: Each year, over 230,000 people survive moderate and severe traumatic brain injury (TBI). As a result, a large number of individuals with TBI endure life-long impairment and disability. Memory disturbance is one of the most disabling consequences of TBI, but there has been little focused research on the cerebral mechanisms of impaired memory. The Research Plan for the NIH's National Center for Medical Rehabilitation Research (NCMRR) points to the need to 1) evaluate the efficacy of neuroimaging techniques, and to 2) develop new and precise quantitative measures of impairment after traumatic brain injury (TBI). The present proposal will address these goals by applying functional MRI (FMRI) and diffusion tensor imaging (DTI) to study which components of working memory are compromised after TBI. Working memory disturbance is one of the most disabling consequences of TBI, but there has been little research conducted in this population. In response to this need, the present proposal will apply FMRI to the study of multiple aspects of working memory in TBI through the use of FMRI. Our pilot data demonstrate that persons with TBI demonstrate altered cerebral representation of working memory processing and diminished white matter integrity in functionally important white matter tracts relative to controls. What is not known, however, are the specific mechanisms of impairment within working memory (e.g., storage, maintenance, central executive) after TBI, or how the functional disconnectivity of critical brain regions relates to post-injury working memory dysfunction. We will use event-related BOLD FMRI and DTI in a 3.0 environment to examine the effects of TBI on storage, maintenance and retrieval during verbal and visuospatial tasks, using paradigms that have been established in healthy individuals. Subjects will consist of 30 persons with severe, moderate, or complicated mild TBI examined at 1 to 3 years post-injury and 10 demographically equivalent controls. Because cognitive effort underlies FMRI activations that are seen during working memory tasks, it is expected that as task demands increase, individuals with TBI will show greater cerebral activations on fMRI when compared to healthy controls. It is expected that individuals with TBI will show greater intensity and dispersion of cerebral activation, even at """"""""simpler"""""""" levels of working memory processing (i.e., within working memory primary systems), suggesting altered reorganization of the cerebral substrate of working memory following TBI. These effects will be related to injury severity characteristics as well as parametric manipulation of memory load. Finally, we will utilize diffusion tensor imaging to examine fractional anisotropy and probabilistic fiber tracking to characterize the functional connectivity among brain regions associated with working memory dysfunction after TBI. The results of the present study will provide a better understanding of the specific mechanisms of working memory and may provide us with the tools to improve both behavioral and physiological interventions.
: Each year, over 230,000 people survive moderate and severe traumatic brain injury (TBI), and a large percentage of these individuals endure life-long impairments and disabilities. The ongoing return of soldiers injured in Iraq and Afghanistan has brought public attention to the effects of traumatic brain injuries. Among these, memory disturbance is one of the most disabling consequences, but there has been little focused research on the brain mechanisms of impaired memory. This study will use two advanced MRI technologies (FMRI: functional magnetic resonance imaging;and DTI: diffusion tensor imaging) to examine changes in the brain that are related to problems in working (short-term) memory. Study findings may yield information that will be useful in brain injury diagnosis, assessment, prediction of outcome, and potentially treatment.
