Attentional modulation of neural responses to action observation: Implications for models of the human ‘mirror’ system

Abstract

Mechanisms underlying human action recognition are mediated by a network of cortical areas located within the premotor cortex, inferior parietal lobe and superior temporal sulcus. Current models suggest that activity within these regions arises relatively automatically during passive observation of meaningful actions, without the need for top-down control. Here we used functional magnetic resonance imaging to determine whether cortical activity associated with action observation is modulated by the strategic allocation of selective attention. Normal observers viewed brief movie clips of reach-to-grasp actions while performing a visual discrimination task at the fovea. The attentional demands of the central task were varied systematically to yield ‘low’ and ‘high’ load conditions, and the efficacy of these manipulations was verified behaviourally prior to scanning. Prior to the experimental runs, localiser scans were acquired to define functional areas involved in action observation. These areas were then used as regions-of-interest in subsequent analyses of the effects of the attentional task on neural responses to action observation. Our results suggest that cortical areas involved in action observation are significantly modulated by attentional load. Thus, although the areas that encode meaningful actions can be engaged relatively automatically, these regions are also influenced by the strategic allocation of selective attention. Our findings have important implications for recent attempts to link the human action-observation system to response properties of ‘mirror neurons’ in monkeys.