Associations between interhemispheric functional connectivity and the Automated Neuropsychological Assessment Metrics (ANAM) in civilian mild TBI

Abstract

This study investigates cognitive deficits and alterations in resting state functional connectivity in civilian mild traumatic brain injury (mTBI) participants with high and low symptoms. Forty-one mTBI participants completed a resting state fMRI scan and the Automated Neuropsychological Assessment Metrics (ANAM) during initial testing (<10 days of injury) and a one month follow up. Data were compared to 30 healthy control subjects. Results from the ANAM demonstrate that mTBI participants performed significantly worse than controls on the code substitution delayed subtest (p=0.032) and weighted throughput score (p=0.001). Among the mTBI patients, high symptom mTBI participants performed worse than those with low symptoms on the code substitution delayed (p=0.017), code substitution (p=0.012), repeated simple reaction time (p=0.031), and weighted throughput score (p=0.009). Imaging results reveal that during the initial visit, low symptom mTBI participants had reduced interhemispheric functional connectivity (IH-FC) within the lateral parietal lobe (p=0.020); however, during follow up, high symptom mTBI participants showed reduced IH-FC compared to the control group within the dorsolateral prefrontal cortex (DLPFC) (p=0.013). Reduced IH-FC within the DLPFC during the follow-up was associated with reduced cognitive performance. Together, these findings suggest that reduced rs-FC may contribute to the subtle cognitive deficits noted in high symptom mTBI participants compared to control subjects and low symptom mTBI participants.

Is Traumatic Brain Injury Associated with Reduced Inter-Hemispheric Functional Connectivity? A Study of Large-Scale Resting State Networks following Traumatic Brain Injury

“…The use of such a template allowed us to maintain a network perspective throughout the analysis; in addition, in a high variability population such as the one analyzed in this study, where several changes in brain structure may occur following a traumatic injury, the use of more extensive seeds addresses some potential problems that might arise with the use of smaller ROIs (e.g., the sensitivity of resting state fMRI results to ROIs coordinates, size and shape, the difficulty of establishing the most representative ROIs for a given RNS and, specifically in the TBI population, the possible confounds due to changes and shifts in brain structure following head injury). 62,63 Our results with chronic TBI patients are partially consistent with results on acute and sub-acute samples by Sours and colleagues 29 and Marquez de la Plata and colleagues 28 using more restricted frontal and parietal ROIs. In particular, we found that TBI participants display significantly less inter-hemispheric FC, but only between networks more involved in externally oriented cognition (FPN and ECN).…”

“…In particular, we found that TBI participants display significantly less inter-hemispheric FC, but only between networks more involved in externally oriented cognition (FPN and ECN). 28,29 These RSNs repeatedly have been found to activate during tasks demanding cognitive flexibility, and to support cognitive functions necessary for successful interaction with the environment including goal directed action, set maintenance, attentional selection, encoding of salience, working memory and mental representations. 12,22,64,65 Given the across-the-board impairment in attention and cognitive functions found in TBI patients of all severities and the extensive neuropsychiatric, emotional, and behavioral problems displayed in everyday life, it is crucial to uncover how these complaints map onto specific aberrant patterns of FC in these large scale networks.…”

“…29 Previous studies have highlighted the importance of characterizing the way networks interact with each other to reach a deeper understanding of the pathophysiological mechanisms of TBI outcome. 21,68 Notably, in our patient sample, FC between areas located in the same hemisphere was higher than in regions belonging to the same RSNs.…”

MR Imaging Applications in Mild Traumatic Brain Injury: An Imaging Update

“…Other functional networks have also been studied in the resting state. Namely, Sours et al found that reduced interhemispheric connectivity in the dorsal lateral prefrontal cortex at rest was associated with mTBI symptoms and cognitive performance at 1-month follow-up (130). An abnormal increase in the number of thalamocortical resting-state networks has also been shown after mTBI, which speaks to a disruption of the normal small world organization of neuronal networks, where clusters of neighboring functional regions are efficiently linked to anatomically distant clusters by longrange neuronal connections (131)(132)(133).…”

Investigation of Multiple Frequency Ranges Using Discrete Wavelet Decomposition of Resting-State Functional Connectivity in Mild Traumatic Brain Injury Patients

“…Following mTBI, researchers have noted reduced interhemispheric functional connectivity (Slobounov et al, 2011;Sours et al, 2014) and increased thalamocortical functional connectivity (Sours et al, 2014;Tang et al, 2011;Zhou et al, 2014). However, the majority of the research probing altered resting-state functional connectivity in the mTBI population has focused on alterations to the default mode network (DMN), a set of regions in the brain that are deactivated during task-related activities, while demonstrating increased activity during rest conditions (Greicius et al, 2003;Raichle et al, 2001).…”