Meeting Abstract
Like other visually active animals, flies generate rapid saccadic movements to control and stabilize their gaze. Saccades enable evasive maneuvers to a threat as well as orientation maneuvers to fixate upon a goal. How rapid body saccades are controlled, and how their valence is determined, remains elusive. We studied visually-guided saccades in rigidly- and magnetically-tethered Drosophila, thereby enabling precise control of a visual stimulus in open- and closed-loop conditions, respectively. We presented a moving bar in open-loop and discovered that changing the vertical size caused a switch in saccade direction relative to the stimulus. Correspondingly, in closed-loop, a moving long vertical bar elicited sustained bouts of fixation saccades towards the bar, whereas a short object elicited aversive saccades away from the object. Bar fixation saccades were narrowly tuned to specific dynamical properties of bar motion. To study the neural circuitry that implements saccade control algorithms, we used two-photon excitation imaging to screen the major motion vision pathways within the fly brain for activity that matches the stimulus dynamics that trigger saccades. Our results correlate the activity of a remarkably small subset of previously uncharacterized cells within the lobula with spatial and temporal dynamics required for visual saccade control, and indicate that fixation and aversive saccades are mediated by parallel visual circuits. We show that simple behavioral algorithms and parallel neural circuits underlie visually-guided saccade control in Drosophila.
