Abstract
Human infants rapidly learn new skills and customs via imitation, but the neural linkages between action perception and production are not well understood. Neuroscience studies in adults suggest that a key component of imitation–identifying the corresponding body part used in the acts of self and other–has an organized neural signature. In adults, perceiving someone using a specific body part (e.g., hand vs. foot) is associated with activation of the corresponding area of the sensory and/or motor strip in the observer’s brain–a phenomenon called neural somatotopy. Here we examine whether preverbal infants also exhibit somatotopic neural responses during the observation of others’ actions. 14-month-old infants were randomly assigned to watch an adult reach towards and touch an object using either her hand or her foot. The scalp electroencephalogram (EEG) was recorded and event-related changes in the sensorimotor mu rhythm were analyzed. Mu rhythm desynchronization was greater over hand areas of sensorimotor cortex during observation of hand actions and was greater over the foot area for observation of foot actions. This provides the first evidence that infants’ observation of someone else using a particular body part activates the corresponding areas of sensorimotor cortex. We hypothesize that this somatotopic organization in the developing brain supports imitation and cultural learning. The findings connect developmental cognitive neuroscience, adult neuroscience, action representation, and behavioral imitation.
Highlights
There is burgeoning interest in the interface connecting neuroscience and social cognition [1,2,3]
Functional magnetic resonance imaging studies of adults have shown a somatotopic response to action observation in premotor and somatosensory cortex [7,8,9]
We addressed a key question about the infant brain response to action observation: Is the pattern of desynchronization of the sensorimotor mu rhythm during observation of goal-directed acts sensitive to the specific means used by the actor? Adult work reveals a somatotopic organization both of hemodynamic responses to action observation using functional magnetic resonance imaging (fMRI) [7] and of EEG mu rhythm responses to action production and motor imagery [28,31]
Summary
There is burgeoning interest in the interface connecting neuroscience and social cognition [1,2,3]. A somatotopic pattern of cortical activation has been reported for infants’ execution of limb movements and in response to direct tactile stimulation of the infant’s body [16], but no prior infant study has investigated the possibility of somatotopy during action observation alone. Such an organization of the developing brain could facilitate infants’ mapping between the acts of self and other–a mapping that is a fundamental component of imitation, interpersonal identification, and cultural learning [15,17]. For infants observing foot actions, the opposite pattern was predicted
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