Comparisons Between Parkinson’s Disease Patients and At-Risk Individuals: Can Olfactory Deficits, Cognitive Measures, and Brain Network Connectivity Serve as Preclinical Markers?
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Although olfactory deficits (hyposmia) are potential early markers of Parkinson’s disease (PD), they are not specific to PD. This study examined whether cognitive deficits and/or aberrant resting-state functional connectivity (FC) within the default mode network (DMN) may serve as additional early markers of PD for at-risk individuals. PD patients, healthy controls, and an at-risk group (AR) including hyposmic first-degree relatives of PD patients and unrelated hyposmic individuals were compared on a neuropsychological test battery and on DMN FC. The PD and AR groups showed significant verbal working memory deficits compared to controls. PD patients also exhibited processing speed deficits. AR individuals showed increased DMN FC between the anterior medial prefrontal cortex and the right middle temporal gyrus compared to controls and PD patients. Working memory deficits and increased DMN FC in addition to hyposmia could indicate the progression towards PD. Future research is needed to determine the findings’ clinical applicability.