Impairment of cross-modality of vision and olfaction in Parkinson disease

Objective To determine whether Parkinson disease (PD) affects cross-modal function of vision and olfaction because it is known that PD impairs various cognitive functions, including olfaction. Methods We conducted behavioral experiments to identify the influence of PD on cross-modal function by contrasting patient performance with age-matched normal controls (NCs). We showed visual effects on the strength and preference of odor by manipulating semantic connections between picture/odorant pairs. In addition, we used brain imaging to identify the role of striatal presynaptic dopamine transporter (DaT) deficits. Results We found that odor evaluation in participants with PD was unaffected by visual information, while NCs overestimated smell when sniffing odorless liquid while viewing pleasant/unpleasant visual cues. Furthermore, DaT deficit in striatum, for the posterior putamen in particular, correlated to few visual effects in participants with PD. Conclusions These findings suggest that PD impairs cross-modal function of vision/olfaction as a result of posterior putamen deficit. This cross-modal dysfunction may serve as the basis of a novel precursor assessment of PD.