Cognitive impairment after a traumatic brain injury (TBI) is widespread and can significantly reduce quality of life for many of the estimated 1.7 million Americans who sustain a TBI each year. Researchers at the Center for BrainHealth at The University of Texas at Dallas have identified complex disruptions in brain network connectivity among people living with chronic TBI that may underlie long-term deficits in higher-order cognitive functions.
A study published in the Journal of International Neuropsychological Society reports that individuals at least six months post-injury show disrupted long-range and between-network connectivity, including altered communication across the two hemispheres. The researchers found significant connectivity changes involving the default mode network (DMN), the dorsal attention network (DAN), and the frontoparietal control network (FPCN)—networks that coordinate internally focused thought, attention to external information, and flexible cognitive control required for everyday tasks.
“Cooperation between the default mode network, dorsal attention network and frontoparietal control network is essential for managing internal trains of thought and adjusting to changing demands in daily life,” said Kihwan Han, Ph.D., lead author and postdoctoral research associate at the Center for BrainHealth. “These networks work together to support planning, learning and problem solving. Our findings suggest that cognitive deficits after TBI may stem from reduced efficiency in how these large-scale networks communicate.”
For the study, the team compared resting-state MRI scans from 40 people with chronic TBI to 17 healthy control participants matched on age, gender and years of education. Participants ranged in age from 19 to 45. All members of the TBI group were at least six months post-injury when scanned, and on average were eight years removed from their injury. None had a prior history of significant, clinically diagnosed neurological or psychiatric disorders before their TBI.
“Much prior research has examined individual brain networks in isolation,” said Daniel Krawczyk, Ph.D., principal investigator and associate professor of cognitive neuroscience and cognitive psychology at the Center for BrainHealth. “This study is among the first to demonstrate how correlations among multiple networks are altered in chronic TBI, revealing disruptions in how those networks communicate with one another.”
The researchers used network-based statistics and graph-theoretic measures to quantify connectivity patterns. They observed statistically significant reductions in connectivity within the DMN and FPCN, as well as diminished connectivity between DMN-DAN and DMN-FPCN in the TBI group compared with controls. These abnormalities were most pronounced in long-range and interhemispheric connections. Graph theory analyses showed reduced global, local and cost efficiency associated with these disrupted network patterns, indicating less efficient information transfer across the brain’s networks.
“If key networks cannot interact normally, the brain’s overall processing becomes less efficient,” Krawczyk added. “Understanding these altered interactions gives us a clearer picture of why many people with chronic TBI experience persistent problems with planning, sustained attention and complex problem solving.”
The study highlights the value of assessing multiple networks simultaneously to better understand deficits in goal-directed cognition and other higher-order cognitive functions after TBI. The authors note that future work should link these connectivity disruptions more directly to behavioral outcomes and investigate whether targeted cognitive interventions can restore or strengthen network interactions even years after injury.
Funding: Supported by the U.S. Department of Defense and The Meadows Foundation.
Source: Shelly Kirkland – UT Center For BrainHealth
Original research: Abstract for “Disrupted Intrinsic Connectivity among Default, Dorsal Attention, and Frontoparietal Control Networks in Individuals with Chronic Traumatic Brain Injury” by Kihwan Han, Sandra B. Chapman and Daniel C. Krawczyk, Journal of International Neuropsychological Society. Published online February 2016 (doi:10.1017/S1355617715001393).
Abstract
Disrupted Intrinsic Connectivity among Default, Dorsal Attention, and Frontoparietal Control Networks in Individuals with Chronic Traumatic Brain Injury
Objectives: Individuals with chronic TBI frequently exhibit impairments in higher-order cognitive functions that require coordination across multiple brain networks. Although network-based approaches promise to clarify such deficits, few studies have systematically examined altered interactions among multiple large-scale networks in chronic TBI.
Method: We characterized resting-state functional connectivity among the default mode network (DMN), dorsal attention network (DAN), and frontoparietal control network (FPCN) in 40 individuals with chronic TBI (average 8 years post-injury) and 17 matched healthy controls. These networks together support internally and externally directed goal-oriented cognition.
Results: Network-based statistics revealed significant reductions in within-DMN and within-FPCN connectivity, and impaired DMN-DAN and DMN-FPCN connections in the TBI group compared with controls (pNBS < .05; |Z| > 2.58). Disruptions were especially evident in long-range and interhemispheric connections. Graph-theoretic analyses indicated reductions in global, local and cost efficiency (p < .05) consistent with less efficient network communication in the TBI group.
Conclusion: Simultaneous assessment of multiple interacting networks improves understanding of deficits in goal-directed cognition and other higher-order cognitive problems in chronic TBI. Further research is needed to clarify behavioral consequences and to evaluate interventions that might restore more efficient network interactions.