A previous report has suggested that PD0325901 L1 and L2 support detection of motion generated by luminance increments and decrements, respectively (Joesch et al., 2010). We found that silencing L2 neurons significantly altered fly responses to a decreasing luminance gradient but did not affect tracking of moving dark edges (ON and OFF motion stimuli in Figures 4A and S5B). Silencing L1 neurons did not affect fly response to either of these stimuli (Figures 4A and S5A), but more subtle deficits for L1 inactivation were seen in further experiments (Figure S6). Apart from L1 and L2, the phenotypic effects were much sparser

for secondary lamina output neurons and lamina-associated feedback neurons. Silencing most neuron types specifically affected fly responses to a small number of visual behaviors (bottom nine rows of Figure 4A), indicating specialized roles for these neurons. find more These behavioral phenotypes were largely consistent across different Split-GAL4 combinations (Figure S4), strongly suggesting that behavioral effects were due to Kir2.1 expression in lamina neurons

rather than off-target consequences of our genetic manipulations. This is corroborated by the fact that silencing some neuron classes, such as L5, had no measurable effect on the behaviors we tested. Likewise, some visual behaviors, such as orientation toward a lateral flickering stripe, were entirely unaffected by silencing any of the 12 neuronal types. It is possible that such behaviors are mediated in part by input from the R7 and R8 photoreceptors that bypass the lamina and terminate in the medulla. We also tested a subset of behaviors while depolarizing neurons by heat activation of dTrpA1. Surprisingly, dTrpA1 expression in the Rutecarpine primary lamina output neurons, L1 and L2, did not dramatically impair visual motion detection (Figure 4B). However, in several instances, when expressed in other neurons, dTrpA1 expression altered fly behavior in unexpected ways. For example, depolarizing T1 neurons dramatically reduced the flight steering responses to most visual stimuli tested (Figure 4B). T1

cells are a mysterious type of columnar neurons that, based on EM reconstructions, appear to be exclusively postsynaptic in both the lamina (Meinertzhagen and O’Neil, 1991 and Rivera-Alba et al., 2011) and the medulla (Takemura et al., 2008). Our data suggest that T1 neurons interact extensively with other lamina cell types, perhaps through gap junctions not resolvable by electron microscopy and that tonic depolarization of these cells is sufficient to disrupt basic visual behaviors. Overall, we observed at least one phenotype for each lamina neuron type except for the lamina tangential cell (Lat). In several cases (L5, T1, Lai), neuronal silencing had no measurable effect on the behaviors we tested (Figure 4A), while activation using dTrpA1 significantly affected behavior (Figure 4B).