The effect of stimulus choice on an EEG-based objective measure of speech intelligibility

ABSTRACTObjectivesRecently an objective measure of speech intelligibility, based on brain responses derived from the electroencephalogram (EEG), has been developed using isolated Matrix sentences as a stimulus. We investigated whether this objective measure of speech intelligibility can also be used with natural speech as a stimulus, as this would be beneficial for clinical applications.DesignWe recorded the EEG in 19 normal-hearing participants while they listened to two types of stimuli: Matrix sentences and a natural story. Each stimulus was presented at different levels of speech intelligibility by adding speech weighted noise. Speech intelligibility was assessed in two ways for both stimuli: (1) behaviorally and (2) objectively by reconstructing the speech envelope from the EEG using a linear decoder and correlating it with the acoustic envelope. We also calculated temporal response functions (TRFs) to investigate the temporal characteristics of the brain responses in the EEG channels covering different brain areas.ResultsFor both stimulus types the correlation between the speech envelope and the reconstructed envelope increased with increasing speech intelligibility. In addition, correlations were higher for the natural story than for the Matrix sentences. Similar to the linear decoder analysis, TRF amplitudes increased with increasing speech intelligibility for both stimuli. Remarkable is that although speech intelligibility remained unchanged in the no noise and +2.5 dB SNR condition, neural speech processing was affected by the addition of this small amount of noise: TRF amplitudes across the entire scalp decreased between 0 to 150 ms, while amplitudes between 150 to 200 ms increased in the presence of noise. TRF latency changes in function of speech intelligibility appeared to be stimulus specific: The latency of the prominent negative peak in the early responses (50-300 ms) increased with increasing speech intelligibility for the Matrix sentences, but remained unchanged for the natural story.ConclusionsThese results show (1) the feasibility of natural speech as a stimulus for the objective measure of speech intelligibility, (2) that neural tracking of speech is enhanced using a natural story compared to Matrix sentences and (3) that noise and the stimulus type can change the temporal characteristics of the brain responses. These results might reflect the integration of incoming acoustic features and top-down information, suggesting that the choice of the stimulus has to be considered based on the intended purpose of the measurement.

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Neural tracking as an objective measure of auditory perception and speech intelligibility

10.1101/2021.11.26.470129 ◽

2021 ◽

Author(s):

Jana Van Canneyt ◽

Marlies Gillis ◽

Jonas Vanthornhout ◽

Tom Francart

Keyword(s):

Speech Perception ◽

Auditory Cortex ◽

Speech Intelligibility ◽

Objective Assessment ◽

Objective Measure ◽

Primary Auditory Cortex ◽

Auditory Pathway ◽

Natural Speech ◽

Linguistic Features ◽

The Brain

The neural tracking framework enables the analysis of neural responses (EEG) to continuous natural speech, e.g., a story or a podcast. This allows for objective investigation of a range of auditory and linguistic processes in the brain during natural speech perception. This approach is more ecologically valid than traditional auditory evoked responses and has great potential for both research and clinical applications. In this article, we review the neural tracking framework and highlight three prominent examples of neural tracking analyses. This includes the neural tracking of the fundamental frequency of the voice (f0), the speech envelope and linguistic features. Each of these analyses provides a unique point of view into the hierarchical stages of speech processing in the human brain. f0-tracking assesses the encoding of fine temporal information in the early stages of the auditory pathway, i.e. from the auditory periphery up to early processing in the primary auditory cortex. This fundamental processing in (mostly) subcortical stages forms the foundation of speech perception in the cortex. Envelope tracking reflects bottom-up and top-down speech-related processes in the auditory cortex, and is likely necessary but not sufficient for speech intelligibility. To study neural processes more directly related to speech intelligibility, neural tracking of linguistic features can be used. This analysis focuses on the encoding of linguistic features (e.g. word or phoneme surprisal) in the brain. Together these analyses form a multi-faceted and time-effective objective assessment of the auditory and linguistic processing of an individual.

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Cortical responses to natural speech reflect probabilistic phonotactics

10.1101/359828 ◽

2018 ◽

Author(s):

Giovanni M. Di Liberto ◽

Daniel Wong ◽

Gerda Ana Melnik ◽

Alain de Cheveigné

Keyword(s):

Low Frequency ◽

English Word ◽

Natural Speech ◽

Neural Encoding ◽

Individual Subject ◽

Brain Responses ◽

Learning Development ◽

The Individual ◽

The Brain

AbstractHumans comprehend speech despite the various challenges of real-world environments, such as loud noise and mispronunciation. Our auditory system is robust to these thanks to the integration of the upcoming sensory input with prior knowledge and expectations built on language-specific regularities. One such regularity regards the permissible phoneme sequences, which determine the likelihood that a word belongs to a given language (phonotactic probability; “blick” is more likely to be an English word than “bnick”). Previous research suggested that violations of these rules modulate brain evoked responses such as the N400 and the late positive complex. Yet several fundamental questions remain unresolved, especially regarding the neural encoding and integration strategy of phonotactic information. Here, we used linear modelling approaches to assess the influence of phonotactic probabilities on the brain responses to narrative speech measured with non-invasive EEG. We found that the relationship between continuous speech and EEG responses is best described when the speech descriptor includes phonotactic probabilities. This provides us with a methodology to isolate and measure the brain responses to phonotactics using natural speech at the individual subject-level. Furthermore, such low-frequency signals showed the strongest speech-EEG interactions at latencies of 100-400 ms, supporting a pre-lexical role of phonotactic information.Significance StatementSpeech is composed of basic units, called phonemes, whose combinations comply with language-specific regularities determining whether a sequence “sounds” as a plausible word. Our ability to detect irregular combinations requires matching incoming sequences with our internal expectations, a process that supports speech segmentation and learning. However, the neural mechanisms underlying this phenomenon have not yet been established. Here, we examine this in the human brain using narrative speech. We identified a brain signal reflecting the likelihood that a word belongs to the language, which may offer new opportunities to investigate speech perception, learning, development, and impairment. Our data also suggest a pre-lexical role of this phenomenon, thus supporting and extending current mechanistic perspectives.

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The effect of stimulus intensity on neural envelope tracking

10.1101/2020.08.11.245761 ◽

2020 ◽

Author(s):

Eline Verschueren ◽

Jonas Vanthornhout ◽

Tom Francart

Keyword(s):

Stimulus Intensity ◽

Speech Processing ◽

Speech Intelligibility ◽

Normal Hearing ◽

Hearing Impaired ◽

Response Functions ◽

Envelope Tracking ◽

Brain Responses ◽

Envelope Reconstruction ◽

Speech Tracking

ABSTRACTObjectivesThe last years there has been significant interest in attempting to recover the temporal envelope of a speech signal from the neural response to investigate neural speech processing. The research focus is now broadening from neural speech processing in normal-hearing listeners towards hearing-impaired listeners. When testing hearing-impaired listeners speech has to be amplified to resemble the effect of a hearing aid and compensate peripheral hearing loss. Until today, it is not known with certainty how or if neural speech tracking is influenced by sound amplification. As these higher intensities could influence the outcome, we investigated the influence of stimulus intensity on neural speech tracking.DesignWe recorded the electroencephalogram (EEG) of 20 normal-hearing participants while they listened to a narrated story. The story was presented at intensities from 10 to 80 dB A. To investigate the brain responses, we analyzed neural tracking of the speech envelope by reconstructing the envelope from EEG using a linear decoder and by correlating the reconstructed with the actual envelope. We investigated the delta (0.5-4 Hz) and the theta (4-8 Hz) band for each intensity. We also investigated the latencies and amplitudes of the responses in more detail using temporal response functions which are the estimated linear response functions between the stimulus envelope and the EEG.ResultsNeural envelope tracking is dependent on stimulus intensity in both the TRF and envelope reconstruction analysis. However, provided that the decoder is applied on data of the same stimulus intensity as it was trained on, envelope reconstruction is robust to stimulus intensity. In addition, neural envelope tracking in the delta (but not theta) band seems to relate to speech intelligibility. Similar to the linear decoder analysis, TRF amplitudes and latencies are dependent on stimulus intensity: The amplitude of peak 1 (30-50 ms) increases and the latency of peak 2 (140-160 ms) decreases with increasing stimulus intensity.ConclusionAlthough brain responses are influenced by stimulus intensity, neural envelope tracking is robust to stimulus intensity when using the same intensity to test and train the decoder. Therefore we can assume that intensity is not a confound when testing hearing-impaired participants with amplified speech using the linear decoder approach. In addition, neural envelope tracking in the delta band appears to be correlated with speech intelligibility, showing the potential of neural envelope tracking as an objective measure of speech intelligibility.

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The Effect of Stimulus Choice on an EEG-Based Objective Measure of Speech Intelligibility

Ear & Hearing ◽

10.1097/aud.0000000000000875 ◽

2020 ◽

Vol 41 (6) ◽

pp. 1586-1597 ◽

Cited By ~ 1

Author(s):

Eline Verschueren ◽

Jonas Vanthornhout ◽

Tom Francart

Keyword(s):

Speech Intelligibility ◽

Objective Measure ◽

Stimulus Choice

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The interplay of top-down focal attention and the cortical tracking of speech

10.1101/813147 ◽

2019 ◽

Author(s):

D Lesenfants ◽

T Francart

Keyword(s):

Auditory Processing ◽

Active Engagement ◽

Top Down ◽

Focal Attention ◽

Brain Responses ◽

Speech Envelope ◽

The Impact ◽

Auditory Processes ◽

The Brain ◽

Speech Response

AbstractMany active neuroimaging paradigms rely on the assumption that the participant sustains attention to a task. However, in practice, there will be momentary distractions, potentially influencing the results. We investigated the effect of focal attention, objectively quantified using a measure of brain signal entropy, on cortical tracking of the speech envelope. The latter is a measure of neural processing of naturalistic speech. We let participants listen to 44 minutes of natural speech, while their electroencephalogram was recorded, and quantified both entropy and cortical envelope tracking. Focal attention affected the later brain responses to speech, between 100 and 300 ms latency. By only taking into account periods with higher attention, the measured cortical speech tracking improved by 47%. This illustrates the impact of the participant’s active engagement in the modeling of the brain-speech response and the importance of accounting for it. Our results suggests a cortico-cortical loop that initiates during the early-stages of the auditory processing, then propagates through the parieto-occipital and frontal areas, and finally impacts the later-latency auditory processes in a top-down fashion. The proposed framework could be transposed to other active electrophysiological paradigms (visual, somatosensory, etc) and help to control the impact of participants’ engagement on the results.

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Neural tracking of the speech envelope in cochlear implant users

10.1101/359299 ◽

2018 ◽

Cited By ~ 1

Author(s):

Ben Somers ◽

Eline Verschueren ◽

Tom Francart

Keyword(s):

Electrical Stimulation ◽

Cochlear Implant ◽

Speech Intelligibility ◽

Recording Conditions ◽

Eeg Recordings ◽

Linear Envelope ◽

Envelope Reconstruction ◽

Speech Envelope ◽

First Time ◽

The Brain

AbstractObjectiveWhen listening to speech, the brain tracks the speech envelope. It is possible to reconstruct this envelope from EEG recordings. However, in people who hear using a cochlear implant (CI), the artifacts caused by electrical stimulation of the auditory nerve contaminate the EEG. This causes the decoder to produce an artifact-dominated reconstruction, which does not reflect the neural signal processing. The objective of this study is to develop and validate a method for assessing the neural tracking of speech envelope in CI users.ApproachTo obtain EEG recordings free of stimulus artifacts, the electrical stimulation is periodically in-terrupted. During these stimulation gaps, artifact-free EEG can be sampled and used to train a linear envelope decoder. Different recording conditions were used to characterize the artifacts and their influence on the envelope reconstruction.Main resultsThe present study demonstrates for the first time that neural tracking of the speech envelope can be measured in response to ongoing electrical stimulation. The responses were validated to be truly neural and not affected by stimulus artifact.SignificanceBesides applications in audiology and neuroscience, the characterization and elimination of stimulus artifacts will enable future EEG studies involving continuous speech in CI users. Measures of neural tracking of the speech envelope reflect interesting properties of the listener’s perception of speech, such as speech intelligibility or attentional state. Successful decoding of neural envelope tracking will open new possibilities to investigate the neural mechanisms of speech perception with a CI.

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Consciousness

10.1093/oso/9780199674923.003.0037 ◽

2018 ◽

Author(s):

Anil K. Seth

Keyword(s):

Conscious Experience ◽

Real Problem ◽

Active Inference ◽

Biological Mechanisms ◽

Specific Content ◽

Brain Responses ◽

Biomimetic Approach ◽

Multiple Levels ◽

In Virtue Of ◽

The Brain

Consciousness is perhaps the most familiar aspect of our existence, yet we still do not know its biological basis. This chapter outlines a biomimetic approach to consciousness science, identifying three principles linking properties of conscious experience to potential biological mechanisms. First, conscious experiences generate large quantities of information in virtue of being simultaneously integrated and differentiated. Second, the brain continuously generates predictions about the world and self, which account for the specific content of conscious scenes. Third, the conscious self depends on active inference of self-related signals at multiple levels. Research following these principles helps move from establishing correlations between brain responses and consciousness towards explanations which account for phenomenological properties—addressing what can be called the “real problem” of consciousness. The picture that emerges is one in which consciousness, mind, and life, are tightly bound together—with implications for any possible future “conscious machines.”

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Decision-related feedback in visual cortex lacks spatial selectivity

Nature Communications ◽

10.1038/s41467-021-24629-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Katrina R. Quinn ◽

Lenka Seillier ◽

Daniel A. Butts ◽

Hendrikje Nienborg

Keyword(s):

Contextual Information ◽

Relevant Information ◽

Common Mechanism ◽

Spatial Selectivity ◽

Population Responses ◽

Stimulus Choice ◽

Visual Areas ◽

Computational Work ◽

Feature Based ◽

The Brain

AbstractFeedback in the brain is thought to convey contextual information that underlies our flexibility to perform different tasks. Empirical and computational work on the visual system suggests this is achieved by targeting task-relevant neuronal subpopulations. We combine two tasks, each resulting in selective modulation by feedback, to test whether the feedback reflected the combination of both selectivities. We used visual feature-discrimination specified at one of two possible locations and uncoupled the decision formation from motor plans to report it, while recording in macaque mid-level visual areas. Here we show that although the behavior is spatially selective, using only task-relevant information, modulation by decision-related feedback is spatially unselective. Population responses reveal similar stimulus-choice alignments irrespective of stimulus relevance. The results suggest a common mechanism across tasks, independent of the spatial selectivity these tasks demand. This may reflect biological constraints and facilitate generalization across tasks. Our findings also support a previously hypothesized link between feature-based attention and decision-related activity.

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Intraventricular injection of antibodies to β1-integrins generates pressure gradients in the brain favoring hydrocephalus development in rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00307.2009 ◽

2009 ◽

Vol 297 (5) ◽

pp. R1312-R1321 ◽

Cited By ~ 8

Author(s):

Gurjit Nagra ◽

Lena Koh ◽

Isabelle Aubert ◽

Minhui Kim ◽

Miles Johnston

Keyword(s):

Fluid Pressure ◽

Active Role ◽

Intraventricular Injection ◽

Pressure Gradients ◽

Tissue Pressure ◽

Before And After ◽

The Matrix ◽

System 2 ◽

Periventricular Area ◽

The Brain

In some tissues, the injection of antibodies to the β1-integrins leads to a reduction in interstitial fluid pressure, indicating an active role for the extracellular matrix in tissue pressure regulation. If perturbations of the matrix occur in the periventricular area of the brain, a comparable lowering of interstitial pressures may induce transparenchymal pressure gradients favoring ventricular expansion. To examine this concept, we measured periventricular (parenchymal) and ventricular pressures with a servo-null micropipette system (2-μm tip) in adult Wistar rats before and after anti-integrin antibodies or IgG/IgM isotype controls were injected into a lateral ventricle. In a second group, the animals were kept for 2 wk after similar injections and after euthanization, the brains were removed and assessed for hydrocephalus. In experiments in which antibodies to β1-integrins ( n = 10) but not isotype control IgG/IgM ( n = 7) were injected, we observed a decline in periventricular pressures relative to the preinjection values. Under similar circumstances, ventricular pressures were elevated ( n = 10) and were significantly greater than those in the periventricular interstitium. We estimated ventricular to periventricular pressure gradients of up to 4.3 cmH2O. In the chronic preparations, we observed enlarged ventricles in many of the animals that received injections of anti-integrin antibodies (21 of 29 animals; 72%) but not in any animal receiving the isotype controls. We conclude that modulation/disruption of β1-integrin-matrix interactions in the brain generates pressure gradients favoring ventricular expansion, suggesting a novel mechanism for hydrocephalus development.

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Motivational system modulates brain responses during exploratory decision-making

Scientific Reports ◽

10.1038/s41598-021-95311-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Chia-Wei Li ◽

Carol Yeh-Yun Lin ◽

Ting-Ting Chang ◽

Nai-Shing Yen ◽

Danchi Tan

Keyword(s):

Decision Making ◽

High Performance ◽

Behavioral Activation ◽

Motivational Orientation ◽

Performance Group ◽

Reward Seeking ◽

Brain Responses ◽

Low Performance ◽

Risk Choice ◽

The Brain

AbstractManagers face risk in explorative decision-making and those who are better at such decisions can achieve future viability. To understand what makes a manager effective at explorative decision-making requires an analysis of the manager’s motivational characteristics. The behavioral activation/inhibition system (BAS/BIS), fitting the motivational orientation of “approach” or “avoidance,” can affect individual decision-making. However, very little is known about the neural correlates of BAS/BIS orientation and their interrelationship with the mental activity during explorative decision-making. We conducted an fMRI study on 111 potential managers to investigate how the brain responses of explorative decision-making interact with BAS/BIS. Participants were separated into high- and low-performance groups based on the median exploration-score. The low-performance group showed significantly higher BAS than that of the high-performance group, and its BAS had significant negative association with neural networks related to reward-seeking during explorative decision-making. Moreover, the BIS of the low-performance group was negatively correlated with the activation of cerebral regions responding to risk-choice during explorative decision-making. Our finding showed that BAS/BIS was associated with the brain activation during explorative decision-making only in the low-performance group. This study contributed to the understanding of the micro-foundations of strategically relevant decision-making and has an implication for management development.

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