Object-Displacement-Sensitive Visual Neurons Drive Freezing in Drosophila

Abstract

Highlights d Small visual objects elicit brief freezing in Drosophila, mediated by LC11 neurons d LC11 responses are inconsistent with existing models for small object detection d Pooling of size-tuned, adapting units explains selectivity for object displacement d Visualized neurochemical inputs to LC11 are consistent with this pooling model

Facilitation of neural responses to targets moving against optic flow

“…The facilitation of TSDN responses to target motion displayed on optic flow in the opposite direction (Fig. 2b) is a novel observation, and difficult to reconcile with the existing models of small target selectivity discussed above 36,39,42 . Indeed, whereas the inhibition is clearly inherited from the pre-synaptic STMDs (Fig.…”

“…This suggests that the target detection pathway receives inhibitory input from widefield motion. We assume that TSDNs receive input from STMDs 11,18 or other target tuned neurons 31,34-36 , potentially directly (dashed lines, pictograms, Fig. 5c, d).…”

“…We can investigate the potential input using the underlying target tuning mechanisms, which can be distilled down into three fundamentally different concepts. For example, visual neurons can become target tuned by receiving inhibitory feedback from the widefield system (39–41), or by using center-surround antagonism together with rapid adaptation (38, 42). Alternatively, they can use an elementary STMD model, which is tuned to the unique spatio-temporal profile of a moving target, with a dark contrast change (OFF) from the leading edge followed by a bright contrast change (ON) by the trailing edge.…”

“…Indeed, as LC11 neurons are clearly size-tuned, they would physiologically classify as STMDs 47 , and might be the Drosophila correlates of the columnar small-field STMDs described in Eristalis 18 . LC11 neurons are especially interesting as they are clearly involved in behavioral responses to small objects 36 . A model based on LC11 physiology generates small object selectivity using a combination of center-surround antagonism and rapid adaptation 36 .…”

“…LC11 neurons are especially interesting as they are clearly involved in behavioral responses to small objects 36 . A model based on LC11 physiology generates small object selectivity using a combination of center-surround antagonism and rapid adaptation 36 . Indeed, LC11 neurons are strongly inhibited by background motion, and this inhibition is believed to take place upstream of LC11 35 , i.e.…”