The goal of these studies is to map out and determine the functions of human cortical structures involved in attention and working memory control. The work will non-invasively map out the control structures in humans utilizing Functional MagnetiC Resonance Imaging (FMRI). FMRI monitors changes in brain blood oxygenation and flow in single subjects without the need of contrast agents. Increased cortical activity produces increased oxygenation and blood flow, resulting in changes in the paramagnetic ions within the tissue. The result is an increase in the apparent transverse relaxation time (T2*) producing a higher MR return signal for the more activated tissue. The project will utilize the FMRI methodology to functionally map human cortex with millimeter resolution tracking small areas (e.g, 4mm diameter disks) of activity on single subjects. We have demonstrated that we can track multiple levels of processing in the visual system and attentional modulation and switching. These techniques will monitor attentional control structures in superior parietal, anterior cingulate, and pulvinar and memory processing in prefrontal and temporal areas. Experiments map out cortical activation during attentional modulation attentional switching (within hemifields, across hemifields between modalities, and between sensory input and memory), interference effects, the development of automatic processing and basic long term learning. Initial mapping will be performed on normal subjects. Patients with clinical neglect (following stroke) and mild traumatic brain injury, will be examined with behavioral tests and FMRI mapping of attention and memory control shortly after injury and at six month and 1 year follow ups. The work will map out normal processing and recovery of attentional selection and switching in human cortex. The ability to track the recovery process may strongly impact assessment and treatment of these patient groups that make up a substantial portion of brain injury patients. The results will provide the basis for detailed modeling of cortical control processing.
