Motion aftereffect transfer in the monofixation syndrome.

If one adapts to a moving repetitive stimulus of stripes that is suddenly stopped, the stripes will appear to move backward. This apparent backward motion is the motion aftereffect (MAE), and its duration is a measure of its magnitude. If one eye adapts to the moving stimulus and the other eye experiences the aftereffect to the stationary stimulus, the aftereffect has been transferred from one eye to the other and is termed the interocular transfer of the MAE. Experimental evidence indicates that the degree of MAE transfer correlates with clinical binocularity. This study compares the MAE transfer in six subjects with the monofixation syndrome to five normal subjects. The stimuli used are sinusoidal stripes generated on two cathode-ray tubes, subtending either 8 degrees or 2 degrees of visual angle with a periodicity of either 0.5 or 3 cycles/degree presented haploscopically. Subjects with the monofixation syndrome differed significantly from normal subjects in the amount of MAE transferred, implying a lack of central neuronal connections in addition to those mediating conscious central fusion in clinical sensory testing.