Fig. 1.

Manipulating spectral sensitivity of the motion pathway to elucidate circuit computations. (A)Schematic offly photo-receptors innervating motion and color pathways. A light point is sampled by six outer photoreceptors (R1–R6) in neighboring ommatidia and by central R7/R8 photoreceptors. These R1–R6s inner-vate LMCs (L1 and L2) in the first optic neuropile, lamina, whereas R7/R8 synapseinthesecondneuropile, medulla. Gap junctions link R7/R8 to R6 just before R1–R6 are brought together (superpositioned) for synaptic transmission (28). (B) In UV flies, UV-sensitive Rh3-opsin is expressed in R1–R6s, which contain nonfunctional Rh1-opsin (ninaE⁸). This circumvents the spectral overlap between motion andR8pathways.(C)Spectral sensitivity of light-induced currents (inset) in dissociated R1–R6s of UV flies, diminishing <1/100,000 at ≥480 nm (mean ± SD; four photoreceptors). (Inset) Example responses to 2-ms flashes (arrows) or 50- or 500-ms stimuli (bars). (D) Although single-photon responses (bumps) can be larger than those of WT (Canton-S) and impulse responses last slightly longer, their responses are very similar to their WT counterparts, indicating normal-like phototransduction (fig. S4, A and B) (35). (E) Photoreceptors of UV flies have normal-like ultrastructure. (F) Electroretinograms (ERGs) show comparable dynamics to those of WT flies: Preferred colors evoke large receptor components and on and off transients, indicating normal synaptic transmission from R1–R6 to LMCs (means T SD; six flies). With UV flies, one can separate the responses for green (R8s) and UV (R1–R7s).