Dissociation of spatial orienting beteen left and right hemisheres.
Y. Tanaka (1999) Perception (Supplement ECVP abstract) 28 pp 75.

An attentional modulation of cortical hemispheres was tested manipulating visual hemifields and responses. Target (rectangle) was presented at two different locations within the left or right visual-field. Reaction time (RT) was measured for detection of the target using left or right (1) hands or (2) feet. Subjects (N=4) were all right-handed. Location repetition revealed longer RTs in the left visual-field with the left hands (-54±8 ms, mean±SE, inhibition of return) or the left feet (-44±14 ms). Similar inhibition occurred with right hands (-34±12 ms) or feet (-24±13 ms). When target appeared in the right visual-field, RTs became shorter (facilitation) with right hands (+56±18 ms) or feet (+41±14 ms). Facilitation disappeared with left hands or feet. This is the first demonstration of the foot response showing common tendencies of detection to the hand response. The results suggest a functional dissociation between two cortical hemispheres; an inhibitory orienting process generated in the right cortex, whereas a facilitatatory process originated from the left cortex, each dominating left/right part of the entire body. The facilitation is analogous to the one observed in fine positional discrimination (Tanaka and Shimojo, 1996; Vis. Res. 36, 2125) or letter identification (Terry et al. 1994; Percept. Psychophys. 55, 279), suggesting a location scrutinizing process in the left cortex.