Sex Differences in the Olfactory System: a Functional MRI Study

IntroductionOlfactory dysfunction is an early marker of neurological disease and a common symptom in psychotic disorders. Previous anatomical and functional research suggests that sex effects may be crucial in the assessment of the olfactory system. Nonetheless, the neural mechanisms through which the factor sex impacts olfactory perception are still not well understood. In this context, we use fMRI to investigate sex differences in the passive processing of chemical stimuli, in order to obtain new neuroscientific data that may help improve the assessment of odor perception.MethodsThirty healthy subjects (17 women) were stimulated with mint and butanol (event-related design) in a 3.0-T MRI scanner. A one-sample t test analysis was performed in order to observe olfactory-related activations. Intergroup differences (women vs. men) and the influence of each aroma were analyzed using a 2x2 ANOVA and post hoc contrasts.ResultsMen and women showed differential activity (males>females) in right superior/middle temporal areas, the right inferior frontal cortex, and the hypothalamus. Both groups showed a predominance of the right hemisphere for the processing of odors.ConclusionFunctional differences between women and men in olfaction are not restricted to specific sensory areas and reflect a more general sex-dependent effect in multisensory integration processes.ImplicationsConsidering sex differences is essential in order to develop more specific and efficient strategies for the assessment and rehabilitation of the olfactory system and for the interpretation of the olfactory loss as an early biomarker of neurological and psychiatric diseases.