Functional alterations in brain activation and deactivation in mild cognitive impairment in response to a graded working memory challenge

N. A. Kochan, M. Breakspear, M. J. Slavin, M. Valenzuela, S. McCraw, H. Brodaty, P. S. Sachdev

Research output: Contribution to journalReview article

32 Citations (Scopus)

Abstract

Aim: To investigate dynamic changes in functional brain activity in mild cognitive impairment (MCI) in response to a graded working memory (WM) challenge with increasing memory load. Methods: In an event-related functional magnetic resonance imaging (fMRI) study, 35 MCI and 22 cognitively normal subjects performed a visuospatial associative WM task with 3 load levels. Potential performance differences were controlled for by individually calibrating the number of items presented at each load. Results: An interaction between group and WM load was observed during stimulus encoding. At lower loads, greater activity in the right anterior cingulate and right precuneus was observed in MCI subjects. As the load increased to higher levels, reduced activation in these regions and greater deactivation in the posterior cingulate-medial precuneus were observed in MCI compared to control subjects. Stronger expression of load-related patterns of activation and deactivation in MCI subjects was associated with greater clinical severity and a more abnormal pattern of performance variability. Conclusion: Patterns of overactivation, underactivation and deactivation during successful encoding in MCI subjects were dependent on WM load. This type of graded cognitive challenge may operate like a 'memory stress test' in MCI and may be a useful biomarker of disease at the predementia stage.

Original languageEnglish
Pages (from-to)553-568
Number of pages16
JournalDementia and Geriatric Cognitive Disorders
Volume30
Issue number6
DOIs
Publication statusPublished - Jan 2011
Externally publishedYes

Keywords

  • Alzheimer's disease
  • Default mode network
  • Functional magnetic resonance imaging
  • Memory
  • Mild cognitive impairment
  • Working memory

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