Flies see second-order motion

Flies see second-order motion Letter

Theobald, JC, Duistermars, BJ, Ringach, DL et al. (2008). Flies see second-order motion . CURRENT BIOLOGY, 18(11), 10.1016/j.cub.2008.03.050

Motion detection is nearly ubiquitous among visual animals. Simple 'first-order' motion in an image is defined by spatiotemporal correlations in luminance, and is useful for tasks such as identifying a bright butterfly crawling on a tree. Humans additionally perceive 'second-order' motion [1], defined by spatiotemporal correlations in higher-order image statistics, such as local contrast or texture. Detecting second-order motion is useful, for example, in identifying a butterfly in flight, because fluttering wings produce a flickering brightness with weak luminance correlations. Second-order motion detection in humans involves sophisticated cortical processing [2]; however, these signals are also extracted by lower vertebrates such as fish [3], suggesting this is not a recent specialization within higher vertebrates. Motivated by this idea, we tested flies, and found their steering reflexes during flight robustly track second-order motion, even in the presence of conflicting first-order motion cues. Second-order motion processing, known in primates, fish, and now invertebrates, reveals convergent evolution of a specific neural computation. © 2008 Elsevier Ltd. All rights reserved.