Multimodal neuroimaging of olfactory processing: the design and development of a novel approach for clinical applications

The olfactory system plays vital roles in health, safety, emotion, memory, and social bonding behaviors, and serves as a window into central nervous system health. Approximately 20% of the population is reported to experience some type of olfactory dysfunction, such as hyposmia, anosmia or dysosmia. However, due to the highly subjective and complex nature of olfaction, these disorders are frequently underdiagnosed, leading to reduced quality of life and the possible overlook of neurological conditions. Existing clinical diagnostic tools lack objectivity and the ability to localize the root of dysfunction. While neuroimaging approaches such as functional magnetic resonance imaging (fMRI) can localize olfactory processing, they tend to be typically limited to research due to high costs and long acquisition times. Functional near-infrared spectroscopy (fNIRS) is a low-cost, non-invasive method of measuring hemodynamic responses related to brain activity by passing infrared light between optodes on the surface of the scalp; however, it is limited to imaging cortical regions due to noise sensitivity and low penetration depth, which impede its ability to image deeper structures such as the olfactory bulb. This project proposes the design and preliminary validation of a NIRS-coupled nasal endoscope to achieve closer proximity to the olfactory epithelium and bulb, for an objective understanding of the patient’s olfactory processing. Traditional external fNIRS and fMRI are performed to establish baseline activation patterns and better understand the current limitations in imaging of the olfactory system. Future work will include engineering, validating and clinically testing the NIRS-coupled nasal endoscope to improve diagnostic precision of olfactory dysfunction.