The authors examined if previously reported anatomical asymmetries between the upper (uVF) and lower visual fields (lVF) influence the preparation and control of visually and memory-guided reaching movements. To manipulate visual field, participants maintained their visual gaze on a cue position presented above or below the location of a target object, thus resulting in reaches completed in respective uVF and lVF of peripersonal. In Experiment 1, participants performed reaches to four targets with indices of difficulty ranging from 3.1 to 5.1 bits under five visualmemory conditions: full vision and memory-guided conditions entailing 0, 2, 5, and 10 s of delay. In Experiment 2, participants reached to the vertex of Müller-Lyer figures in 3 visual-memory conditions: full vision, and memory-guided conditions entailing 0, and 2 s of delay. In accord with duplex theories of vision (e.g., Milner & Goodale, 1992), it was hypothesized that the introduction of a visual delay and/or the introduction of context-dependent illusory structure would differentially bias the efficiency and effectiveness of uVF and lVF reaches. Although data displayed mixed supported for the existence of an lVF advantage for movement execution, neither the introduction of delay nor contextual illusions succeeded in differentiating visual fields. Thus, performance advantages for movements made in the lower visual field do not appear associated with preferential connections to parietal (i.e., dorsal-action) and temporal (i.e., ventral-perception) architectures.
Brownell is with the College of Kinesiology, University of Saskatchewan. Rolheiser is with the Dept. of Human Physiology, University of Oregon. Heath is with the School of Kinesiology, University of Western Ontario. Binsted is with the Faculty of Health and Social Development, University of British Columbia, Okanagan.