Meeting Abstract
In studying insect flight behaviors, the sufficiency of the visual system often overshadows the contributions of other sensory pathways. Illuminating the roles of non-visual pathways is complicated by the fact that insect flight requires vision. Thus the roles of other modalities cannot be isolated by suppressing vision. Here we present a novel paradigm that disentangles the behavioral contributions of multiple intact sensory pathways by means of sensory conflict, the simultaneous and independent presentation of multimodal sensory stimuli. We examine flower-tracking behavior in the hawkmoth Manduca sexta. Moths hover in front of a flower while feeding by means of a long proboscis. As the flower sways, the moth weaves side to side, maintaining a frontal position. The potential role of non-visual sensory pathways in this behavior has received little attention. But the proboscis is covered with mechanosensors and could provide sensory information. To explore this possibility, we constructed a robotic two-part fictive flower that allows independent presentation of visual and mechanosensory cues. Moths track lateral flower motion stimuli in an assay spanning both coherent motion, in which visual and mechanosensory cues are the same, and sensory conflict, in which the modalities receive different motion stimuli. Our frequency-domain system identification analysis shows that the tracking behavior is, in fact, multi-sensory and is predominantly mediated by the mechanosensory pathway. Furthermore, empirically derived models are consistent with a parallel neural computation in which visual and mechanosensory pathways sum linearly and each pathway in itself is sufficient for driving tracking behavior robustly. When multiple sensory pathways elicit strong behavioral responses, this parallel architecture furnishes robustness via redundancy.
