Fig. 3. Examples of wavelet transforms of the γ-filtered single-trial event-related potentials from seven experiments at different halothane levels, selected from four concentration ranges (W: 0.0 MAC^LR, L: 0.4–0.6 MAC^LR, M: 1.0–1.25 MAC^LR, and H: 2.1–2.5 MAC^LR). One MAC^LRis the minimum alveolar concentration at which the righting reflex is lost. Each horizontal trace represents wavelet power calculated from a single data trial consisting of 200 ms of prestimulus and 1,000 ms of poststimulus activity. To minimize frequency overlap resulting from continuous wavelet decomposition, the wavelet power was averaged within 10-Hz-wide spectral windows of 20–30, 31–40, 41–50, and 51–60 Hz in each trial. To construct each image, 60 single-trial wavelet power traces from seven experiments were stacked to arrive at 420 trials.  Horizontal black lines are drawn to separate the trials from separate experiments. The same amplitude scale is used to display all images. The spectral power of the early response (0–100 ms) was the highest at low γ frequencies (20–30 Hz) at all concentrations. In contrast, late γ power was highest in the 31- to 50-Hz window at low (L) and medium (M) concentrations. Halothane augmented late γ oscillations in the frequency range of 31–50 Hz and at medium concentrations, which included the concentration at which the righting reflex was abolished. The augmented activity exhibited high temporal variations from trial to trial and even more from animal to animal.