Figure 2.

Microglomerular density is increased in the mushroom body lips when an olfactory memory is formed. A, Microglomerular density was measured in each medial calyx (red frame), both in the lip—receiving olfactory input from the PNs exiting the AL—and in the collar—receiving visual input from the optic lobe (OL). ORNs, Olfactory receptor neurons. Microglomeruli were counted in 400 μm² circles placed in the medial lip (continuous outlines) and collar (dotted outlines) (see Materials and Methods). B, Estimated densities of microglomeruli averaged over 8 circles for both the lip and collar of each animal. Bees from the paired group showed a density significantly higher than that in the 3 control groups, in the lip only. *p < 0.05; **p < 0.01.