Fig. 5. Optical responses in the antennal lobe (AL) elicited by electrical stimulation of the medial nerve (MN) and the lateral nerve (LN). (A) Real image of the moth brain (boxed area of inset). The boxed area in the schematic drawing corresponds to the MOS-type image sensor used by optical recording. Scale bar, 500 µm. OL, optic lobe; PC, protocerebrum. (B) Optical responses in the AL. All optical images were superimposed on the bright real image of the AL. Consistent response patterns in the macroglomerular complex (MGC) were evoked by the electrical stimulation of the medial nerve (MN) or the lateral nerve (LN). The pattern was initially a depolarization of the antennal nerve (AN; 3.6–7.2 ms after the onset of the stimulation) and, subsequently, a depolarization of the MGC (4.8–9.6 ms). At 7.2 ms from the stimulus of the MN, the area strongly (>0.4% of the background fluorescence) responding to stimulation of the MN was restricted to the medial half of the MGC. By contrast, the area strongly (>0.4% of the background fluorescence) responding to stimulation of the LN was restricted to the lateral half of the MGC. (C) Time course of the optical signals in the AL evoked by stimulation of the MN (upper panel) and the LN (lower panel). The optical signal was calculated by averaging signals recorded in areas that had a response of >0.3% (–F/F) at 7.2 ms from the stimulus onset and filtered at 246 Hz (F_c). The response, evoked in the MGC, had a peak at 7.2 ms after the stimulus onset. The response had another slow component (arrowheads) after the first peak of the depolarization. The annodal break was visible just after the stimuli (S).