Figure 5. Basket cell axon arbor wiring compared with minimum-length tree.

(A) Example putative inhibitory large basket cell axon arbor (coronal view) showing bouton locations (upper), its Minimum Spanning Tree (MST) graph (middle), and overlay of axon arbor and graph (lower) demonstrating different wiring patterns used to connect same bouton set as shown by dotted circles (white). (Key: axon  =  grey lines, graph  =  red lines, boutons  =  yellow dots; anatomical axes: A, anterior; D, dorsal; L, lateral; P, posterior). (B) Example of the shortest path from axon origin (root vertex) of this neuron to a selected bouton (upper, see region of interest) for the biological arbor (middle) was initially directed away from the bouton but virtually direct thereafter (0.87 mm path length) yet for the length-minimized tree (lower) the course was tortuous (2.28 mm path length), including two trajectory reversals (see blue asterisk), because the artificial arbor lacked wire present in axon arbor (dotted blue lines). Arrows show direction of flow from axon origin to bouton. (Key: shortest path  =  thick black lines, unvisited arbor wiring  =  grey lines, axon wiring absent in graph  =  dotted blue lines.).