Speech rhythms and multiplexed oscillatory sensory coding in the human brain

Neocortical and Hippocampal Theta Oscillations Track Audiovisual Integration and Replay of Speech Memories

"Are you talkin' to me?!" If you ever watched the masterpiece "Taxi Driver" directed by Martin Scorsese, you certainly recall the monologue during which Travis Bickle rehearses an imaginary confrontation in front of a mirror. While remembering this scene, you recollect a myriad of speech features across visual and auditory senses with a smooth sensation of unified memory. The aim of this study was to investigate how the fine-grained synchrony between coinciding visual and auditory features impacts brain oscillations when forming multisensory speech memories. We developed a memory task presenting participants with short synchronous or asynchronous movie clips focused on the face of speakers in real interviews, all the while undergoing magnetoencephalography recording. In the synchronous condition, the natural alignment between visual and auditory onsets was kept intact. In the asynchronous condition, auditory onsets were delayed to present lip movements and speech sounds in antiphase specifically with respect to the theta oscillation synchronizing them in the original movie. Our results first showed that theta oscillations in the neocortex and hippocampus were modulated by the level of synchrony between lip movements and syllables during audiovisual speech perception. Second, theta asynchrony between the lip movements and auditory envelope during audiovisual speech perception reduced the accuracy of subsequent theta oscillation reinstatement during memory recollection. We conclude that neural theta oscillations play a pivotal role in both audiovisual integration and memory replay of speech.

Rhythm training improves word-reading in children with dyslexia

Specific learning disorder with reading deficit (SLD-reading), or dyslexia, is one of the most common neurodevelopmental disorders. Intensive training with reading specialists is recommended, but delayed access to care is common. In this study, we tested an innovative user-friendly and accessible intervention, the medical device Mila-Learn, which is a video game based on cognitive and rhythmic training to improve phonological and reading ability. This randomized placebo-controlled trial (ClinicalTrials.gov NCT05154721) included children aged 7 to 11 y/o with SLD-reading. The children were in 2nd to 5th grade and had been in school for more than 3 years. The exclusion criteria were reading or writing remediation during the past 12 months, previous use of Mila-Learn, and severe chronic illness. The patients, who were all native French speakers, were recruited from throughout France and were randomly assigned to Mila-Learn or a matched-placebo game for an 8-week training. The primary variable was nonword decoding. The secondary variables included phonological skills, 2-min word-reading accuracy and speed, grapheme-to-phoneme conversion skills, and self-esteem. Between September 2021 and April 2023, 151 children were assigned to Mila-Learn (n = 75; male = 36; female = 39) or the placebo (n = 76; male = 42; female = 34). We registered 39 adverse events; only one was due to the protocol and was in the placebo group. We found no differences between the groups in nonword decoding in the intention-to-treat (N = 151; p = 0.39) or per-protocol analysis (N = 93; p = 0.21). However, the per-protocol analysis revealed the superiority of Mila-Learn over the placebo by 5.05 score points (95% CI 0.21; 10.3, p < 0.05) for 2-minute word-reading accuracy and by 5.44 score points (95% CI 0.57; 10.99, p < 0.05) for 2-min word-reading speed. We found no other significant effects. Mila-Learn is safe for children with SLD-reading who might benefit from this medical device.Study registration: ClinicalTrials.gov NCT05154721-13/12/2021.

Phase-amplitude coupling within MEG data can identify eloquent cortex

Objective.Proper identification of eloquent cortices is essential to minimize post-surgical deficits in patients undergoing resection for epilepsy and tumors. Current methods are subjective, vary across centers, and require significant expertise, underscoring the need for more objective pre-surgical mapping. Phase-amplitude coupling (PAC), the interaction between the phase of low-frequency oscillations and the amplitude of high-frequency activity, has been implicated in task-induced brain activity and may serve as a biomarker for functional mapping. Our objective was to develop a novel PAC-based algorithm to non-invasively identify somatosensory eloquent cortex using magnetoencephalography (MEG) data in epilepsy patients.Approach.We analyzed somatosensory and spontaneous MEG recordings from 30 subjects with drug-resistant epilepsy. PAC was calculated on source-reconstructed data (5-12 Hz for low frequencies and 30-300 Hz for high frequencies), followed by rank-2 tensor decomposition. Density-based clustering compared active brain regions during somatosensory task and spontaneous data at a population level. We employed a linear mixed-effects model to quantify changes in PAC between somatosensory and resting-state data. We developed a patient-specific support vector machine (SVM) classifier to identify active brain regions based on PAC values during the somatosensory task.Main results.Five of six expected brain regions were active during left and right-sided stimulation (p=1.08×10-8, hypergeometric probability test). The mixed-effects model confirmed task-specific PAC in anatomically relevant brain regions (p < 0.01). The SVM classifier gave a specificity of 99.46% and a precision of 66.9%. These results demonstrate that the PAC algorithm reliably identifies somatosensory cortex activation at both individual and population levels with statistical significance.Significance.This study demonstrates the feasibility of using PAC as a non-invasive marker for identifying functionally relevant brain regions during somatosensory task in epilepsy patients. Future work will evaluate its applicability for mapping other eloquent cortices, including language, motor, and auditory areas.

Anatomically distinct cortical tracking of music and speech by slow (1-8Hz) and fast (70-120Hz) oscillatory activity

Music and speech encode hierarchically organized structural complexity at the service of human expressiveness and communication. Previous research has shown that populations of neurons in auditory regions track the envelope of acoustic signals within the range of slow and fast oscillatory activity. However, the extent to which cortical tracking is influenced by the interplay between stimulus type, frequency band, and brain anatomy remains an open question. In this study, we reanalyzed intracranial recordings from thirty subjects implanted with electrocorticography (ECoG) grids in the left cerebral hemisphere, drawn from an existing open-access ECoG database. Participants passively watched a movie where visual scenes were accompanied by either music or speech stimuli. Cross-correlation between brain activity and the envelope of music and speech signals, along with density-based clustering analyses and linear mixed-effects modeling, revealed both anatomically overlapping and functionally distinct mapping of the tracking effect as a function of stimulus type and frequency band. We observed widespread left-hemisphere tracking of music and speech signals in the Slow Frequency Band (SFB, band-passed filtered low-frequency signal between 1-8Hz), with near zero temporal lags. In contrast, cortical tracking in the High Frequency Band (HFB, envelope of the 70-120Hz band-passed filtered signal) was higher during speech perception, was more densely concentrated in classical language processing areas, and showed a frontal-to-temporal gradient in lag values that was not observed during perception of musical stimuli. Our results highlight a complex interaction between cortical region and frequency band that shapes temporal dynamics during processing of naturalistic music and speech signals.

Binaural Temporal Fine Structure Sensitivity for Children With Developmental Dyslexia

PURPOSE

Atypical temporal processing is thought to be involved in the phonological difficulties that characterize children with developmental dyslexia (DYS). The temporal sampling (TS) theory of dyslexia posits that the processing of low-frequency envelope modulations is impaired, but the processing of binaural temporal fine structure (TFS) is preserved in children with DYS.

METHOD

Binaural TFS sensitivity was assessed for children with DYS utilizing the methods developed by Flanagan et al. for typically developing (TD) children. New results for 58 children with DYS (ages 7-9.6 years) were compared with those for 30 age-matched controls (chronological age-matched [CA]) reported in Flanagan et al. Threshold frequency, that is, the highest frequency at which an interaural phase difference (IPD) of 30° or 180° could be distinguished from an IPD of 0° was determined using a two-interval forced-choice task in which the frequency was adaptively varied, with stimuli presented via headphones.

RESULTS

For those who were able to perform the task above chance, the median TFS180 thresholds were: DYS = 886 Hz; CA = 999Hz. For TFS30 thresholds: DYS = 388 Hz; CA = 442 Hz. A linear mixed-effects model with dependent variable threshold frequency and fixed effects of group (CA and DYS) and phase (180° and 30°) showed no significant difference between groups (p > .05) and no significant interaction between group and phase. Both groups performed more poorly than young typically hearing adults (p < .001) for both phases.

CONCLUSIONS

Binaural TFS sensitivity does not differ significantly for children with DYS and TD children. For both groups, the development of binaural TFS sensitivity is protracted. The results are consistent with TS theory.

EEG responses to onset-edge and steady-state segments of continuous speech under selective auditory attention modulation

Electroencephalography (EEG) signals provide valuable insights into the neural mechanisms of speech perception. However, it still remains unclear how neural responses dynamically align with continuous speech under selective attention modulation in the complex auditory environments. This study examined the evoked and induced EEG responses, their correlations with speech features, and cortical distributions for the target and ignored speech in two-talker competing scenarios. Results showed that selective attention increased the evoked EEG power for the target speech compared to the ignored speech. In contrast, the induced power indicated no significant differences. Low-frequency EEG power and phase responses reliably indexed the target speech identification amid competing streams. Cortical distribution analyses revealed that the evoked power differences between the target and ignored speech were concentrated in the central and parietal cortices. Significant induced power differences between the target and ignored speech presented only at the onset-edge segments in the left temporal cortex. Comparisons between onset-edge and steady-state segments showed the evoked power differences in the right central and temporal cortices and the induced power differences in the frontal cortex for the ignored speech. No significant differences of the cortical distribution were observed between the onset-edge and steady-state segments for the target speech. These findings underscore the distinct contributions of the evoked and induced neural activities and their cortical distributions to selective auditory attention and segment-specific speech perception.

Predictive coding and dimension-selective attention enhance the lateralization of spoken language processing

Hemispheric lateralization in speech and language processing exemplifies functional brain specialization. Seminal work in patients with left hemisphere damage highlighted the left-hemispheric dominance in language functions. However, speech processing is not confined to the left hemisphere. Hence, some researchers associate lateralization with auditory processing asymmetries: slow temporal and fine spectral acoustic information is preferentially processed in right auditory regions, while faster temporal information is primarily handled by left auditory regions. Other scholars posit that lateralization relates more to linguistic processing, particularly for speech and speech-like stimuli. We argue that these seemingly distinct accounts are interdependent. Linguistic analysis of speech relies on top-down processes, such as predictive coding and dimension-selective auditory attention, which enhance lateralized processing by engaging left-lateralized sensorimotor networks. Our review highlights that lateralization is weaker for simple sounds, stronger for speech-like sounds, and strongest for meaningful speech. Evidence shows that predictive speech processing and selective attention enhance lateralization. We illustrate that these top-down processes rely on left-lateralized sensorimotor networks and provide insights into the role of these networks in speech processing.

Neural speech tracking in a virtual acoustic environment: audio-visual benefit for unscripted continuous speech

The audio-visual benefit in speech perception-where congruent visual input enhances auditory processing-is well-documented across age groups, particularly in challenging listening conditions and among individuals with varying hearing abilities. However, most studies rely on highly controlled laboratory environments with scripted stimuli. Here, we examine the audio-visual benefit using unscripted, natural speech from untrained speakers within a virtual acoustic environment. Using electroencephalography (EEG) and cortical speech tracking, we assessed neural responses across audio-visual, audio-only, visual-only, and masked-lip conditions to isolate the role of lip movements. Additionally, we analysed individual differences in acoustic and visual features of the speakers, including pitch, jitter, and lip-openness, to explore their influence on the audio-visual speech tracking benefit. Results showed a significant audio-visual enhancement in speech tracking with background noise, with the masked-lip condition performing similarly to the audio-only condition, emphasizing the importance of lip movements in adverse listening situations. Our findings reveal the feasibility of cortical speech tracking with naturalistic stimuli and underscore the impact of individual speaker characteristics on audio-visual integration in real-world listening contexts.

Impact of age-related hearing loss on decompensation of left DLPFC during speech perception in noise: a combined EEG-fNIRS study

Understanding speech-in-noise is a significant challenge for individuals with age-related hearing loss (ARHL). Evidence suggests that increased activity in the frontal cortex compensates for impaired speech perception in healthy aging older adults. However, whether older adults with ARHL still show preserved compensatory function and the specific neural regulatory mechanisms underlying such compensation remains largely unclear. Here, by utilizing a synchronized EEG-fNIRS test, we investigated the neural oscillatory characteristics of the theta band and synchronous hemodynamic changes in the frontal cortex during a speech recognition task in noise. The study included healthy older adults (n = 26, aged 65.4 ± 2.8), those with mild hearing loss (n = 26, aged 66.3 ± 3.8), and those with moderate to severe hearing loss (n = 26, aged 67.5 ± 3.7). Results showed that, relative to healthy older adults, older adults with ARHL exhibited lower activation and weakened theta band neural oscillations in the left dorsolateral prefrontal cortex (DLPFC) under noisy conditions, and this decreased activity correlated with high-frequency hearing loss. Meanwhile, we found that the connectivity of the frontoparietal network was significantly reduced, which might depress the top-down articulatory prediction function affecting speech recognition performance in ARHL older adults. The results suggested that healthy aging older adults might exhibit compensatory attentional resource recruitment through a top-down auditory-motor integration mechanism. In comparison, older adults with ARHL reflected decompensation of the left DLPFC involving the frontoparietal integration network during speech recognition tasks in noise.

MINT: A toolbox for the analysis of multivariate neural information coding and transmission

Information theory has deeply influenced the conceptualization of brain information processing and is a mainstream framework for analyzing how neural networks in the brain process information to generate behavior. Information theory tools have been initially conceived and used to study how information about sensory variables is encoded by the activity of small neural populations. However, recent multivariate information theoretic advances have enabled addressing how information is exchanged across areas and used to inform behavior. Moreover, its integration with dimensionality-reduction techniques has enabled addressing information encoding and communication by the activity of large neural populations or many brain areas, as recorded by multichannel activity measurements in functional imaging and electrophysiology. Here, we provide a Multivariate Information in Neuroscience Toolbox (MINT) that combines these new methods with statistical tools for robust estimation from limited-size empirical datasets. We demonstrate the capabilities of MINT by applying it to both simulated and real neural data recorded with electrophysiology or calcium imaging, but all MINT functions are equally applicable to other brain-activity measurement modalities. We highlight the synergistic opportunities that combining its methods afford for reverse engineering of specific information processing and flow between neural populations or areas, and for discovering how information processing functions emerge from interactions between neurons or areas. MINT works on Linux, Windows and macOS operating systems, is written in MATLAB (requires MATLAB version 2018b or newer) and depends on 4 native MATLAB toolboxes. The calculation of one possible way to compute information redundancy requires the installation and compilation of C files (made available by us also as pre-compiled files). MINT is freely available at https://github.com/panzerilab/MINT with DOI doi.org/10.5281/zenodo.13998526 and operates under a GNU GPLv3 license.

Asymmetric Sampling in Time: Evidence and perspectives

Auditory and speech signals are undisputedly processed in both left and right hemispheres, but this bilateral allocation is likely unequal. The Asymmetric Sampling in Time (AST) hypothesis proposed a division of labor that has its neuroanatomical basis in the distribution of neuronal ensembles with differing temporal integration constants: left auditory areas house a larger proportion of ensembles with shorter temporal integration windows (tens of milliseconds), suited to process rapidly changing signals; right auditory areas host a larger proportion with longer time constants (∼150-300 ms), ideal for slowly changing signals. Here we evaluate the large body of findings that clarifies this relationship between auditory temporal structure and functional lateralization. In this reappraisal, we unpack whether this relationship is influenced by stimulus type (speech/nonspeech), stimulus temporal extent (long/short), task engagement (high/low), or (imaging) modality (hemodynamic/electrophysiology/behavior). We find that the right hemisphere displays a clear preference for slowly changing signals whereas the left-hemispheric preference for rapidly changing signals is highly dependent on the experimental design. We consider neuroanatomical properties potentially linked to functional lateralization, contextualize the results in an evolutionary perspective, and highlight future directions.

Cortical and behavioral tracking of rhythm in music: Effects of pitch predictability, enjoyment, and expertise

The cortical tracking of stimulus features is a crucial neural requisite of how we process continuous music. We here tested whether cortical tracking of the beat, typically related to rhythm processing, is modulated by pitch predictability and other top-down factors. Participants listened to tonal (high pitch predictability) and atonal (low pitch predictability) music while undergoing electroencephalography. We analyzed their cortical tracking of the acoustic envelope. Cortical envelope tracking was stronger while listening to atonal music, potentially reflecting listeners' violated pitch expectations and increased attention allocation. Envelope tracking was also stronger with more expertise and enjoyment. Furthermore, we showed cortical tracking of pitch surprisal (using IDyOM), which suggests that listeners' expectations match those computed by the IDyOM model, with higher surprisal for atonal music. Behaviorally, we measured participants' ability to finger-tap to the beat of tonal and atonal sequences in two experiments. Finger-tapping performance was better in the tonal condition, indicating a positive effect of pitch predictability on behavioral rhythm processing. Cortical envelope tracking predicted tapping performance for tonal music, as did pitch-surprisal tracking for atonal music, indicating that high and low predictability might impose different processing regimes. Taken together, our results show various ways that top-down factors impact musical rhythm processing.

Eye Movements in Silent Visual Speech Track Unheard Acoustic Signals and Relate to Hearing Experience

Behavioral and neuroscientific studies have shown that watching a speaker's lip movements aids speech comprehension. Intriguingly, even when videos of speakers are presented silently, various cortical regions track auditory features, such as the envelope. Recently, we demonstrated that eye movements track low-level acoustic information when attentively listening to speech. In this study, we investigated whether ocular speech tracking occurs during visual speech and how it influences cortical silent speech tracking. Furthermore, we compared data from hearing individuals, congenitally deaf individuals, and those who became deaf or hard of hearing (DHH) later in life to assess how audiovisual listening experience and auditory deprivation (early vs late onset) affect neural and ocular speech tracking during silent lip-reading. Using magnetoencephalography (MEG), we examined ocular and neural speech tracking of 75 participants observing silent videos of a speaker played forward and backward. Our main finding is a clear ocular unheard speech tracking effect with dominance of <1 Hz, which was not present for lip movements. Similarly, we observed an ≤ 1.3 Hz effect of neural unheard speech tracking in temporal regions for hearing participants. Importantly, neural tracking was not directly linked to ocular tracking. Strikingly, across listening groups, deaf participants with auditory experience showed higher ocular speech tracking than hearing participants, while no ocular speech tracking effect was revealed for congenitally deaf participants in a very small sample. This study extends previous work by demonstrating the involvement of eye movements in speech processing, even in the absence of acoustic input.

Temporal Structure of Music Improves the Cortical Encoding of Speech

Long- and short-term musical training has been proposed to improve the efficiency of cortical tracking of speech, which refers to the synchronization of brain oscillations and the acoustic temporal structure of external stimuli. Here, we study how musical sequences with different rhythm structures can guide the temporal dynamics of auditory oscillations synchronized with the speech envelope. For this purpose, we investigated the effects of prior exposure to rhythmically structured musical sequences on cortical tracking of speech in Basque-Spanish bilingual adults (Experiment 1; N = 33, 22 female, Mean age = 25 years). We presented participants with sentences in Basque and Spanish preceded by musical sequences that differed in their rhythmical structure. The rhythmical structure of the musical sequences was created to (1) reflect and match the syllabic structure of the sentences, (2) reflect a regular rhythm but not match the syllabic structure of the sentences, and (3) follow an irregular rhythm. Participants' brain responses were recorded using electroencephalography, and speech-brain coherence in the delta and theta bands was calculated. Results showed stronger speech-brain coherence in the delta band in the first condition, but only for Spanish stimuli. A follow-up experiment including a subset of the initial sample (Experiment 2; N = 20) was conducted to investigate whether language-specific stimuli properties influenced the Basque results. Similar to Experiment 1, we found stronger speech-brain coherence in the delta and theta bands when the sentences were preceded by musical sequences that matched their syllabic structure. These results suggest that not only the regularity in music is crucial for influencing cortical tracking of speech, but so is adjusting this regularity to optimally reflect the rhythmic characteristics of listeners' native language(s). Despite finding some language-specific differences across frequencies, we showed that rhythm, inherent in musical signals, guides the adaptation of brain oscillations, by adapting the temporal dynamics of the oscillatory activity to the rhythmic scaffolding of the musical signal.

A preliminary EEG study on persuasive communication towards groupness

Social neuroscience has acknowledged the role of persuasion but examined either the Persuader's or the Receiver's neural mechanisms. This study explored electrophysiological (EEG) correlates of Persuader and Receiver during a naturalistic persuasive interaction, in which Persuader aimed to convince Receiver that adopting a group decision-making orientation was the best solution to manage a group dynamic. EEG data - frequency bands: delta (0.5-3.5 Hz), theta (4-7.5 Hz), alpha (8-12.5 Hz), beta (13-30 Hz) and gamma (30.5-50 Hz) - were collected from 14 Persuaders and 14 Receivers. Findings indicated that the strategic efforts of Persuaders to enhance groupness are linked to activation in specific EEG bands (delta, theta and alpha) that distinguish them from Receivers. There is a significant distribution of these activations in the frontal areas of the Persuaders (especially, frontal right hemisphere for theta band), contrasting with the more temporal and posterior activations observed in Receivers (where the frontal areas are generally less activated). The study concludes that, under the same behavioral conditions in terms of group orientation, persuasive interaction shows specific EEG markers that connote the role of the Persuader characterized by greater attentional effort during the interaction.

Learning to operate an imagined speech Brain-Computer Interface involves the spatial and frequency tuning of neural activity

Brain-Computer Interfaces (BCI) will revolutionize the way people with severe impairment of speech production can communicate. While current efforts focus on training classifiers on vast amounts of neurophysiological signals to decode imagined speech, much less attention has been given to users' ability to adapt their neural activity to improve BCI-control. To address whether BCI-control improves with training and characterize the underlying neural dynamics, we trained 15 healthy participants to operate a binary BCI system based on electroencephalography (EEG) signals through syllable imagery for five consecutive days. Despite considerable interindividual variability in performance and learning, a significant improvement in BCI-control was globally observed. Using a control experiment, we show that a continuous feedback about the decoded activity is necessary for learning to occur. Performance improvement was associated with a broad EEG power increase in frontal theta activity and focal enhancement in temporal low-gamma activity, showing that learning to operate an imagined-speech BCI involves dynamic changes in neural features at different spectral scales. These findings demonstrate that combining machine and human learning is a successful strategy to enhance BCI controllability.

On-beat rhythm and working memory are associated with better speech-in-noise perception for older adults with hearing loss

Even with the use of hearing aids (HAs), speech in noise perception remains challenging for older adults, impacting communication and quality of life outcomes. The association between music perception and speech-in-noise (SIN) outcomes is of interest, as there is evidence that professionally trained musicians are adept listeners in noisy environments. Thus, this study explored the association between music processing, cognitive factors, and the outcome variable of SIN perception, in older adults with hearing loss. Forty-two HA users aged between 57 and 90 years with a symmetrical, moderate-to-moderately severe hearing loss participated in this study. Our findings suggest that on-beat rhythm accuracy, pitch perception, and working memory all positively contribute to SIN perception for older adults with hearing loss. These findings provide key insights into the relationship between music, cognitive factors, and SIN perception, which may inform future interventions, rehabilitation, and the mechanisms that support better SIN perception.

The impact of speaker accent on discourse processing: A frequency investigation

Previous studies indicate differences in native and foreign speech processing (Lev-Ari, 2018), with mixed evidence for differences between dialectal and foreign accent processing (Adank, Evans, Stuart-Smith, & Scott, 2009; Floccia et al., 2006, 2009; Girard, Floccia, & Goslin, 2008). Two theories have been proposed: The Perceptual Distance Hypothesis suggests that dialectal accent processing is an attenuated version of foreign accent processing (Clarke & Garrett, 2004), while the Different Processes Hypothesis argues that foreign and dialectal accents are processed via distinct mechanisms (Floccia, Butler, Girard, & Goslin, 2009). A recent single-word ERP study suggested flexibility in these mechanisms (Thomas, Martin, & Caffarra, 2022). The present study deepens this investigation by investigating differences in native, dialectal, and foreign accent processing across frequency bands during extended speech. Electroencephalographic data was recorded from 30 participants who listened to dialogues of approximately six minutes spoken in native, dialectal and foreign accents. Power spectral density estimation (1-35 Hz) was performed. Linear mixed models were done in frequency windows of particular relevance to discourse processing. Frequency bands associated with phoneme [gamma], syllable [theta], and prosody [delta] were considered along with those of general cognitive mechanisms [alpha and beta]. Results show power differences in the Gamma frequency range. While in higher frequency ranges foreign accent processing is differentiated from power amplitudes of native and dialectal accent processing, in low frequencies we do not see any accent-related power amplitude modulations. This suggests that there may be a difference in phoneme processing for native accent types and foreign accent, while we speculate that top-down mechanisms during discourse processing may mitigate the effects observed with short units of speech.

Frequency-specific cortico-subcortical interaction in continuous speaking and listening

Speech production and perception involve complex neural dynamics in the human brain. Using magnetoencephalography, our study explores the interaction between cortico-cortical and cortico-subcortical connectivities during these processes. Our connectivity findings during speaking revealed a significant connection from the right cerebellum to the left temporal areas in low frequencies, which displayed an opposite trend in high frequencies. Notably, high-frequency connectivity was absent during the listening condition. These findings underscore the vital roles of cortico-cortical and cortico-subcortical connections within the speech production and perception network. The results of our new study enhance our understanding of the complex dynamics of brain connectivity during speech processes, emphasizing the distinct frequency-based interactions between various brain regions.

The human auditory cortex concurrently tracks syllabic and phonemic timescales via acoustic spectral flux

Dynamical theories of speech processing propose that the auditory cortex parses acoustic information in parallel at the syllabic and phonemic timescales. We developed a paradigm to independently manipulate both linguistic timescales, and acquired intracranial recordings from 11 patients who are epileptic listening to French sentences. Our results indicate that (i) syllabic and phonemic timescales are both reflected in the acoustic spectral flux; (ii) during comprehension, the auditory cortex tracks the syllabic timescale in the theta range, while neural activity in the alpha-beta range phase locks to the phonemic timescale; (iii) these neural dynamics occur simultaneously and share a joint spatial location; (iv) the spectral flux embeds two timescales-in the theta and low-beta ranges-across 17 natural languages. These findings help us understand how the human brain extracts acoustic information from the continuous speech signal at multiple timescales simultaneously, a prerequisite for subsequent linguistic processing.

Infant low-frequency EEG cortical power, cortical tracking and phase-amplitude coupling predicts language a year later

Cortical signals have been shown to track acoustic and linguistic properties of continuous speech. This phenomenon has been measured in both children and adults, reflecting speech understanding by adults as well as cognitive functions such as attention and prediction. Furthermore, atypical low-frequency cortical tracking of speech is found in children with phonological difficulties (developmental dyslexia). Accordingly, low-frequency cortical signals may play a critical role in language acquisition. A recent investigation with infants Attaheri et al., 2022 [1] probed cortical tracking mechanisms at the ages of 4, 7 and 11 months as participants listened to sung speech. Results from temporal response function (TRF), phase-amplitude coupling (PAC) and dynamic theta-delta power (PSD) analyses indicated speech envelope tracking and stimulus-related power (PSD) for delta and theta neural signals. Furthermore, delta- and theta-driven PAC was found at all ages, with theta phases displaying stronger PAC with high-frequency amplitudes than delta. The present study tests whether these previous findings replicate in the second half of the full cohort of infants (N = 122) who were participating in this longitudinal study (first half: N = 61, (1); second half: N = 61). In addition to demonstrating good replication, we investigate whether cortical tracking in the first year of life predicts later language acquisition for the full cohort (122 infants recruited, 113 retained) using both infant-led and parent-estimated measures and multivariate and univariate analyses. Increased delta cortical tracking in the univariate analyses, increased ~2Hz PSD power and stronger theta-gamma PAC in both multivariate and univariate analyses were related to better language outcomes using both infant-led and parent-estimated measures. By contrast, increased ~4Hz PSD power in the multi-variate analyses, increased delta-beta PAC and a higher theta/delta power ratio in the multi-variate analyses were related to worse language outcomes. The data are interpreted within a "Temporal Sampling" framework for developmental language trajectories.

Concurrent processing of the prosodic hierarchy is supported by cortical entrainment and phase-amplitude coupling

Models of phonology posit a hierarchy of prosodic units that is relatively independent from syntactic structure, requiring its own parsing. It remains unexplored how this prosodic hierarchy is represented in the brain. We investigated this foundational question by means of an electroencephalography (EEG) study. Thirty young adults listened to German sentences containing manipulations at different levels of the prosodic hierarchy. Evaluating speech-to-brain cortical entrainment and phase-amplitude coupling revealed that prosody's hierarchical structure is maintained at the neural level during spoken language comprehension. The faithfulness of this tracking varied as a function of the hierarchy's degree of intactness as well as systematic interindividual differences in audio-motor synchronization abilities. The results underscore the role of complex oscillatory mechanisms in configuring the continuous and hierarchical nature of the speech signal and situate prosody as a structure indispensable from theoretical perspectives on spoken language comprehension in the brain.

Simultaneous EEG recording of cortical tracking of speech and movement kinematics

RATIONALE

Cortical activity is coupled with streams of sensory stimulation. The coupling with the temporal envelope of heard speech is known as the cortical tracking of speech (CTS), and that with movement kinematics is known as the corticokinematic coupling (CKC). Simultaneous measurement of both couplings is desirable in clinical settings, but it is unknown whether the inherent dual-tasking condition has an impact on CTS or CKC.

AIM

We aim to determine whether and how CTS and CKC levels are affected when recorded simultaneously.

METHODS

Twenty-three healthy young adults underwent 64-channel EEG recordings while listening to stories and while performing repetitive finger-tapping movements in 3 conditions: separately (audio- or tapping-only) or simultaneously (audio-tapping). CTS and CKC values were estimated using coherence analysis between each EEG signal and speech temporal envelope (CTS) or finger acceleration (CKC). CTS was also estimated as the reconstruction accuracy of a decoding model.

RESULTS

Across recordings, CTS assessed with reconstruction accuracy was significant in 85 % of the subjects at phrasal frequency (0.5 Hz) and in 68 % at syllabic frequencies (4-8 Hz), and CKC was significant in over 85 % of the subjects at movement frequency and its first harmonic. Comparing CTS and CKC values evaluated in separate recordings to those in simultaneous recordings revealed no significant difference and moderate-to-high levels of correlation.

CONCLUSION

Despite the subtle behavioral effects, CTS and CKC are not evidently altered by the dual-task setting inherent to recording them simultaneously and can be evaluated simultaneously using EEG in clinical settings.

Functional connectivity of stimulus-evoked brain responses to natural speech in post-stroke aphasia

Objective. One out of three stroke-patients develop language processing impairment known as aphasia. The need for ecological validity of the existing diagnostic tools motivates research on biomarkers, such as stimulus-evoked brain responses. With the aim of enhancing the physiological interpretation of the latter, we used EEG to investigate how functional brain network patterns associated with the neural response to natural speech are affected in persons with post-stroke chronic aphasia.Approach. EEG was recorded from 24 healthy controls and 40 persons with aphasia while they listened to a story. Stimulus-evoked brain responses at all scalp regions were measured as neural envelope tracking in the delta (0.5-4 Hz), theta (4-8 Hz) and low-gamma bands (30-49 Hz) using mutual information. Functional connectivity between neural-tracking signals was measured, and the Network-Based Statistics toolbox was used to: (1) assess the added value of the neural tracking vs EEG time series, (2) test between-group differences and (3) investigate any association with language performance in aphasia. Graph theory was also used to investigate topological alterations in aphasia.Main results. Functional connectivity was higher when assessed from neural tracking compared to EEG time series. Persons with aphasia showed weaker low-gamma-band left-hemispheric connectivity, and graph theory-based results showed a greater network segregation and higher region-specific node strength. Aphasia also exhibited a correlation between delta-band connectivity within the left pre-frontal region and language performance.Significance.We demonstrated the added value of combining brain connectomics with neural-tracking measurement when investigating natural speech processing in post-stroke aphasia. The higher sensitivity to language-related brain circuits of this approach favors its use as informative biomarker for the assessment of aphasia.

Imitation of Multisyllabic Items by Children With Developmental Language Disorder: Evidence for Word-Level Atypical Speech Envelope and Pitch Contours

PURPOSE

Developmental language disorder (DLD) is a multifaceted disorder. Recently, interest has grown in prosodic aspects of DLD, but most investigations of possible prosodic causes focus on speech perception tasks. Here, we focus on speech production from a speech amplitude envelope (AE) perspective. Perceptual studies have indicated a role for difficulties in AE processing in DLD related to sensory/neural processing of prosody. We explore possible matching AE difficulties in production.

METHOD

Fifty-seven children with and without DLD completed a computerized imitation task, copying aloud 30 familiar targets such as "alligator." Children with DLD (n = 20) were compared with typically developing children (age-matched controls [AMC], n = 21) and younger language controls (YLC, n = 16). Similarity of the child's productions to the target in terms of the continuous AE and pitch contour was computed using two similarity metrics, correlation, and mutual information. Both the speech AE and the pitch contour contain important information about stress patterning and intonational information over time.

RESULTS

Children with DLD showed significantly reduced imitation for both the AE and pitch contour metrics compared to AMC children. The opportunity to repeat the targets had no impact on performance for any group. Word length effects were similar across groups.

CONCLUSIONS

The spoken production of multisyllabic words by children with DLD is atypical regarding both the AE and the pitch contour. This is consistent with a theoretical explanation of DLD based on impaired sensory/neural processing of low-frequency (slow) amplitude and frequency modulations, as predicted by the temporal sampling theory.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.27165690.

Entrainment of neural oscillations during language processing in Early-Stage schizophrenia

BACKGROUND

Impairments in language processing in schizophrenia (ScZ) are a central aspect of the disorder but the underlying pathophysiology mechanisms are unclear. In the current study, we tested the hypothesis that neural oscillations are impaired during speech tracking in early-stage ScZ and in participants at clinical high-risk for psychosis (CHR-P).

METHOD

Magnetoencephalography (MEG) was used in combination with source reconstructed time-series to examine delta and theta-band entrainment during continuous speech. Participants were presented with a 5-minute audio recording during which they either attened to the story or word level. MEG-data were obtained from n = 22 CHR-P participants, n = 23 early-stage ScZ-patients, and n = 44 healthy controls (HC). Data were analysed with a Mutual Information (MI) approach to compute statistical dependence between the MEG and auditory signal, thus estimating individual speech-tracking ability. MEG-activity was reconstructed in a language network (bilateral inferior frontal cortex [F3T; Broca's], superior temporal areas [STS3, STS4; Wernicke's areas], and primary auditory cortex [bilateral HES; Heschl's gyrus]). MEG-data were correlated with clinical symptoms.

RESULTS

Theta-band entrainment in left Heschl's gyrus, averaged across groups, was significantly lower in the STORY compared to WORD condition (p = 0.022), and averaged over conditions, significantly lower in CHR-Ps (p = 0.045), but intact in early ScZ patients (p = 0.303), compared to controls. Correlation analyses between MEG data and symptom indicated that lower theta-band tracking in CHR-Ps was linked to the severity of perceptual abnormalities (p = 0.018).

CONCLUSION

Our results show that CHR-P participants involve impairments in theta-band entrainment during speech tracking in left primary auditory cortex while higher-order speech processing areas were intact. Moreover, the severity of aberrant perceptual experiences in CHR-P participants correlated with deficits in theta-band entrainment. Together, these findings highlight the possibility that neural oscillations during language processing could reveal fundamental abnormalities in speech processing which may constitute candidate biomarkers for early detection and diagnosis of ScZ.

Recent advances in neurotechnology-based biohybrid robots

Biohybrid robots retain the innate biological characteristics and behavioral traits of animals, making them valuable in applications such as disaster relief, exploration of unknown terrains, and medical care. This review aims to comprehensively discuss the evolution of biohybrid robots, their key technologies and applications, and the challenges they face. By analyzing studies conducted on terrestrial, aquatic, and aerial biohybrid robots, we gain a deeper understanding of how these technologies have made significant progress in simulating natural organisms, improving mechanical performance, and intelligent control. Additionally, we address challenges associated with the application of electrical stimulation technology, the precision of neural signal monitoring, and the ethical considerations for biohybrid robots. We highlight the importance of future research focusing on developing more sophisticated and biocompatible control methods while prioritizing animal welfare. We believe that exploring multimodal monitoring and stimulation technologies holds the potential to enhance the performance of biohybrid robots. These efforts are expected to pave the way for biohybrid robotics technology to introduce greater innovation and well-being to human society in the future.

Experience with the cochlear implant enhances the neural tracking of spectrotemporal patterns in the Alberti bass

Cochlear implant (CI) users experience diminished music enjoyment due to the technical limitations of the CI. Nonetheless, behavioral studies have reported that rhythmic features are well-transmitted through the CI. Still, the gradual improvement of rhythm perception after the CI switch-on has not yet been determined using neurophysiological measures. To fill this gap, we here reanalyzed the electroencephalographic responses of participants from two previous mismatch negativity studies. These studies included eight recently implanted CI users measured twice, within the first six weeks after CI switch-on and approximately three months later; thirteen experienced CI users with a median experience of 7 years; and fourteen normally hearing (NH) controls. All participants listened to a repetitive four-tone pattern (known in music as Alberti bass) for 35 min. Applying frequency tagging, we aimed to estimate the neural activity synchronized to the periodicities of the Alberti bass. We hypothesized that longer experience with the CI would be reflected in stronger frequency-tagged neural responses approaching the responses of NH controls. We found an increase in the frequency-tagged amplitudes after only 3 months of CI use. This increase in neural synchronization may reflect an early adaptation to the CI stimulation. Moreover, the frequency-tagged amplitudes of experienced CI users were significantly greater than those of recently implanted CI users, but still smaller than those of NH controls. The frequency-tagged neural responses did not just reflect spectrotemporal changes in the stimuli (i.e., intensity or spectral content fluctuating over time), but also showed non-linear transformations that seemed to enhance relevant periodicities of the Alberti bass. Our findings provide neurophysiological evidence indicating a gradual adaptation to the CI, which is noticeable already after three months, resulting in close to NH brain processing of spectrotemporal features of musical rhythms after extended CI use.

Cross-linguistic and acoustic-driven effects on multiscale neural synchrony to stress rhythms

We investigated how neural oscillations code the hierarchical nature of stress rhythms in speech and how stress processing varies with language experience. By measuring phase synchrony of multilevel EEG-acoustic tracking and intra-brain cross-frequency coupling, we show the encoding of stress involves different neural signatures (delta rhythms = stress foot rate; theta rhythms = syllable rate), is stronger for amplitude vs. duration stress cues, and induces nested delta-theta coherence mirroring the stress-syllable hierarchy in speech. Only native English, but not Mandarin, speakers exhibited enhanced neural entrainment at central stress (2 Hz) and syllable (4 Hz) rates intrinsic to natural English. English individuals with superior cortical-stress tracking capabilities also displayed stronger neural hierarchical coherence, highlighting a nuanced interplay between internal nesting of brain rhythms and external entrainment rooted in language-specific speech rhythms. Our cross-language findings reveal brain-speech synchronization is not purely a "bottom-up" but benefits from "top-down" processing from listeners' language-specific experience.

Multi-timescale neural dynamics for multisensory integration

Carrying out any everyday task, be it driving in traffic, conversing with friends or playing basketball, requires rapid selection, integration and segregation of stimuli from different sensory modalities. At present, even the most advanced artificial intelligence-based systems are unable to replicate the multisensory processes that the human brain routinely performs, but how neural circuits in the brain carry out these processes is still not well understood. In this Perspective, we discuss recent findings that shed fresh light on the oscillatory neural mechanisms that mediate multisensory integration (MI), including power modulations, phase resetting, phase-amplitude coupling and dynamic functional connectivity. We then consider studies that also suggest multi-timescale dynamics in intrinsic ongoing neural activity and during stimulus-driven bottom-up and cognitive top-down neural network processing in the context of MI. We propose a new concept of MI that emphasizes the critical role of neural dynamics at multiple timescales within and across brain networks, enabling the simultaneous integration, segregation, hierarchical structuring and selection of information in different time windows. To highlight predictions from our multi-timescale concept of MI, real-world scenarios in which multi-timescale processes may coordinate MI in a flexible and adaptive manner are considered.

Altered neural synchronization in response to 2 Hz amplitude-modulated tones in the auditory cortex of children with Autism Spectrum Disorder: An MEG study

OBJECTIVE

Some studies have hypothesized that atypical neural synchronization at the delta frequency band in the auditory cortex is associated with phonological and language skills in children with Autism Spectrum Disorder (ASD), but it is still poorly understood. This study investigated this neural activity and addressed the relationships between auditory response and behavioral measures of children with ASD.

METHODS

We used magnetoencephalography and individual brain models to investigate 2 Hz Auditory Steady-State Response (ASSR) in 20 primary-school-aged children with ASD and 20 age-matched typically developing (TD) controls.

RESULTS

First, we found a between-group difference in the localization of the auditory response, so as the topology of 2 Hz ASSR was more superior and posterior in TD children when comparing to children with ASD. Second, the power of 2 Hz ASSR was reduced in the ASD group. Finally, we observed a significant association between the amplitude of neural response and language skills in children with ASD.

CONCLUSIONS

The study provided the evidence of reduced neural response in children with ASD and its relation to language skills.

SIGNIFICANCE

These findings may inform future interventions targeting auditory and language impairments in ASD population.

Amplitude modulation structure in French and German poetry: universal acoustic physical structures underpin different poetic rhythm structures

French and German poetry are classically considered to utilize fundamentally different linguistic structures to create rhythmic regularity. Their metrical rhythm structures are considered poetically to be very different. However, the biophysical and neurophysiological constraints upon the speakers of these poems are highly similar. Scientifically, this suggests that at the level of the acoustic physical structures that are produced orally, the two poetic genres may be rhythmically extremely similar. Here, we apply a language-blind computational model of linguistic rhythm based on features of the amplitude envelope (AE) to compute these physical stimulus characteristics. The model was applied to recordings of the recitation of metrical French and German poems by native speakers. Poems in free verse were not considered in the study. The results indicated that the acoustic physical structures of the poems were identical for the two languages in terms of temporal modulation patterns in the AE. This challenges the linguistic view that German poetry utilizes lexical stress to create prosodic alternation between strong and weak syllables, while French poetry relies on accentuation at the level of prosodic phrasing. Nevertheless, minor differences in physical structure could be detected by applying further modelling drawn, respectively, from the birdsong and neural connectivity literatures.

Entrainment echoes in the cerebellum

Evidence accumulates that the cerebellum's role in the brain is not restricted to motor functions. Rather, cerebellar activity seems to be crucial for a variety of tasks that rely on precise event timing and prediction. Due to its complex structure and importance in communication, human speech requires a particularly precise and predictive coordination of neural processes to be successfully comprehended. Recent studies proposed that the cerebellum is indeed a major contributor to speech processing, but how this contribution is achieved mechanistically remains poorly understood. The current study aimed to reveal a mechanism underlying cortico-cerebellar coordination and demonstrate its speech-specificity. In a reanalysis of magnetoencephalography data, we found that activity in the cerebellum aligned to rhythmic sequences of noise-vocoded speech, irrespective of its intelligibility. We then tested whether these "entrained" responses persist, and how they interact with other brain regions, when a rhythmic stimulus stopped and temporal predictions had to be updated. We found that only intelligible speech produced sustained rhythmic responses in the cerebellum. During this "entrainment echo," but not during rhythmic speech itself, cerebellar activity was coupled with that in the left inferior frontal gyrus, and specifically at rates corresponding to the preceding stimulus rhythm. This finding represents evidence for specific cerebellum-driven temporal predictions in speech processing and their relay to cortical regions.

On the speech envelope in the cortical tracking of speech

The synchronization between the speech envelope and neural activity in auditory regions, referred to as cortical tracking of speech (CTS), plays a key role in speech processing. The method selected for extracting the envelope is a crucial step in CTS measurement, and the absence of a consensus on best practices among the various methods can influence analysis outcomes and interpretation. Here, we systematically compare five standard envelope extraction methods the absolute value of Hilbert transform (absHilbert), gammatone filterbanks, heuristic approach, Bark scale, and vocalic energy), analyzing their impact on the CTS. We present performance metrics for each method based on the recording of brain activity from participants listening to speech in clear and noisy conditions, utilizing intracranial EEG, MEG and EEG data. As expected, we observed significant CTS in temporal brain regions below 10 Hz across all datasets, regardless of the extraction methods. In general, the gammatone filterbanks approach consistently demonstrated superior performance compared to other methods. Results from our study can guide scientists in the field to make informed decisions about the optimal analysis to extract the CTS, contributing to advancing the understanding of the neuronal mechanisms implicated in CTS.

Dissociating prosodic from syntactic delta activity during natural speech comprehension

Decoding human speech requires the brain to segment the incoming acoustic signal into meaningful linguistic units, ranging from syllables and words to phrases. Integrating these linguistic constituents into a coherent percept sets the root of compositional meaning and hence understanding. One important cue for segmentation in natural speech is prosodic cues, such as pauses, but their interplay with higher-level linguistic processing is still unknown. Here, we dissociate the neural tracking of prosodic pauses from the segmentation of multi-word chunks using magnetoencephalography (MEG). We find that manipulating the regularity of pauses disrupts slow speech-brain tracking bilaterally in auditory areas (below 2 Hz) and in turn increases left-lateralized coherence of higher-frequency auditory activity at speech onsets (around 25-45 Hz). Critically, we also find that multi-word chunks-defined as short, coherent bundles of inter-word dependencies-are processed through the rhythmic fluctuations of low-frequency activity (below 2 Hz) bilaterally and independently of prosodic cues. Importantly, low-frequency alignment at chunk onsets increases the accuracy of an encoding model in bilateral auditory and frontal areas while controlling for the effect of acoustics. Our findings provide novel insights into the neural basis of speech perception, demonstrating that both acoustic features (prosodic cues) and abstract linguistic processing at the multi-word timescale are underpinned independently by low-frequency electrophysiological brain activity in the delta frequency range.

Neural Tracking of Speech Acoustics in Noise Is Coupled with Lexical Predictability as Estimated by Large Language Models

Adults heard recordings of two spatially separated speakers reading newspaper and magazine articles. They were asked to listen to one of them and ignore the other, and EEG was recorded to assess their neural processing. Machine learning extracted neural sources that tracked the target and distractor speakers at three levels: the acoustic envelope of speech (delta- and theta-band modulations), lexical frequency for individual words, and the contextual predictability of individual words estimated by GPT-4 and earlier lexical models. To provide a broader view of speech perception, half of the subjects completed a simultaneous visual task, and the listeners included both native and non-native English speakers. Distinct neural components were extracted for these levels of auditory and lexical processing, demonstrating that native English speakers had greater target-distractor separation compared with non-native English speakers on most measures, and that lexical processing was reduced by the visual task. Moreover, there was a novel interaction of lexical predictability and frequency with auditory processing; acoustic tracking was stronger for lexically harder words, suggesting that people listened harder to the acoustics when needed for lexical selection. This demonstrates that speech perception is not simply a feedforward process from acoustic processing to the lexicon. Rather, the adaptable context-sensitive processing long known to occur at a lexical level has broader consequences for perception, coupling with the acoustic tracking of individual speakers in noise.

Speech and music recruit frequency-specific distributed and overlapping cortical networks

To what extent does speech and music processing rely on domain-specific and domain-general neural networks? Using whole-brain intracranial EEG recordings in 18 epilepsy patients listening to natural, continuous speech or music, we investigated the presence of frequency-specific and network-level brain activity. We combined it with a statistical approach in which a clear operational distinction is made between shared, preferred, and domain-selective neural responses. We show that the majority of focal and network-level neural activity is shared between speech and music processing. Our data also reveal an absence of anatomical regional selectivity. Instead, domain-selective neural responses are restricted to distributed and frequency-specific coherent oscillations, typical of spectral fingerprints. Our work highlights the importance of considering natural stimuli and brain dynamics in their full complexity to map cognitive and brain functions.

Early language experience modulates the tradeoff between acoustic-temporal and lexico-semantic cortical tracking of speech

Cortical tracking of speech is relevant for the development of speech perception skills. However, no study to date has explored whether and how cortical tracking of speech is shaped by accumulated language experience, the central question of this study. In 35 bilingual children (6-year-old) with considerably bigger experience in one language, we collected electroencephalography data while they listened to continuous speech in their two languages. Cortical tracking of speech was assessed at acoustic-temporal and lexico-semantic levels. Children showed more robust acoustic-temporal tracking in the least experienced language, and more sensitive cortical tracking of semantic information in the most experienced language. Additionally, and only for the most experienced language, acoustic-temporal tracking was specifically linked to phonological abilities, and lexico-semantic tracking to vocabulary knowledge. Our results indicate that accumulated linguistic experience is a relevant maturational factor for the cortical tracking of speech at different levels during early language acquisition.

Predicting language outcome at birth

Even though most children acquire language effortlessly, not all do. Nowadays, language disorders are difficult to diagnose before 3-4 years of age, because diagnosis relies on behavioral criteria difficult to obtain early in life. Using electroencephalography, I investigated whether differences in newborns' neural activity when listening to sentences in their native language (French) and a rhythmically different unfamiliar language (English) relate to measures of later language development at 12 and 18 months. Here I show that activation differences in the theta band at birth predict language comprehension abilities at 12 and 18 months. These findings suggest that a neural measure of language discrimination at birth could be used in the early identification of infants at risk of developmental language disorders.

Perception of temporal structure in speech is influenced by body movement and individual beat perception ability

The subjective experience of time flow in speech deviates from the sound acoustics in substantial ways. The present study focuses on the perceptual tendency to regularize time intervals found in speech but not in other types of sounds with a similar temporal structure. We investigate to what extent individual beat perception ability is responsible for perceptual regularization and if the effect can be eliminated through the involvement of body movement during listening. Participants performed a musical beat perception task and compared spoken sentences to their drumbeat-based versions either after passive listening or after listening and moving along with the beat of the sentences. The results show that the interval regularization prevails in listeners with a low beat perception ability performing a passive listening task and is eliminated in an active listening task involving body movement. Body movement also helped to promote a veridical percept of temporal structure in speech at the group level. We suggest that body movement engages an internal timekeeping mechanism, promoting the fidelity of auditory encoding even in sounds of high temporal complexity and irregularity such as natural speech.

Atypical low-frequency cortical encoding of speech identifies children with developmental dyslexia

Slow cortical oscillations play a crucial role in processing the speech amplitude envelope, which is perceived atypically by children with developmental dyslexia. Here we use electroencephalography (EEG) recorded during natural speech listening to identify neural processing patterns involving slow oscillations that may characterize children with dyslexia. In a story listening paradigm, we find that atypical power dynamics and phase-amplitude coupling between delta and theta oscillations characterize dyslexic versus other child control groups (typically-developing controls, other language disorder controls). We further isolate EEG common spatial patterns (CSP) during speech listening across delta and theta oscillations that identify dyslexic children. A linear classifier using four delta-band CSP variables predicted dyslexia status (0.77 AUC). Crucially, these spatial patterns also identified children with dyslexia when applied to EEG measured during a rhythmic syllable processing task. This transfer effect (i.e., the ability to use neural features derived from a story listening task as input features to a classifier based on a rhythmic syllable task) is consistent with a core developmental deficit in neural processing of speech rhythm. The findings are suggestive of distinct atypical neurocognitive speech encoding mechanisms underlying dyslexia, which could be targeted by novel interventions.

Exploring the Interplay Between Language Comprehension and Cortical Tracking: The Bilingual Test Case

Cortical tracking, the synchronization of brain activity to linguistic rhythms is a well-established phenomenon. However, its nature has been heavily contested: Is it purely epiphenomenal or does it play a fundamental role in speech comprehension? Previous research has used intelligibility manipulations to examine this topic. Here, we instead varied listeners' language comprehension skills while keeping the auditory stimulus constant. To do so, we tested 22 native English speakers and 22 Spanish/Catalan bilinguals learning English as a second language (SL) in an EEG cortical entrainment experiment and correlated the responses with the magnitude of the N400 component of a semantic comprehension task. As expected, native listeners effectively tracked sentential, phrasal, and syllabic linguistic structures. In contrast, SL listeners exhibited limitations in tracking sentential structures but successfully tracked phrasal and syllabic rhythms. Importantly, the amplitude of the neural entrainment correlated with the amplitude of the detection of semantic incongruities in SLs, showing a direct connection between tracking and the ability to understand speech. Together, these findings shed light on the interplay between language comprehension and cortical tracking, to identify neural entrainment as a fundamental principle for speech comprehension.

A multimodal approach to automated hierarchical assessment of bulbar involvement in amyotrophic lateral sclerosis

Introduction

As a hallmark feature of amyotrophic lateral sclerosis (ALS), bulbar involvement leads to progressive declines of speech and swallowing functions, significantly impacting social, emotional, and physical health, and quality of life. Standard clinical tools for bulbar assessment focus primarily on clinical symptoms and functional outcomes. However, ALS is known to have a long, clinically silent prodromal stage characterized by complex subclinical changes at various levels of the bulbar motor system. These changes accumulate over time and eventually culminate in clinical symptoms and functional declines. Detection of these subclinical changes is critical, both for mechanistic understanding of bulbar neuromuscular pathology and for optimal clinical management of bulbar dysfunction in ALS. To this end, we developed a novel multimodal measurement tool based on two clinically readily available, noninvasive instruments-facial surface electromyography (sEMG) and acoustic techniques-to hierarchically assess seven constructs of bulbar/speech motor control at the neuromuscular and acoustic levels. These constructs, including prosody, pause, functional connectivity, amplitude, rhythm, complexity, and regularity, are both mechanically and clinically relevant to bulbar involvement.

Methods

Using a custom-developed, fully automated data analytic algorithm, a variety of features were extracted from the sEMG and acoustic recordings of a speech task performed by 13 individuals with ALS and 10 neurologically healthy controls. These features were then factorized into 10 composite outcome measures using confirmatory factor analysis. Statistical and machine learning techniques were applied to these composite outcome measures to evaluate their reliability (internal consistency), validity (concurrent and construct), and efficacy for early detection and progress monitoring of bulbar involvement in ALS.

Results

The composite outcome measures were demonstrated to (1) be internally consistent and structurally valid in measuring the targeted constructs; (2) hold concurrent validity with the existing clinical and functional criteria for bulbar assessment; and (3) outperform the outcome measures obtained from each constituent modality in differentiating individuals with ALS from healthy controls. Moreover, the composite outcome measures combined demonstrated high efficacy for detecting subclinical changes in the targeted constructs, both during the prodromal stage and during the transition from prodromal to symptomatic stages.

Discussion

The findings provided compelling initial evidence for the utility of the multimodal measurement tool for improving early detection and progress monitoring of bulbar involvement in ALS, which have important implications in facilitating timely access to and delivery of optimal clinical care of bulbar dysfunction.

Atypical beta-band effects in children with dyslexia in response to rhythmic audio-visual speech

OBJECTIVE

Previous studies have reported atypical delta phase in children with dyslexia, and that delta phase modulates the amplitude of the beta-band response via delta-beta phase-amplitude coupling (PAC). Accordingly, the atypical delta-band effects in children with dyslexia may imply related atypical beta-band effects, particularly regarding delta-beta PAC. Our primary objective was to explore beta-band oscillations in children with and without dyslexia, to explore potentially atypical effects in the beta band in dyslexic children.

METHODS

We collected EEG data during a rhythmic speech paradigm from 51 children (21 control; 30 dyslexia). We then assessed beta-band phase entrainment, beta-band angular velocity, beta-band power responses and delta-beta PAC.

RESULTS

We found significant beta-band phase entrainment for control children but not for dyslexic children. Furthermore, children with dyslexia exhibited significantly faster beta-band angular velocity and significantly greater beta-band power. Delta-beta PAC was comparable in both groups.

CONCLUSION

Atypical beta-band effects were observed in children with dyslexia. However, delta-beta PAC was comparable in both dyslexic and control children.

SIGNIFICANCE

These findings offer further insights into the neurophysiological basis of atypical rhythmic speech processing by children with dyslexia, suggesting the involvement of a wide range of frequency bands.

Neural attentional filters and behavioural outcome follow independent individual trajectories over the adult lifespan

Preserved communication abilities promote healthy ageing. To this end, the age-typical loss of sensory acuity might in part be compensated for by an individual's preserved attentional neural filtering. Is such a compensatory brain-behaviour link longitudinally stable? Can it predict individual change in listening behaviour? We here show that individual listening behaviour and neural filtering ability follow largely independent developmental trajectories modelling electroencephalographic and behavioural data of N = 105 ageing individuals (39-82 y). First, despite the expected decline in hearing-threshold-derived sensory acuity, listening-task performance proved stable over 2 y. Second, neural filtering and behaviour were correlated only within each separate measurement timepoint (T1, T2). Longitudinally, however, our results raise caution on attention-guided neural filtering metrics as predictors of individual trajectories in listening behaviour: neither neural filtering at T1 nor its 2-year change could predict individual 2-year behavioural change, under a combination of modelling strategies.

Contributions of listening effort and intelligibility to cortical tracking of speech in adverse listening conditions

Cortical tracking of speech is vital for speech segmentation and is linked to speech intelligibility. However, there is no clear consensus as to whether reduced intelligibility leads to a decrease or an increase in cortical speech tracking, warranting further investigation of the factors influencing this relationship. One such factor is listening effort, defined as the cognitive resources necessary for speech comprehension, and reported to have a strong negative correlation with speech intelligibility. Yet, no studies have examined the relationship between speech intelligibility, listening effort, and cortical tracking of speech. The aim of the present study was thus to examine these factors in quiet and distinct adverse listening conditions. Forty-nine normal hearing adults listened to sentences produced casually, presented in quiet and two adverse listening conditions: cafeteria noise and reverberant speech. Electrophysiological responses were registered with electroencephalogram, and listening effort was estimated subjectively using self-reported scores and objectively using pupillometry. Results indicated varying impacts of adverse conditions on intelligibility, listening effort, and cortical tracking of speech, depending on the preservation of the speech temporal envelope. The more distorted envelope in the reverberant condition led to higher listening effort, as reflected in higher subjective scores, increased pupil diameter, and stronger cortical tracking of speech in the delta band. These findings suggest that using measures of listening effort in addition to those of intelligibility is useful for interpreting cortical tracking of speech results. Moreover, reading and phonological skills of participants were positively correlated with listening effort in the cafeteria condition, suggesting a special role of expert language skills in processing speech in this noisy condition. Implications for future research and theories linking atypical cortical tracking of speech and reading disorders are further discussed.

Decoding speech information from EEG data with 4-, 7- and 11-month-old infants: Using convolutional neural network, mutual information-based and backward linear models

BACKGROUND

Computational models that successfully decode neural activity into speech are increasing in the adult literature, with convolutional neural networks (CNNs), backward linear models, and mutual information (MI) models all being applied to neural data in relation to speech input. This is not the case in the infant literature.

NEW METHOD

Three different computational models, two novel for infants, were applied to decode low-frequency speech envelope information. Previously-employed backward linear models were compared to novel CNN and MI-based models. Fifty infants provided EEG recordings when aged 4, 7, and 11 months, while listening passively to natural speech (sung or chanted nursery rhymes) presented by video with a female singer.

RESULTS

Each model computed speech information for these nursery rhymes in two different low-frequency bands, delta and theta, thought to provide different types of linguistic information. All three models demonstrated significant levels of performance for delta-band neural activity from 4 months of age, with two of three models also showing significant performance for theta-band activity. All models also demonstrated higher accuracy for the delta-band neural responses. None of the models showed developmental (age-related) effects.

COMPARISONS WITH EXISTING METHODS

The data demonstrate that the choice of algorithm used to decode speech envelope information from neural activity in the infant brain determines the developmental conclusions that can be drawn.

CONCLUSIONS

The modelling shows that better understanding of the strengths and weaknesses of each modelling approach is fundamental to improving our understanding of how the human brain builds a language system.

Neural tracking of continuous acoustics: properties, speech-specificity and open questions

Human speech is a particularly relevant acoustic stimulus for our species, due to its role of information transmission during communication. Speech is inherently a dynamic signal, and a recent line of research focused on neural activity following the temporal structure of speech. We review findings that characterise neural dynamics in the processing of continuous acoustics and that allow us to compare these dynamics with temporal aspects in human speech. We highlight properties and constraints that both neural and speech dynamics have, suggesting that auditory neural systems are optimised to process human speech. We then discuss the speech-specificity of neural dynamics and their potential mechanistic origins and summarise open questions in the field.