The main purpose of this work is to study a direct effect of low levels of visible light on mammalian cerebral cortical tissue. This project is based on the original observation that light enhances release of a neurotransmitter molecule (gamma- aminobutyric acid, GABA) from excised tissue. Since the levels of light necessary for this response are estimated to penetrate through the top of the head, light may affect mammalian brain tissue while it is still in the body. The overall or long-term objective in the project is clarifying the relevance of responses to light penetrating the body in the living state. More immediately, the objectives are aimed at examining how light may have functional effects by: 1) establishing first to what extent the most fundamental measure of function, glucose metabolism, is affected by light in surface brain tissue, and then 2) focusing on the photosensitive molecule(s) which will further delineate what cellular processes/functions can be candidates for the physiological consequences of light.
