Fig. 1.

Simultaneous neuronal and behavioral recordings. (A) Schematic of the setup for whole-cell patch-clamp recordings during flight. (B) Maximal intensity projection of the Gal4 line R27B03 crossed to UAS-eGFP showing the dendrites of three labeled HS cells of one lobula plate (approximately 30 µm in depth) in green. Neuropil staining shown in purple. (Scale bar: 50 µm.) (C) Example traces obtained from one fly. Periods of closed-loop stripe fixation are interspersed with 3 s of open-loop stimulus presentation (shaded gray areas), when a square wave pattern drifts horizontally in the cell’s preferred direction (PD) (here at 0.5 Hz temporal frequency). The traces indicate the optomotor behavior measured as difference between wing stroke amplitudes (L-R), the membrane potential (V) of an HS cell recorded simultaneously, and the response of the same HS cell to a similar stimulus during quiescence. HS cells depolarize in response to PD motion and hyperpolarize in response to null direction (ND) motion (Fig. S1). The motor output shows a similar directional dependence. Rightward stimulus motion elicits increases in L-R, corresponding to a right turn. During the closed-loop portion of the flight trials, the cells responded robustly to the horizontal motion of the stripe. Flies occasionally perform fast turns in the opposite direction of stimulus motion. These internally generated turns coincide with brief changes in the membrane potential of HS cells (purple arrowheads). (D) Mean and SEM (gray envelopes) of behavioral (L-R, green) and neuronal responses during flight (blue) and quiescence (black) of 11 flies for temporal frequencies of 2 and 7 Hz. Light gray areas indicate time of stimulus motion. (E) Mean and SEM of steady-state HS cell responses during quiescence (black) and flight (blue) and of behavioral responses (green), calculated during the second second of open-loop stimulus presentation. ND responses (Fig. S1) were subtracted from PD responses.