Functional brain network modularity predicts response to cognitive training after brain injury

Abstract

Objective: We tested the value of measuring modularity, a graph theory metric indexing the relative extent of integration and segregation of distributed functional brain networks, for predicting individual differences in response to cognitive training in patients with brain injury.

Methods: Patients with acquired brain injury (n = 11) participated in 5 weeks of cognitive training and a comparison condition (brief education) in a crossover intervention study design. We quantified the measure of functional brain network organization, modularity, from functional connectivity networks during a state of tonic attention regulation measured during fMRI scanning before the intervention conditions. We examined the relationship of baseline modularity with pre- to posttraining changes in neuropsychological measures of attention and executive control.

Results: The modularity of brain network organization at baseline predicted improvement in attention and executive function after cognitive training, but not after the comparison intervention. Individuals with higher baseline modularity exhibited greater improvements with cognitive training, suggesting that a more modular baseline network state may contribute to greater adaptation in response to cognitive training.

Conclusions: Brain network properties such as modularity provide valuable information for understanding mechanisms that influence rehabilitation of cognitive function after brain injury, and may contribute to the discovery of clinically relevant biomarkers that could guide rehabilitation efforts.

Figure 1. Examples of modular brain graphs

Brain graphs illustrating identified modules, with the nodes and edges in each module represented by a different color. Representative graphs are shown for the individuals with the lowest and highest baseline modularity (respectively, 0.25 and 0.48) at a cost of 0.15.

Figure 2. Relationship between baseline measures of integrated modularity and behavior with response to training

Relationship of baseline integrated modularity (A) or baseline attention/executive functions (B) with change in attention/executive functions after cognitive training (black symbols) and education interventions (white symbols). *p < 0.05.