Abstract
In the adult brain, passive looking at tools preferentially activates the medial fusiform gyrus and regions in the dorsal “grasping-circuit”. It is surprising that a purely perceptual task that involves no explicit action activates dorsal visuo-motor regions. This has sparked a debate about whether the dorsal preference for tools reflects (1) a functional link between objects and action representations resulting from experience or (2) automatic processing of affordances (object features that afford for action). Investigating how the tool network develops can help to resolve this debate. We present data of an fMRI study in which adults and 6 to 10-year old children performed a passive viewing task with colour photographs of familiar tools and animals. Regions that responded more to tools than animals were the ventral medial fusiform gyrus, and the dorsal areas V3/dLOC, VIP, LIP, AIP and inferior frontal gyrus. Children and adults showed a similar pattern of cortical regions with a tool preference. A whole-brain group comparison indeed showed that there was no difference across age. Even young children thus activate areas that are part of the dorsal grasping circuit when they passively look at tools. In addition, a behavioural study with the same participants showed that affordances of graspable objects automatically influence actions in an adult-like manner from 6 years onwards. We thus report developmental consistency of the link between tools and actions from early childhood onwards, both in cortical organization and behaviour. These results are consistent with two possible developmental paths: (1) in contrast to the face-network, that keeps on developing until at least 10 years of age, experience before the 6th year of life is sufficient for the tool-network to stabilize into an adult-like organization, or (2) that automatic processing of affordances is present at birth. Future directions will be discussed.
European Commission Early Stage Career Marie Curie Fellowship fMEST-CT-2005-020725.