Figure 1.

Effect of anesthesia on blood oxygenation level-dependent activation. Functional images of the stimulation of two whiskers (A2 and A3) are shown from a single subject before (A), during (B), and after (C) fentanyl+isoflurane anesthesia. Before anesthesia, a cluster of activation in the whisker barrel cortex contralateral to the stimulated whiskers can be seen extending through all layers of cortex. The activated area in the cortex contracts primarily to layer IV during anesthesia, and subsequently expands during recovery. The color bar represents the magnitude of the correlation coefficient. The blood oxygenation level-dependent time course averaged across the subjects (D) showed a decrease in magnitude during anesthesia (E), followed by recovery of the signal (F). Error bars represent the s.e.m. The horizontal gray bar indicates the timing of the stimulus presentation.