For each task, subjects will receive at least eight consecutive administrations. It has been shown in repeated trials, that almost all normal subjects are able to increase the number of items retrieved and almost exhaust their lexical memory after several trials. The relationship of the retrieval slope to brain tissue volume loss in cortical regions that critically support lexical memory will be analyzed. As noted above, the majority of VHIS participants have been able to return to gainful employment, which has been identified as one of the most important self-perceived determinants of a good quality of life. Phase III will continue to evaluate factors impacting the ability to return to work, particularly in relation to the frontal lobe functions outlined above.
Many factors contribute to quality of life and outcome after a brain injury.
One of the least studied factors is genetic predisposition for recovery of function. Each subject will generate a family pedigree of neurological injury, and additional information such as social status, educational status and learning disability that will be used to predict outcome. Molecular epidemiologic studies have supported a role for allelic variants in recovery from acute and chronic brain injury. Candidate genes for molecular characterization will be selected based upon previous studies suggesting genetic factors that may contribute to the remodeling and survival of neurons following head trauma as well as behavioral recovery. These include APO-E alleles, as well as serotonin, dopamine and other neurotransmitter receptor and transporter genes which have been associated with certain behavioral phenotypes.