Biology subjects

Cervantes Constantino, F.

Publications and source records attributed to Cervantes Constantino, F..

7 recordsLinked to original sources

bioRxiv2025

Never mind the repeat: How speech expectations reduce tracking at the cocktail party

When the brain focuses on a conversation in a noisy environment, it exploits past experience to prioritize relevant elements from the auditory scene. This prompts the question of what changes occur in the selective neural processing of speech mixtures as listeners garner prior experience about single speech objects. In three different priming experiments, we quantified cortical selection of temporal landmarks from continuous speech, applying the temporal response function (TRF) method to single-trial electroencephalography (EEG) recordings. The designs specifically addressed how attention interacts with exact (Experiment 1), voice (Experiment 2a), or message (Experiment 2b) content priming of the target or background speakers in cortical responses to speech. Our results demonstrate that, during multispeaker listening, attentional gains typical of cortical responses under speech selection are met with attenuations as a consequence of prior experience. The changes were observed at the P2 processing stage (220-320 ms) of speech envelope onset processing and were specific to responses to primed speech targets (Experiment 1). Suppressions at stages earlier than the P2, or under partial priming conditions (Experiments 2a and 2b), were not observed. An exploratory analysis suggests the observed P2 reduction predicts listeners ability to report target words, consistent with this component encoding in part temporal prediction error about onset edge cues exclusive to target speech. Our results show that at this late and definitive stage of selective attention, the auditory system may test the evidence for its own predictive model of the noise-invariant speech stream. Precise inference of its temporal structure is bound to tag all checkpoints where auditory evidence can be most reliably connected into higher-order representations of continuous speech.

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bioRxiv2024

Cortical tracking of speakers' formant changes predicts selective listening

A social scene is particularly informative when people are distinguishable. To understand somebody amid a cocktail party chatter, we automatically index their voice. This ability is underpinned by parallel processing of vocal spectral contours from speech sounds, but it has not yet been established how this occurs in the brains cortex. We investigate single-trial neural tracking of slow frequency modulations in speech using electroencephalography. Participants briefly listened to unfamiliar single speakers, and in addition, they performed a cocktail party comprehension task. Quantified through stimulus reconstruction methods, robust tracking was found in neural responses to slow (delta-theta range) modulations of frequency contours in the fourth and fifth formant band, equivalent to the 3.5-5 KHz audible range. Instantaneous frequency spacing ({Delta}F), which also yields indexical information from the vocal tract, was similarly decodable. Moreover, EEG evidence of listeners spectral tracking abilities predicted their chances of succeeding at selective listening when faced with two-speaker speech mixtures. In summary, the results indicate that the communicating brain can rely on locking of cortical rhythms to major changes led by upper resonances of the vocal tract. Their corresponding articulatory mechanics hence continuously issue a fundamental credential for listeners to target in real time.

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bioRxiv2020

Differential neural encoding of sound under visual attention is shaped by audiovisual precision and unimodal uncertainty priors

Selective attentional biases arising from one sensory modality may manifest in another. The effects of visuospatial attention, often considered a foundation for visual object perception, are unclear in the auditory domain during audiovisual (AV) scene processing. This study investigates temporal and spatial factors that facilitate such cross-modal bias transfer at the neural level. Auditory encoding of random tone pips in AV scenes was investigated via a temporal response function model (TRF) of the participants electroencephalogram (N=30). The spatially uninformative pips were associated with spatially distributed visual contrast reversals ( flips) through asynchronous, probabilistic AV temporal onset distributions. Participants deployed visuospatial selection on these AV stimuli to perform a task. A late (~300 ms) cross-modal transfer of the unimodal attentional bias was found on the neural representation of pips. Transfer depended on the selected visual input being (i) presented during or shortly after a related sound in a relatively limited temporal window (<165 ms); and (ii) positioned across limited (1:4) visual foreground to background ratios. In addition, the magnitude of attentional enhancement was proportional to the proximity of flips to the foreground area. The results indicate that ongoing neural representations of sounds can incorporate relevant visuospatial attributes for auditory stream segregation.

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bioRxiv2019

Neural signals relating future cooperation from prisoner’s dilemma feedback are outcome-contingent

Electing whether to cooperate with someone else is well typified in the iterated prisoners dilemma (iPD) game, although the neural processes that unfold after its distinct outcomes have been only partly described. Recent theoretical models emphasize the ubiquity of intuitive cooperation, raising questions on the neural timelines involved. We studied the outcome stage of an iPD with electroencephalography (EEG) methods. Results showed that neural signals that are modulated by the iPD outcomes can also be indicative of future choice, in an outcome-dependent manner: (i) after zero-gain suckers payoffs (unreciprocated cooperation), a participants decision thereafter may be indicated by changes to the feedback-related negativity (FRN); (ii) after one-sided non-cooperation (participant gain), by the P3; (iii) after mutual cooperation, by late frontal delta-band modulations. Critically, faster choices to reciprocate cooperation were predicted, on a single-trial basis, by P3 and frontal delta modulations at the immediately preceding trial. Delta band signaling is considered in relation to homeostatic regulation processing in the literature. The findings relate feedback to decisional processes in the iPD, providing a first neural account of the brief timelines implied in heuristic modes of cooperation.

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bioRxiv2018

The neural representation of missing speech and the influence of prior knowledge on cortical fidelity and latency

In naturally noisy listening conditions, for example at a cocktail party, noise disruptions may completely mask significant parts of a sentence, and yet listeners may still perceive the missing speech as being present. Here we demonstrate that dynamic speech-related auditory cortical activity, as measured by magnetoencephalography (MEG), which can ordinarily be used to directly reconstruct to the physical speech stimulus, can also be used to \"reconstruct\" acoustically missing speech. The extent to which this occurs depends on the extent that listeners are familiar with the missing speech, which is consistent with this neural activity being a dynamic representation of perceived speech even if acoustically absence. Our findings are two-fold: first, we find that when the speech is entirely acoustically absent, the acoustically absent speech can still be reconstructed with performance up to 25% of that of acoustically present speech without noise; and second, that this same expertise facilitates faster processing of natural speech by approximately 5 ms. Both effects disappear when listeners have no or very little prior experience with a given sentence. Our results suggest adaptive mechanisms of consolidation of detailed representations about speech, and the enabling of strong expectations this entails, as identifiable factors assisting automatic speech restoration over ecologically relevant timescales.

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bioRxiv2017

Functional significance of spectrotemporal response functions obtained using magnetoencephalography

The spectrotemporal response function (STRF) model of neural encoding quantitatively associates dynamic auditory neural (output) responses to a spectrogram-like representation of a dynamic (input) stimulus. STRFs were experimentally obtained via whole-head human cortical responses to dynamic auditory stimuli using magnetoencephalography (MEG). The stimuli employed consisted of unpredictable pure tones presented at a range of rates. The predictive power of the estimated STRFs was found to be comparable to those obtained from the cortical single and multiunit activity literature. The STRFs were also qualitatively consistent with those obtained from electrophysiological studies in animal models; in particular their local-field-potential-generated spectral distributions and multiunit-activity-generated temporal distributions. Comparison of these MEG STRFs with others obtained using natural speech and music stimuli reveal a general structure consistent with common baseline auditory processing, including evidence for a transition in low-level neural representations of natural speech by 100 ms, when an appropriately chosen stimulus representation was used. It is also demonstrated that MEG-based STRFs contain information similar to that obtained using classic auditory evoked potential based approaches, but with extended applications to long-duration, non-repeated stimuli.\n\nAuthor summaryThe spectrotemporal response function (STRF) model of linking dynamic acoustic stimuli to dynamic neural responses is applied to whole-head non-invasive magnetoencephalography (MEG) recordings of the human auditory cortex. MEG STRFs were consistent predictors of neural activity, quantitatively and qualitatively, by comparison to those obtained from animal models using local field potential or multiunit activity as neural responses. Comparison of STRFs using stimuli as diverse as tone clouds, natural speech, and music revealed a common structure consistent with shared baseline auditory processing, when an appropriately chosen stimulus representation was used.

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bioRxiv2017

Dynamic cortical representations of perceptual filling-in for missing acoustic rhythm

In the phenomenon of perceptual filling-in, missing sensory information can be reconstructed via interpolation from adjacent contextual cues by what is necessarily an endogenous, not yet well understood, neural process. In this investigation, sound stimuli were chosen to allow observation of fixed cortical oscillations driven by contextual (but missing) sensory input, thus entirely reflecting endogenous neural activity. The stimulus employed was a 5 Hz frequency-modulated tone, with brief masker probes (noise bursts) occasionally added. For half the probes, the rhythmic frequency modulation was moreover removed. Listeners reported whether the tone masked by each probe was perceived as being rhythmic or not. Time-frequency analysis of neural responses obtained by magnetoencephalography (MEG) shows that for maskers without the underlying acoustic rhythm, trials where rhythm was nonetheless perceived show higher evoked sustained rhythmic power than trials for which no rhythm was reported. The results support a model in which perceptual filling-in is aided by differential co-modulations of cortical activity at rates directly relevant to human speech communication. We propose that the presence of rhythmically-modulated neural dynamics predicts the subjective experience of a rhythmically modulated sound in real time, even when the perceptual experience is not supported by corresponding sensory data.

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