Driver‐Dunckley, E. D.

Abstract Background The amygdala is closely connected to the olfactory bulb and involved in olfactory processing as well. It is a particularly susceptible region that accumulates a‐synuclein pathology in Parkinson's disease (PD). Our previous work revealed olfactory bulb gene alterations related to neuroinflammation, and neurotransmitter dysfunction to be associated with olfactory function. We aimed to extend this work and assess gene expression changes, affected pathways and co‐expression networks by transcriptomic profiling of the amygdala in subjects with and without clinicopathologically defined PD. Method Bulk RNA sequencing was performed on frozen human amygdala of 20 PD and 20 controls without dementia or any other neurodegenerative disorder, from the Arizona Study of Aging and Neurodegenerative Disorders. Result Differential expression analysis, corrected for age, sex and post‐mortem interval revealed 40 significantly differentially expressed genes (DEGs) in PD. Downregulated genes were mainly related to altered hemoglobin expression while upregulated genes included inflammatory markers and glutamine transporter. Significantly enriched pathways were involved in oxygen and carbon dioxide transport, cellular oxidant detoxification and regulation of glutamine secretion. Cell enrichment revealed these genes to be mainly expressed in neurons. Co‐expression network analysis using Weighted correlation network analysis (WGCNA ) subsequently identified four significant modules correlated with both PD and premortem olfactory dysfunction which were involved in pathways related to neuroinflammatory processes, mitochondrial, endoplasmic reticulum and lysosomal dysfunction. Conclusion These preliminary results suggest cellular alterations in the amygdala related to mitochondrial dysfunction, altered oxygen homeostasis, oxidative stress, inflammation as well as glutamatergic neurotransmitter dysfunction that may contribute to neurodegeneration in PD.

Background and purposeIt is believed that progressive Lewy‐type synucleinopathy (LTS) is primarily responsible for the worsening of motor and non‐motor Parkinson's disease (PD) signs and symptoms. Characterization of quantitative electroencephalography (QEEG) abnormalities across the spectrum of LTS to PD dementia (PD‐D) may provide insight into the pathophysiology of PD cortical dysfunction. Here our enlarged EEG database was leveraged to characterize spectral QEEG abnormalities in asymptomatic autopsy‐defined groups of control participants and incidental Lewy body disease (ILBD) and three clinically defined groups of participants with PD (cognitively normal PD, mild cognitive impairment PD, and PD‐D).MethodsThe PD cohort was studied as part of the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND). AZSAND utilizes its Brain and Body Donation Program to perform prospective, standardized, regular longitudinal pre‐mortem assessments until death. Resting EEG from subjects was analyzed for spectral domain QEEG measures of background rhythm frequency and global relative power in delta, theta, alpha and beta bands.ResultsThe various spectral QEEG measures showed differential changes specific to the groups compared. Important findings were background rhythm frequency showing the most pairwise differences across the groups, and this also was the only significant difference between control and ILBD. An increase in delta bandpower was characteristic of worsening cognitive deficits.ConclusionsDifferent patterns of change amongst QEEG measures across LTS and PD cognitive states suggest that they correlate with heterogeneous pathophysiologies of cortical dysfunction within the PD clinical spectrum. In addition, the biomarker application of a specific spectral QEEG measure needs to be selectively suited to its study purpose.