For analysis of dendrite overlap between arbors of neighboring SACs, pairs with somata separated by 80-160 μm were selected because their dendrites are known to interact25. Images were processed using Fiji or Photoshop software. To estimate the amount of dendritic overlap that would occur by chance if two SAC arbors occupy the same territory, we flipped or rotated the image of one SAC, realigned cell body position, and merged images. This method was inspired by the work of Wassle and Boycott on tiling of RGC dendrites49. We measured total overlapping pixels in real and flipped images, interpreting ratios of >1 (real/flipped) as indicated non-random interactions between SACs.
