Extended Data Fig. 8: The goal-dependent scaling of PFL3 spike-rate tuning curves is not a simple consequence of the fly’s instantaneous walking dynamics.

a, Heatmap showing mean PFL3 spiking activity as a function of heading (x-axis) and forward walking velocity (y-axis). We combined our six recordings from right PFL3 neurons with our 15 recordings from left PFL3 neurons by flipping the heading-relative-to-the-cell’s-preferred-heading prior to averaging. b, Heatmap showing mean PFL3 spiking activity as a function of heading (x-axis) and turning velocity (y-axis). In this panel, we flipped the flies’ turning velocity for the right PFL3 neuron recordings so that we could combine their data with the left PFL3 recordings. c, Given that PFL3 spiking activity varies with the flies’ locomotor behaviour and because flies that perform menotaxis show different walking statistics depending on their angular orientation relative to the goal¹¹—flies walk forward faster when aligned with their goal, for example—one possibility is that the goal-dependent modulation observed in PFL3 activity is not due to a genuine goal input. To the address this possibility, we replotted the population-averaged, PFL3 spike-rate tuning curves to heading, parsed by the flies’ goal angle—as in Fig. 3f—but in this case, we only included timepoints when the fly was nominally standing still. Our criteria for the fly standing still was that the filtered forward walking velocity was below 0.5 mm/s and the fly’s turning velocity was between −5 °/s and 5 °/s. For right PFL3 neurons, the goal-heading-relative-to-the-cells’-preferred-heading values were flipped prior to averaging. Thin lines: individual cells; thick line: mean across cell. That a qualitatively similar scaling in the amplitude of PFL3 tuning curves is observed when flies are standing still, or nearly still, suggests that PFL3 goal-direction modulation is not a simple consequence of the fly’s walking dynamics, but is more likely generated by FC2 inputs, or some similar goal-input signals, which maintain a baseline activity level in standing flies (Extended Data Fig. 3q). d, Mean forward walking velocity, analyzed as described in panel c. e, Mean turning velocity, analyzed as described in panel c.

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