Early dysfunction of functional connectivity in healthy elderly with subjective memory complaints

Area of Science:

• Neuroscience
• Cognitive Science
• Gerontology

Background:

• Subjective memory complaints (SMC) are increasingly linked to dementia risk and early Alzheimer's disease biomarkers.
• The clinical relevance of SMC as predictors for objective memory decline remains an open question.
• Understanding the neural underpinnings of SMC is crucial for early detection and intervention strategies.

Purpose of the Study:

• To investigate functional brain connectivity differences in individuals with SMC compared to those with mild cognitive impairment (MCI) and healthy controls.
• To determine if SMC are associated with distinct patterns of brain signal synchronization during a memory task.

Main Methods:

• Magnetoencephalography (MEG) was used to record brain signals from 56 participants (19 MCI, 12 SMC, 25 healthy controls).
• Synchronization likelihood, a measure of functional connectivity derived from nonlinear dynamical systems theory, was calculated.
• Connectivity patterns were compared across the three groups during a memory-related task.

Main Results:

• Individuals with SMC exhibited a connectivity pattern similar to healthy controls but with a generally lower synchronization value.
• The brain connectivity profile of SMC subjects differed significantly from those diagnosed with MCI.
• Hypo-synchronization in SMC may represent an early stage where the brain's memory networks are beginning to falter without compensatory mechanisms.

Conclusions:

• Subjective memory complaints may reflect an initial stage of neural network changes, characterized by reduced brain signal synchronization.
• The observed hypo-synchronization in SMC individuals suggests a potential preclinical phase preceding more significant cognitive impairment.
• Functional connectivity analysis using MEG provides insights into the neurophysiological differences between SMC, MCI, and healthy aging.