Hemispheric asymmetry in a perceptual priming task: evidence from patients with unilateral brain damage.

The present study examined the relationship between unilateral brain damage and the effect of nonverbal perceptual priming using a picture-fragment completion task. Subjects consisted of 11 left brain-damaged patients, 8 right brain-damaged patients, and 10 healthy normal controls. The mean score of normal controls was significantly higher than those of left and right brain-damaged patients. Although there were significant effects of priming in all the groups, a significant difference in amplitude of priming effects was found only between right brain-damaged patients and normal controls. The correlation between amount of fragmentation at which there was identification and priming effect was not significant. We conclude that the right hemisphere is more involved in perceptual priming of form than is the left hemisphere, and form-dependent processing in the perceptual priming task has an asymmetrical distribution in the right and left hemispheres.