Cortical activation during imitative behavior: An fMRI study

A previous behavioural study on healthy subjects and callosotomized patients showed that subjects imitated mainly in mirror mode when free to choose the imitation mode, using the right limb to copy a left limb gesture of the facing model; when asked to use the same limb as the model, patients still perform in mirror mode, but controls imitated in anatomical mode, using the right limb for imitating a right limb gesture. These data suggest that the anatomical mode of imitation recruites both hemispheres, being linked to the integrity of the corpus callosum. The present study aims at investigating with fMRI the neural correlates of imitative perspective-taking, specially the anatomical mode. Functional MRI was performed in 10 control subjects of the previously tested groups, asked to Observe or Imagine-to-Imitate-with-the-same-limb, in separete runs, intransitive gestures. Different cortical activation in the two conditions were observed: opercular part of left inferior frontal gyrus, left inferior parietal lobule, right temporo-parietal junction and bilateral parietal opercular cortices were activated in Imagine-to-Imitate condition only. Present data confirm previous behavioural observations and indicate that neural circuitry underpinning the anatomical imitation of intransitive gesture likely requires the cooperation of both hemispheres, and therefore the integrity of the corpus callosum.