Objective: To assess the pattern of RS functional connectivity in PD patients, related to olfactory psychometric test, to elucidate olfactory-dependent cortical-subcortical functional networks.

Background: Olfactory dysfunction is a salient non-motor feature of PD. It manifests years before the development of Parkinsonian motor symptoms. Using resting state fMRI in PD patients, previous studies showed altered neuronal activity in the amygdaloid complex and hippocampal formation during olfactory stimulation. In this study, we argue that olfactory performances could influence the functional connectivity within key brain areas of PD patients.

Methods: We enrolled 12 de novo drug-naïve PD patients (6 males and 6 females, mean age: 58.4±4.2 years, H&Y 1.5, UPDRS median motor subscore 26, MMSE 27, BDI 15) and 10 age-matched normal controls (NC) None of the patients took anti-Parkinsonian drugs, as Levo-Dopa or dopaminoagonists, and antidepressive treatments. Olfactory function was studied by using the Sniffin Sticks Test. MRI study was performed with a 3T MRI scanner. Standard image data preparation, normalization and preprocessing and statistical analysis and visualization were performed with the Brain Voyager QX software.

Results: PD patients were hyposmic as indicated by mean scores of TDI (20.2). NC were normosmic (mean score: 37.3) (P 0.05). At MRI examination, all subjects did not present structural abnormalities, also in olfactory areas. Caudate was defined, as ROI, to study olfactory-dependent RS functional networks in PD patients. The PD patients showed increased positive striato-cortical connectivity in the left frontal areas and decreased connectivity in the right occipital area. The cortical functional connectivity with the caudate was negatively correlated with the TDI scores in the bilateral frontal areas, left occipital area and precuneus. There were no significant clusters were the TDI scores positively correlated with cortical functional connectivity with the caudate.

Conclusions: This study showed that the patterns of RS functional connectivity differ according to olfactory performance in de novo and drug-naïve PD patients and NC. A correlation analysis revealed that olfactory performance was negatively associated with cortical connectivity with the caudate. These data suggest that RS functional connectivity should be closely correlated with the level of olfactory performance in de novo PD patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/resting-state-functional-connectivity-in-olfactory-network-in-de-novo-parkinsons-disease/