The sensory and cognitive basis of three-dimensional distance estimation in a teleost fish - WCUB, ENWW

Research Summary:Animal navigation, or more specifically the problem of how animals learn, remember and use information from their spatial environment, has received increasing interest particularly over the last fifty years, with the 2014 Nobel Prize awarded for the discovery of brain cells responsible for encoding space in the hippocampus and entorhinal cortex of mammals1,2. Homing navigation, the ability to return to a goal following a foraging journey, pursuit of a mate or predator avoidance for example, is perhaps the most broadly studied form of navigation, with evidence of its widespread importance across the vertebrate and invertebrate clades. Here, we are separating it from 'true navigation', the ability to return home even after experimental displacement (birds3; turtles4). For simplicity, homing can be split into three broad strands: trail following, such as following a pheromone trail deposited on the outward journey; piloting between learned visual landmarks; and, path integration. The latter involves the animal continuously updating its distance and direction from its origin (home nest) independently of visual landmarks, such that it can follow a direct vector home regardless of the series of vectors making up the outward journey5-7. In order to path integrate, an animal needs to be able to continuously keep track of the distance and direction of its travel. The former metric will be the focus of this project; using the Mexican cavefish Astyanax fasciatus as my model system, I aim to use a simple behavioural task that has been pre-tested in a pilot study, to explore
both the sensory and cognitive basis of distance estimation in teleost fish across three-dimensional space. Unlike the directional component required for path integration, there have thus far been no empirical studies investigating the accuracy or mechanisms of distance estimation in fish. The project therefore has two core themes: (i) Can fish estimate distance, and if so with what accuracy? (ii) What sensory information do they use to estimate distance? Pelagic fish are interesting experimental subjects for the study of spatial cognition because they must navigate through volumetric space, extracting and encoding relevant sensory information from both the horizontal and vertical planes. This provides additional scope for investigating any differences between the sensory and cognitive basis of odometry across the orthogonal planes. Unlike surface bound animals, such as rats, that show anisotropic representation of space at behavioural and neural levels with lower accuracy vertical encoding, freely moving fish are perhaps more likely to show isotropic representation of space, with equal accuracy in both planes, as has recently been found in
hummingbirds8,9 and at the neural level in bats10,11, both of which also freely exploit volumetric space.

BBSRC Priority Area: This project fits into the integrative animal and plant biology theme in the Interdisciplinary Bioscience DTP