Hemispheric processing of categorical and coordinate spatial relations in the absence of low spatial frequencies.

Right-handed participants performed the categorical and coordinate spatial relation judgments on stimuli presented to either the left visual field - right hemisphere (LVF-RH) or the right visual field - left hemisphere (RVF-LH). The stimulus patterns were formulated either by bright dots or contrast-balanced dots. When the stimuli were bright, an RVF-LH advantage was observed for the categorical task, whereas an LVF-RH advantage was observed for the coordinate task. When the stimuli were contrast balanced, the RVF-LH advantage was observed for the categorical task, but the LVF-RH advantage was eliminated for the coordinate task. Because the contrast-balanced dots are largely devoid by of low spatial frequency content, these results suggest that processing of low spatial frequency is responsible for the right hemisphere advantage for the coordinate spatial processing.