Alterations in resting-state network dynamics along the Alzheimer's disease continuum

Area of Science:

• Neuroscience
• Cognitive Neurology
• Brain Imaging

Background:

• Human brain activity organizes into dynamic resting-state networks (RSNs) operating on sub-second timescales.
• Alzheimer's disease (AD) impacts cognitive, structural, and metabolic functions, but its effects on fast RSN temporal dynamics remain understudied.

Purpose of the Study:

• To investigate how AD affects the temporal dynamics of RSNs.
• To correlate these fast brain dynamics with cognitive, structural, and metabolic abnormalities in AD.

Main Methods:

• Magnetoencephalography (MEG) and hybrid PET/MR imaging were used in healthy elders, subjective cognitive decline (SCD), amnestic mild cognitive impairment (aMCI), and AD patients.
• Hidden Markov Modeling (HMM) analyzed RSN power envelope fluctuations to assess state dynamics.
• Correlations were examined between HMM state properties, cognitive scores, hippocampal volume, and brain glucose metabolism.

Main Results:

• AD patients exhibited reduced activation frequency and duration of the posterior default-mode network (DMN) compared to healthy elders.
• No significant differences in posterior DMN dynamics were observed in SCD or aMCI patients.
• Posterior DMN activation duration correlated positively with right dorsolateral prefrontal cortex (DLPFC) glucose metabolism, but not with cognitive scores or hippocampal volume.

Conclusions:

• AD patients show altered posterior DMN activation dynamics at rest, indicating synaptic and neural dysfunction.
• The right DLPFC may influence posterior DMN activation, potentially relating to mind-wandering episodes.
• These findings suggest a neural correlate for decreased mind-wandering reported in pathological aging.