Association of exercise with better olfactory performance and higher functional connectivity between the olfactory cortex and the prefrontal cortex: a resting-state fNIRS study

Abstract Background Olfactory deterioration is suggested to be a predictor of some neurodegenerative diseases. Methodology : Our study compared the functional connectivity between the olfactory cortex and the prefrontal cortex in healthy individuals who exercised regularly and healthy persons who did not. We also assessed their odor threshold. Participants were aged 55 years or older, and the two groups were balanced for age, sex, body mass index, and educational level. Results We found that compared with individuals who did not exercise, exercisers had a significantly lower threshold for detecting odors. In addition, the olfactory cortex had stronger connectivity with the PFC in exercisers than in non-exercisers. More specifically, when the PFC was grouped into three subregions, namely, the ventrolateral prefrontal cortex (VLPFC), dorsolateral prefrontal cortex (DLPFC), and frontopolar cortex (FPA), Pearson correlation analysis revealed stronger connectivity between the VLPFC and the OFC, between the OFC and the FPA, and between the left and right OFC hemispheres in the exercisers. In addition, Granger causality indicated higher directional connectivity from the DLPFC to the OFC in exercisers than in non-exercisers. Conclusion Our findings indicate that the exercise group not only had better olfactory performance but also had stronger functional connectivity between the olfactory cortex and the PFC than non-exercise group.