**Author details**

*Sino-Nasal and Olfactory System Disorders*

emotion and cognitive processing.

nected at a fiber level [44].

**5. Conclusion**

other diseases.

**Figure 8.**

**Acknowledgements**

**Conflict of interest**

Research (C) (No. 18 K03185).

*has the potential of becoming a novel biomarker.*

Dopamine deficiency in PD may affect vision-olfaction integration, including

The laterality of DaT level in the putamen related to odor preference is of further interest. That is, the left is associated with pleasant smells and the right is associated with unpleasant smells. A recent study has shown that a pleasant odor is associated with bilateral or left AMG activation, and an unpleasant odor is associated with activation of the right AMG [27]. The left/right difference for smell-evoked emotion may be linked to AMG processing, because these regions are strongly con-

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

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

*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* 

The author of this manuscript has no conflict of interest.

**122**

Motoyasu Honma School of Medicine, Showa University, Tokyo, Japan

\*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, provided the original work is properly cited.
