[Impairment of Cross-modality: A New Cognitive Dysfunction in Parkinson's Disease]

It is known that Parkinson's disease impairs various cognitive functions including olfaction. However, until recently it was unclear whether Parkinson's disease also affects cross-modal function of vision and olfaction. A recent study showed that odor evaluation in patients with Parkinson's disease is unaffected by visual information, while healthy controls overestimated smell, when sniffing odorless liquid while viewing pleasant or unpleasant visual cues. Dopamine transporter deficit in the striatum, in particular in the posterior putamen, correlated with the limited visual effect in patients with Parkinson's disease. The findings suggest that Parkinson's disease impairs cross-modal function of vision and olfaction due to posterior putamen deficit. This review discusses that the cross-modal dysfunction may serve as the basis of novel precursor assessment of Parkinson's disease.