Evangelista C.,University of Queensland |
Evangelista C.,Australian Research Council Center for Excellence in Vision Science |
Kraft P.,University of Queensland |
Kraft P.,Australian Research Council Center for Excellence in Vision Science |
And 8 more authors.
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2014
Although it is widely accepted that honeybees use the polarized-light pattern of the sky as a compass for navigation, there is little direct evidence that this information is actually sensed during flight. Here, we ask whether flying bees can obtain compass cues derived purely from polarized light, and communicate this information to their nest-mates through the 'waggle dance'. Bees, from an observation hive with vertically oriented honeycombs, were trained to fly to a food source at the end of a tunnel, which provided overhead illumination that was polarized either parallel to the axis of the tunnel, or perpendicular to it. When the illumination was transversely polarized, bees danced in a predominantly vertical direction with waggles occurring equally frequently in the upward or the downward direction. They were thus using the polarized-light information to signal the two possible directions in which they could have flown in natural outdoor flight: either directly towards the sun, or directly away from it. When the illumination was axially polarized, the bees danced in a predominantly horizontal direction with waggles directed either to the left or the right, indicating that they could have flown in an azimuthal direction that was 90° to the right or to the left of the sun, respectively. When the first half of the tunnel provided axial illumination and the second half transverse illumination, bees danced along all of the four principal diagonal directions, which represent four equally likely locations of the food source based on the polarized-light information that they had acquired during their journey. We conclude that flying bees are capable of obtaining and signalling compass information that is derived purely from polarized light. Furthermore, they deal with the directional ambiguity that is inherent in polarized light by signalling all of the possible locations of the food source in their dances, thus maximizing the chances of recruitment to it. © 2014 The Author(s) Published by the Royal Society. All rights reserved.
Mannion D.J.,University of Sydney |
Mannion D.J.,Australian Research Council Center for Excellence in Vision Science |
McDonald J.S.,University of Sydney |
Clifford C.W.G.,University of Sydney |
Clifford C.W.G.,Australian Research Council Center for Excellence in Vision Science
NeuroImage | Year: 2010
Perception of the spatial structure of the environment results from visual system processes which integrate local information to produce global percepts. Here, we investigated whether particular global spatial arrangements evoke greater responses in the human visual system, and how such anisotropies relate to those evident in the responses to the local elements that comprise the global form. We presented observers with Glass patterns; images composed of randomly positioned dot pairings (dipoles) spatially arranged to produce a percept of translational or polar global form. We used functional magnetic resonance imaging (fMRI) to infer the magnitude of neural activity within early retinotopic regions of visual cortex (V1, V2, V3, V3A/B, and hV4) while the angular arrangement of the dipoles was modulated over time to sample the range of orientations. For both translational and polar Glass patterns, V1 showed an increased response to vertical dipole orientations and all visual areas showed a bias towards dipole orientations that were radial to the point of fixation. However, areas V1, V2, V3, and hV4 also demonstrated a bias, only present for polar Glass patterns, towards dipole orientations that were tangential to the point of fixation. This enhanced response to tangential orientations within polar form indicates sensitivity to curvature or more global form characteristics as early as primary visual cortex. © 2010 Elsevier Inc.