Isolating Neural Signatures of Conscious Speech Perception with a No-Report Sine-Wave Speech Paradigm.
Yunkai Zhu, Charlotte Li, Camille Hendry, James Glass, Enriqueta Canseco-Gonzalez, Michael A Pitts, Andrew R Dykstra
The Journal of neuroscience : the official journal of the Society for Neuroscience February 21, 2024 DOI: 10.1523/JNEUROSCI.0145-23.2023 via PubMed
Summary
A left-lateralized, near-vertex negativity in EEG, occurring 200–300 ms after stimulus onset, distinguishes sine-wave speech tokens perceived as speech from those perceived as noise, even when task-irrelevant. This response, interpreted as a phonological perceptual awareness negativity, was absent for frequency-flipped control tokens never perceived as speech. The P3b component was enhanced only for tokens both perceived as speech and task-relevant. The findings suggest that neural correlates of conscious perception, across different types of conscious content, are most likely midlatency negative-going brain responses in content-specific sensory areas.
Study at a glance
| Characteristics | Observational cohort Peer reviewed |
|---|---|
| Population | Humans of both sexes |
| Keywords | EEG Awareness Consciousness Perception Speech |
| Citations | 8 |
| Key finding | Conscious speech perception, compared to perception of physically identical tokens as noise, elicits a left-lateralized, near-vertex negativity between 200 and 300 ms, while the P3b is only enhanced when tokens are both perceived as speech and task-relevant. |
Abstract
Identifying neural correlates of conscious perception is a fundamental endeavor of cognitive neuroscience. Most studies so far have focused on visual awareness along with trial-by-trial reports of task-relevant stimuli, which can confound neural measures of perceptual awareness with postperceptual processing. Here, we used a three-phase sine-wave speech paradigm that dissociated between conscious speech perception and task relevance while recording EEG in humans of both sexes. Compared with tokens perceived as noise, physically identical sine-wave speech tokens that were perceived as speech elicited a left-lateralized, near-vertex negativity, which we interpret as a phonological version of a perceptual awareness negativity. This response appeared between 200 and 300 ms after token onset and was not present for frequency-flipped control tokens that were never perceived as speech. In contrast, the P3b elicited by task-irrelevant tokens did not significantly differ when the tokens were perceived as speech versus noise and was only enhanced for tokens that were both perceived as speech and relevant to the task. Our results extend the findings from previous studies on visual awareness and speech perception and suggest that correlates of conscious perception, across types of conscious content, are most likely to be found in midlatency negative-going brain responses in content-specific sensory areas.