The mechanism of anesthetic-induced loss of consciousness (LOC) is unknown, but is hypothesized to involve a disruption of cortical functional interactions. As a physiological model to study these interactions, we will use flash-induced event-related potentials (ERP) intracortically recorded from rat's primary visual, parietal associaion, and prefrontal association cortices. (1) A novel frequency-domain method, cross- wavelet bicoherence, will be used to determine the effects of volatile anesthetics on cortical ERP synchronization with particular attention to LOC. It is hypothesized that ERP synchronization will be disrupted by the anesthetics upon LOC. (2) A novel time-domain method, transfer entropy, will be used to determine the effects of anesthetics on feedforward (FF) and feedback (FB) cortical information transfers with particular attention to LOC. It is hypothesized that the volatile anesthetics will produce a greater reduction in FB than FF information transfer upon LOC. The proposed work should establish if the disruption of cortical functional interactions correlates with the anesthetic-induced LOC, and should facilitate, in the long run, the development of better methods for anesthetic depth monitoring and of safer anesthetic agents. ? ? ?
