A common network in the left cerebral hemisphere represents planning of tool use pantomimes and familiar intransitive gestures at the hand-independent level.

Evidence from neuropsychology and neuroimaging implicates parietal and frontal areas of the left cerebral hemisphere in the representation of skills involving the use of tools and other artifacts. On the basis of neuropsychological data, it has been claimed that 1) independent mechanisms within the left hemisphere may support the representation of these skills (transitive actions) versus meaningful gestures that do not involve manipulating objects (intransitive actions), and 2) both cerebral hemispheres may participate in the representation of intransitive gestures. Functional magnetic resonance imaging was used to test these hypotheses in 12 healthy adults while they planned and executed tool use pantomimes or intransitive gestures with their dominant right (Exp. 1) or nondominant left (Exp. 2) hands. Even when linguistic processing demands were controlled, planning either type of action was associated with asymmetrical increases in the same regions of left parietal (the intraparietal sulcus, supramarginal gyrus, and caudal superior parietal lobule) and dorsal premotor cortices. Effects were greater for tool use pantomimes, but only when the right hand was involved. Neither group nor individual analyses revealed evidence for greater bilateral activity during intransitive gesture planning. In summary, at the hand-independent level, transitive and intransitive actions are represented in a common, left-lateralized praxis network.