The P600-as-P3 hypothesis revisited: Single-trial analyses reveal that the late EEG positivity following linguistically deviant material is reaction time aligned
Single-trial ERP analysis of spoken sentence comprehension with overt judgement.
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Morphosyntactic and semantic violations.
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P600 was strongly reaction time locked and N400 was stimulus locked.
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As reaction time locking is a property of the P3, data supports P600-as-P3 proposal.
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Ties P600 to a systemic norpepinephrine release by the Locus Coeruleus.
Abstract
The P600, a late positive ERP component following linguistically deviant stimuli, is commonly seen as indexing structural, high-level processes, e.g. of linguistic (re)analysis. It has also been identified with the P3 (P600-as-P3 hypothesis), which is thought to reflect a systemic neuromodulator release facilitating behavioural shifts and is usually response time aligned. We investigated single-trial alignment of the P600 to response, a critical prediction of the P600-as-P3 hypothesis. Participants heard sentences containing morphosyntactic and semantic violations and responded via a button press. The elicited P600 was perfectly response aligned, while an N400 following semantic deviations was stimulus aligned. This is, to our knowledge, the first single-trial analysis of language processing data using within-sentence behavioural responses as temporal covariates. Results support the P600-as-P3 perspective and thus constitute a step towards a neurophysiological grounding of language-related ERPs.
