Retinal factors in motion processing anomalies

The goal of the proposed research is to investigate the phenomenon of "spatial suppression", a curious paradox of visual motion sensitivity in which normal observers fail to discriminate the motion of a highly visible stimulus. This counter-intuitive psyc hophysical effect is a potential clinical test for inhibitory dysfunction in normal ageing and various psychiatric disorders, such as schizophrenia, depression and migraine. Establishing the neural basis of this psychophysical effect, and thereby validati ng its use as a clinical test is therefore of primary importance. The methodology that we will adopt in this project will combine simple psychophysical measures of visual motion sensitivity in young and older subjects, with anatomical measurements of the photoreceptor layer of the retina in those same subjects. We will use the Kongsberg Adaptive Optics Ophthalmoscope to measure photoreceptor density and regularity to establish whether there is any connection between these anatomical measures and the pheno menon of spatial suppression in visual motion perception.