SUPRATHRESHOLD CONTRAST SENSITIVITY IN EXPERIMENTALLY STRABISMIC MONKEYS

Human strabismic amblyopes show deficits in spatial vision that can be revealed in a variety of visual tasks. In particular, they show a red uced sensitivity to contrast for a wide range of spatial frequencies. The ability of strabismic amblyopes to process contrast information at levels well above detection threshold is less well understood and som ewhat controversial. In the course of investigating the neural basis o f strabismic amblyopia we studied contrast processing both at and abov e detection threshold in experimentally strabismic monkeys (Macaca nem estrina). First we trained them to perform a contrast detection task a nd measured their contrast sensitivity for a wide range of spatial fre quencies. Then we trained them to discriminate between two gratings th at were identical except for their contrast. We show that these monkey s exhibit deficits in both tasks. The deficits in the contrast discrim ination task cannot be solely attributed to their deficit at threshold .