Lexical versus conceptual anticipation during sentence processing: frontal positivity and N400 ERP components

Area of Science:

• Cognitive Neuroscience
• Psycholinguistics
• Event-Related Potentials (ERPs)

Background:

• The N400 event-related potential (ERP) component is a well-established marker of semantic processing during language comprehension.
• Late positive ERP components also play a role in sentence comprehension, but their specific functions are less understood.
• Previous research suggests multiple late positive components with distinct scalp topographies exist.

Purpose of the Study:

• To investigate the lexical versus conceptual specificity of a post-N400 frontal positivity.
• To determine if this positivity is sensitive to the predictability of sentence-final words.
• To differentiate the processing roles of the N400 and anterior positivity in sentence comprehension.

Main Methods:

• Participants completed high- and low-constraint sentences with various word types: the most preferred word (best completion), near synonyms, and semantically dissimilar congruent words.
• Event-related potentials (ERPs) were recorded during sentence comprehension.
• Analysis focused on the N400 and anterior positivity components, examining their sensitivity to cloze probability and semantic similarity.

Main Results:

• The N400 component was sensitive to both word predictability (cloze probability) and semantic similarity to the best completion.
• This indicates the N400 reflects broader conceptual expectations that can be met by alternative words.
• An anterior positivity was elicited by all unpredictable final words, regardless of semantic similarity to the best completion, suggesting sensitivity to specific lexical expectations.

Conclusions:

• The N400 reflects conceptual expectations in sentence comprehension.
• A distinct anterior positivity component is sensitive to lexical expectations, specifically tracking the predictability of the exact word encountered.
• These findings highlight distinct neural mechanisms for processing conceptual versus lexical information during language understanding.