Assymetrical long-range interaction reversed with adaptation to upside-down reversed optical transformation

Abstract

Long-range interaction was found to be extended and exaggerated at upper visual fields compared with lower visual fields (Tanaka et al, 2005; VSS, companion paper). Here we tested whether this asymmetry is reversed across upper and lower visual fields with prism adaptation to upside-down reversing retinal images. Experiments were carried out for 7 days. At the 1 st day before adaptation, long-range interaction was tested both at the upper and the lower visual fields (eccentricity, 3.2 deg, 2 subjects). The asymmetry between upper and lower visual field was found with upper visual field 2.2 times extended (up to 20 lambda distance) to the horizontal direction with the overall magnitude of facilitation 94% more exaggerated (2 subjects). The asymmetry reversed between upper and lower visual fields at the 4th day; the long-range interaction became 1.7 times more extended (up to 17lambda distance) and with overall facilitation 104% exaggerated at the upper visual field as compared with the lower visual field (2 subjects). This reversal lasted over the rest of adaptation period up to the 6 th day, and persisted 1.5 hours after removing the prisms. No reversal was found for control experiments without adaptation (2 subjects). This is the first psychophysical demonstration of up-down perceptual reversal with prism adaptation. The asymmetry of long-range interaction and its reversal between the upper and lower visual fields suggest anisotropy of bilateral mirror symmetrical connection (Tanaka et. al. 2003) between upper and lower visual fields.