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Differences and the relationship in default mode network intrinsic activity and functional connectivity in mild

Marina Weiler1, Camila Vieira Ligo Teixeira, Mateus Henrique Nogueira

  • 11 Laboratory of Neuroimaging, University of Campinas , Campinas, Brazil .

Brain Connectivity
|July 16, 2014
PubMed

Insights

Default mode network (DMN) activity and connectivity are linked in Alzheimer's disease (AD) and mild cognitive impairment (MCI). Reduced DMN intrinsic activity disrupts brain organization, contributing to cognitive decline in AD spectrum disorders.

Area of Science:

  • Neuroscience
  • Cognitive Neurology
  • Medical Imaging

Background:

  • Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) are associated with disruptions in the default mode network (DMN).
  • Previous research indicates impaired DMN functional connectivity and reduced intrinsic activity (amplitude of low-frequency fluctuations - ALFFs) in AD.
  • The relationship between DMN intrinsic activity, functional connectivity, and cognitive function in early-stage AD and aMCI requires further investigation.

Purpose of the Study:

  • To investigate the relationship between DMN intrinsic activity (ALFFs) and functional connectivity in patients with mild AD, aMCI, and healthy controls.
  • To examine differences in DMN ALFFs and functional connectivity across these groups.
  • To explore the association between DMN metrics and cognitive performance.

Main Methods:

  • Functional connectivity analysis using a seed in the posterior cingulate cortex (PCC) to define the DMN.
  • Calculation of regional average ALFFs within the DMN mask.
  • Comparison of ALFFs and functional connectivity between 32 mild AD patients, 20 aMCI patients, and 29 healthy controls.
  • Correlation analysis between DMN metrics and cognitive test results.

Main Results:

  • aMCI patients exhibited decreased temporal ALFFs compared to controls, and compared to AD patients, showed higher PCC ALFFs but lower temporal ALFFs.
  • Mild AD patients had lower PCC ALFFs than controls.
  • While aMCI showed no significant connectivity differences, AD patients displayed reduced connectivity in frontal, parietal, and PCC regions.
  • PCC ALFFs were correlated with functional connectivity across most DMN subregions.
  • Cognitive performance correlated with DMN connectivity but not with ALFFs.

Conclusions:

  • DMN functional connectivity and intrinsic activity (ALFFs) are interconnected in individuals with AD and aMCI.
  • Diminished PCC ALFFs appear to disrupt the DMN's functional organization, contributing to cognitive impairments observed in the AD spectrum.
  • These findings highlight the importance of DMN integrity for cognitive function in neurodegenerative diseases.
Keywords:
Alzheimer's diseaseamnestic mild cognitive impairmentdementiaepisodic memoryfunctional MRI

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