Reduction in posterior cortical alpha rhythms during eye opening is more abnormal in patients with dementia due to Lewy bodies than Alzheimer’s disease: An EEG study

Abstract

AbstractBackgroundAlzheimer’s disease (AD) is the first‐most common neurodegenerative disorder due to an abnormal accumulation of amyloid and tau proteins in the brain and explains about 60‐70% of 50 million of patients with dementia worldwide (WHO report, www.who.int). Disease with Lewy Bodies (DLB) is emerging as another important cause of dementia with visual hallucinations, cognitive fluctuations, or REM sleep behavior disorder in the pathological aging. Notably, DLB patients may show not only distinctive post‐mortem intra‐neuronal Lewy bodies but also abnormal accumulation of amyloid and proteins in the brain, raising in‐vivo diagnostic issues (Kantarci et al., 2020). Furthermore, resting state eyes‐closed electroencephalographic (rsEEG) alpha (8‐10 Hz) rhythms in posterior cortical sources showed differences between AD and DLB patients with dementia (Babiloni et al., 2017). Here we tested the hypothesis that cortical sources of rsEEG alpha rhythms during eyes opening may be more abnormal in DLB than AD patients with dementia.MethodsClinical and rsEEG rhythms in demographic‐ and age‐matched AD (N = 30), DLB (N = 28), and healthy cognitively unimpaired (Nold, N = 30) persons were available from an international archive. Pathological groups were matched as cognitive status (i.e., dementia grade). Individual alpha frequency peak was used to determine the alpha frequency band on personal basis. The eLORETA freeware estimated rsEEG alpha cortical sources. “Reactivity” to eyes opening was computed computing the percentage of the reduction in the rsEEG alpha (eLORETA) source activity during eyes open over closed condition in posterior (i.e., central, parietal, and occipital) cortical regions of interest.ResultsAs compared to the Nold subjects, the patients with dementia due to DLB and AD showed lower “reactivity” to eyes opening in posterior cortical regions (p < 0.05 corrected), this poor “reactivity” being significantly more evident in the former than the latter (Figure 1).ConclusionsThese novel results suggest that neurophysiological oscillatory mechanisms regulating cortical arousal in the visual system during external visual stimuli are more abnormal in DLB than AD patients with dementia, possibly concurring to visual misperceptions and hallucinations reported in DLB patients.