Abstract
For many aftereffects, adapting one eye while covering the other eye leads to an aftereffect in the covered eye. This is referred to as interocular transfer (IOT). IOT is seen with the tilt aftereffect, the motion aftereffect and the contrast threshold elevation aftereffect. The amount of IOT is often viewed as an indicator of the availability of binocularly-driven cells mediating the aftereffect. For most aftereffects, IOT is not 100%, an indicator of the presence of monocularly-driven cells. The present study assessed the amount of IOT for the Eye-direction Aftereffect (EDAE). While occluding one eye, observers viewed an adapting stimulus of an image of a face looking in one direction for 20 s, followed by a test stimulus of the same face looking slightly off-center. On half the trials, the uncovered eye was used to measure the EDAE. On the other half, the occluder was removed from the unadapted eye to the adapted eye during the test phase. The EDAE was observed on all trials; following adaptation, the test images always appeared to be gazing at the center. The time required to dissipate the EDAE was recorded. The duration of the EDAE was, statistically, the same for both the adapted eye and the unadapted eye, indicating complete IOT. This finding favors the idea that the EDAE is mediated exclusively by binocularly-driven cells. In a second experiment, using both eyes, observers viewed the adapting stimulus for 20 s by fixating on the nose and then looking at the forehead during test. The EDAE continued to be observed under these conditions, indicating that the EDAE is not retinocentric. These results of these two experiments are consistent with previous fMRI data suggesting that the aftereffect is mediated late in the visual pathway.