Understanding the intentions of others while watching their actions is a fundamental building block of social behavior. The neural and functional mechanisms underlying this ability are still poorly understood. To investigate these mechanisms we used functional magnetic resonance imaging. Twenty-three subjects watched three kinds of stimuli: grasping hand actions without a context, context only (scenes containing objects), and grasping hand actions performed in two different contexts. In the latter condition the context suggested the intention associated with the grasping action (either drinking or cleaning). Actions embedded in contexts, compared with the other two conditions, yielded a significant signal increase in the posterior part of the inferior frontal gyrus and the adjacent sector of the ventral premotor cortex where hand actions are represented. Thus, premotor mirror neuron areas—areas active during the execution and the observation of an action—previously thought to be involved only in action recognition are actually also involved in understanding the intentions of others. To ascribe an intention is to infer a forthcoming new goal, and this is an operation that the motor system does automatically.

Self-recognition has been demonstrated by a select number of primate species and is often used as an index of self-awareness. Whether a specialized neural mechanism for self-face recognition in humans exists remains unclear. We used event-related fMRI to investigate brain regions selectively activated by images of one's own face. Ten righthanded normal subjects viewed digital morphs between their own face and a gender-matched familiar other presented in a random sequence. Subjects were instructed to press a button with the right hand if the image looked like their own face, and another button if it looked like a familiar or scrambled face. Contrasting the trials in which images contain more bselfQ with those containing more familiar botherQ revealed signal changes in the right hemisphere (RH) including the inferior parietal lobule, inferior frontal gyrus, and inferior occipital gyrus. The opposite contrast revealed voxels with higher signal intensity for images of botherQ than for bselfQ in the medial prefrontal cortex and precuneus. Additional contrasts against baseline revealed that activity in the bselfQ minus botherQ contrasts represent signal increases compared to baseline (null events) in bselfQ trials, while activity in the botherQ minus bselfQ contrasts represent deactivations relative to baseline during bselfQ trials. Thus, a unique network involving frontoparietal structures described as part of the bmirror neuron systemQ in the RH underlies self-face recognition, while regions comprising the bdefault/resting stateQ network deactivate less for familiar others. We provide a model that reconciles these findings and previously published work to account for the modulations in these two networks previously implicated in social cognition. D 2004 Elsevier Inc. All rights reserved.

No abstract