MEG spectral patterns in the progression from MCI to AD

Resumen

BackgroundAlzheimer's disease (AD) is the most prevalent type of dementia. The relevance of the symptomatic pre-dementia or mild cognitive impairment (MCI) is central to stablishing a prognosis of the disease. Considering the scarcity of studies within this field and its potential clinical relevance, we conducted a longitudinal magnetoencephalography (MEG) study in two groups: stable (sMCI) and progressive (pMCI) MCIs during a 4-years followed- up.MethodWe compared the power spectra in source space measured by MEG during 5 minutes of resting state eyes-closed from 49 MCIs (24 pMCI and 25 sMCI) within three frequency bands: delta (1,5-4Hz), theta (4-8Hz) and alpha (8-12Hz). The procedure for statistical comparisons relied on the cluster-based permutation test (CBPT) and was carried out independently for each frequency band. As both groups did differ in age and educational level, both factors were included as covariates in the statistical tests. Finally, we performed Spearman correlation analyses between the significant power differences and the neuropsychological scores and hippocampal volumes.ResultpMCI patients showed a significant power increase within theta range (4-8Hz), compared with the sMCI group (CBPT p <0.05). The significant cluster within this frequency band mainly involved right medial temporal regions, including inferior temporal gyrus, fusiform gyrus, parahippocampal gyrus, hippocampus and amygdala. Besides, the pMCI group exhibited a power shift to lower frequencies than the sMCI group. The correlation analysis carried out with all participants showed a direct association between power results and general cognitive status (Mini-mental state examination; rho= -0.344; p= 0.021), working memory (inverse digit span test; rho= -0.285; p= 0.049) and episodic memory (immediate recall; rho= -0.405; p= 0.004; and delayed recall; rho= -0.358; p= 0.016).ConclusionOur results are aligned with previous reports with (EEG)/MEG spectral analysis performed in those MCI that finally progressed to AD. The Progression to AD involved the electrophysiological disruption of the medial temporal lobe structures. Besides, we found that this slowness pattern was related with worse performance in several cognitive measures, such as global cognitive status, episodic and working memory, entitle this MEG profile to be considered as AD-progression biomarker.