3; Table 3). The anterior intraparietal sulcus

is a core component of the putative human mirror neuron system (Grafton & Hamilton, 2007). It is thought to contribute to the understanding of ‘immediate’ action goals, such as grasping to eat vs. to place in macaque monkeys (Fogassi et al., 2005), or taking a cookie vs. a diskette in humans (Hamilton & Grafton, 2006). In monkeys, the anterior bank of the intraparietal sulcus changes its connectivity and response patterns when the animals train to use tools (Hihara et al., 2006), enabling an integration of visual and somatosensory stimuli. This is argued to support tool use Cell Cycle inhibitor through assimilation of the tool into the monkey’s body schema (Maravita & Iriki, 2004), such that ‘tools become hands’ (Umiltàet al., 2008). However, human left anterior inferior parietal click here lobule displays a specific response to observed tool use (as opposed to unassisted manual prehension) that is absent in monkeys (Peeters et al., 2009). This suggests that hominoid anterior inferior parietal cortex may be evolutionarily derived

to play a new role in coding the distinct functional properties of hand-held tools (Johnson-Frey et al., 2005; Peeters et al., 2009; Jacobs et al., 2010; Povinelli et al., 2010). The centre of anterior inferior parietal cortex activation reported here is somewhat posterior (−50, −36, 42 vs. −52, −26, 34) to that of Peeters et al. (2009); however, extraction of the volume of interest used by Peeters et al. (coordinates from Orban, pers. comm.) confirms that the same effect of stimulus is indeed present in this region. This response to increasingly complex Paleolithic toolmaking is consistent with the hypothesis that human technological evolution was supported, at least in part, by the emergence of enhanced neural mechanisms for representing the causal properties of hand-held tools (Johnson-Frey, 2003; Wolpert, 2003; Peeters Vasopressin Receptor et al., 2009). The main effect in the prefrontal cortex was centred on the inferior frontal sulcus. In macaques, this region is heavily interconnected with the anterior

inferior parietal lobule (Pandya & Seltzer, 1982) and the parietal operculum (Preuss & Goldman-Rakic, 1989), in keeping with the co-activation observed here, and suggesting involvement in the integration of visuospatial and somatosensory information. In an fMRI study with macaques, there was activation in this area during the observation of actions (Nelissen et al., 2005). In contrast to more the posterior premotor cortex (F5c) where mirror neurons were originally recorded, the ventral prefrontal cortex also responded to abstract or context-free stimuli, including isolated hands, robotic hands and shapes (Nelissen et al., 2005), indicating representation and integration of actions at a relatively high level.