Sevoflurane's Effect on Neurocognition Study

This is a non-randomized, clinical trial study of healthy volunteer subjects, which will employ neuroimaging and behavioral measures to characterize the effects of inhalational sevoflurane on pain processing and cognitive function. Sedative doses of sevoflurane will be targeted, and steady-state end-tidal (expired) concentrations achieved, while subjects perform a pain and memory cognitive task. At both no-drug baseline and the targeted doses, task and resting-state functional magnetic resonance imaging (MRI) scans will be acquired, and this data will be analyzed subsequently for task-related brain activity(from pain processing and memory formation) and functional connectivity. This work will use a systems neuroscience approach to fill an important knowledge gap about the central effects of inhalational sevoflurane in the context of painful stimulation. The investigators propose to complete the following 3 Aims, at a sedative dose of Sevoflurane, compared to no-drug baseline, using functional MRI: Aim 1: Determine how the brain response to acute pain stimulation is modulated by sevoflurane. It is anticipated that sevoflurane will correlate to decreased activation in both somatosensory (thalamus, insula, primary somatosensory/motor) and affective (anterior cingulate) components of the pain processing brain areas. Aim 2: Determine how memory encoding is modulated by sevoflurane, in the context of periodic painful stimulation. It is anticipated that sevoflurane will correlate to decreased activation in both the explicit memory (hippocampus, parahippocampus) and associative learning (amygdala, anterior cingulate) brain systems. Aim 3: Determine the neural effects of inhalational sevoflurane on brain connectivity both at rest and during the combined pain and memory task performance. It is anticipated that hypothesize that sevoflurane will cause widespread dose-dependent decreases in long-range functional connectivity between brain areas known to be involved in pain processing and to the default mode network, and that this connectivity will differ between the resting (task-free) and periodic pain states.