Perceptual warping exposes categorical representations for speech in human brainstem responses
The brain transforms continuous acoustic events into discrete category representations to downsample the speech signal for our perceptual-cognitive systems. Such phonetic categories are highly malleable, and their percepts can change depending on surrounding stimulus context. Previous work suggests...
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| Format: | Article |
| Language: | English |
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Elsevier
2023-04-01
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| Series: | NeuroImage |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S1053811923000484 |
| _version_ | 1828048356746723328 |
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| author | Jared A. Carter Gavin M. Bidelman |
| author_facet | Jared A. Carter Gavin M. Bidelman |
| author_sort | Jared A. Carter |
| collection | DOAJ |
| description | The brain transforms continuous acoustic events into discrete category representations to downsample the speech signal for our perceptual-cognitive systems. Such phonetic categories are highly malleable, and their percepts can change depending on surrounding stimulus context. Previous work suggests these acoustic-phonetic mapping and perceptual warping of speech emerge in the brain no earlier than auditory cortex. Here, we examined whether these auditory-category phenomena inherent to speech perception occur even earlier in the human brain, at the level of auditory brainstem. We recorded speech-evoked frequency following responses (FFRs) during a task designed to induce more/less warping of listeners’ perceptual categories depending on stimulus presentation order of a speech continuum (random, forward, backward directions). We used a novel clustered stimulus paradigm to rapidly record the high trial counts needed for FFRs concurrent with active behavioral tasks. We found serial stimulus order caused perceptual shifts (hysteresis) near listeners’ category boundary confirming identical speech tokens are perceived differentially depending on stimulus context. Critically, we further show neural FFRs during active (but not passive) listening are enhanced for prototypical vs. category-ambiguous tokens and are biased in the direction of listeners’ phonetic label even for acoustically-identical speech stimuli. These findings were not observed in the stimulus acoustics nor model FFR responses generated via a computational model of cochlear and auditory nerve transduction, confirming a central origin to the effects. Our data reveal FFRs carry category-level information and suggest top-down processing actively shapes the neural encoding and categorization of speech at subcortical levels. These findings suggest the acoustic-phonetic mapping and perceptual warping in speech perception occur surprisingly early along the auditory neuroaxis, which might aid understanding by reducing ambiguity inherent to the speech signal. |
| first_indexed | 2024-04-10T18:55:05Z |
| format | Article |
| id | doaj.art-c9359ae68ae44440ab9afc03ff8754fd |
| institution | Directory Open Access Journal |
| issn | 1095-9572 |
| language | English |
| last_indexed | 2024-04-10T18:55:05Z |
| publishDate | 2023-04-01 |
| publisher | Elsevier |
| record_format | Article |
| series | NeuroImage |
| spelling | doaj.art-c9359ae68ae44440ab9afc03ff8754fd2023-02-01T04:25:09ZengElsevierNeuroImage1095-95722023-04-01269119899Perceptual warping exposes categorical representations for speech in human brainstem responsesJared A. Carter0Gavin M. Bidelman1Institute for Intelligent Systems, University of Memphis, Memphis, TN, USA; School of Communication Sciences and Disorders, University of Memphis, Memphis, TN, USA; Division of Clinical Neuroscience, School of Medicine, Hearing Sciences – Scottish Section, University of Nottingham, Glasgow, Scotland, UKDepartment of Speech, Language and Hearing Sciences, Indiana University, Bloomington, IN, USA; Program in Neuroscience, Indiana University, Bloomington, IN, USA; Corresponding author at: Speech, Language and Hearing Sciences, 2631 East Discovery Parkway, Bloomington, IN 47408, USA.The brain transforms continuous acoustic events into discrete category representations to downsample the speech signal for our perceptual-cognitive systems. Such phonetic categories are highly malleable, and their percepts can change depending on surrounding stimulus context. Previous work suggests these acoustic-phonetic mapping and perceptual warping of speech emerge in the brain no earlier than auditory cortex. Here, we examined whether these auditory-category phenomena inherent to speech perception occur even earlier in the human brain, at the level of auditory brainstem. We recorded speech-evoked frequency following responses (FFRs) during a task designed to induce more/less warping of listeners’ perceptual categories depending on stimulus presentation order of a speech continuum (random, forward, backward directions). We used a novel clustered stimulus paradigm to rapidly record the high trial counts needed for FFRs concurrent with active behavioral tasks. We found serial stimulus order caused perceptual shifts (hysteresis) near listeners’ category boundary confirming identical speech tokens are perceived differentially depending on stimulus context. Critically, we further show neural FFRs during active (but not passive) listening are enhanced for prototypical vs. category-ambiguous tokens and are biased in the direction of listeners’ phonetic label even for acoustically-identical speech stimuli. These findings were not observed in the stimulus acoustics nor model FFR responses generated via a computational model of cochlear and auditory nerve transduction, confirming a central origin to the effects. Our data reveal FFRs carry category-level information and suggest top-down processing actively shapes the neural encoding and categorization of speech at subcortical levels. These findings suggest the acoustic-phonetic mapping and perceptual warping in speech perception occur surprisingly early along the auditory neuroaxis, which might aid understanding by reducing ambiguity inherent to the speech signal.http://www.sciencedirect.com/science/article/pii/S1053811923000484Frequency following response (FFR)Categorical perception (CP)Nonlinear dynamicsHysteresis |
| spellingShingle | Jared A. Carter Gavin M. Bidelman Perceptual warping exposes categorical representations for speech in human brainstem responses NeuroImage Frequency following response (FFR) Categorical perception (CP) Nonlinear dynamics Hysteresis |
| title | Perceptual warping exposes categorical representations for speech in human brainstem responses |
| title_full | Perceptual warping exposes categorical representations for speech in human brainstem responses |
| title_fullStr | Perceptual warping exposes categorical representations for speech in human brainstem responses |
| title_full_unstemmed | Perceptual warping exposes categorical representations for speech in human brainstem responses |
| title_short | Perceptual warping exposes categorical representations for speech in human brainstem responses |
| title_sort | perceptual warping exposes categorical representations for speech in human brainstem responses |
| topic | Frequency following response (FFR) Categorical perception (CP) Nonlinear dynamics Hysteresis |
| url | http://www.sciencedirect.com/science/article/pii/S1053811923000484 |
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