Passive Speech Research Articles

How teaching surgeons communicate: An analysis of intraoperative discourse among male and female surgeons

BackgroundOur objective was to compare the use of agentic (“I”) and communal (“we”) spoken intraoperative discourse between male and female attending and resident surgeons. MethodsWe analyzed transcripts involving attending and resident surgeons from 5 specialties at a single Midwestern academic teaching hospital. We adapted and expanded Grebelsky-Lichtman's codes, assessed rater agreement, and systematically coded transcripts for agentic and communal terms. Differences between genders and roles were evaluated using Mann-Whitney U tests. ResultsIn the operating room, attendings used significantly more Action Demands, Rationality, Collective Speech, Passive Speech, Nurturing Speech, and Degree Modifiers. Conversely, residents used significantly more Assertive Speech, and Display Solution. Attendings were also more likely to use Action Demands combined with Passive Speech. No significant gender differences were found in any categories. ConclusionsLanguage use in the OR is more closely associated with professional role rather than gender and may reflect underlying power dynamics and the nature of the surgical teaching environment.

The left posterior sMMN: a marker of syntactic processing compensation in agrammatic aphasia

ABSTRACT Background Agrammatic aphasia poses challenges in assessing grammatical abilities due to language comprehension difficulties. The suitability of sMMN as an indicator of syntactic processing abilities in these individuals remains uncertain. Aims Two ERP experiments were conducted to investigate whether early syntactic mismatch negativity (sMMN) could assess the syntactic processing ability of Chinese-speaking individuals with agrammatic aphasia. Methods & Procedures Prior to the ERP experiments, the Western Aphasia Battery (WAB) and the Northwestern Assessment of Verbs and Sentences-Chinese (NAVS-C) were used to screen people with agrammatism. ERP data were collected for both the agrammatic group (AG) (n = 12) and the control group (CG) (n = 12). The first experiment (Experiment 1) involved a passive tone oddball task to control for the influence of primary sound perception. The second experiment (Experiment 2: experiment 2a and experiment 2b) investigated syntactic processing through a passive speech oddball task. Experiment 2a examined the processing of correct sentences and syntactic violation sentences in context. In contrast, Experiment 2b assessed well-formed sequences and ill-formed sequences out of context. Outcomes & Results The results revealed that frontocentral distributed acoustic MMNs were recorded for the CG between 176 - 196ms in Experiment 1, but not for the AG. In Experiment 2, during the 143 - 173ms window, the left anterior sMMN was exclusively observed for the CG, while the left posterior sMMN was specific to the AG. Furthermore, the amplitudes of the left posterior sMMN (143-173ms) were found to have a negative correlation with scores on sentence comprehension tests: the more negative the sMMN, the lower the scores of people with agrammatic aphasia. Notably, this left posterior MMN was absent in Experiment 1. Conclusions The early posterior sMMN, discovered for the first time in our study, appears to be more sensitive in detecting syntactic processing impairments in agrammatics compared to the early anterior sMMN. This finding has the potential to enhance the precision of aphasia assessment.

In‐Sensor Passive Speech Classification with Phononic Metamaterials

AbstractMitigating the energy requirements of artificial intelligence requires novel physical substrates for computation. Phononic metamaterials have vanishingly low power dissipation and hence are a prime candidate for green, always‐on computers. However, their use in machine learning applications has not been explored due to the complexity of their design process. Current phononic metamaterials are restricted to simple geometries (e.g., periodic and tapered) and hence do not possess sufficient expressivity to encode machine learning tasks. A non‐periodic phononic metamaterial, directly from data samples, that can distinguish between pairs of spoken words in the presence of a simple readout nonlinearity is designed and fabricated, hence demonstrating that phononic metamaterials are a viable avenue towards zero‐power smart devices.

Osteological Analysis of Hard Palate in North Indian Skulls and its Forensic Significance: A Cross-sectional Study

Introduction: Various therapeutic procedures, such as cleft palate surgery, uvulopalatopharyngoplasty, nasopharyngoscopy, and nasogastric intubation, rely on the morphometric measurements of the hard palate. Additionally, it plays a crucial role in passive speech articulation. Therefore, understanding the morphological and osteological diversity of the hard palate holds clinical significance. Aim: To assess the normal and aberrant morphology and morphometry of the hard palate. Materials and Methods: The present cross-sectional study was initiated in December 2017 and completed in December 2021. It was conducted on 100 dry adult human skulls collected from the Department of Anatomy, Government Medical College, Amritsar, Punjab, India. The palate was analysed to determine the mean palatal length, breadth, and height. Additionally, the palatal index and palatal height index were calculated. Different osteological parameters of the lesser palatine foramen, including its number, distance from the greater palatine foramen, palatomaxillary suture, and interpalatine suture, were measured. Mean, standard deviation, range, and p-value were calculated for the metric parameters. Results: The mean palatal length, breadth, and height were 46.16±4.18 mm, 33.01±2.67 mm, and 11.06±1.88 mm, respectively. In the present study, 83% of skulls belonged to the leptostaphyline type, 10% to the mesostaphyline type, and 7% to the brachystaphyline type. The number of lesser palatine foramen varied from 0-2 on both sides, with predominance of a single foramen on both sides. The distances of the lesser palatine foramen from the greater palatine foramen, palatomaxillary suture, and intermaxillary suture were found to be 3.55±1.56 mm, 11.45±2.42 mm, and 17.57±3.06 mm on the right side, and 3.38±1.57 mm, 10.90±2.39 mm, and 17.47±2.99 mm on the left side, respectively. Conclusion: The data provided by this study will be helpful in various disciplines of medical, dental, and anthropometrical sciences.

Transfer of statistical learning from passive speech perception to speech production

Communicating with a speaker with a different accent can affect one’s own speech. Despite the strength of evidence for perception-production transfer in speech, the nature of transfer has remained elusive, with variable results regarding the acoustic properties that transfer between speakers and the characteristics of the speakers who exhibit transfer. The current study investigates perception-production transfer through the lens of statistical learning across passive exposure to speech. Participants experienced a short sequence of acoustically variable minimal pair (beer/pier) utterances conveying either an accent or typical American English acoustics, categorized a perceptually ambiguous test stimulus, and then repeated the test stimulus aloud. In the canonical condition, /b/–/p/ fundamental frequency (F0) and voice onset time (VOT) covaried according to typical English patterns. In the reverse condition, the F0xVOT relationship reversed to create an “accent” with speech input regularities atypical of American English. Replicating prior studies, F0 played less of a role in perceptual speech categorization in reverse compared with canonical statistical contexts. Critically, this down-weighting transferred to production, with systematic down-weighting of F0 in listeners’ own speech productions in reverse compared with canonical contexts that was robust across male and female participants. Thus, the mapping of acoustics to speech categories is rapidly adjusted by short-term statistical learning across passive listening and these adjustments transfer to influence listeners’ own speech productions.

The Assessment of Psychomotor Development in Full-Term Children at 12 Months of Age with Munich Functional Development Diagnostics Depending on the Feeding Method: A Cross-Sectional Study

Background: Psychomotor development is the most important outcome determining the proper growth and development of children. Optimizing childcare and modifying risk factors can provide the child with the best conditions to realize their developmental potential. The study aimed to assess the impact of the feeding method on the psychomotor development of full-term children at 12 months of age with Munich Functional Developmental Diagnostics (MFDD). Methods: The study included 242 full-term children who were examined at 12 months of age by a child neurologist using MFDD. The children were divided into two groups depending on the feeding method: breastfed (146) vs. formula-fed (93). We analysed selected obstetric and neonatal risk factors as well as MFDD scores within the groups. Results: The only axis on the MFDD scale on which we observed a difference between the groups was social skills. No differences were noted between the groups in the analysis of the gross and fine motor skills, with regard to perception or active and passive speech. Conclusions: The full-term, exclusively breastfed infants over their first 6 months of age or longer have greater social skills in comparison with the formula-fed infants when measured on the MFDD axis.

Statistical learning across passive listening adjusts perceptual weights of speech input dimensions

Statistical learning across passive exposure has been theoretically situated with unsupervised learning. However, when input statistics accumulate over established representations – like speech syllables, for example – there is the possibility that prediction derived from activation of rich, existing representations may support error-driven learning. Here, across five experiments, we present evidence for error-driven learning across passive speech listening. Young adults passively listened to a string of eight beer - pier speech tokens with distributional regularities following either a canonical American-English acoustic dimension correlation or a correlation reversed to create an accent. A sequence-final test stimulus assayed the perceptual weight – the effectiveness – of the secondary dimension in signaling category membership as a function of preceding sequence regularities. Perceptual weight flexibly adjusted according to the passively experienced regularities even when the preceding regularities shifted on a trial-by-trial basis. The findings align with a theoretical view that activation of established internal representations can support learning across statistical regularities via error-driven learning. At the broadest level, this suggests that not all statistical learning need be unsupervised. Moreover, these findings help to account for how cognitive systems may accommodate competing demands for flexibility and stability: instead of overwriting existing representations when short-term input distributions depart from the norms, the mapping from input to category representations may be dynamically – and rapidly – adjusted via error-driven learning from predictions derived from internal representations.

Speech Production Errors in Children With Cleft Palate With or Without Cleft Lip.

The purpose of this study was to describe the frequency of speech production errors in children with cleft palate with or without cleft lip (CP±L) and explore characteristics related to speech production errors. Fifty-six children with nonsyndromic CP±L between the ages of 4;0 and 7;11 (years;months) were included in this study. The children's audio-recorded production of a sentence repetition task was transcribed using narrow transcription and coded for speech error type. Children used, on average, 18 speech errors during the sentence repetition task that sampled 59 phoneme targets. On average, phonological errors were used most frequently, with nine errors per sample, followed by anterior oral speech errors at four errors per sample, and non-oral compensatory errors at three errors per sample. Individual-level characteristics including age and cleft type were related to frequency of phonological errors and anterior oral speech errors, respectively. One treatment-level characteristic, hypernasality, was related to use of non-oral compensatory errors and passive speech errors. This study identified the most frequent speech production errors as phonological errors, followed by anterior oral speech errors and non-oral compensatory errors. Individual-level and treatment-level characteristics were related to speech production errors. Future research should explore additional characteristics that may influence use of speech production errors. Clinically, this study adds information regarding speech error types that should be monitored throughout cleft care, including phonological errors that were most prevalent among this sample. https://doi.org/10.23641/asha.22044095.

Better speech outcomes after very early palatal repair?—A longitudinal case-control study in Ugandan children with cleft palate

IntroductionChildren born with cleft palate with or without cleft lip (CP±L) tend to use less oral pressure consonants and more glottal sounds in their babbling. The purpose of very early palatal repair (i.e., one-stage palatal closure prior to 6 months of age) is to make the palate functional before the onset of speech acquisition to reduce the anchoring of wrong patterns in the child's developing phonological system. As a result, less compensatory articulation errors are expected to be present. Currently, no detailed longitudinal speech outcomes after very early palatal closure are available. This study aimed to provide longitudinal speech outcomes in Ugandan children with CP±L who received palatal closure prior to the age of 6 months. MethodsTen children with CP±L were assessed at a mean age of 5 and 10 years old. Speech understandability, speech acceptability, resonance, nasal airflow and articulation were perceptually rated by two experienced speech-language pathologists. Velopharyngeal function was estimated using the velopharyngeal composite score (VPC-sum). Information regarding speech therapy, fistula rate, and secondary (speech) surgery was collected. The outcomes were compared with the longitudinal outcomes of an age- and gender-matched control group of 10 Ugandan children without CP±L. ResultsSpeech understandability and acceptability improved significantly over time in the group with CP±L (all p's ≤ 0.05, all Z's > −2.43). At both test dates, significantly worse judgments were found for the group with CP±L compared to the control group for these variables and variables related to passive speech errors (all p's ≤ 0.05, all Z's > 2.49). A statistically significant difference with the control group was found for the presence of compensatory articulation errors at the age of 5 years but not at the age of 10 years, indicating a catch up by the children with CP±L. ConclusionWhether a one-stage palatal closure prior to the age of 6 months is more favorable for speech outcomes compared to one-stage palatal closure at 12 months is still not clear. Speech of the children with CP±L improved over time, but significantly differed from the control group at the age of 5 and 10 years old. Limited access to health care facilities and possible influence of malnutrition on wound healing need to be considered when interpreting the results. Whether palatal closure prior to the age of 6 months is transferable to other countries is subject for further research, including both longitudinal and prospective designs with larger samples.

Speech Perception under the Tent: A Domain-general Predictive Role for the Cerebellum.

The role of the cerebellum in speech perception remains a mystery. Given its uniform architecture, we tested the hypothesis that it implements a domain-general predictive mechanism whose role in speech is determined by connectivity. We collated all neuroimaging studies reporting cerebellar activity in the Neurosynth database (n = 8206). From this set, we found all studies involving passive speech and sound perception (n = 72, 64% speech, 12.5% sounds, 12.5% music, and 11% tones) and speech production and articulation (n = 175). Standard and coactivation neuroimaging meta-analyses were used to compare cerebellar and associated cortical activations between passive perception and production. We found distinct regions of perception- and production-related activity in the cerebellum and regions of perception-production overlap. Each of these regions had distinct patterns of cortico-cerebellar connectivity. To test for domain-generality versus specificity, we identified all psychological and task-related terms in the Neurosynth database that predicted activity in cerebellar regions associated with passive perception and production. Regions in the cerebellum activated by speech perception were associated with domain-general terms related to prediction. One hallmark of predictive processing is metabolic savings (i.e., decreases in neural activity when events are predicted). To test the hypothesis that the cerebellum plays a predictive role in speech perception, we examined cortical activation between studies reporting cerebellar activation and those without cerebellar activation during speech perception. When the cerebellum was active during speech perception, there was far less cortical activation than when it was inactive. The results suggest that the cerebellum implements a domain-general mechanism related to prediction during speech perception.

Speech Outcomes Following Orticochea Pharyngoplasty in Patients With History of Cleft Palate and Noncleft Velopharyngeal Dysfunction.

To report speech outcomes following Orticochea pharyngoplasty in 43 patients with cleft palate and noncleft velopharyngeal dysfunction. A retrospective surgical audit of patients undergoing Orticochea pharyngoplasty between 2004 and 2012, with speech as a primary outcome measure. Patients known to a regional UK cleft center. Forty-three patients underwent Orticochea pharyngoplasty by a single surgeon in a UK regional cleft center. Twenty-one patients had undergone a prior procedure for velopharyngeal dysfunction. Pre- and postoperative speech samples were assessed blindly using the Cleft Audit Protocol for Speech-Augmented by a specialist cleft speech and language therapist, external to the team. Speech samples were rated on the following parameters: hypernasality, hyponasality, audible nasal emission, nasal, turbulence, and passive cleft speech characteristics. Statistical differences in pre- and postoperative speech scores were tested using the Wilcoxon matched-pairs signed-ranks test. Inter- and intrareliability scores were calculated using weighted Cohen κ. Whole group: A statistically significant difference in pre- and postoperative scores for hypernasality (P < .001), hyponasality (P < .05), nasal emission (P < .01), and passive cleft speech characteristics (P < .01) were reported. Patients with cleft diagnoses: A statistically significant difference in scores for hypernasality (P < .001), nasal emission (P < .01), and passive cleft speech characteristics (P < .01) were reported for this group of patients. Patients with noncleft diagnoses: The only parameter to demonstrate a statistically significant difference was hypernasality (P < .01) in this group. Orticochea pharyngoplasty is a successful surgical procedure in treating velopharyngeal dysfunction in both the cleft and noncleft populations.

Principal Component Analysis of Munich Functional Developmental Diagnosis.

Objectives: Munich Functional Developmental Diagnosis (MFDD) is a scale for assessing the psychomotor development of children in the first months or years of life. The tool is based on standardized tables of physical development and is used to detect developmental deficits. It consists of eight axes on which the following skills are assessed: crawling, sitting, walking, grasping, perception, speaking, speech understanding, social skills. Methods: The study included 110 children in the first year of life examined with the MFDD by the same physician. The score obtained on a given axis was coded as a negative value (defined in months) below the child’s age-specific developmental level. Next, we examined the dimensionality of the scale and the intercorrelation of its axes using polychoric correlation and principal component analysis. Results: Correlation matrix analysis showed high correlation of MFDD axes 1–4, and MFDD 6–8. The PCA identified three principal components consisting of children’s development in the areas of large and small motor skills (axis 1–4), perception (axis 5), active speech, passive speech and social skills (axis 6–8). The three dimensions obtained together account for 80.27% of the total variance. Conclusions: MFDD is a three-dimensional scale that includes motor development, perception, and social skills and speech. There is potential space for reduction in the number of variables in the scale.

Privacy-Preserving Deep Speaker Separation for Smartphone-Based Passive Speech Assessment.

Goal: Smartphones can be used to passively assess and monitor patients’ speech impairments caused by ailments such as Parkinson’s disease, Traumatic Brain Injury (TBI), Post-Traumatic Stress Disorder (PTSD) and neurodegenerative diseases such as Alzheimer’s disease and dementia. However, passive audio recordings in natural settings often capture the speech of non-target speakers (cross-talk). Consequently, speaker separation, which identifies the target speakers’ speech in audio recordings with two or more speakers’ voices, is a crucial pre-processing step in such scenarios. Prior speech separation methods analyzed raw audio. However, in order to preserve speaker privacy, passively recorded smartphone audio and machine learning-based speech assessment are often performed on derived speech features such as Mel-Frequency Cepstral Coefficients (MFCCs). In this paper, we propose a novel Deep MFCC bAsed SpeaKer Separation (Deep-MASKS). Methods: Deep-MASKS uses an autoencoder to reconstruct MFCC components of an individual’s speech from an i-vector, x-vector or d-vector representation of their speech learned during the enrollment period. Deep-MASKS utilizes a Deep Neural Network (DNN) for MFCC signal reconstructions, which yields a more accurate, higher-order function compared to prior work that utilized a mask. Unlike prior work that operates on utterances, Deep-MASKS operates on continuous audio recordings. Results: Deep-MASKS outperforms baselines, reducing the Mean Squared Error (MSE) of MFCC reconstruction by up to 44% and the number of additional bits required to represent clean speech entropy by 36%.

Correction: Experience with speech sounds is not necessary for cue trading by budgerigars (Melopsittacus undulatus).

[This corrects the article DOI: 10.1371/journal.pone.0177676.].

Experience with speech sounds is not necessary for cue trading by budgerigars (Melopsittacus undulatus).

The influence of experience with human speech sounds on speech perception in budgerigars, vocal mimics whose speech exposure can be tightly controlled in a laboratory setting, was measured. Budgerigars were divided into groups that differed in auditory exposure and then tested on a cue-trading identification paradigm with synthetic speech. Phonetic cue trading is a perceptual phenomenon observed when changes on one cue dimension are offset by changes in another cue dimension while still maintaining the same phonetic percept. The current study examined whether budgerigars would trade the cues of voice onset time (VOT) and the first formant onset frequency when identifying syllable initial stop consonants and if this would be influenced by exposure to speech sounds. There were a total of four different exposure groups: No speech exposure (completely isolated), Passive speech exposure (regular exposure to human speech), and two Speech-trained groups. After the exposure period, all budgerigars were tested for phonetic cue trading using operant conditioning procedures. Birds were trained to peck keys in response to different synthetic speech sounds that began with “d” or “t” and varied in VOT and frequency of the first formant at voicing onset. Once training performance criteria were met, budgerigars were presented with the entire intermediate series, including ambiguous sounds. Responses on these trials were used to determine which speech cues were used, if a trading relation between VOT and the onset frequency of the first formant was present, and whether speech exposure had an influence on perception. Cue trading was found in all birds and these results were largely similar to those of a group of humans. Results indicated that prior speech experience was not a requirement for cue trading by budgerigars. The results are consistent with theories that explain phonetic cue trading in terms of a rich auditory encoding of the speech signal.

Electrophysiological Evidence for Early and Interactive Symbol Access and Rule Processing in Retrieving and Combining Language Constructions.

The human brain stores an immense repertoire of linguistic symbols (morphemes, words) and combines them into a virtually unlimited set of well-formed strings (phrases, sentences) that serve as efficient communicative tools. Communication is hampered, however, if strings include meaningless items (e.g., "pseudomorphemes"), or if the rules for combining string elements are violated. Prior research suggests that, when participants attentively process sentences in a linguistic task, syntactic processing can occur quite early, but lexicosemantic processing, or any interaction involving this factor, is manifest later in time (ca. 400 msec or later). In contrast, recent evidence from passive speech perception paradigms suggests early processing of both combinatorial (morphosyntactic) and storage-related (lexicosemantic) properties. A crucial question is whether these parallel processes might also interact early in processing. Using ERPs in an orthogonal design, we presented spoken word strings to participants while they were distracted from incoming speech to obtain information about automatic language processing mechanisms unaffected by task-related strategies. Stimuli were either (1) well-formed miniconstructions (short pronoun-verb sentences), (2) "unstored" strings containing a pseudomorpheme, (3) "ill-combined" strings violating subject-verb agreement rules, or (4) double violations including both types of errors. We found that by 70-210 msec after the onset of the phrase-final syllable that disambiguated the strings, interactions of lexicosemantic and morphosyntactic deviance were evident in the ERPs. These results argue against serial processing of lexical storage, morphosyntactic combination and their interaction, and in favor of early, simultaneous, and interactive processing of symbols and their combinatorial structures.

Attention modulates somatosensory influences in passive speech listening

ABSTRACTPrevious studies showed that manipulating the speech production system influenced speech perception. This influence was mediated by task difficulty, listening conditions, and attention. In the present study we investigated the specificity of a somatosensory manipulation – a spoon over the tongue – in passive listening. We measured the mismatch negativity (MMN) while participants listened to vowels that differ in their articulation – the tongue height – and familiarity – native and unknown vowels. The same participants heard the vowels in a spoon and no-spoon block. The order of the blocks was counterbalanced across participants. Results showed no effect of the spoon. Instead, starting with the spoon enhanced the MMN amplitude. A second experiment showed the same MMN enhancement for starting with a somatosensory manipulation applied to a non-articulator – the hand. This result suggests that starting a study with a somatosensory manipulation raises attention to the task.

No evidence of somatotopic place of articulation feature mapping in motor cortex during passive speech perception.

The motor theory of speech perception has experienced a recent revival due to a number of studies implicating the motor system during speech perception. In a key study, Pulvermüller et al. (2006) showed that premotor/motor cortex differentially responds to the passive auditory perception of lip and tongue speech sounds. However, no study has yet attempted to replicate this important finding from nearly a decade ago. The objective of the current study was to replicate the principal finding of Pulvermüller et al. (2006) and generalize it to a larger set of speech tokens while applying a more powerful statistical approach using multivariate pattern analysis (MVPA). Participants performed an articulatory localizer as well as a speech perception task where they passively listened to a set of eight syllables while undergoing fMRI. Both univariate and multivariate analyses failed to find evidence for somatotopic coding in motor or premotor cortex during speech perception. Positive evidence for the null hypothesis was further confirmed by Bayesian analyses. Results consistently show that while the lip and tongue areas of the motor cortex are sensitive to movements of the articulators, they do not appear to preferentially respond to labial and alveolar speech sounds during passive speech perception.

Decoding Articulatory Features from fMRI Responses in Dorsal Speech Regions

The brain's circuitry for perceiving and producing speech may show a notable level of overlap that is crucial for normal development and behavior. The extent to which sensorimotor integration plays a role in speech perception remains highly controversial, however. Methodological constraints related to experimental designs and analysis methods have so far prevented the disentanglement of neural responses to acoustic versus articulatory speech features. Using a passive listening paradigm and multivariate decoding of single-trial fMRI responses to spoken syllables, we investigated brain-based generalization of articulatory features (place and manner of articulation, and voicing) beyond their acoustic (surface) form in adult human listeners. For example, we trained a classifier to discriminate place of articulation within stop syllables (e.g., /pa/ vs /ta/) and tested whether this training generalizes to fricatives (e.g., /fa/ vs /sa/). This novel approach revealed generalization of place and manner of articulation at multiple cortical levels within the dorsal auditory pathway, including auditory, sensorimotor, motor, and somatosensory regions, suggesting the representation of sensorimotor information. Additionally, generalization of voicing included the right anterior superior temporal sulcus associated with the perception of human voices as well as somatosensory regions bilaterally. Our findings highlight the close connection between brain systems for speech perception and production, and in particular, indicate the availability of articulatory codes during passive speech perception. Sensorimotor integration is central to verbal communication and provides a link between auditory signals of speech perception and motor programs of speech production. It remains highly controversial, however, to what extent the brain's speech perception system actively uses articulatory (motor), in addition to acoustic/phonetic, representations. In this study, we examine the role of articulatory representations during passive listening using carefully controlled stimuli (spoken syllables) in combination with multivariate fMRI decoding. Our approach enabled us to disentangle brain responses to acoustic and articulatory speech properties. In particular, it revealed articulatory-specific brain responses of speech at multiple cortical levels, including auditory, sensorimotor, and motor regions, suggesting the representation of sensorimotor information during passive speech perception.

Dual-echo fMRI can detect activations in inferior temporal lobe during intelligible speech comprehension

The neural basis of speech comprehension has been investigated intensively during the past few decades. Incoming auditory signals are analysed for speech-like patterns and meaningful information can be extracted by mapping these sounds onto stored semantic representations. Investigation into the neural basis of speech comprehension has largely focused on the temporal lobe, in particular the superior and posterior regions. The ventral anterior temporal lobe (vATL), which includes the inferior temporal gyrus (ITG) and temporal fusiform gyrus (TFG) is consistently omitted in fMRI studies. In contrast, PET studies have shown the involvement of these ventral temporal regions. One crucial factor is the signal loss experienced using conventional echo planar imaging (EPI) for fMRI, at tissue interfaces such as the vATL. One method to overcome this signal loss is to employ a dual-echo EPI technique. The aim of this study was to use intelligible and unintelligible (spectrally rotated) sentences to determine if the vATL could be detected during a passive speech comprehension task using a dual-echo acquisition. A whole brain analysis for an intelligibility contrast showed bilateral superior temporal lobe activations and a cluster of activation within the left vATL. Converging evidence implicates the same ventral temporal regions during semantic processing tasks, which include language processing. The specific role of the ventral temporal region during intelligible speech processing cannot be determined from this data alone, but the converging evidence from PET, MEG, TMS and neuropsychology strongly suggest that it contains the stored semantic representations, which are activated by the speech decoding process.