Spatiotemporal correlations of spontaneous blood oxygenation level dependent (BOLD) signals measured in the resting brain have been found to imply many resting-state coherent networks under both awake/conscious and anesthetized/unconscious conditions. To understand the resting-state brain networks in the unconscious state, spontaneous BOLD signals from the rat sensorimotor cortex were studied across a wide range of anesthesia levels induced by isoflurane. Distinct resting-state networks covering functionally specific sub-regions of the sensorimotor system were observed under light anesthesia with 1.0 % isoflurane; however, they gradually merged into a highly synchronized and spatially less-specific network under deep anesthesia with 1.8 % isoflurane. The EEG power correlations recorded using three electrodes from a separate group of rats showed similar dependency on anesthesia depth, suggesting the neural origin of the change in functional connectivity specificity. The specific-to-less-specific transition of resting-state networks may reflect a functional reorganization of the brain at different anesthesia levels or brain states.
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Acknowledgments The authors thank Ms. Jennifer Taylor for helpful comments. This work was in part supported by NIH Grants: NS041262, NS041262S1, NS057560, NS070839, P41 RR08079, P41 EB015894, P30NS057091 and P30NS076408; and the Keck Foundation.
- Animal models
- Functional MRI (fMRI)
- Functional connectivity
- Neural origin
- Resting-state fMRI (rs-fMRI)