Meeting Abstract

85.6  Monday, Jan. 6 11:30  Flies use visual elevation to modulate different responses to translational and rotational displacements THEOBALD, J.C.*; MAZO, C.; Florida International University, Miami; Florida International University, Miami theobald@fiu.edu

When a flying insect deviate from its intended path, it uses the optic flow field help steer back. Unexpected rotational optic flow indicates an unintended change in heading, while unexpected translational optic flow indicates an unintended change in position. Any object that contrasts with its background can contribute to rotational optic flow, but due to the geometry of parallax only relatively near objects contribute to translational optic flow. Far away features, even the high contrast sun and moon, appear fixed while position deviates, offering no information to correct translational perturbations. For many insects in nature, the nearest objects are below, leading to the prediction that insects might respond more strongly to translational optic flow that occurs beneath them. In these experiments rigidly tethered fruit flies steered in response to computer generated flow fields. When correcting for unintended rotations, flies weight the motion in their upper and lower visual fields about equally. However, when correcting for unintended translations, flies weight the motion in the lower visual fields more strongly. These results are consistent with the interpretation that flow fields are filtered to concentrate on directions where flies likely get the strongest signals during natural flight conditions.