DIFFERENT NEURAL SYSTEMS FOR THE RECOGNITION OF ANIMALS AND MAN-MADE TOOLS

USING positron emission tomography, we mapped brain activity in normal volunteers during the recognition of visual stimuli representing livi ng (animals) and nonliving (artefacts) entities. The subjects had to d ecide whether pairs of visual stimuli were different representations o f the same object, or different objects. Animal recognition was associ ated with activations in the inferior temporo-occipital areas, bilater ally, whereas artefact recognition engaged a predominantly left hemisp heric network, involving the left dorsolateral frontal cortex. These f indings, which concur with clinical observations in neurological patie nts, provide in vivo evidence for a fractionation of the neural substr ates of semantic knowledge in man.