ALTERATIONS OF BRAIN RESTING STATE FUNCTIONAL CONNECTIVITY AND DEFAULT MODE NETWORK IN THE SUBACUTE PHASE OF MILD TRAUMATIC BRAIN INJURY

Open Access
Author:
Johnson, Brian
Graduate Program:
Kinesiology
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 15, 2011
Committee Members:
  • Semyon Slobounov, Thesis Advisor
Keywords:
  • subacute
  • default mode network
  • mTBI
  • rs-fcMRI
Abstract:
There are a number of symptoms, both neurological and behavioral, associated with a single episode of mild traumatic brain injury (mTBI). Neuropsychological testing and conventional neuroimaging techniques are not sufficiently sensitive to detect these changes, which adds to the complexity and difficulty in relating symptoms from mTBI to their underlying structural or functional deficits. With the inability of traditional brain imaging techniques to properly assess the severity of brain damage induced by mTBI, there is hope that more advanced neuroimaging applications will be more sensitive, as well as specific, in accurately assessing mTBI. In this study, we used resting state functional magnetic resonance imaging to evaluate the default mode network (DMN) in the subacute phase of mTBI. Fourteen concussed student- athletes who were asymptomatic based upon clinical symptoms resolution and clearance for aerobic exercise by medical professionals were scanned using resting state functional magnetic resonance imaging. Nine additional asymptomatic, yet not medically cleared athletes were recruited to investigate the effect of a single episode of mTBI versus multiple mTBIs on the resting state DMN. In concussed individuals the resting state DMN showed a reduced number of connections and strength of connections in the posterior cingulate and lateral parietal cortices. However an increased number of connections and strength of connections was seen in the medial prefrontal cortex of the mTBI group. Connections between the left dorso-lateral prefrontal cortex and left lateral parietal cortex showed a significant reduction in magnitude as the number of concussions increased. Regression analysis also indicated an overall loss of connectivity as the number of mTBI episodes increased. Our findings indicate that alterations in the brain resting state default mode network in the subacute phase of injury may be of use clinically in assessing the severity of mTBI and offer insight into the pathophysiology of the disorder.