Parallel processing in speech perception with local and global representations of linguistic context
- University of Connecticut, United States
- University of Maryland, United States
- University of Pennsylvania, United States
Abstract
Speech processing is highly incremental. It is widely accepted that human listeners continuously use the linguistic context to anticipate upcoming concepts, words, and phonemes. However, previous evidence supports two seemingly contradictory models of how a predictive context is integrated with the bottom-up sensory input: Classic psycholinguistic paradigms suggest a two-stage process, in which acoustic input initially leads to local, context-independent representations, which are then quickly integrated with contextual constraints. This contrasts with the view that the brain constructs a single coherent, unified interpretation of the input, which fully integrates available information across representational hierarchies, and thus uses contextual constraints to modulate even the earliest sensory representations. To distinguish these hypotheses, we tested magnetoencephalography responses to continuous narrative speech for signatures of local and unified predictive models. Results provide evidence that listeners employ both types of models in parallel. Two local context models uniquely predict some part of early neural responses, one based on sublexical phoneme sequences, and one based on the phonemes in the current word alone; at the same time, even early responses to phonemes also reflect a unified model that incorporates sentence level constraints to predict upcoming phonemes. Neural source localization places the anatomical origins of the different predictive models in non-identical parts of the superior temporal lobes bilaterally, with the right hemisphere showing a relative preference for more local models. These results suggest that speech processing recruits both local and unified predictive models in parallel, reconciling previous disparate findings. Parallel models might make the perceptual system more robust, facilitate processing of unexpected inputs, and serve a function in language acquisition.
Data availability
The raw data and predictors used in this study are available for download from Dryad at https://doi.org/10.5061/dryad.nvx0k6dv0
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Data from: Parallel processing in speech perception with local and global representations of linguistic contextDryad Digital Repository, doi:10.5061/dryad.nvx0k6dv0.
Article and author information
Author details
Christian Brodbeck
Shohini Bhattasali
Funding
University of Maryland (BBI Seed Grant)
- Jonathan Z Simon
- Ellen Lau
National Science Foundation (BCS-1749407)
- Ellen Lau
National Institutes of Health (R01DC014085)
- Jonathan Z Simon
National Science Foundation (SMA-1734892)
- Jonathan Z Simon
Office of Naval Research (MURI Award N00014-18-1-2670)
- Philip Resnik
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Human subjects: The study was approved by the IRB of the University of Maryland under the protocol titled "MEG Studies of Speech and Language Processing" (reference # 01153), on August 22, 2018 and September 9, 2019 (approval duration: 1 year). All participants provided written informed consent prior to the start of the experiment.
Copyright
© 2022, Brodbeck et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Parallel processing in speech perception with local and global representations of linguistic context
eLife 11:e72056.
https://doi.org/10.7554/eLife.72056
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