Sensory information is initially registered within anatomically and functionally segregated brain networks, but is also integrated across modalities in higher cortical areas. Although considerable research has focused on uncovering the neural correlates of multisensory integration for the modalities of vision and audition, much less effort has been devoted to understanding interactions between vision and olfaction. Here we asked whether odours affect neural activity evoked by images of familiar visual objects that carry characteristic smells (e.g., orange, mint, rose). We employed scalp-recorded electroencephalography to measure visual event-related potentials (ERPs) to briefly presented photographs of familiar, odour-related objects, such as an orange or mint leaves. On each trial, participants (N = 26) inhaled either a matching odour (e.g., orange scent for a photograph of an orange fruit), a non-matching odour (e.g., mint scent for a photograph of an orange fruit), an irrelevant odour (coffee), or plain air. Participants maintained their attention on the visual stimuli by judging the shape of a border surrounding each picture. The N1 component of the visual ERP, 100-170ms after image presentation, was reliably enhanced for matching odours in female participants, but not in males. This is consistent with evidence that females are superior in detecting, discriminating and identifying odours, and that they have a higher grey matter concentration in olfactory areas of the orbitofrontal cortex. We conclude that early visual processing is influenced by olfaction due to learned associations between odours and the objects that emit them, and that these associations are stronger in females than males.

olfaction; vision; event-related potentials; electroencephalography