Discrete Repetition Effects for Visual Words Compared to Faces and Animals, but No Modulation by Expectation: An Event‐Related Potential Study

TL;DR

The study found that repetition effects in the brain differ for words, faces, and animals, but these effects were not influenced by expectations.

Contribution

The study provides new insights into how repetition effects vary across stimulus categories and challenges the predictive coding account of repetition suppression.

Findings

Repetition effects in the N250 component were present in all stimulus categories.

Repetition effects for words occurred earlier and showed distinct topographic patterns compared to faces and animals.

No evidence was found for repetition effects modulated by repetition probability across any category.

Abstract

Repetition suppression (RS) refers to the reduction of neuronal responses to repeated stimuli as compared to nonrepeated stimuli. The predictive coding account of RS proposes that its magnitude is modulated by repetition probability (P(rep)) and that this modulation increases with prior experience with the stimulus category. To test these proposals, we examined RS and its modulation by P(rep) for three stimulus categories for which participants had different expertise (Asian faces, written Chinese words and animals) using EEG. Cantonese speakers watched paired stimuli (S1–S2) of a given category with S2 being the same or a different stimulus as S1. Attributes of S1 (e.g., the sex of the first face) served as a cue for the repetition probability of S2. There were significant repetition effects and distinct topographic distributions across stimulus categories. Repetition effects in the N250 component were present in all stimulus categories, but in words, they appeared earlier and showed distinct topographic patterns compared to faces and animals. These results suggest that repetition effects differ between stimulus categories, presumably depending on prior experience and stimulus properties, such as spatial frequency. Importantly, we failed to find evidence for effects of P(rep) across any of the three categories. These null findings of P(rep) effects are putatively indicating an absence of expectancy modulation of repetition effects.

Visual words, faces and animals showed consistent N250r effects with distinct topographic distributions. The repetition effects for words occurred earlier than for faces and animals. We failed to find EEG evidence for repetition effects modulated by expectation in any of the three visual stimulus categories.

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