Consonant-vowel Syllables Research Articles

Sound identification in human auditory cortex: Differential contribution of local field potentials and high gamma power as revealed by direct intracranial recordings

High gamma power has become the principal means of assessing auditory cortical activation in human intracranial studies, albeit at the expense of low frequency local field potentials (LFPs). It is unclear whether limiting analyses to high gamma impedes ability of clarifying auditory cortical organization. We compared the two measures obtained from posterolateral superior temporal gyrus (PLST) and evaluated their relative utility in sound categorization. Subjects were neurosurgical patients undergoing invasive monitoring for medically refractory epilepsy. Stimuli (consonant–vowel syllables varying in voicing and place of articulation and control tones) elicited robust evoked potentials and high gamma activity on PLST. LFPs had greater across-subject variability, yet yielded higher classification accuracy, relative to high gamma power. Classification was enhanced by including temporal detail of LFPs and combining LFP and high gamma. We conclude that future studies should consider utilizing both LFP and high gamma when investigating the functional organization of human auditory cortex.

Aquisição da sílaba consoante vogal (CV) por crianças com desenvolvimento fonológico típico e atípico

OBJETIVO: descrever e comparar a aquisição da sílaba consoante vogal em crianças com desenvolvimento fonológico típico e atípico, investigando as variáveis linguísticas e extralinguísticas intervenientes neste processo. MÉTODOS: análise da fala de 24 crianças, 12 com desenvolvimento típico e 12 atípico, equiparadas quanto ao sexo, entre 1:0 a 3:11;29 (grupo típico) e 4:0 a 6:11;29 (grupo atípico com desvio fonológico evolutivo). As amostras foram coletadas transversalmente, com base na Avaliação Fonológica da Criança. Foram analisadas palavras com a sílaba alvo consoante vogal, com corpus de 888 palavras do típico e 2.233 do atípico. Foram consideradas como variantes da variável dependente a produção correta, apagamento de consoante da sílaba, epêntese, metátese e outros. Como variáveis independentes intervenientes consideraram-se os fatores extralinguísticos idade, sexo e tipo de desenvolvimento e as variáveis linguísticas tonicidade, classe de sons, número de sílabas, contexto silábico seguinte e precedente, posição na palavra e pé métrico. Os dados foram analisados estatisticamente por meio do VARBRUL. RESULTADO: foram selecionadas como variáveis estatisticamente significantes para a produção correta de consoante vogal, idade e classe de sons, para típicos; classe de sons, sexo, idade e pé métrico, para atípicos; e classe de sons, sexo, idade, tonicidade e tipo de desenvolvimento, típicos e atípicos em conjunto. Verificou-se que ambos os grupos utilizam as mesmas estratégias de reparo, porém em maior frequência no grupo com desvio fonológico. Sendo as produções corretas mais frequentes no grupo típico. CONCLUSÃO: um maior número de variáveis estatisticamente significantes foram selecionadas no grupo atípico para produção correta, e ocorre uma maior frequência de estratégia neste grupo.

Estimating feedforward vs. feedback control of speech production through kinematic analyses of unperturbed articulatory movements.

To estimate the contributions of feedforward vs. feedback control systems in speech articulation, we analyzed the correspondence between initial and final kinematics in unperturbed tongue and jaw movements for consonant-vowel (CV) and vowel-consonant (VC) syllables. If movement extents and endpoints are highly predictable from early kinematic information, then the movements were most likely completed without substantial online corrections (feedforward control); if the correspondence between early kinematics and final amplitude or position is low, online adjustments may have altered the planned trajectory (feedback control) (Messier and Kalaska, 1999). Five adult speakers produced CV and VC syllables with high, mid, or low vowels while movements of the tongue and jaw were tracked electromagnetically. The correspondence between the kinematic parameters peak acceleration or peak velocity and movement extent as well as between the articulators' spatial coordinates at those kinematic landmarks and movement endpoint was examined both for movements across different target distances (i.e., across vowel height) and within target distances (i.e., within vowel height). Taken together, results suggest that jaw and tongue movements for these CV and VC syllables are mostly under feedforward control but with feedback-based contributions. One type of feedback-driven compensatory adjustment appears to regulate movement duration based on variation in peak acceleration. Results from a statistical model based on multiple regression are presented to illustrate how the relative strength of these feedback contributions can be estimated.

Control of spoken vowel acoustics and the influence of phonetic context in human speech sensorimotor cortex.

Speech production requires the precise control of vocal tract movements to generate individual speech sounds (phonemes) which, in turn, are rapidly organized into complex sequences. Multiple productions of the same phoneme can exhibit substantial variability, some of which is inherent to control of the vocal tract and its biomechanics, and some of which reflects the contextual effects of surrounding phonemes ("coarticulation"). The role of the CNS in these aspects of speech motor control is not well understood. To address these issues, we recorded multielectrode cortical activity directly from human ventral sensory-motor cortex (vSMC) during the production of consonant-vowel syllables. We analyzed the relationship between the acoustic parameters of vowels (pitch and formants) and cortical activity on a single-trial level. We found that vSMC activity robustly predicted acoustic parameters across vowel categories (up to 80% of variance), as well as different renditions of the same vowel (up to 25% of variance). Furthermore, we observed significant contextual effects on vSMC representations of produced phonemes that suggest active control of coarticulation: vSMC representations for vowels were biased toward the representations of the preceding consonant, and conversely, representations for consonants were biased toward upcoming vowels. These results reveal that vSMC activity for phonemes are not invariant and provide insight into the cortical mechanisms of coarticulation.

Categorical speech perception during active discrimination of consonants and vowels

Categorical perception of phonemes describes the phenomenon that, when phonemes are classified they are often perceived to fall into distinct categories even though physically they follow a continuum along a feature dimension.While consonants such as plosives have been proposed to be perceived categorically, the representation of vowels has been described to be more continuous. We aimed at testing this difference in representation at a behavioral and neurophysiological level using human magnetoencephalography (MEG).To this end, we designed stimuli based on natural speech by morphing along a phonological continuum entailing changes of the voiced stop-consonant or the steady-state vowel of a consonant–vowel (CV) syllable. Then, while recording MEG, we presented participants with consecutive pairs of either same or different CV syllables. The differences were such that either both CV syllables were from within the same category or belonged to different categories. During the MEG experiment, the participants actively discriminated the stimulus pairs.Behaviorally, we found that discrimination was easier for the between-compared to the within-category contrast for both consonants and vowels. However, this categorical effect was significantly stronger for the consonants compared to vowels, in line with a more continuous representation of vowels. At the neural level, we observed significant repetition suppression of MEG evoked fields, i.e. lower amplitudes for physically same compared to different stimulus pairs, at around 430 to 500ms after the onset of the second stimulus. Source reconstruction revealed generating sources of this repetition suppression effect within left superior temporal sulcus and gyrus, posterior to Heschl׳s gyrus. A region-of-interest analysis within this region showed a clear categorical effect for consonants, but not for vowels, providing further evidence for the important role of left superior temporal areas in categorical representation during active phoneme discrimination.

Forced-Attention Dichotic Listening With University Students With Dyslexia

Rapidly changing environments in day-to-day activities, enriched with stimuli competing for attention, require a cognitive control mechanism to select relevant stimuli, ignore irrelevant stimuli, and shift attention between alternative features of the environment. Such attentional orchestration is essential to the acquisition of reading skills. In the present forced attention dichotic listening study, adults with moderate and severe dyslexia and nondisabled adults were tested on their ability to switch attention between ears for immediate recall. Blocks of pairs of consonant–vowel syllables were counterbalanced into left-ear first or right-ear first ordered conditions. Significant order effects showed that only those with severe dyslexia were poorer in switching attention to the left ear, whereas both groups with dyslexia were poorer switching attention to the right ear. Shifting left appears to be a normative function of reading level, whereas inferior ability to disengage attending to the left ear to report from the right ear qualifies as a dysfunctional facet of dyslexia with etiological significance. No support was found for the traditional proposition that dyslexia may be associated with atypical left hemisphere lateralization. Combining these results with previous dichotic and neuroimaging research implicates a dysfunctional frontostriatal cognitive control network in dyslexia. With due caution, the results suggest that a neurobiological feature of dyslexia may be a lack of control in downwardly modulating excessive left inferior frontal cortex activations. The results are consistent with impoverished connectedness between left anterior and posterior language areas and, pending future confirmation of these findings, suggest the need for a reconceptualization of remedial programming.

Sources of pathology underlying listening disorders in children

Some children referred to audiology and developmental disability services have listening difficulties, despite normal audiograms. These children may be tested for ‘auditory processing disorder’ (APD), a controversial construct suggesting that neural dysfunction in the central auditory system leads to impaired auditory perception. An important question, not currently tested in clinical evaluation, is whether listening difficulties result from problems with bottom-up auditory sensory processing or top-down modulating cognition. Perceptual variability and poor performance on standardized tests suggest that listening difficulties are primarily cognitive in origin. However, evidence for impaired olivocochlear function and temporal processing deficits may implicate peripheral or central auditory dysfunction in some cases. Wide-spread, top-down modulation of auditory cortical, brainstem and ear function suggests that afferent and efferent control systems may not be simple to segregate. During normal maturation, hearing appears to develop in proportion to the complexity of both stimuli and tasks. But some younger individuals have mature hearing, highlighting individual differences that suggest APD may be due to a generalized developmental delay. Recent studies have investigated specific hypotheses showing, for example, that spatial hearing and executive function are compromised in some children with listening difficulties. Using speech stimuli (e.g. consonant–vowel syllables) to examine auditory brainstem responses, and psychophysiological relations between dichotic hearing and cortical physiology, various effects of auditory experience and development point the way to promising approaches for further studies of APD. Newer technology, from genetic sequencing to MRI, may have the sensitivity to test whether and how frequently APD is associated with impaired processing in the auditory system.

No, there is no 150 ms lead of visual speech on auditory speech, but a range of audiovisual asynchronies varying from small audio lead to large audio lag.

An increasing number of neuroscience papers capitalize on the assumption published in this journal that visual speech would be typically 150 ms ahead of auditory speech. It happens that the estimation of audiovisual asynchrony in the reference paper is valid only in very specific cases, for isolated consonant-vowel syllables or at the beginning of a speech utterance, in what we call “preparatory gestures”. However, when syllables are chained in sequences, as they are typically in most parts of a natural speech utterance, asynchrony should be defined in a different way. This is what we call “comodulatory gestures” providing auditory and visual events more or less in synchrony. We provide audiovisual data on sequences of plosive-vowel syllables (pa, ta, ka, ba, da, ga, ma, na) showing that audiovisual synchrony is actually rather precise, varying between 20 ms audio lead and 70 ms audio lag. We show how more complex speech material should result in a range typically varying between 40 ms audio lead and 200 ms audio lag, and we discuss how this natural coordination is reflected in the so-called temporal integration window for audiovisual speech perception. Finally we present a toy model of auditory and audiovisual predictive coding, showing that visual lead is actually not necessary for visual prediction.

Functional asymmetry and effective connectivity of the auditory system during speech perception is modulated by the place of articulation of the consonant- A 7T fMRI study.

To differentiate between stop-consonants, the auditory system has to detect subtle place of articulation (PoA) and voice-onset time (VOT) differences between stop-consonants. How this differential processing is represented on the cortical level remains unclear. The present functional magnetic resonance (fMRI) study takes advantage of the superior spatial resolution and high sensitivity of ultra-high-field 7 T MRI. Subjects were attentively listening to consonant–vowel (CV) syllables with an alveolar or bilabial stop-consonant and either a short or long VOT. The results showed an overall bilateral activation pattern in the posterior temporal lobe during the processing of the CV syllables. This was however modulated strongest by PoA such that syllables with an alveolar stop-consonant showed stronger left lateralized activation. In addition, analysis of underlying functional and effective connectivity revealed an inhibitory effect of the left planum temporale (PT) onto the right auditory cortex (AC) during the processing of alveolar CV syllables. Furthermore, the connectivity result indicated also a directed information flow from the right to the left AC, and further to the left PT for all syllables. These results indicate that auditory speech perception relies on an interplay between the left and right ACs, with the left PT as modulator. Furthermore, the degree of functional asymmetry is determined by the acoustic properties of the CV syllables.

Auditory attention in a dynamic scene: Behavioral and electrophysiological correlates

The ability to direct and redirect selective auditory attention varies substantially across individuals with normal hearing thresholds, even when sounds are clearly audible. We hypothesized that these differences can come from both differences in the spectrotemporal fidelity of subcortical sound representations and in the efficacy of cortical attentional networks that modulate neural representations of the auditory scene. Here, subjects were presented with an initial stream from straight ahead and a second stream (from either left or right), each comprised of four monotonized consonant-vowel syllables. Listeners were instructed to report the contents of either the first stream (holding attentional focus) or the second stream (switching attentional focus). Critically, the direction of the second stream informed subjects whether to hold or to switch attention. Pilot results suggest that when the lateral angle of the second stream is small, task performance is linked to subcortical encoding fidelity of suprathreshold sound (as measured using brainstem frequency-following responses obtained separately in the same subjects). Using a paradigm that allows simultaneous collection of behavioral measures, FFRs, and cortical responses, here we test whether differences in top-down attentional control explain subject variability when the second stream’s lateral angle is large and coding fidelity does not limit performance.

The neural basis of sublexical speech and corresponding nonspeech processing: A combined EEG–MEG study

We addressed the neural organization of speech versus nonspeech sound processing by investigating preattentive cortical auditory processing of changes in five features of a consonant–vowel syllable (consonant, vowel, sound duration, frequency, and intensity) and their acoustically matched nonspeech counterparts in a simultaneous EEG–MEG recording of mismatch negativity (MMN/MMNm). Overall, speech–sound processing was enhanced compared to nonspeech sound processing. This effect was strongest for changes which affect word meaning (consonant, vowel, and vowel duration) in the left and for the vowel identity change in the right hemisphere also. Furthermore, in the right hemisphere, speech–sound frequency and intensity changes were processed faster than their nonspeech counterparts, and there was a trend for speech-enhancement in frequency processing. In summary, the results support the proposed existence of long-term memory traces for speech sounds in the auditory cortices, and indicate at least partly distinct neural substrates for speech and nonspeech sound processing.

How brain asymmetry relates to performance – a large-scale dichotic listening study

All major mental functions including language, spatial and emotional processing are lateralized but how strongly and to which hemisphere is subject to inter- and intraindividual variation. Relatively little, however, is known about how the degree and direction of lateralization affect how well the functions are carried out, i.e., how lateralization and task performance are related. The present study therefore examined the relationship between lateralization and performance in a dichotic listening task for which we had data available from 1839 participants. In this task, consonant-vowel syllables are presented simultaneously to the left and right ear, such that each ear receives a different syllable. When asked which of the two they heard best, participants typically report more syllables from the right ear, which is a marker of left-hemispheric speech dominance. We calculated the degree of lateralization (based on the difference between correct left and right ear reports) and correlated it with overall response accuracy (left plus right ear reports). In addition, we used reference models to control for statistical interdependency between left and right ear reports. The results revealed a u-shaped relationship between degree of lateralization and overall accuracy: the stronger the left or right ear advantage, the better the overall accuracy. This u-shaped asymmetry-performance relationship consistently emerged in males, females, right-/non-right-handers, and different age groups. Taken together, the present study demonstrates that performance on lateralized language functions depends on how strongly these functions are lateralized. The present study further stresses the importance of controlling for statistical interdependency when examining asymmetry-performance relationships in general.

Vowel locus equations as a measure of vowel coarticulatory aggressiveness

Studies in locus equations, a quantification of the degree to which F2 at vowel onset (or consonant place) can be predicted by F2 at vowel midpoint (or vowel place), have shown that the slope of locus equations is a reverse measure of coarticulatory resistance of consonants, in consonant-vowel (CV) sequences with C fixed and V varying. This study presents the first application of locus equations to the measure of coarticulatory properties of vowels. The locus equations analysis for vowels, on our articulatory data (collected with electromagnetic articulograph, EMA) of CV syllables from 7 Taiwan Mandarin speakers, with V fixed and C varying, shows that vowel /i/ has the greatest slope among vowels at tongue body, whereas vowel /a/ and /u/ mostly do not distinguish from each other, and at the tongue tip, the slope does not vary across the three vowels /i/, /a/ and /u/. Based on the CV model theory of gestural coordination (C-V in-phase relation) and the formula of linear regression, we claim that the slope of vowel locus equations is positively related to coarticulatory aggressiveness of vowel, which is further supported by a comparison with a well-established measure of vowel coarticulatory aggressive, based on contextual variability, on the same data.

Sequence Complexity Effects on Speech Production in Healthy Speakers and Speakers with Hypokinetic or Ataxic Dysarthria

The present study investigated the effects of sequence complexity, defined in terms of phonemic similarity and phonotoactic probability, on the timing and accuracy of serial ordering for speech production in healthy speakers and speakers with either hypokinetic or ataxic dysarthria. Sequences were comprised of strings of consonant-vowel (CV) syllables with each syllable containing the same vowel, /a/, paired with a different consonant. High complexity sequences contained phonemically similar consonants, and sounds and syllables that had low phonotactic probabilities; low complexity sequences contained phonemically dissimilar consonants and high probability sounds and syllables. Sequence complexity effects were evaluated by analyzing speech error rates and within-syllable vowel and pause durations. This analysis revealed that speech error rates were significantly higher and speech duration measures were significantly longer during production of high complexity sequences than during production of low complexity sequences. Although speakers with dysarthria produced longer overall speech durations than healthy speakers, the effects of sequence complexity on error rates and speech durations were comparable across all groups. These findings indicate that the duration and accuracy of processes for selecting items in a speech sequence is influenced by their phonemic similarity and/or phonotactic probability. Moreover, this robust complexity effect is present even in speakers with damage to subcortical circuits involved in serial control for speech.

Reactive cognitive-control processes in free-report consonant–vowel dichotic listening

The relevance of cognitive-control processes has been frequently discussed and studied in the context of dichotic listening. Experimental and clinical studies indicate that directing attention to either of the two simultaneously presented phonological stimuli, but especially to the left-ear stimulus increases the requirements for cognitive-control processes. Here, we extend this view by reporting the results of a behavioural and a functional magnetic-resonance imaging (fMRI) experiment designed to analyse the involvement of cognitive-control processes also in a free-report dichotic-listening paradigm. It was hypothesised that dichotically presented pairs of stop–consonant–vowel syllables would provide different demands for cognitive-control processes as a function of the spectro-temporal overlap of the two stimuli. Accordingly, in Experiment 1 it was shown that dichotic syllables of high (e.g., /ba/ and /ga/) as opposed to low spectro-temporal overlap (e.g., /ba/ and /ka/) produce significantly faster and more correct answers, and are more often perceived as one syllable. In Experiment 2 it was further shown that pairs of low as compared to high spectro-temporal overlap trigger a more pronounced activation predominately in left-hemispheric, speech-associated brain regions, namely left posterior inferior sulcus/gyrus, bilaterally in pre-supplementary motor and mid-cingulate cortex as well as in the inferior parietal lobe. Taken together, behavioural and functional data indicate a stronger involvement of reactive cognitive control in the processing of low-overlap as opposed to high-overlap stimulus pairs. This supports the notion that higher-order, speech-related cognitive-control processes also are involved in a free-report dichotic-listening paradigm.

P 45. The right planum temporale is involved in auditory attention-evidence from TMS

It is well known that the planum temporale (PT) carries out spectro-temporal analysis of auditory stimuli, which is crucial for speech, for example. There are suggestions, however, that the PT is also involved in auditory attention, specifically in the discrimination and selection of left and right ear stimuli. We aimed to provide a direct test for the role of the PT in auditory attention. Fourteen participants (7 men, 7 women) completed the Bergen Dichotic Listening Test. In this test two different consonant–vowel syllables (e.g., “ba” and “da”) are presented simultaneously, one to each ear, and participants are asked to report the sound they heard best or most clearly. Each participant completed the test three times, that is, after repetitive transcranial magnetic stimulation (rTMS) for 10 min at a frequency of 1 Hz had been applied to the left and the right PT (located with anatomical brain scans), and after sham stimulation with a placebo coil (control). The order of left, right and sham PT stimulation was counterbalanced. After sham stimulation the typical right ear advantage emerged, that is, participants reported relatively more right than left ear stimuli reflecting a left-hemispheric dominance for language. However, rTMS over the right but not left PT significantly reduced the right ear advantage. This was the result of participants reporting more left and fewer right ear stimuli after right PT stimulation, suggesting there was a leftward shift in stimulus selection. Our findings support the notion that the PT, and the right PT in particular, is involved in stimulus selection and auditory attention, although its primary function is auditory perception.

Audiovisual attention boosts letter‐speech sound integration

We studied attention effects on the integration of written and spoken syllables in fluent adult readers by using event-related brain potentials. Auditory consonant-vowel syllables, including consonant and frequency changes, were presented in synchrony with written syllables or their scrambled images. Participants responded to longer-duration auditory targets (auditory attention), longer-duration visual targets (visual attention), longer-duration auditory and visual targets (audiovisual attention), or counted backwards mentally. We found larger negative responses for spoken consonant changes when they were accompanied by written syllables than when they were accompanied by scrambled text. This effect occurred at an early latency (∼ 140 ms) during audiovisual attention and later (∼ 200 ms) during visual attention. Thus, audiovisual attention boosts the integration of speech sounds and letters.

A One-Hour Sleep Restriction Impacts Brain Processing in Young Children Across Tasks: Evidence From Event-Related Potentials

The effect of mild sleep restriction on cognitive functioning in young children is unclear, yet sleep loss may impact children's abilities to attend to tasks with high processing demands. In a preliminary investigation, six children (6.6–8.3 years of age) with normal sleep patterns performed three tasks: attention (“Oddball”), speech perception (consonant–vowel syllables), and executive function (Directional Stroop). Event-related potentials (ERPs) responses were recorded before (Control) and following 1 week of 1-hour per day of sleep restriction. Brain activity across all tasks following Sleep Restriction differed from activity during Control Sleep, indicating that minor sleep restriction impacts children's neurocognitive functioning.

Longitudinal Study of Early Vocalization Development in Toddlers with and without Cleft Palate from 6 to 18 Months of Age

Objectives: Early vocalization shows a close relationship with speech sound development and influences the onset of first words. This study explored longitudinally early vocalization development in toddlers with and without cleft palate from 6 to 18 months of age. Methods: The participants included 3 toddlers with cleft palate and 3 typically developing toddlers. Their vocalization samples were obtained with 3-month intervals from 6 or 7 to 18 months of age. The vocalization samples were analyzed based on the Stark assessment of early vocal development-revised and measures on vocalization types and each vocalization ratio were obtained. Results: Results indicated that group differences were observed in the ratio of level 2 at 18 months of age; toddlers with cleft palate exhibited a larger ratio of level 2 vocalization at 18 months of age. Two toddlers with cleft palate showed delayed vocalization developmental patterns during the entire period of the study. Toddlers with cleft palate showed decreases in level 2 which includes fully-resonant nuclei and two closant- vocant combinations. However, they did not exhibit remarkable changes in level 4 and 5 which include single consonant-vowel syllable, repeated canonical syllable, and jargon. Typically developing toddlers showed decreases in level 2 vocalization and progressive increases in level 4 and 5. Conclusion: This study suggested that toddlers with cleft palate generally showed delayed vocalization development compared to typically developing toddlers. The study results have implications for monitoring the development of pre-linguistic vocalization in toddlers with cleft palate.

Knowledge-Based Features for Place Classification of Unvoiced Stops

AbstractThe classification of unvoiced stops in consonant–vowel (CV) syllables, segmented from continuous speech, is investigated by features related to speech production. As burst and vocalic transitions contribute to identification of stops in the CV context, features are computed from both regions. Although formants are the truly discriminating articulatory features, their estimation from the speech signal is a challenge especially in unvoiced regions like the release burst of stops. This may be compensated partially by sub-band energy-based features. In this work, formant features from the vocalic region are combined with features from the burst region comprising sub-band energies, as well as features from a formant tracking method developed for unvoiced regions. The overall combination of features at the classifier level obtains an accuracy of 84.4%, which is significantly better than that obtained with solely sub-band features on unvoiced stops in CV syllables of TIMIT.