**Abstract**

Cross-modality in function is a fundamental ability in humans and is closely associated with the basic functions. Several studies have demonstrated that vision strongly influences other senses such as hearing, touch, taste, and smell. However, the dysfunction in this cross-modality caused by disease, is poorly understood. In addition to evidence that Parkinson's disease (PD) impairs various cognitive functions including olfaction, a recent study showed that olfactory function is unaffected by visual information in patients with PD. This finding suggests that the link between vision and olfaction is underactive in PD. This chapter reviews the cross-modal dysfunction and dwells on the possibility of a novel precursor assessment for PD.

**Keywords:** cross-modality, vision, olfaction, Parkinson's disease, striatum
