Fig. 5. Functional magnetic resonance signal change associated with noxious stimuli in anatomically defined regions of interest: thalamus (A ), insular cortex (B ), anterior cingulate cortex (C ), and primary sensory cortex (D ). The vertical axis  represents a parameter estimate proportional to the signal change above baseline (in arbitrary units). The horizontal axis  displays the predicted plasma concentration of ketamine. Black bars = anatomic right; white bars = anatomic left; gray bars = midline structures. * Statistically significant reduction in signal from saline.