Abnormal event‐related EEG theta responses in patients with dementia with Lewy bodies and Parkinson's disease dementia

Abstract

AbstractBackgroundParkinson's disease with dementia (PDD) and dementia with Lewy bodies (DLB) are characterized by intracellular Lewy bodies in the brain neurons and clinical symptoms including cognitive impairment and flucations, motor symptoms, and hallucinations with some differences, namely non‐motor symptoms appear earlier in DLB over PDD patients (McKeith et al., 2017). An unmet need in the actual diagnostic criteria is the availability of biomarkers probing working brain cognitive systems. A promising biomarker may be derived from the frequency analysis of electroencephalographic oscillatory responses (EROs) during cognitive demands, as a decrease of frontal‐central EROs at theta (4‐7 Hz) frequencies was reapatedly demonstrated in Alzheimer’s disease patients with mild cognitive impairment and dementia over cognitively unimpaired (CU) persons (Yener et al., 2007; Guntekin et al., 2008). In this line, the present study tested the hypothesis of abnormal event‐related EROs at theta frequencies in PDD and DLB patients.MethodElectroencephalographic activity was recorded during a visual oddball paradigm (i.e., 30% of target stimuli requiring mental counting intermingled with 70% of stimuli to be ignored) in 15 PDD, 12 DLB, and 15 CU persons. EROs at theta power and phase‐locking were computed for the oddball target stimuli and compared among the groups (ANOVA, p < 0.05).ResultAs compared to the CU group, both PDD and DLB groups showed a strong topographically widespread reduction in ERO theta power (p < 0.005) (Figure 1). They also showed a strong reduction in ERO theta phase‐locking, especially in frontal‐central locations (p < 0.0001)( Figure 2).ConclusionThe present study showed that ERO theta power and phase‐locking during a standard visual oddball paradigm probing visual focused attention and short‐term memory may be suitable biomarkers to investigate working cognitive brain systems in both PDD and LBD patients.