Fig. 2. Examples of flash-induced, γ-filtered (20–60 Hz) event-related potential images from data recorded in the striate cortex of the same rat at selected halothane, isoflurane, and desflurane concentrations (W: 0.0 MAC^LR, L: 0.5 MAC^LR, M: 1.0 MAC^LR, and H: 2.0 MAC^LR). One MAC^LRis the minimum alveolar concentration at which the righting reflex is lost. Each horizontal trace represents 200 ms of prestimulus and 1,000 ms of poststimulus activity; potential variations are color coded. In the waking state (W), bursts of γ oscillations were present after each flash and repeated at approximately 200-ms intervals with decaying amplitude over 1,000 ms after stimulus. Anesthetic agents at low (L) concentration disrupted the periodicity of γ bursts and transformed them into a more continuous activity spanning most of the 100- to 1,000-ms poststimulus period at medium (M) concentration. At high (H) concentration, late γ oscillations were diminished, but the early components of the evoked response, confined to 0–100 ms, were still present.