Specific versus Nonspecific Connectivity: A Transition of the Resting Network from Light to Deep Anesthesia

Introduction Coherent spontaneous hemodynamic fluctuations have been widely observed in many brain networks of different species, and they were hypothesized to reflect underlying “functional connectivity” [1] of the brain and imply many “resting networks” . Since it is known that the anesthesia can significantly affect brain activity and state; it can probably also influence these resting networks. Previous studies [3-4] have demonstrated that the magnitudes of spontaneous blood-oxygen-level-dependent (BOLD) and cerebral blood flow (CBF) fluctuations in deeply anesthetized rats decreased as the isoflurane concentration increased. However, the significance of these studies was limited by the narrow range of anesthesia depths (1.8~2.2% isoflurane). To better understand how the depth of anesthesia can affect spontaneous hemodynamic fluctuation, BOLD signals were acquired from rats under a much wider range of anesthesia (1.0 to 1.8% isoflurane) in the present study; and the modulation of the resting networks at different anesthesia levels were examined base on the spatiotemporal correlations of spontaneous BOLD fluctuations.