Speech Production Areas Research Articles

Do young EFL learners benefit from task repetition?

ABSTRACT Previous research has shown that task repetition can positively affect L2 oral performance. However, few studies have explored the effects of task repetition on young EFL learners’ production. Also, task repetition research has paid little attention to effects of spacing examined through longer time intervals between the two occasions of task performance. Therefore, this study investigated the impact of immediate and delayed task repetition on young learners’ oral production in terms of complexity, accuracy, and fluency. Forty-four learners aged between 10 and 12 studying at a private language institute in Tehran, Iran, were randomly assigned to one of the three groups in the study: no repetition (NR), immediate task repetition (ITR) and delayed task repetition (DTR). The participants were asked to watch a short silent movie and narrate its story. In the ITR condition, participants repeated the task immediately after their first enactment; the DTR group repeated the same task after 1 month ; and the NR group carried out the task only once. The results showed that ITR had positive impacts on all the three areas of speech production, while DTR could improve accuracy and partly fluency. Also, among the examined areas of oral language production, complexity was found to be the least affected area.

Transcranial direct current stimulation (tDCS) enhances internal source monitoring abilities in healthy participants.

Source monitoring refers to the ability to identify the origin of a memory, for example, whether you remember saying something or thinking about it, and confusions of these sources have been associated with the experience of auditory verbal hallucinations (AVHs). Both AVHs and source confusions are reported to originate from dysfunctional brain activations in the prefrontal cortex (PFC) and the superior temporal gyrus (STG); specifically, it is assumed that a hypoactive PFC and a hyperactive STG gives rise to AVHs and source confusions. We set out to test this assumption by trying to mimic this hypertemporal/hypofrontal model in healthy individuals with transcranial direct current stimulation (tDCS): the inhibitory cathode was placed over the left PFC and the excitatory anode over the left dorsolateral STG. Participants completed a reality monitoring task (distinguishing between external and internal memory sources) and an internal source monitoring task (distinguishing between two or more internal memory sources) in two separate experiments (offline vs. online tDCS). In the offline experiment (n = 34), both source monitoring tasks were completed after tDCS stimulation, and in the online experiment (n = 27) source monitoring tasks were completed while simultaneously being stimulated with tDCS. We found that internal source monitoring abilities were significantly enhanced during active online tDCS, while reality monitoring abilities were unaffected by stimulation in both experiments. We speculate, based on combining the present findings with previous studies, that there might be different brain areas involved in reality and internal source monitoring. While internal source monitoring seems to involve speech production areas, specifically Broca’s area, as suggested in the present study, reality monitoring seems to rely more on the STG and DLPFC, as shown in other studies of the field.

Damage to Broca's area does not contribute to long-term speech production outcome after stroke.

Broca’s area in the posterior half of the left inferior frontal gyrus has long been thought to be critical for speech production. The current view is that long-term speech production outcome in patients with Broca’s area damage is best explained by the combination of damage to Broca’s area and neighbouring regions including the underlying white matter, which was also damaged in Paul Broca’s two historic cases. Here, we dissociate the effect of damage to Broca’s area from the effect of damage to surrounding areas by studying long-term speech production outcome in 134 stroke survivors with relatively circumscribed left frontal lobe lesions that spared posterior speech production areas in lateral inferior parietal and superior temporal association cortices. Collectively, these patients had varying degrees of damage to one or more of nine atlas-based grey or white matter regions: Brodmann areas 44 and 45 (together known as Broca’s area), ventral premotor cortex, primary motor cortex, insula, putamen, the anterior segment of the arcuate fasciculus, uncinate fasciculus and frontal aslant tract. Spoken picture description scores from the Comprehensive Aphasia Test were used as the outcome measure. Multiple regression analyses allowed us to tease apart the contribution of other variables influencing speech production abilities such as total lesion volume and time post-stroke. We found that, in our sample of patients with left frontal damage, long-term speech production impairments (lasting beyond 3 months post-stroke) were solely predicted by the degree of damage to white matter, directly above the insula, in the vicinity of the anterior part of the arcuate fasciculus, with no contribution from the degree of damage to Broca’s area (as confirmed with Bayesian statistics). The effect of white matter damage cannot be explained by a disconnection of Broca’s area, because speech production scores were worse after damage to the anterior arcuate fasciculus with relative sparing of Broca’s area than after damage to Broca’s area with relative sparing of the anterior arcuate fasciculus. Our findings provide evidence for three novel conclusions: (i) Broca’s area damage does not contribute to long-term speech production outcome after left frontal lobe strokes; (ii) persistent speech production impairments after damage to the anterior arcuate fasciculus cannot be explained by a disconnection of Broca’s area; and (iii) the prior association between persistent speech production impairments and Broca’s area damage can be explained by co-occurring white matter damage, above the insula, in the vicinity of the anterior part of the arcuate fasciculus.

Perceptual and acoustic evaluation of speech production in Down syndrome: A case series

ABSTRACT People with Down syndrome (DS) can experience difficulties with speech production that can impact on speech intelligibility. In previous research, both perceptual and acoustic analysis has shown that people with DS can have difficulties with speech production in the areas of respiration, phonation, articulation, resonance and prosody. However, these studies have investigated various aspects of speech production separately. No study has examined all components of speech production in one single study and considered how these components, if impaired, may impact on speech intelligibility in DS. This paper presents the data of three male speakers with DS and three age- and gender-matched controls as a case series. The participants’ speech samples were analysed using a number of perceptual and acoustic parameters, across the major components of speech production – respiration, phonation, articulation, resonance, and prosody. Results showed that different areas of speech production were affected in each participant, to different extents. The main perceptual difficulties included poor voice quality, monopitch, and monoloudness. Acoustic findings showed a higher mean F0, lower harmonics-to-noise ratio and longer voice onset times. These preliminary findings show that people with DS can present with mixed profiles of speech production that can affect speech intelligibility. When assessing speech production in DS, clinicians need to evaluate all components of speech production and consider how they may be impacting intelligibility.

Speech synthesis from ECoG using densely connected 3D convolutional neural networks

Objective. Direct synthesis of speech from neural signals could provide a fast and natural way of communication to people with neurological diseases. Invasively-measured brain activity (electrocorticography; ECoG) supplies the necessary temporal and spatial resolution to decode fast and complex processes such as speech production. A number of impressive advances in speech decoding using neural signals have been achieved in recent years, but the complex dynamics are still not fully understood. However, it is unlikely that simple linear models can capture the relation between neural activity and continuous spoken speech. Approach. Here we show that deep neural networks can be used to map ECoG from speech production areas onto an intermediate representation of speech (logMel spectrogram). The proposed method uses a densely connected convolutional neural network topology which is well-suited to work with the small amount of data available from each participant. Main results. In a study with six participants, we achieved correlations up to r = 0.69 between the reconstructed and original logMel spectrograms. We transfered our prediction back into an audible waveform by applying a Wavenet vocoder. The vocoder was conditioned on logMel features that harnessed a much larger, pre-existing data corpus to provide the most natural acoustic output. Significance. To the best of our knowledge, this is the first time that high-quality speech has been reconstructed from neural recordings during speech production using deep neural networks.

Laterality of anterior temporal lobe repetitive transcranial magnetic stimulation determines the degree of disruption in picture naming

The bilateral anterior temporal lobes play a key role in semantic representation. This is clearly demonstrated by the performance of patients with semantic dementia, a disorder characterised by a progressive and selective decline in semantic memory over all modalities as a result of anterior temporal atrophy. Although all patients exhibit a progressive decline in both single-word production and comprehension, those with greater atrophy to the left anterior temporal lobe show a stronger decline in word production than comprehension. This asymmetry has been attributed to the greater connectivity of the left anterior temporal lobe with left-lateralised speech production mechanisms. Virtual lesioning of the left ATL using offline repetitive transcranial magnetic stimulation (rTMS) has been shown to disrupt picture naming, but, the impact of right ATL rTMS is yet to be explored. We tested the prediction that disruption of picture naming in normal participants by rTMS should be greater for the left than the right ATL. We found a significant increase in picture naming latencies specifically for stimulation of the left ATL only. Neither left nor right ATL TMS slowed performance in a number naming control task. These results support the hypothesis that although both temporal lobes are part of a widespread semantic network in the human brain, the left anterior temporal lobe possesses a stronger connection to left-lateralised speech production areas than the right temporal lobe.

Frontal Top-Down Signals Increase Coupling of Auditory Low-Frequency Oscillations to Continuous Speech in Human Listeners

SummaryHumans show a remarkable ability to understand continuous speech even under adverse listening conditions. This ability critically relies on dynamically updated predictions of incoming sensory information, but exactly how top-down predictions improve speech processing is still unclear. Brain oscillations are a likely mechanism for these top-down predictions [1, 2]. Quasi-rhythmic components in speech are known to entrain low-frequency oscillations in auditory areas [3, 4], and this entrainment increases with intelligibility [5]. We hypothesize that top-down signals from frontal brain areas causally modulate the phase of brain oscillations in auditory cortex. We use magnetoencephalography (MEG) to monitor brain oscillations in 22 participants during continuous speech perception. We characterize prominent spectral components of speech-brain coupling in auditory cortex and use causal connectivity analysis (transfer entropy) to identify the top-down signals driving this coupling more strongly during intelligible speech than during unintelligible speech. We report three main findings. First, frontal and motor cortices significantly modulate the phase of speech-coupled low-frequency oscillations in auditory cortex, and this effect depends on intelligibility of speech. Second, top-down signals are significantly stronger for left auditory cortex than for right auditory cortex. Third, speech-auditory cortex coupling is enhanced as a function of stronger top-down signals. Together, our results suggest that low-frequency brain oscillations play a role in implementing predictive top-down control during continuous speech perception and that top-down control is largely directed at left auditory cortex. This suggests a close relationship between (left-lateralized) speech production areas and the implementation of top-down control in continuous speech perception.

The role of the dominant versus the non-dominant hemisphere: An fMRI study of Aphasia recovery following stroke

Background: Speech production is one of the most frequently affected cognitive functions following stroke; however, the neural mechanisms underlying the recovery of speech function are still incompletely understood.Aims: The current study aims to address the differential contributions of the dominant and non-dominant hemispheres in recovery from aphasia following stroke by comparing data from four stroke patients and 12 control participants to assess the patterns of activation during speech production tasks during functional magnetic resonance imaging (fMRI) scanning.Methods & Procedures: Four chronic stroke patients (three left-hemisphere lesion and one right-hemisphere lesion) diagnosed with Broca’s aphasia at the acute phase, but now recovered to near normal speech ability, were tested on speech production tasks (phonemic fluency, categorical fluency and picture naming) whilst undergoing fMRI. These patients were compared with 12 healthy controls undergoing the same procedure.Outcomes & Results: Individual subject analysis showed activation peaks in perilesional areas in three out of four patients. This included one patient with right-hemisphere lesion, who also showed predominant perilesional activation. Group analysis of control participants showed predominately left-hemisphere activation, but not exclusively so. Laterality indexes were calculated and showed predominant left-hemisphere lateralisation in the control group (LI = 0.4). Three out of the four patients showed speech lateralised to the same hemisphere as their lesion and the fourth patient showed speech lateralised to the opposite hemisphere to their lesion. Different speech production tasks resulted in varying lateralisation indices (LIs) within participants.Conclusions: The data suggest that perilesional areas support recovery of speech in the chronic phase post-stroke regardless of the site of the lesion. The study has implications for the understanding of functional recovery as well as for the paradigms used in fMRI to localise speech production areas. Specifically, a variety of speech tasks are required to elicit activation that is representative of the range of cortical involvement in speech in healthy adults and that also allows for accurate reporting of the extent of recovery experienced in patients.

Nonlinear frequency compression in hearing aids: impact on speech and language development.

The research questions of this study were: (1) Are children using nonlinear frequency compression (NLFC) in their hearing aids getting better access to the speech signal than children using conventional processing schemes? The authors hypothesized that children whose hearing aids provided wider input bandwidth would have more access to the speech signal, as measured by an adaptation of the Speech Intelligibility Index, and (2) are speech and language skills different for children who have been fit with the two different technologies; if so, in what areas? The authors hypothesized that if the children were getting increased access to the speech signal as a result of their NLFC hearing aids (question 1), it would be possible to see improved performance in areas of speech production, morphosyntax, and speech perception compared with the group with conventional processing. Participants included 66 children with hearing loss recruited as part of a larger multisite National Institutes of Health-funded study, Outcomes for Children with Hearing Loss, designed to explore the developmental outcomes of children with mild to severe hearing loss. For the larger study, data on communication, academic and psychosocial skills were gathered in an accelerated longitudinal design, with entry into the study between 6 months and 7 years of age. Subjects in this report consisted of 3-, 4-, and 5-year-old children recruited at the North Carolina test site. All had at least at least 6 months of current hearing aid usage with their NLFC or conventional amplification. Demographic characteristics were compared at the three age levels as well as audibility and speech/language outcomes; speech-perception scores were compared for the 5-year-old groups. Results indicate that the audibility provided did not differ between the technology options. As a result, there was no difference between groups on speech or language outcome measures at 4 or 5 years of age, and no impact on speech perception (measured at 5 years of age). The difference in Comprehensive Assessment of Spoken Language and mean length of utterance scores for the 3-year-old group favoring the group with conventional amplification may be a consequence of confounding factors such as increased incidence of prematurity in the group using NLFC. Children fit with NLFC had similar audibility, as measured by a modified Speech Intelligibility Index, compared with a matched group of children using conventional technology. In turn, there were no differences in their speech and language abilities.

Different Neural Networks Are Involved in Audiovisual Speech Perception Depending on the Context

How are we able to easily and accurately recognize speech sounds despite the lack of acoustic invariance? One proposed solution is the existence of a neural representation of speech syllable perception that transcends its sensory properties. In the present fMRI study, we used two different audiovisual speech contexts both intended to identify brain areas whose levels of activation would be conditioned by the speech percept independent from its sensory source information. We exploited McGurk audiovisual fusion to obtain short oddball sequences of syllables that were either (a) acoustically different but perceived as similar or (b) acoustically identical but perceived as different. We reasoned that, if there is a single network of brain areas representing abstract speech perception, this network would show a reduction of activity when presented with syllables that are acoustically different but perceived as similar and an increase in activity when presented with syllables that are acoustically similar but perceived as distinct. Consistent with the long-standing idea that speech production areas may be involved in speech perception, we found that frontal areas were part of the neural network that showed reduced activity for sequences of perceptually similar syllables. Another network was revealed, however, when focusing on areas that exhibited increased activity for perceptually different but acoustically identical syllables. This alternative network included auditory areas but no left frontal activations. In addition, our findings point to the importance of subcortical structures much less often considered when addressing issues pertaining to perceptual representations.

Mandarin Neutral Tone—does It Change Target

It is known that in Mandarin each of the five lexical tones can be assigned with an articulatorily functional target: [high] for tone 1, [rise] for tone 2, [low] for tone 3, [fall] for tone 4 and [mid] for tone 5 (the first four tones are known as full tones while tone 5 is called neutral tone). Given that the targets of full tones can change (e.g., from tone 3 to tone 2) in certain speech conditions (e.g. tone sandhi), it is natural to ask whether the same is true for Mandarin neutral tone. This is still an unresolved question, the solution of which can contribute to our understanding of articulatory “strength” as an index of speech communication which is less well explored than other areas of speech production. Motivated by the above concerns, this study uses speech production experiment to test whether the target of Mandarin neutral tone has similar target values (in terms of target slope, height, duration and strength) to those of other tones in Mandarin under three speech conditions: emotion (anger, happiness, disgust and neural emotion), sentence position of the neutral tone (sentence medial and final) and tones preceding the neutral tone (all full tones in Mandarin). The results reveal that the neutral tone is highly likely to change its target in certain combinations of the aforementioned three speech conditions. This study not only further supports previous studies on the impact of emotion, sentence position and tonal contexts on the target behavior of tones, but also highlights the possibility of Mandarin neutral tone changing from weak to strong in articulation for the purpose of effective communication, providing further evidence for “strength” as a communication index.

Effects of diet on early stage cortical perception and discrimination of syllables differing in voice-onset time: A longitudinal ERP study in 3 and 6 month old infants

The influence of diet on cortical processing of syllables was examined at 3 and 6 months in 239 infants who were breastfed or fed milk or soy-based formula. Event-related potentials to syllables differing in voice-onset-time were recorded from placements overlying brain areas specialized for language processing. P1 component amplitude and latency measures indicated that at both ages infants in all groups could extract and discriminate categorical information from syllables. Between-syllable amplitude differences—present across groups—were generally greater for SF infants. Responses peaked earlier over left hemisphere speech-perception than speech-production areas. Encoding was faster in BF than formula-fed infants. The results show that in preverbal infants: (1) discrimination of phonetic information occurs in early stages of cortical processing; (2) areas overlying brain regions of speech perception are activated earlier than those involved in speech production; and (3) these processes are differentially modulated by infant diet and environmental factors.

Reading Aloud Boosts Connectivity through the Putamen

Functional neuroimaging and lesion studies have frequently reported thalamic and putamen activation during reading and speech production. However, it is currently unknown how activity in these structures interacts with that in other reading and speech production areas. This study investigates how reading aloud modulates the neuronal interactions between visual recognition and articulatory areas, when both the putamen and thalamus are explicitly included. Using dynamic causal modeling in skilled readers who were reading regularly spelled English words, we compared 27 possible pathways that might connect the ventral anterior occipito-temporal sulcus (aOT) to articulatory areas in the precentral cortex (PrC). We focused on whether the neuronal interactions within these pathways were increased by reading relative to picture naming and other visual and articulatory control conditions. The results provide strong evidence that reading boosts the aOT–PrC pathway via the putamen but not the thalamus. However, the putamen pathway was not exclusive because there was also evidence for another reading pathway that did not involve either the putamen or the thalamus. We conclude that the putamen plays a special role in reading but this is likely to vary with individual reading preferences and strategies.

The Effect of Lexical Frequency on Phonological Processes in English

It has been observed that lexical frequency affects various areas of speech production. In this paper, we attempt to analyze the effect of lexical frequency on the application of phonological processes. Specifically, as to the relationship between lexical frequency and lenition, we explain that, if a word is easily accessed since it is predictable and frequent, the leniting and automating processes will be processed more easily. However, if a word is less frequent and predictable, the leniting processes could be suppressed because more complete articulation will be required for the word. In addition, we pursued the way to encode the effect of lexical frequency in Optimality Theory. By analyzing the different application mode of vowel reduction in high-frequency and low-frequency words, we provide an analysis of the effect of lexical frequency on phonological processes with the assumption of different constraint rankings.

Whole-Brain Morphometric Study of Schizophrenia Revealing a Spatially Complex Set of Focal Abnormalities

Neuroanatomic abnormalities in schizophrenia may underlie behavioral manifestations. Characterization of such abnormalities is required for interpreting functional data. Frontotemporal abnormalities have been documented by using predetermined region-of-interest approaches, but deformation-based morphometry permits examination of the entire brain. To perform whole-brain analyses of structural differences between patients with schizophrenia and controls, to examine sex and medication effects, and to apply a high-dimensional nonlinear pattern classification technique to quantify the degree of separation between patients and controls, thereby testing the potential of this new technique as an aid to diagnostic procedures. Whole-brain morphologic analysis using high-dimensional shape transformations. Schizophrenia Research Center, University of Pennsylvania Medical Center. Neuroleptic-naïve and previously treated patients with DSM-IV schizophrenia (n = 69) and sociodemographically matched controls (n = 79). Gray matter, white matter, and ventricular cerebrospinal fluid volumes in the brain. Magnetic resonance images showed reduced gray matter and increased ventricular cerebrospinal fluid volumes in patients with schizophrenia in the whole brain and in specific foci: the hippocampus and adjacent white matter, the cingulate and orbitofrontal cortex, the frontotemporal and parietotemporal areas, and the occipital areas near the lingual gyrus. The classifier had a mean classification accuracy of 81.1% for men and women combined (82% for women and 85% for men, when each group was treated separately), determined via cross-validation. This study confirms previous findings of reduced frontotemporal volumes and suggests new hypotheses, especially involving occipital association and speech production areas. It also suggests finer localization of volume reduction in the hippocampus and other limbic structures and in the frontal lobe. Pattern classification showed high sensitivity and specificity for the diagnosis of schizophrenia, suggesting the potential utility of magnetic resonance imaging as a diagnostic aid.

How reading differs from object naming at the neuronal level

This paper uses whole brain functional neuroimaging in neurologically normal participants to explore how reading aloud differs from object naming in terms of neuronal implementation. In the first experiment, we directly compared brain activation during reading aloud and object naming. This revealed greater activation for reading in bilateral premotor, left posterior superior temporal and precuneus regions. In a second experiment, we segregated the object-naming system into object recognition and speech production areas by factorially manipulating the presence or absence of objects (pictures of objects or their meaningless scrambled counterparts) with the presence or absence of speech production (vocal vs. finger press responses). This demonstrated that the areas associated with speech production (object naming and repetitively saying “OK” to meaningless scrambled pictures) corresponded exactly to the areas where responses were higher for reading aloud than object naming in Experiment 1. Collectively the results suggest that, relative to object naming, reading increases the demands on shared speech production processes. At a cognitive level, enhanced activation for reading in speech production areas may reflect the multiple and competing phonological codes that are generated from the sublexical parts of written words. At a neuronal level, it may reflect differences in the speed with which different areas are activated and integrate with one another.

Speech production models—Constraints and control strategies

Our modeling includes five areas of speech production. (1) Extension of the three-parameter vocal tract area function model of Fant (1960) to include bandwidths and to allow for variations of length and degree of asymmetry of the tongue section, and covariation of these parameters as well as overall VT length and configurations in the laryngeal region. (2) Algorithms for inverse transform, i.e., deriving VT parameters from formant frequencies. (3) Control strategies for synthesis of combinations of vocalic sounds from VT area function parameters. (4) A study of essential cavity structures of fricatives and stops with a discussion of source functions, in part based on data from Fant (1960). (5) Discussion of how source-filter interaction may be implemented and how it affects control strategies in formant synthesis based on underlying vocal tract simulations. [This work has been supported by grants from the Swedish Board of Technical Development and the Swedish Telecom.]

Speech production.

This is a status report on three areas of speech production: (1) Functional properties of the speech production apparatus: the current state of knowledge of the respiratory, phonatory and articulatory systems is briefly discussed. (2) Control principles underlying speech production: the nature of the supposed invariance underlying segment production, theories of coarticulation, the relation between control units and linguistic units, peripheral neurophysiology and mechanics, and Action Theory. (3) The biological basis of the speech production process: discussion of whether discontinuity in vocal tract evolution is accompanied by discontinuity in linguistic evolution, presentation of evidence that babbling is an important precursor to early speech, and a discussion of interhemispheric and intrahemispheric localization of linguistic functions.

Basic directions in automatic speech recognition

This paper represents a view of basic problems in automatic speech recognition drawn from the vantage point of applied linguistics. The basic areas of speech production, articulatory phonetics, acoustic analysis, acoustic phonetics, and phonetic sequences of natural speech are crucial to flexible automatic speech recognition, especially for the long-range goal of recognizing continuous-flow large-vocabulary natural speech of different speakers. Articulatory phonetics provides a link between the physical events of speech and the elements of the phonological code. The processes of speech production are basic to articulatory phonetics while the acoustic theory of speech production provides a basis for the phonetic interpretation of the acoustic. speech waveform. Formant frequencies are particularly important acoustic parameters and recent improvements in formant tracking are encouraging for speech recognition. Even if complete phonetic recognition is realized, however, there remains the conversion of phonetic strings to lexical strings. This problem requires extensive phonetic analysis of actual spoken language.