A Simple Vision-Based Algorithm for Decision Making in Flying Drosophila

Abstract

Animals must quickly recognize objects in their environment and act accordingly. Previous studies indicate that looming visual objects trigger avoidance reflexes in many species [1-5]; however, such reflexes operate over a close range and might not detect a threatening stimulus at a safe distance. We analyzed how fruit flies (Drosophila melanogaster) respond to simple visual stimuli both in free flight and in a tethered-flight simulator. Whereas Drosophila, like many other insects, are attracted toward long vertical objects [6-10], we found that smaller visual stimuli elicit not weak attraction but rather strong repulsion. Because aversion to small spots depends on the vertical size of a moving object, and not on looming, it can function at a much greater distance than expansion-dependent reflexes. The opposing responses to long stripes and small spots reflect a simple but effective object classification system. Attraction toward long stripes would lead flies toward vegetative perches or feeding sites, whereas repulsion from small spots would help them avoid aerial predators or collisions with other insects. The motion of flying Drosophila depends on a balance of these two systems, providing a foundation for studying the neural basis of behavioral choice in a genetic model organism.

Olfaction in vector-host interactions

“…Forward flight also requires input from mechanosensory cues, provided at least in part by the Johnston's organ (Budick et al 2007). Drosophila also orient towards vertical silhouettes, which in the flight simulator is represented by a vertical band of LEDs that are turned off; this visual stimulus presumably mimics a suitable landing or feeding site (Maimon et al 2008). In nature, such a visual stimulus directly ahead would appear to expand during approach, causing the fly to slow its progress before landing.…”

Dynamics of escaping flight initiations of Drosophila melanogaster

“…This reverse engineering feat has not been without challenges; roughly, we can classify these challenges into three major categories: 1) modeling sensors (particularly vision), [1]- [3], and actuators (unsteady effects of flapping), [4]- [6]; 2) mapping variations of wing and body kinematics to the production of aerodynamic forces and moments, [7]- [11]; and 3) understanding mechano-sensorial connections that trigger such kinematic variations, [12]- [20]. Further difficulties are also faced at a higher stratus of insect flight control, in particular, recognizing patterns of behavior and understanding decision-making processes [21]. Figure 1 illustrates the authors' view of the macroscopic components of insect flight control, and the general approaches followed for its study, as presented in literature [1]- [20].…”

Analysing visual behaviour in Drosophila Dscam2 mutants using optimised optomotor and operant control assays

“…Flies have been found to orientate towards and fixate on dark bars in both walking (Bülthoff, 1980) and flying assays (Heisenberg, 1984, Heisenberg & Wolf, 1979, Maimon et al, 2008, Wolf & Heisenberg, 1980. Similar to the fixation observed in Buridan's paradigm, this is a very robust response under optimal conditions, with sustained object fixation measured in a nearly continuous 32-hour period (Götz, 1987).…”

“…The introduction of random bar displacements in this assay improves fixation behaviour, likely because the displacement triggers the attention of the fly (Heisenberg & Wolf, 1979). The strength of the fixation and anti-fixation response has been found to be dependent on bar length (Maimon et al, 2008). When the bar length becomes smaller, anti-fixation behaviour will become the dominant choice (Maimon et al, 2008).…”

“…The decision to fixate or anti-fixate to an object such as a bar has been shown to be dependent on bar length (Maimon et al, 2008) and the assay. For example, a light bar on a dark background elicits an anti-fixation response in some assays (Bülthoff, 1980, Collett & Land, 1975 but not in others (Maimon et al, 2008, Reiser & Dickinson, 2008. These behaviours also provide a means for studying attention-like mechanisms in flies.…”