HEMISPHERIC-DIFFERENCES IN THE INTERFERENCE AMONG COMPONENTS OF COMPOUND GRATINGS

The relationship between local/global and high/low spatial-frequency p rocessing in hemispheric asymmetries was explored. Subjects were requi red to judge the orientation of a high- or low-spatial-frequency compo nent of a compound grating presented in the left visual field (LVF) or right visual field (RVF). In Experiment 1, attention was focused on o ne or the other component. A signal detection analysis indicated that sensitivity (d') to the high-spatial-frequency target was reduced more by the presence of the low-spatial-frequency component when both were presented in the LVF rather than in the RVF. In Experiment 2, subject s determined whether a target orientation was present, independent of spatial frequency at only a single level (i.e., at the high- or low-sp atial-frequency level), as opposed to both or neither level. An RVF/LH (left hemisphere) advantage was found when the decision was based on the orientation of the high-frequency component. The asymmetrical infl uence of visual field of presentation and spatial frequency upon sensi tivity is discussed in terms of hemispheric differences in the magnitu de of inhibition between spatial-frequency channels and in the role of transient channel activity to capture and direct higher order attenti onal processes.