Functional neuroimaging techniques such as blood-oxygen level dependent (BOLD) magnetic resonance imaging and positron emission tomography (PET) reveal task-induced alterations in neuronal activity and metabolism. The objective of the current research is to understand the changes in baseline brain activity following task induction in humans. Specifically, the current study will characterize alterations in metabolism (detected via PET) and functional connectivity of the brain (detected via fMRI) following learning of an implicit visuomotor rotation task. This research will provide important evidence about the intrinsic structure of the brain, the effect of learning on brain metabolism, and provide new avenues to research metabolic defects in brain function. The experimental focus will be to specifically test the hypothesis that transient, task-related local activity changes result in long-term increases in aerobic glycolysis in resting brain. Currently, functional imaging techniques rely upon the assumption of a true baseline state both before and after task-related stimulation. While this assumption allows for simple data analysis, global alterations in glucose metabolism have been reported following complex stimuli. All external stimuli result in slight alterations in brain structure and function;these alterations could result from simple or more complex visual, visuomotor, or cognitive tasks. Defects in the encoding of information into neuronal circuits or defects in retrieval of such information represent an important area with great clinical relevance, especially due to the increasing burden of Alzheimer's disease in the aging population.
The specific aims are to: 1) Characterize the effect of rotation learning upon subsequent baseline glucose metabolism (measured via FDG-PET) and functional connectivity (measured via alterations in spontaneous fMRI BOLD signal). Determine regional specificity of baseline metabolic alterations and task-specific activity increases. 2) Characterize the persistent metabolic changes following rotation learning into aerobic glycolysis or oxidative phosphorylation. Determine the oxygen-glucose-index (OGI) throughout the brain using measurements of regional blood flow, oxygen consumption, and glucose consumption via PET. Determine correlations between metabolic changes (OGI) and spontaneous BOLD activity. The objective of this research project is to use functional brain imaging to understand exactly how baseline brain activity changes after learning. This research will provide important information about how the brain is structured and how diseases such as Alzheimer's and stroke may alter brain activity and metabolism.
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