INTRODUCTION: Recognition memory is often explained within dual-process models distinguishing familiarity and recollection. The FN400 event-related potential component has been associated with familiarity, yet its functional interpretation remains debated and is typically examined during retrieval rather than encoding. This interpretation remains debated, particularly regarding its relation to conceptual fluency or semantic priming.

AIM(S): This study investigated whether familiarity-related neural activity indexed by the FN400 can be observed during the encoding phase of a recognition paradigm, and whether habitual dietary inflammation status modulates this effect while using food as potentially ecologically valid stimuli.

METHOD(S): Middle-aged to older adults (M = 57.3 years) completed an Old/New learning task during EEG recording with healthy, unhealthy, and control object stimuli. Participants were divided into pro- and anti-inflammatory groups based on the Dietary Inflammatory Index (DII) calculated from Food Frequency Questionnaire responses. FN400 amplitudes (300-500) were analyzed using repeated-measures ANOVAs (including: Stimuli, Electrodes/Clusters, and Group).

RESULTS: No significant main effects of stimulus type, dietary group, or their interaction were observed for FN400 amplitudes (all p>.05), effect sizes were small. Significant findings were limited to topographic differences across electrode clusters and Electrode x Stimulus interaction. Exploratory inspection suggested possible early P2 modulation distinguishing food from control stimuli, indicating potential attentional or perceptual salience.

CONCLUSIONS: Findings suggest that FN400 familiarity effects may be less robust during encoding than retrieval. Methodological factors such as static food stimuli and categorical dietary grouping may have reduced sensitivity. Future research should employ continuous dietary measures, multisensory or personalised food stimuli, and broader ERP analyses to clarify familiarity-related neural dynamics during encoding.