Figure 3.

Brightness increment (L1: ON-edge) and decrement (L2: OFF-edge) detecting pathways. Information on moving ON- and OFF-edges is mediated by anatomically distinct pathways that originate with the ME terminals of two LA cell types, L1 and L2. In the ME, both provide input to relay neurons that are either unicolumnar (L1: Mi1; L2: Tm1/2: black) or multi-columnar (L1: Tm3; L2: Tm4: orange, note wider dendrites). Both provide input in turn to neurons T4 and T5 (blue), that integrate information from both the uni- and multicolumnar ME relay neurons and that project in turn to the LOP. T4 and T5 have postsynaptic dendrites in single layers of their respective neuropil (pink): strata M10 in the ME and Lo1 in the LO. Both also receive minority inputs from additional pathways that originate with a third LA cell type L3 (T4: Mi9; T5: Tm9; green). (A) ON-edge (L1 + L3 to T4) pathway. The proximal axon of Tm3, which projects from the ME to Lo4 of the LO, is omitted (dashed line). (B) OFF-edge (L2 + L3 to T5) pathway. The proximal axon of Tm4, which projects to deeper strata of the LO, is likewise omitted (dashed line).