Odours influence distributed patterns of brain activity for matching visual objects

• ¹ The University of Queensland, Queensland Brain Institute, Australia
• ² The University of Queensland, Centre for Advanced Imaging, Australia
• ³ The University of Queensland, School of Psychology, Australia

Recent evidence suggests that primary sensory areas of the brain might in fact be multisensory. Here we asked whether early visual cortex is influenced by olfactory stimuli. It is known that olfaction can influence visual perception during binocular rivalry and the attentional blink. Moreover, regions of occipital cortex are active during odour perception, suggesting that odours might be coded in visual regions. Here, we used functional magnetic resonance imaging (fMRI) and multivariate pattern analysis (MVPA) to investigate whether odours influence the neural representation of matching visual objects. Participants (N = 20 females) were presented with images of living objects with a characteristic odour (e.g., mint, orange, banana) and nonliving objects with no associated odour (e.g., box, mug, cupboard). During presentation of each visual stimulus, participants inhaled either banana, orange or mint odour. Crucially, the living objects were paired with either a matching odour (e.g., a picture of an orange with orange odour) or non-matching odour (e.g., picture of a banana with orange odour). Throughout the experiment participants maintained fixation and performed an unrelated visual task. Our analyses focused on decoding between distributed patterns of brain activity evoked by living objects relative to nonliving objects. We found significant decoding of living versus nonliving images in primary visual cortex (V1), lateral occipital complex and lingual gyrus. Critically, classification accuracy was significantly higher in V1 bilaterally and in right lingual gyrus when the living objects were paired with matching odours than with non-matching odours, suggesting that odours selectively boost the representation of matching visual objects in these areas. We conclude that early visual cortex codes for olfactory object information, and that multisensory interactions between olfaction and vision serve to enhance object identification processes.