Maolin Qiu1, Ramachandran Ramani2, Vivien Rekkas1, Nallakkandi Rajeevan1, Fuyuze S. Tokoglu1, Robert Todd Constable1,3
1Diagnostic Radiology, Yale University, New Haven, CT, USA; 2Anesthesiology, Yale University, New Haven, CT, USA; 3Biomedical Engineering, Yale University, New Haven, CT, USA
Task-induced neuronal activity in the presence of general anesthesia is the result of two counteracting factors: the anesthetic and the task. The former is supposed to suppress neuronal activity in general, while the latter is commonly used in fMRI and usually stimulates focal neuronal activity. It has been demonstrated in a limited number of animal models that the total amount of energy consumed by neurons or the level of neuronal activity in the sensorimotor region must reach the same level regardless of how deep the animal was anesthetized in order to accomplish certain task. However this result has not been observed in humans where the auditory and visual regions were examined in the presence of 0.25 MAC sevoflurane. Among many differences between these experiments, several issues remain to be clarified: e.g., will the strength of the functional stimulus affect the outcome? Will a strong functional stimulus dominates the observed changes in neuronal activity by emphasizing the primary projection against secondary associations? How the level of anesthesia affects the observation? Here we report the results from the study designed and conducted to address these issues.