**5. Conclusion**

It is essential to investigate the onset of cross-modality dysfunction in the future. Studies are currently focusing on early detection of PD, including signs of declining olfactory ability and rapid eye movement-related sleep disorders, as precursory biomarkers for PD [24–26, 45]. This approach may provide a new view of precursors, if the dysfunction develops before onset of movement disorders in PD (**Figure 8**). Furthermore, it is necessary to examine whether cross-modal dysfunction occurs in other diseases with striatum deficit, such as multiple system atrophy [46] and Huntington's disease [47]. Cross-modal dysfunction may also lead to diagnoses of other diseases.

#### **Figure 8.**

*Conceivable onsets of cross-modality dysfunction. Declining olfactory ability and rapid eye movement-related sleep disorder are known to be precursory biomarkers for Parkinson's disease. Cross-modality dysfunction also has the potential of becoming a novel biomarker.*

## **Acknowledgements**

The author thanks his original collaborators, Dr. Masaoka, Dr. Kuroda, Dr. Futamura, Dr. Shiromaru, Dr. Izumizaki, and Dr. Kawamura (Showa University School of Medicine). This paper was supported by Grant-in-aids for Scientific Research (C) (No. 18 K03185).

**123**

**Author details**

Motoyasu Honma

School of Medicine, Showa University, Tokyo, Japan

provided the original work is properly cited.

\*Address all correspondence to: mhonma@med.showa-u.ac.jp

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Cross-Modality Dysfunction between the Visual and Olfactory Systems in Parkinson's Disease*

*DOI: http://dx.doi.org/10.5772/intechopen.90116*
