Fig. 2. Original record of spontaneous and flash-induced bursts at 1.8% isoflurane anesthesia in one experiment. ( A ) Spontaneous bursts followed by bursts induced by monocular flash stimulation. In this example, the flashes were presented every 5 s; flash markers are shown in the lowest trace . Note that spontaneous bursts can also be seen during flash stimulation. ( B ) Comparison of single spontaneous ( left ) and flash-induced ( right ) bursts on an expanded time scale. Signals were recorded with epidural electrodes at positions that correspond approximately to cortical structures as indicated. M1 = primary motor cortex; OB = olfactory bulb; S1FL = somatosensory cortex, forelimb area; S1Tr = somatosensory cortex, trunk area; V1B = primary visual cortex, binocular region; V1M = primary visual cortex, monocular region. Note the similarity of spontaneous and flash-induced bursts and their maximum amplitude in M1. A visual evoked potential to flash is seen in V1M (marked with arrow ). This is followed by a burst of larger potentials in more frontal areas with a latency of approximately 300 ms.