Convergent projections of layer 2/3 pyramidal cells onto the same dendritic branches. (A and B) Two pairs of dendritic spines on the same dendritic branches demonstrated simultaneous Ca2+ transients (green arrows). The upper and lower images in each pair show Alexa Fluor 594 and Fluo-5F fluorescence, respectively. The images immediately before and after 2pMAPG at one of the Ca2+ transient-evoking pixels are shown. These images were taken from a larger Ca2+ imaging region. (C) An example of a pair of dendritic spines on the same dendritic branch that showed Ca2+ transients at different times (green arrows). One of the images (Before) was obtained before the start of 2pMAPG mapping and the other two images (After 1 and 2) were taken immediately after 2pMAPG at different pixels. These images were taken from larger Ca2+ imaging regions. (D) Distribution of the distances between somata in pairs of presynaptic cells innervating the same postsynaptic cell. White bars indicate pairs innervating different dendritic branches. Black bars indicate pairs innervating the same dendritic branch.