Fig. 3. Fixed-effect group activation in response to nociceptive stimulation during saline infusion (A ), ketamine predicted plasma concentration of 50 ng/ml (B ), and ketamine predicted plasma concentration of 200 ng/ml (C ). The images consist of a color-rendered statistical map of activation (Z scores) registered onto high-resolution structural scans that have been transformed to standardized brain geometry (Talairach space). For clarity, 10 representative images are shown. The standard threshold for voxel activation was taken as Z > 2.3 (P < 0.05), and clusters were defined with a significance threshold of P = 0.01. Color is used to display the Z scores for voxel activation, from red (lowest Z) to yellow (highest Z). Anatomic left (L ) and right (R ) are marked and with labels indicating relevant anatomic sites.