Adaptive mechanisms in visual motion processing and a possible link to evolution

Abstract

In daily life, people are exposed to a range of static and moving visual images, e.g. if a pedestrian aims to cross a road, s/he needs to be able to separate between static and moving objects. S/he also needs to estimate the speed of an approaching car. It is particularly important that people are able to separate their own head movements from movements in their environment. The vestibulo-ocular reflex stabilizes retinal images during head movements and suppresses oscillopsia when people move quickly (e.g. while running). In patients with bilateral vestibular failure (BVF), the function of the vestibulo-ocular reflex is lost. At low velocities, prior research has already demonstrated decreased visual motion sensitivity in these patients 1–2, which could be an adaptive process to compensate for oscillopsia. We now examine whether this decreased sensitivity holds true at the entire range of velocities, which would further confirm an adaptive process to suppress oscillopsia. We apply a motion coherence task which has the advantages that it affords a controlled setting to test at a range of velocities in both healthy volunteers and patients with BVF. With this paradigm, we will also test the additional hypothesis that faster motion is generally spotted more easily than slower motion (in both patients and healthy volunteers).