NNR methods are now available to investigate metabolic requirements of the activated human brain. Ny goal is to use these methods with suitable temporal and spatial resolution to study metabolic changes of the visual cortex during visual stimulation. The metabolic parameters to be evaluated during stimulation are lactate concentration, cerebral metabolic rate of glucose consumption (CMRglc) and cerebral metabolic rate of oxygen consumption (CMRO2). Lactate will be measured directly from the 1H Changes in CNRglc will be calculated from measured decreases in the brain glucose concentrations during stimulation using a method we have recently established. The flux from labeled 1-13C glucose to 4- glutamate will be used to calculate the TCA cycle activity and from that we will derive CMRO2. This flux is to be measured with 1H NMR sensitivity by heteronculear 1H-13C editing methods. It is planned to measure this turnover during hemispheric excitation of the VI region and to use the resting hemisphere as a control for the activated half. All of these methods have been developed in my laboratory to the point where they have the requisite sensitivity, and their feasibility has been demonstrated. They will now be applied to obtain quantitative, reproducible results.
The aim i s to quantify the degree of coupling between these parameters during sensory stimulation.
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