Dynamic Glass Patterns Have Little Effect on Coherent Motion Detection Thresholds

Abstract

Dynamic Glass patterns (dGPs) are fields of coherently oriented dipoles that are updated rapidly (>5 Hz). Although they have no oriented motion energy, individual Glass patterns yield a weak percept of coherent motion, and in the case of dGPs, this effect is so prominent that subjects can confuse them for real coherent motion fields at short presentation durations (Krekelberg et al 2003, Nature 424 674–677). It has even been suggested that dGPs processing involves some of the neural circuitry used for motion processing. The detection thresholds for fields of coherently moving dots increase significantly when they are superimposed on incoherent motion noise. Similarly, detecting coherent Glass patterns is more difficult in the presence of superimposed incoherent dipoles. Here, we asked if Glass patterns and coherent motion interfere with each other at or before the site mediating their detection. We measured detection coherence thresholds for dGPs and coherent motion stimuli alone or in the presence of incoherent noise patterns (randomly oriented dipoles or moving dots). dGPs and coherent motion stimuli were affected very differently by different noise fields. Remarkably, coherent motion threholds were largely unaffected by the presence of dense, randomly oriented dipole fields while dGP thresholds were elevated by both incoherent motion and random dipoles to an equal degree. These results are consistent with our recent neuroimaging data indicating different processing networks for coherent motion and dGPs.