Direction of Information Flow in Alzheimer's Disease and MCI Patients

Area of Science:

• Neuroscience
• Biomedical Engineering
• Gerontology

Background:

• Mild cognitive impairment (MCI) is a transitional stage between normal aging and Alzheimer's disease (AD).
• Understanding the neurophysiological underpinnings of MCI is crucial for early detection and intervention.
• The interplay between cerebrovascular and AD-related lesions in MCI progression remains incompletely understood.

Purpose of the Study:

• To investigate abnormalities in the directionality of electroencephalographic (EEG) synchronization in amnesic MCI and AD.
• To determine if cerebrovascular and AD lesions act as additive factors in the development of MCI.

Main Methods:

• EEG data were collected from normal elderly, amnesic MCI, and mild AD subjects at rest.
• Directed Transfer Function (DTF) was used to analyze the direction of information flow in EEG signals across various frequency bands (δ, θ, α, β, γ).
• Interhemispheric EEG functional coupling was assessed to evaluate group differences and the influence of vascular load.

Main Results:

• Parieto-to-frontal EEG synchronization directionality was reduced in MCI and AD compared to normal elderly for α and β rhythms.
• Interhemispheric EEG functional coupling did not differ significantly between groups.
• However, θ, α1, α2, and β1 frequency band coupling was higher in MCI patients with greater vascular load, suggesting an additive effect.

Conclusions:

• Abnormal directionality of parieto-to-frontal EEG synchronization is evident in both amnesic MCI and AD.
• These findings support an additive model where MCI results from the combined impact of cerebrovascular and neurodegenerative lesions.
• This highlights the potential of EEG synchronization analysis for understanding MCI pathophysiology.