Understanding Effects of Late-Life Depressive Symptoms on Event-Related Oscillations in Cognitively Unimpaired Seniors and Individuals With Mild Cognitive Impairment

Abstract

Background Late-life depression often co-occurs with neurological disorders such as dementia, significantly impacting cognitive function and overall well-being. Mild cognitive impairment represents a critical stage between normal aging and dementia, often accompanied by depressive symptoms. Electroencephalography (EEG) offers a non-invasive method to investigate underlying neural mechanisms associated with depressive symptoms and cognitive dysfunction.Methods This study included 80 participants categorized into four groups: MCI without depressive symptoms (MCI), MCI with depressive symptoms (MCI-d), cognitively unimpaired individuals without depressive symptoms (CU), and cognitively unimpaired individuals with depressive symptoms (CU-d). Participants underwent neuropsychological evaluations and EEG recordings during a visual oddball paradigm. Event-related oscillations (EROs) in delta, theta, alpha, and beta frequencies were analyzed in frontal, central, parietal, temporal, and occipital electrode locations.Results Delta ERO showed a significant decrease in amplitude in CU-d, MCI, and MCI-d groups compared to CU in frontal, central, and parietal regions. In the temporal area, MCI-d exhibited lower delta amplitudes compared to both CU and CU-d, while MCI showed lower amplitudes compared to CU. No significant differences were observed in theta, alpha, and beta frequencies. Correlation analyses revealed moderate to strong associations between frontal, central, parietal, and temporal delta amplitudes with various neuropsychological test scores, indicating a link between delta oscillations and cognitive function.Discussion Our findings suggest that delta oscillations may serve as potential marker for cognitive dysfunction, particularly in individuals with MCI and depressive symptoms. Notably, lower delta amplitudes were observed in cognitively unimpaired individuals with depressive symptoms compared to those without, underlining the impact of depressive symptoms on cognitive function in healthy elderly individuals. Further studies can bring out that neurophysiological measures may help revealing the effect of depressive symptoms on cognition that was undetected by cognitive testing.