Fig. 1

The maintenance of spatial orientation and the ellipsoid body (EB) circuit in Drosophila. a A schematic of a fly head and EB (blue circle), which can be mapped to 360° of the visual field (partially represented by the black arcs). When a visual cue (the yellow bar in the visual field) is presented, the EB responds to it with localized activity, or the activity bump (yellow square in EB). b Top: When a visual cue is removed (dashed bar), the activity bump persists, representing the memory regarding the orientation of the visual cue. Bottom: When the fly changes its orientation in darkness, the activity bump shifts accordingly, indicating the ability to maintain spatial orientation in the dark¹⁰. c An activity bump, which is localized neural activity (middle) in response to a visual stimulus (top), is considered as a neural representation of working memory of the task-relevant stimulus if the bump persists after the offset of the stimulus. Theories suggest that the activity bump can be maintained by a network with local recurrent excitation and global feedback inhibition (bottom). Green circles: excitatory neurons. Red circle: inhibitor neurons. Arrows: synaptic connections. d The circuit considered in the study consists of three classes of observed neurons (PEI, PEN, and EIP) that connect the EB and protocerebral bridge (PB). EIP neurons project from the EB (both C and P rings) to the PB and form two feedback loops with the PEI and PEN neurons separately. We also consider ring neurons (black) that innervate the C-ring (R1) or P-ring. e We performed the simulated spatial orientation task under three conditions. For all three conditions, the cue was turned on at t = 0 s and remained for 1 s. In the first condition, the cue was turned off at t = 1 s. In the second condition, the cue remained on but its location (azimuthal angle) began to shift after t = 1 s. In the third condition, the cue was turned off at t = 1 s, after which the fruit fly body began to rotate horizontally