Transitive and intransitive gesture execution and observation compared to resting state: the hemodynamic measures (fNIRS).

The present study explored cortical correlates of gesture execution and observation in peripersonal space, using functional near-infrared spectroscopy (fNIRS). Moreover, a direct comparison was realized between resting state condition and execution/observation. Meaningful gestures produced in the presence (transitive action) or in the absence (intransitive action) of the object were considered in a real context (situated representation of gestures). Subjects were required to execute or observe transitive versus intransitive gestures during fNIRS registration. Gesture execution was related to higher brain activity (increased oxygenated hemoglobin levels) with respect to observation in motor areas (premotor cortex, PMC; supplementary motor cortex, SM1). In contrast, the posterior parietal cortex was similarly activated in case of both execution and observation task. Moreover, both tasks showed increased brain activity within these areas compared to resting state. Finally, it was shown that action execution and observation of transitive gestures was supported by similar parietal posterior areas. These findings support the hypothesis of a partial common network for observation and execution of gestures within peripersonal space, mainly in transitive condition.