Appendix 4—figure 5. Estimating a dark-adapted Drosophila R1-R6 photoreceptor’s receptive field and its half-width.
Flash response amplitudes Vn were initially normalized to V0, the maximum response elicited by an on-axis light-point. A Gaussian curve was then fitted to these normalized values, yielding an estimate of the receptive field. Half-maximum width of this Gaussian function, ∆ρ, defined the tested photoreceptor’s acceptance angle. The schematic fly eye inset clarifies how a single photoreceptor integrates light from the world spatially through its receptive field (green area), whilst being bounded by the ommatidial lens system. For a standard measurement, each tested photoreceptor’s intracellular responses to 2–5 repetitions of pseudorandom scans (as shown in Appendix 4—figure 4) were averaged.