Interocular transfer of fMRI adaptation in stereodeficient observers

Abstract

Simultaneous binocular input during a critical period after birth is necessary to maintain and develop the structure of the visual system, otherwise visual processing might be disrupted. If binocular vision is impaired during this period subjects can develop alternating fixation (ensuring normal monocular function of each eye) or amblyopia (vision in one eye is impaired). Testing the interocular transfer of figural adaptation after-effects is one way to investigate binocular integration of the visual input psychophysically. In this study, we investigated binocular integration using orientation-selective fMRI adaptation. We tested 20 normally-sighted subjects and 18 subjects with impaired binocular visual development (10 with alternating fixation and 8 with unilateral amblyopia). In all investigated cortical areas, normally-sighted subjects showed significant monocular orientation-selective adaptation that partially transferred to the non-adapted eye. Observers with impaired visual development showed monocular orientation-selective adaptation, but this adaptation did not transfer to the non-adapted eye. These results demonstrate that fMRI adaptation is a useful tool for the investigation of the neuronal mechanisms of binocular integration in the adult human brain.