Appendix 8—figure 5. Fast rhabdomere movements are predicted to improve the resolvability of fast front-to-back moving objects the most.

(A) Two bright dots, 6.8^o apart, cross a photoreceptor’s receptive field (RF; ∆ρ_start = 8.1^o) either in back-to-front (red, left) or front-to-back (blue, middle) at 409 ^o/s (i). (B) The new photoreceptor model translated the light-induced back-to-front rhabdomere motion into concurrent RF narrowing (∆ρ_end = 4.0^o) and front-to-back movement (as reversed by the ommatidium lens). (C) Consequently, the light input from the dots was transformed into two intensity spikes. These spikes were further apart in time for the front-to-back moving dots and for the opposing stimuli. (D) The two peaks in in the corresponding model-predicted R1-R6 output (blue) for front-to-back moving dots (highlighted by arrows) indicated that the dots were neurally detectable. In contrast, the predicted R1-R6 output for back-to-front moving dots (red) failed to separate these two point-objects at 19°C. (E) An example of intracellular recordings from one R1-R6 photoreceptor to the same two stimuli at 25°C. This cell’s voltage responses also resolved the front-to-back moving dots better than their back-to-front moving counterparts. These and other comparable simulations and recordings suggest that microsaccadic rhabdomere movements improve the neural resolution (and representation) of fast moving visual objects.