III - 97 . Dynamic motor - related input to visual interneurons in Drosophila

Active locomotion, like flight or walking, leads to an increase in the response gain of visual neurons in flies and mice. In addition to such long-term modulations in sensory processing, can motor actions influence visual processing on faster timescales in these model organisms, akin to how saccadic eye movements modulate primate vision every few hundred milliseconds? In this study, we describe a dynamic motor-related input to visual neurons in Drosophila. We glued flies to a custom platform and performed whole-cell patch clamp recordings during tethered flight from two specific classes of fourth-order visual neurons: horizontal system (HS) cells and vertical system (VS) cells. We found that in addition to their visual responses, HS cells show transient motor-related potentials during rapid left or right turns of the wings. These potentials were clear even in the absence of visual input, while flies viewed a blank screen and made spontaneous turns. The potentials appeared at the early phase of each wing turn event but did not persist during maintained turns. The amplitudes of the transient potentials were positively correlated with the magnitudes of the turns. The transient potentials were cell type specific — strongest in one HS cell, moderate in the other two, and very weak in VS neurons. We developed an algorithm to cull hundreds of individual rapid wing-turn events and motor-related potentials, and we measured their relative timing. Transient potentials were essentially synchronous with wing turns, but many individual potentials clearly initiated prior to detectable changes in wingbeat amplitude, suggesting an internal origin for the signal. In sum, we describe a cell-type-specific motor-related input to the fly visual system, which serves to modulate vision during rapid flight turns. This efference-copy-like signal in a genetic model organism provides an attractive platform to study the functions of dynamic motor signals in sensory processing.