless stop consonant in a real word results in the activation of the lexical-semantic network of its voiced competitor, i.e., does acoustically modified time prime penny via dime. Results for normal subjects showed semantic priming for related pairs and mediated priming for voiced competitors, consistent with cascade models of language processing allowing for interaction between phonological and semantic levels of processing. Although Broca's aphasics showed semantic priming (dime primed penny), they failed to show priming in the context of a lexical competitor. These results are consistent with the hypothesis that these patients have a lexical processing deficit characterized by an overall reduction in lexical activation.

Aged↗
PubMed2006

Learning phonetic categories by tracking movements.

We explore in this study how infants may derive phonetic categories from adult input that are highly variable. Neural networks in the form of self-organizing maps (SOMs; ) were used to simulate unsupervised learning of Mandarin tones. In Simulation 1, we trained the SOMs with syllable-sized continuous F(0) contours, produced by multiple speakers in connected speech, and with the corresponding velocity profiles (D1). No attempt was made to reduce the large amount of variability in the input or to add to the input any abstract features such as height and slope of the F(0) contours. In the testing phase, reasonably high categorization rate was achieved with F(0) profiles, but D1 profiles yielded almost perfect categorization of the four tones. Close inspection of the learned prototypical D1 profile clusters revealed that they had effectively eliminated surface variability and directly reflected articulatory movements toward the underlying targets of the four tones as proposed by . Additional simulations indicated that a further learning step was possible through which D1 prototypes with one-to-one correspondence to the tones were derived from the prototype clusters learned in Simulation 1. Implications of these findings for theories of language acquisition, speech perception and speech production are discussed.

Humans↗
PubMed2007

Effects of prosodically modulated sub-phonetic variation on lexical competition.

Eye movements were monitored as participants followed spoken instructions to manipulate one of four objects pictured on a computer screen. Target words occurred in utterance-medial (e.g., Put the cap next to the square) or utterance-final position (e.g., Now click on the cap). Displays consisted of the target picture (e.g., a cap), a monosyllabic competitor picture (e.g., a cat), a polysyllabic competitor picture (e.g., a captain) and a distractor (e.g., a beaker). The relative proportion of fixations to the two types of competitor pictures changed as a function of the position of the target word in the utterance, demonstrating that lexical competition is modulated by prosodically conditioned phonetic variation.

Attention↗
PubMed2001

Event-related brain potentials (ERPs) in schizophrenia for tonal and phonetic oddball tasks.

BACKGROUND: Prior studies using simple target detection ("oddball") tasks with pure tones have reported asymmetric reduction of the P3 event-related potential (ERP). This study investigated the time course and topography of ERPs recorded during both tonal and phonetic oddball tasks. METHODS: Event-related potentials of 66 patients (14 unmedicated) diagnosed with schizophrenia (n = 46) or schizoaffective disorder (n = 20) and 32 healthy adults were recorded from 30 scalp electrodes during two oddball tasks using consonant-vowel syllables or complex tones. Overlapping ERP components were identified and measured by covariance-based principal components analysis. RESULTS: Schizophrenic patients showed marked, task-independent reductions of early negative potentials (N1, N2) but not reduced P3 amplitude or abnormal P3 asymmetry. Task-related hemispheric asymmetries of the N2/P3 complex were similar in healthy adults and schizophrenic patients. Poorer task performance in patients was related to ERP amplitudes, but could not account for reductions of early negativities. CONCLUSIONS: The findings suggest that both patients and control subjects activated lateralized cortical networks required for pitch (right frontotemporal) and phoneme (left parietotemporal) discrimination. Task-independent reductions of negativities between 80 and 280 msec after stimulus onset suggest a deficit of automatic stimulus classification in schizophrenia, which may be partly compensated by later effortful processing.

Adult↗
PubMed2001

Event-related potentials in schizophrenia during tonal and phonetic oddball tasks: relations to diagnostic subtype, symptom features and verbal memory.

BACKGROUND: This study compares event-related potentials for paranoid patients (n = 13) versus matched undifferentiated patients and unmedicated patients (n = 14) versus matched healthy adults. METHODS: Event-related potentials of right-handed patients and control subjects were recorded from 30 electrodes during oddball tasks using consonant-vowel syllables or complex tones. Patients were also assessed using the Positive and Negative Syndrome Scale, the Thought Disorder Index, and the Wechsler Memory Scale. RESULTS: Paranoid patients did not differ from undifferentiated patients in N1 or P3 amplitude but showed larger N2 at frontocentral sites to phonetic stimuli, as well as larger N2 over left than right hemisphere. Unmedicated patients showed reduced N2, but not N1 or P3, compared to control subjects. CONCLUSIONS: The N2 findings are consistent with neuropsychological evidence of greater verbal abilities and left hemisphere dominance in paranoid than nonparanoid schizophrenia. The findings also confirm the relationship of P3 to total Brief Psychiatric Rating Scale score, negative symptoms, and verbal associative memory.

Adult↗