Top-Down Executive Control in Traumatic Brain Injury (TBI), PTSD and Combined

Traumatic brain injury (TBI) and PTSD both are characterized by deficits in attention, yet it is unclear as to whether this is related to an inability to focus on relevant information or ignore non-relevant information. History of TBI and PTSD are common to returning soldiers from OEF/OIF and thus is highly relevant to veteran health care. It is unclear how TBI and PTSD separately, and together, affect one's ability to focus attention versus inhibit distracting stimuli. This research investigates this issue by use of a working memory paradigm with functional magnetic resonance imaging (fMRI) that entails the subject being instructed to ignore some stimuli and remember other stimuli resulting in discrete biomarkers of (1) task-related enhancement of neural processes as well as (2) suppression of task-irrelevant neural processes. In this way, the specific aspect of attention in TBI and PTSD will be elucidated in addition to exploring whether PTSD and TBI have an additive, or even synergist, effect when combined.

Inclusion criteria

• All subjects will be between 18 and 40 years of age.
• In order to be included in the mTBI group, participants must have sustained between 1 and 3 mild TBIs. The criteria for TBI will be consistent with what the VA currently uses (i.e., American Congress of Rehabilitative Medicine).
• More specifically, patients will have sustained a traumatically induced physiologic disruption of brain function as indicated by at least one of the following:

• any period of loss of consciousness,
• any loss of memory for events immediately before or after the accident,
• any alteration in mental status at the time of the accident, and
• focal neurologic deficits.
• Additional criteria for TBI include:

• TBI must have been sustained during OEF or OIF and
• TBI must consist of less than 30 minutes loss of consciousness, posttraumatic amnesia of less than 1 hour, and no positive CT/MRI findings.
• For PTSD group inclusion, psychiatric diagnoses will be established via the PTSD Clinical Checklist- Military (PCL-M) and the Clinician Administered PTSD Scale (CAPS).
• For PTSD/mTBI group inclusion, the above criteria must be met for both PTSD and mTBI.
• Control subjects will be OEF/OIF veterans with a history of exposure to combat without current or previous diagnosis of PTSD and no history of TBI.

Exclusion criteria

• Subjects who meet diagnostic criteria for drug abuse/dependence over the past year will be excluded.
• Individuals will be excluded if they have neurological confounds (e.g., baseline history of a CNS opportunistic infection, CNS neoplasm, neurosyphilis, current seizure disorder, demyelinating diseases), learning disorder, or current psychiatric disorders involving psychosis (schizophrenia, bipolar disorder with psychosis).
• Patients will also be excluded from the study if they are claustrophobic or are taking cardiovascular medications as these are contraindications for fMRI.
• All 4 subject groups will be matched for age and education.