Olfactory training with multisensory stimulation: neural insights into cross-modal integration.

BACKGROUND: Olfactory training (OT) has emerged as a first-line non-pharmacological treatment for olfactory dysfunction. This study aimed to determine whether multisensory stimulation during OT improves olfactory recovery and to explore the underlying neurobiological mechanisms. METHODOLOGY: Individuals aged 18-80 years with post-viral or idiopathic olfactory dysfunction lasting for at least one month were recruited. Participants were allocated to either multisensory OT (MOT, odor-congruent video clips during OT) or conventional OT (COT) for three months. A subset of participants underwent resting-state fMRI at baseline and post-training to evaluate changes in olfactory network connectivity, using the piriform cortex and orbitofrontal cortex as the predefined seed regions. Statistical analyses were performed using repeated-measures ANOVA to evaluate changes over time and between groups. RESULTS: Ninety-five patients (MOT=51, COT=44) were included. Significant improvements in odor discrimination and composite TDI scores were observed across participants without significant session x group interaction. In the MOT group, pre-post gains were observed in odor discrimination, identification, and TDI. In the MRI subgroup (MOT=21, COT=18), MOT was associated with reduced functional connectivity between the right orbitofrontal cortex and the superior occipital, superior temporal, and postcentral gyri. CONCLUSIONS: MOT was associated with olfactory improvement over the training period. Although between-group differences were not statistically significant, exploratory neuroimaging findings suggest post-MOT functional reorganization between olfactory and visual, auditory, and somatosensory regions. Incorporating multisensory stimulation into OT warrants further investigation as a potential strategy for olfactory rehabilitation.