Optic flow based spatial vision in insects

Abstract

The optic flow, i.e., the displacement of retinal images of objects in the environment induced by self-motion, is an important source of spatial information, especially for fast-flying insects. Spatial information over a wide range of distances, from the animal's immediate surroundings over several hundred metres to kilometres, is necessary for mediating behaviours, such as landing manoeuvres, collision avoidance in spatially complex environments, learning environmental object constellations and path integration in spatial navigation. To facilitate the processing of spatial information, the complexity of the optic flow is often reduced by active vision strategies. These result in translations and rotations being largely separated by a saccadic flight and gaze mode. Only the translational components of the optic flow contain spatial information. In the first step of optic flow processing, an array of local motion detectors provides a retinotopic spatial proximity map of the environment. This local motion information is then processed in parallel neural pathways in a task-specific manner and used to control the different components of spatial behaviour. A particular challenge here is that the distance information extracted from the optic flow does not represent the distances unambiguously, but these are scaled by the animal’s speed of locomotion. Possible ways of coping with this ambiguity are discussed.

Unraveling the neural basis of spatial orientation in arthropods

“…The importance of optic flow information for proper spatial orientation, especially in fast flying insects, is thoroughly reviewed by Martin Egelhaaf (Egelhaaf 2023 ). The author illustrates the crucial role of optic flow signaling for collision avoidance, during landing, in landscape learning, when negotiating gaps, and in distance estimation during path integration.…”

The potential underlying mechanisms during learning flights

“… 2008 ), allow insects to maneuver around obstacles and navigate through complex environments. These strategies rely on the insect’s perception of its immediate surroundings, such as visual cues that inform the insect of the distance and direction of nearby objects (Egelhaaf 2023 ). By using local control strategies, insects can stay on course, even in the presence of obstacles, and this might be sufficient for an insect new to their environment to navigate (Fig.…”

“… 2010 ; Doussot et al. 2020 ; Egelhaaf 2023 ), learned during previous journeys, allows the insect to follow a previously defined path. This route may be combined with a second guidance strategy: path integration.…”

Analysis of collision avoidance in honeybee flight

“…Honeybees have been shown to estimate the distances to nearby objects by using the motion of images in their retina, known as optic flow [1]. The ability to perceive range from optic flow is also manifest in a 'centring response' which enables bees to fly safely in narrow tunnels, by balancing the optic flow in the two eyes to maintain equidistance to the two walls [2][3][4]. A more detailed review of the perception of the world in three dimensions by honeybees, and the role of optic flow in the control of flight speed, landing and visual odometry can be found in [5].…”