Abstract
Recently we found that both the strength and dynamics of contrast adaptation differ between the fovea and near periphery when adapting and testing at the same orientation. In the present study we compared adaptation at the two loci when the adapt and test orientations were orthogonal. Participants adapted to horizontal or vertical Gabor patches (90% contrast, 1.5 cycle/degree, diameter of 5°, counterphase flickering at 5Hz) viewed centrally or in the periphery (10 degree eccentricity). Contrast thresholds were tracked using a yes/no detection task before, during, and after a 5 min adaptation block. In the fovea, cross-orientation aftereffects were only exhibited after adapting to vertical Gabor patches, showing an orientation asymmetry. Specifically, vertical adaptors produced larger sensitivity losses on horizontal tests than vice versa, despite no consistent differences in threshold changes at each adapting orientation. This asymmetry may be related to other evidence for anisotropies in orientation coding such as the “horizontal effect” (Essock et al. 2003), and to differences in the cross-axis effects in other domains such as luminance vs. chromatic contrast (Webster and Mollon, 1994). However, these cross-orientation asymmetries were much less evident in the visual periphery. Our results suggest that the effects of contrast adaptation on the orthogonal orientation is both orientation and eccentricity dependent, and point to further differences either in the properties of adaptation or the adapted mechanisms in the fovea and periphery. EY023268 to Fang Jiang, EY10834 to Michael A. Webster
Acknowledgement: EY023268 to Fang Jiang, EY10834 to Michael A. Webster