Extended Data Fig. 4: LNO1 and SpsP cells have [Ca²⁺] responses that are strongly tuned to the fly’s egocentric translation direction–in both walking and flying flies–with responses suggesting that these cells provide sign-inverting input to PFN_v and PFN_d cells, respectively.

Connectivity data and cell-type names are based on those in neuPrint²⁰, hemibrain:v1.1. a, LNO1 neurons are a class of cells (two total neurons per side, four per brain) that receive extensive synaptic input outside the central complex and provide extensive synaptic input to PFN_v cells in the noduli, with each PFN_v cell on average receive 131 synapses from LNO1s²⁰. b, Mean GCaMP signals in PFN_v and LNO1 cells in the nodulus as a function of the simulated traveling direction of the fly (via open-loop optic flow). Dotted rectangle indicates a repeated-data column, in this panel and throughout. c, Single-fly (colored circles) and population means ± s.e.m. (black bars) of the average signal in the final 2.5 s of the optic flow epoch. Sinusoidal fits shown in this panel (Methods), and throughout. d, Each SpsP cell (two total neurons per side, four per brain) receives extensive synaptic input outside the central complex and provides extensive synaptic input to PFN_d cells on one side of the protocerebral bridge, with each PFN_d cell on average receive 56 synapses from SpsP cells²⁰. e, Same as panel b, but mean GCaMP signals in PFN_d and SpsP cells in the bridge as a function of the simulated traveling direction of the fly (via open-loop optic flow). A closed-loop bright dot was not present on the LED display when collecting the PFN_d data. f, Same as panel c, but averaging the bridge signal in panel e. g, Same as panel b, but analyzing the PFN_d signal in the noduli. A closed-loop bright dot was not present on the LED display. h, Same as panel c, but averaging the nodulus signal in panel g. i, The optic-flow-simulated egocentric traveling angle at which the activity of each cell type is strongest is depicted with a line at the associated angle. Note that the left-vs-right angular differences measured in the noduli are smaller, and closer to 90°, than the left-vs-right angular differences measured in the bridge. This difference might be a purposeful shift in optic-flow tuning related to the use of orthogonal and non-orthogonal PFN axes under different behavioral contexts (see Supplementary Text) and/or originate from differences in how SpsP cells in the bridge and LNO1 cells in the noduli balance optic-flow with proprioceptive/efference-copy inputs to generate their signals. j, Data collected from tethered flies walking on a floating ball in complete darkness are shown in this panel and all subsequent panels in this figure. Mean PFN_v GCaMP signals in the bridge as a function of the fly’s forward speed. k, Right-minus-left PFN_v GCaMP signals in the bridge as a function of the fly’s sideslip speed. l–m, Same as panel j and k, but analyzing LNO1 signals in the nodulus. n, o, Same as panel j and k, but analyzing PFN_d signals in the bridge. p–q, Same as panel j, k, but analyzing SpsP signals in the bridge. In panel b, e, g, j–q, thin lines represent single-fly means and thick lines represent population means. Note that PFN_v and LNO1 cells have sign-inverted responses, and that PFN_d and SpsP cells have sign-inverted responses. The response signs to optic-flow simulating the fly’s body translating forward and leftward (rightward) in flight are the same as the signs of responses to the fly walking forward and side-slipping leftward (rightward) when walking. Thus, these data are consistent with all these neurons being sensitive to the fly’s egocentric translation direction, as assessed via optic flow (dominantly) in flight, and via proprioception or efference-copy (dominantly) in walking.