Information processing speed in multiple sclerosis: Relevance of default mode network dynamics

Neuroimage Clin. 2018 May 15;19:507-515. doi: 10.1016/j.nicl.2018.05.015. eCollection 2018.

Abstract

Objective: To explore the added value of dynamic functional connectivity (dFC) of the default mode network (DMN) during resting-state (RS), during an information processing speed (IPS) task, and the within-subject difference between these conditions, on top of conventional brain measures in explaining IPS in people with multiple sclerosis (pwMS).

Methods: In 29 pwMS and 18 healthy controls, IPS was assessed with the Letter Digit Substitution Test and Stroop Card I and combined into an IPS-composite score. White matter (WM), grey matter (GM) and lesion volume were measured using 3 T MRI. WM integrity was assessed with diffusion tensor imaging. During RS and task-state fMRI (i.e. symbol digit modalities task, IPS), stationary functional connectivity (sFC; average connectivity over the entire time series) and dFC (variation in connectivity using a sliding window approach) of the DMN was calculated, as well as the difference between both conditions (i.e. task-state minus RS; ΔsFC-DMN and ΔdFC-DMN). Regression analysis was performed to determine the most important predictors for IPS.

Results: Compared to controls, pwMS performed worse on IPS-composite (p = 0.022), had lower GM volume (p < 0.05) and WM integrity (p < 0.001), but no alterations in sFC and dFC at the group level. In pwMS, 52% of variance in IPS-composite could be predicted by cortical volume (β = 0.49, p = 0.01) and ΔdFC-DMN (β = 0.52, p < 0.01). After adding dFC of the DMN to the model, the explained variance in IPS increased with 26% (p < 0.01).

Conclusion: On top of conventional brain measures, dFC from RS to task-state explains additional variance in IPS. This highlights the potential importance of the DMN to adapt upon cognitive demands to maintain intact IPS in pwMS.

Keywords: Cognition; Default mode network; Dynamic functional connectivity; Functional connectivity; Information processing speed; Multiple sclerosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Brain Mapping / methods
  • Cognition / physiology
  • Diffusion Tensor Imaging / methods
  • Female
  • Humans
  • Image Processing, Computer-Assisted / methods
  • Male
  • Middle Aged
  • Multiple Sclerosis / pathology*
  • Multiple Sclerosis / physiopathology*
  • Neural Pathways / pathology*
  • Neural Pathways / physiopathology
  • Time Factors
  • White Matter / pathology*
  • Young Adult