scholarly journals Cortical tracking of speech reveals top-down reconstructive processes

2019 ◽  
Author(s):  
Sankar Mukherjee ◽  
Alice Tomassini ◽  
Leonardo Badino ◽  
Aldo Pastore ◽  
Luciano Fadiga ◽  
...  
Keyword(s):  
Predictive Model ◽  
Experimental Test ◽  
Speech Comprehension ◽  
Missing Information ◽  
Top Down ◽  
Sensory Signals ◽  
Analysis By Synthesis ◽  
Neural Entrainment ◽  
Speech Envelope ◽  
Cortical Entrainment

AbstractCortical entrainment to the (quasi-) rhythmic components of speech seems to play an important role in speech comprehension. It has been suggested that neural entrainment may reflect top-down temporal predictions of sensory signals. Key properties of a predictive model are its anticipatory nature and its ability to reconstruct missing information. Here we put both these two properties to experimental test. We acoustically presented sentences and measured cortical entrainment to both acoustic speech envelope and lips kinematics acquired from the speaker but not visible to the participants. We then analyzed speech-brain and lips-brain coherence at multiple negative and positive lags. Besides the well-known cortical entrainment to the acoustic speech envelope, we found significant entrainment in the delta range to the (latent) lips kinematics. Most interestingly, the two entrainment phenomena were temporally dissociated. While entrainment to the acoustic speech peaked around +0.3 s lag (i.e., when EEG followed speech by 0.3 s), entrainment to the lips was significantly anticipated and peaked around 0-0.1 s lag (i.e., when EEG was virtually synchronous to the putative lips movement). Our results demonstrate that neural entrainment during speech listening involves the anticipatory reconstruction of missing information related to lips movement production, indicating its fundamentally predictive nature and thus supporting analysis by synthesis models.

scholarly journals Visual cortical entrainment to unheard acoustic speech reflects intelligibility of lip movements and is mediated by dorsal stream regions

2018 ◽  
Author(s):  
A. Hauswald ◽  
C. Lithari ◽  
O. Collignon ◽  
E. Leonardelli ◽  
N. Weisz
Keyword(s):  
Visual Cortex ◽  
Acoustic Signal ◽  
Temporal Cortex ◽  
Dorsal Stream ◽  
List Type ◽  
Top Down ◽  
Entrainment Effect ◽  
Speech Envelope ◽  
Cortical Entrainment ◽  
Visual Cortical

AbstractSuccessful lip reading requires a mapping from visual to phonological information [1]. Recently, visual and motor cortices have been implicated in tracking lip movements (e.g. [2]). It remains unclear, however, whether visuo-phonological mapping occurs already at the level of the visual cortex, that is, whether this structure tracks the acoustic signal in a functionally relevant manner. In order to elucidate this, we investigated how the cortex tracks (i.e. entrains) absent acoustic speech signals carried by silent lip movements. Crucially, we contrasted the entrainment to unheard forward (intelligible) and backward (unintelligible) acoustic speech. We observed that the visual cortex exhibited stronger entrainment to the unheard forward acoustic speech envelope compared to the unheard backward acoustic speech envelope. Supporting the notion of a visuo-phonological mapping process, this forward-backward difference of occipital entrainment was not present for actually observed lip movements. Importantly, the respective occipital region received more top-down input especially from left premotor, primary motor, somatosensory regions and, to a lesser extent, also from posterior temporal cortex. Strikingly, across participants, the extent of top-down modulation of visual cortex stemming from these regions partially correlates with the strength of entrainment to absent acoustic forward speech envelope but not to present forward lip movements. Our findings demonstrate that a distributed cortical network, including key dorsal stream auditory regions [3–5], influence how the visual cortex shows sensitivity to the intelligibility of speech while tracking silent lip movements.HighlightsVisual cortex tracks better forward than backward unheard acoustic speech envelopeEffects not “trivially” caused by correlation of visual with acoustic signalStronger top-down control of visual cortex during forward display of lip movementsTop-down influence correlates with visual cortical entrainment effectResults seem to reflect visuo-phonological mapping processes

scholarly journals Lacking Effects of Envelope Transcranial Alternating Current Stimulation Indicate the Need to Revise Envelope Transcranial Alternating Current Stimulation Methods

2020 ◽  
Vol 15 ◽  
pp. 263310552093662
Author(s):  
Jules Erkens ◽  
Michael Schulte ◽  
Matthias Vormann ◽  
Christoph S Herrmann
Keyword(s):  
Time Lag ◽  
Alternating Current ◽  
Optimal Time ◽  
Speech Comprehension ◽  
Time Lags ◽  
Beneficial Effects ◽  
Significant Difference ◽  
Transcranial Alternating Current Stimulation ◽  
Speech Envelope ◽  
Cortical Entrainment

In recent years, several studies have reported beneficial effects of transcranial alternating current stimulation (tACS) in experiments regarding sound and speech perception. A new development in this field is envelope-tACS: The goal of this method is to improve cortical entrainment to the speech signal by stimulating with a waveform based on the speech envelope. One challenge of this stimulation method is timing; the electrical stimulation needs to be phase-aligned with the naturally occurring cortical entrainment to the auditory stimuli. Due to individual differences in anatomy and processing speed, the optimal time-lag between presentation of sound and applying envelope-tACS varies between participants. To better investigate the effects of envelope-tACS, we performed a speech comprehension task with a larger amount of time-lags than previous experiments, as well as an equal amount of sham conditions. No significant difference between optimal stimulation time-lag condition and best sham condition was found. Further investigation of the data revealed a significant difference between the positive and negative half-cycles of the stimulation conditions but not for sham. However, we also found a significant learning effect over the course of the experiment which was of comparable size to the effects of envelope-tACS found in previous auditory tACS studies. In this article, we discuss possible explanations for why our findings did not match up with those of previous studies and the issues that come with researching and developing envelope-tACS.

scholarly journals Pushing the Envelope: Developments in Neural Entrainment to Speech and the Biological Underpinnings of Prosody Perception

2019 ◽  
Vol 9 (3) ◽  
pp. 70 ◽  
Author(s):  
Brett Myers ◽  
Miriam Lense ◽  
Reyna Gordon
Keyword(s):  
Phase Locking ◽  
Future Research ◽  
Speech Comprehension ◽  
Linguistic Processing ◽  
Prosodic Cues ◽  
Electrophysiological Studies ◽  
Neural Entrainment ◽  
Stimulus Reconstruction ◽  
Neural Underpinnings ◽  
Speech Envelope

Prosodic cues in speech are indispensable for comprehending a speaker’s message, recognizing emphasis and emotion, parsing segmental units, and disambiguating syntactic structures. While it is commonly accepted that prosody provides a fundamental service to higher-level features of speech, the neural underpinnings of prosody processing are not clearly defined in the cognitive neuroscience literature. Many recent electrophysiological studies have examined speech comprehension by measuring neural entrainment to the speech amplitude envelope, using a variety of methods including phase-locking algorithms and stimulus reconstruction. Here we review recent evidence for neural tracking of the speech envelope and demonstrate the importance of prosodic contributions to the neural tracking of speech. Prosodic cues may offer a foundation for supporting neural synchronization to the speech envelope, which scaffolds linguistic processing. We argue that prosody has an inherent role in speech perception, and future research should fill the gap in our knowledge of how prosody contributes to speech envelope entrainment.

scholarly journals Transcranial alternating current stimulation with speech envelopes modulates speech comprehension

2017 ◽  
Author(s):  
Anna Wilsch ◽  
Toralf Neuling ◽  
Jonas Obleser ◽  
Christoph S. Herrmann
Keyword(s):  
Auditory Cortex ◽  
Speech Signal ◽  
Speech Intelligibility ◽  
Sentence Comprehension ◽  
Average Frequency ◽  
Speech Comprehension ◽  
Time Lags ◽  
Transcranial Alternating Current Stimulation ◽  
Speech Envelope ◽  
Cortical Entrainment

AbstractCortical entrainment of the auditory cortex to the broadband temporal envelope of a speech signal is crucial for speech comprehension. Entrainment results in phases of high and low neural excitability, which structure and decode the incoming speech signal. Entrainment to speech is strongest in the theta frequency range (4–8 Hz), the average frequency of the speech envelope. If a speech signal is degraded, entrainment to the speech envelope is weaker and speech intelligibility declines. Besides perceptually evoked cortical entrainment, transcranial alternating current stimulation (tACS) entrains neural oscillations by applying an electric signal to the brain. Accordingly, tACS-induced entrainment in auditory cortex has been shown to improve auditory perception. The aim of the current study was to modulate speech intelligibility externally by means of tACS such that the electric current corresponds to the envelope of the presented speech stream (i.e., envelope-tACS). Participants performed the Oldenburg sentence test with sentences presented in noise in combination with envelope-tACS. Critically, tACS was induced at time lags of 0 to 250 ms in 50-ms steps relative to sentence onset (auditory stimuli were simultaneous to or preceded tACS). We performed single-subject sinusoidal, linear, and quadratic fits to the sentence comprehension performance across the time lags. We could show that the sinusoidal fit described the modulation of sentence comprehension best. Importantly, the average frequency of the sinusoidal fit was 5.12 Hz, corresponding to the peaks of the amplitude spectrum of the stimulated envelopes. This finding was supported by a significant 5-Hz peak in the average power spectrum of individual performance time series. Altogether, envelope tACS modulates intelligibility of speech in noise, presumably by enhancing and disrupting (time lag with in-or out-of-phase stimulation, respectively) cortical entrainment to the speech envelope in auditory cortex.

scholarly journals Aging affects the balance of neural entrainment and top-down neural modulation in the listening brain

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Molly J. Henry ◽  
Björn Herrmann ◽  
Dunja Kunke ◽  
Jonas Obleser
Keyword(s):  
Top Down ◽  
Neural Modulation ◽  
Neural Entrainment

scholarly journals Cortical entrainment to music and its modulation by expertise

2015 ◽  
Vol 112 (45) ◽  
pp. E6233-E6242 ◽  
Author(s):  
Keith B. Doelling ◽  
David Poeppel
Keyword(s):  
Music Perception ◽  
Musical Training ◽  
Low Frequency ◽  
Oscillatory Activity ◽  
Cortical Oscillations ◽  
Bidirectional Relationship ◽  
Delta Activity ◽  
Tightly Coupled ◽  
Neural Entrainment ◽  
Cortical Entrainment

Recent studies establish that cortical oscillations track naturalistic speech in a remarkably faithful way. Here, we test whether such neural activity, particularly low-frequency (<8 Hz; delta–theta) oscillations, similarly entrain to music and whether experience modifies such a cortical phenomenon. Music of varying tempi was used to test entrainment at different rates. In three magnetoencephalography experiments, we recorded from nonmusicians, as well as musicians with varying years of experience. Recordings from nonmusicians demonstrate cortical entrainment that tracks musical stimuli over a typical range of tempi, but not at tempi below 1 note per second. Importantly, the observed entrainment correlates with performance on a concurrent pitch-related behavioral task. In contrast, the data from musicians show that entrainment is enhanced by years of musical training, at all presented tempi. This suggests a bidirectional relationship between behavior and cortical entrainment, a phenomenon that has not previously been reported. Additional analyses focus on responses in the beta range (∼15–30 Hz)—often linked to delta activity in the context of temporal predictions. Our findings provide evidence that the role of beta in temporal predictions scales to the complex hierarchical rhythms in natural music and enhances processing of musical content. This study builds on important findings on brainstem plasticity and represents a compelling demonstration that cortical neural entrainment is tightly coupled to both musical training and task performance, further supporting a role for cortical oscillatory activity in music perception and cognition.

The thalamus interrupts top-down attentional control for permitting exploratory shiftings to sensory signals

Neuroreport ◽  
2001 ◽  
Vol 12 (9) ◽  
pp. 2041-2048 ◽  
Author(s):  
George Andrew Michael ◽  
Muriel Boucart ◽  
Jean-Fran??ois Degreef ◽  
Olivier Godefroy
Keyword(s):  
Attentional Control ◽  
Top Down ◽  
Sensory Signals

scholarly journals High-frequency neural activity predicts word parsing in ambiguous speech streams

2016 ◽  
Vol 116 (6) ◽  
pp. 2497-2512 ◽  
Author(s):  
Anne Kösem ◽  
Anahita Basirat ◽  
Leila Azizi ◽  
Virginie van Wassenhove
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Acoustic Properties ◽  
Neural Oscillations ◽  
Speech Comprehension ◽  
Top Down ◽  
Linguistic Representations ◽  
High Frequency Activity ◽  
Speech Percept ◽  
The Brain

During speech listening, the brain parses a continuous acoustic stream of information into computational units (e.g., syllables or words) necessary for speech comprehension. Recent neuroscientific hypotheses have proposed that neural oscillations contribute to speech parsing, but whether they do so on the basis of acoustic cues (bottom-up acoustic parsing) or as a function of available linguistic representations (top-down linguistic parsing) is unknown. In this magnetoencephalography study, we contrasted acoustic and linguistic parsing using bistable speech sequences. While listening to the speech sequences, participants were asked to maintain one of the two possible speech percepts through volitional control. We predicted that the tracking of speech dynamics by neural oscillations would not only follow the acoustic properties but also shift in time according to the participant's conscious speech percept. Our results show that the latency of high-frequency activity (specifically, beta and gamma bands) varied as a function of the perceptual report. In contrast, the phase of low-frequency oscillations was not strongly affected by top-down control. Whereas changes in low-frequency neural oscillations were compatible with the encoding of prelexical segmentation cues, high-frequency activity specifically informed on an individual's conscious speech percept.

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