Object Recognition in the Cerebral Hemispheres as Revealed by Visual Field Experiments

Abstract

Visual object recognition contains several stages of information processing carried out along the ventral visual pathway. Brain imaging and behavioural studies have suggested hemispheric asymmetries in object recognition, but the results do not provide a coherent view about the direction of the asymmetries or about the processing stage at which the asymmetries emerge. In order to clarify the contribution of the hemispheres to object recognition, two visual field experiments using normal participants were conducted. Experiment 1 used five different decision-making tasks to study processing at different stages of object recognition. The results showed that familiar objects were recognised faster when presented to the left visual field (LVF) than to the right visual field (RVF) in tasks requiring decisions between familiar objects vs scrambled objects or between familiar objects vs coherent novel objects, suggesting that the right hemisphere is superior in matching visual stimuli to stored representations. Experiment 2 replicated the LVF advantage in object decisions with the novel objects from Experiment 1 that had an unfamiliar overall shape but basic features similar to those of familiar objects. In addition, a RVF advantage emerged with chimeric objects composed by changing parts of familiar objects. The results suggest that the right hemisphere is superior at accessing the overall shape of objects from memory whereas the left hemisphere is superior at analysing whether the parts of objects match to memory representations.