Semantical visual information facilitates odor imagery: a combined
neurophysiological and psychological approach
Abstract
Odor imagery (OI) or the ability to mentally simulate the presence of a
smell, is a difficult cognitive function and is still misunderstood.
Moreover, the neurophysiological approaches to OI have provided
diverging results. In particular, brain activity in the olfactory
network during OI seems to be influenced by the characteristics of the
visual cues used to facilitate this task. In this study, we compared
different types of visual cues (plain color patches, pictures and words)
during OI in good odor imagers, using functional magnetic resonance
imaging. Thirty right-handed participants were instructed to focus on
the odors evoked by visual cues of different types. Psychological
ratings of success/failure of OI as well as pleasantness and intensity
of odor images were also collected. Our results show that across visual
conditions, the OI task induced activity in the orbitofrontal cortex,
insula, supplementary motor area and dorsolateral prefrontal cortex.
Strikingly, no significant activity was found in the piriform cortex
(primary olfactory brain region) despite an overall success in the OI
according to psychological ratings (83% to 93% depending on the
condition). This observation of successful OI without significant
involvement of the primary olfactory regions in non-experts contradicts
most of the existing literature on the topic. Psychological and
neurophysiological comparisons between types of visual cues only
revealed little effect of visual condition, although semantical cues
seem to require fewer cognitive resources to generate odor images. This
assumption remains to be confirmed using specific tools for the
measurement of cognitive load.