Three approaches to investigating functional compromise to the default mode network after traumatic axonal injury
Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, USA.Brain Imaging and Behavior (Impact Factor: 4.6). 07/2012; 8(3). DOI: 10.1007/s11682-012-9191-2
The default mode network (DMN) is a reliably elicited functional neural network with potential clinical implications. Its discriminant and prognostic utility following traumatic axonal injury (TAI) have not been previously investigated. The present study used three approaches to analyze DMN functional connectedness, including a whole-brain analysis [A1], network-specific analysis [A2], and between-node (edge) analysis [A3]. The purpose was to identify the utility of each method in distinguishing between healthy and brain-injured individuals, and determine whether observed differences have clinical significance. Resting-state fMRI was acquired from 25 patients with TAI and 17 healthy controls. Patients were scanned 6-11 months post-injury, and functional and neurocognitive outcomes were assessed the same day. Using all three approaches, TAI subjects revealed significantly weaker functional connectivity (FC) than controls, and binary logistic regressions demonstrated all three approaches have discriminant value. Clinical outcomes were not correlated with FC using any approach. Results suggest that compromise to the functional connectedness of the DMN after TAI can be identified using resting-state FC; however, the degree of functional compromise to this network, as measured in this study, may not have clinical implications in chronic TAI.
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- " cognitive changes ( Bonelle et al . , 2011 ; Sharp et al . , 2011 ) . In patients with moderate to severe TBI , increased functional connectivity between core nodes of the DMN is commonly observed , and especially with the posterior cingulate and precuneus regions ( Hillary et al . , 2014 ; Palacios et al . , 2013 ; Sharp et al . , 2011 ; but see Arenivas et al . , 2014 ; Pandit et al . , 2013 ) . However , there is also evidence that TBI is associated with decreased connectivity in some nodes of the DMN and increased connectivity in other nodes ( Venkatesan et al . , 2015 ) , possibly reflecting the distinct role of different nodes within the network . Similar non - uniformity of network changes has b"
ABSTRACT: Recent advances in neuroimaging methodologies sensitive to axonal injury have made it possible to assess in vivo the extent of traumatic brain injury (TBI) -related disruption in neural structures and their connections. The objective of this paper is to review studies examining connectivity in TBI with an emphasis on structural and functional MRI methods that have proven to be valuable in uncovering neural abnormalities associated with this condition. We review studies that have examined white matter integrity in TBI of varying etiology and levels of severity, and consider how findings at different times post-injury may inform underlying mechanisms of post-injury progression and recovery. Moreover, in light of recent advances in neuroimaging methods to study the functional connectivity among brain regions that form integrated networks, we review TBI studies that use resting-state functional connectivity MRI methodology to examine neural networks disrupted by putative axonal injury. The findings suggest that TBI is associated with altered structural and functional connectivity, characterized by decreased integrity of white matter pathways and imbalance and inefficiency of functional networks. These structural and functional alterations are often associated with neurocognitive dysfunction and poor functional outcomes. TBI has a negative impact on distributed brain networks that lead to behavioral disturbance.
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- "Emerging evidence suggests that dynamic brain functional connectivity may index changes in neural activity patterns underlying critical aspects of cognition or clinically relevant information (Allen et al. 2014; Calhoun et al. 2014; Hutchison et al. 2013a; Kucyi and Davis 2015; Park and Friston 2013; Tagliazucchi and Laufs 2014; Tagliazucchi et al. 2012). Furthermore, understanding the relationship between static and dynamic DMN functional connectivity with brain behavior will be critical to elucidate more fully the role of DMN signals in both healthy cognition and mental illness (Arenivas et al. 2014; Tam et al. 2014). Despite the number of studies focusing on DMN static and dynamic functional connectivity and mental state, to date, some previous studies have suggested that DMN functional connectivity is associated with brain cognitive function (Bonnelle et al. 2012; Buckner et al. 2008; Kucyi and Davis 2014). "
ABSTRACT: Characterization of the default mode network (DMN) as a complex network of functionally interacting dynamic systems has received great interest for the study of DMN neural mechanisms. In particular, understanding the relationship of intrinsic resting-state DMN brain network with cognitive behaviors is an important issue in healthy cognition and mental disorders. However, it is still unclear how DMN functional connectivity links to cognitive behaviors during resting-state. In this study, we hypothesize that static and dynamic DMN nodal topology is associated with upcoming cognitive task performance. We used graph theory analysis in order to understand better the relationship between the DMN functional connectivity and cognitive behavior during resting-state and task performance. Nodal degree of the DMN was calculated as a metric of network topology. We found that the static and dynamic posterior cingulate cortex (PCC) nodal degree within the DMN was associated with task performance (Reaction Time). Our results show that the core node PCC nodal degree within the DMN was significantly correlated with reaction time, which suggests that the PCC plays a key role in supporting cognitive function.
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- "Imaging data from the current investigation utilized an atomically based seed region approach to the analysis of OFC connectivity in veterans with TBI. Recent studies applying resting state functional connectivity in individuals with TBI have found decreased functional connectivity in the default mode network (DMN) (Arenivas et al. 2014; Mayer et al. 2011). Some studies have identified an increase in functional connectivity in frontal portions of the DMN (Palacios et al. 2013) and reductions in functional connectivity in posterior portions of the DMN (Johnson et al. 2012; Zhou et al. 2012). "
ABSTRACT: More female soldiers are now serving in combat theaters than at any other time. However, little is known about possible sex differences underlying the neuropathology and manifestation of one of modern war's signature injuries, traumatic brain injury (TBI). The paucity of information regarding sex differences in TBI is particularly evident when examining changes in executive function and emotion regulation associated with post concussive events. The current study objective was to observe whether patterns of orbitofrontal (OFC) functional connectivity would differ between female veterans with TBI and their male counterparts. The study further sought to determine whether OFC connectivity might be differentially associated with clinical measures of aggression and hostility. Seventeen female veterans and 24 male veterans, age 18 to 25, who met criteria for TBI completed resting state magnetic resonance imaging (MRI) and clinical assessment measures. Imaging data were analyzed using left and right seed regions of the OFC, and regression analyses were conducted to observe the relationship between resting state connectivity and self-reported aggression. Females and males in this study differed in OFC connectivity, with females demonstrating greater connectivity between left and right OFC and parietal and occipital regions and males demonstrating greater connectivity between left and right OFC and frontal and temporal regions. Significant associations between resting state connectivity and clinical measures were found only in male veterans. These findings suggest that TBI may interact with sex-specific patterns of brain connectivity in male and female veterans and exert divergent effects on clinical profiles of aggression post-injury.
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