Comparison of Activation Patterns in Mirror Neurons and the Swallowing Network During Action Observation and Execution: A Task-Based fMRI Study

Sensory stimuli undergoing sudden changes draw attention and preferentially enter our awareness. We used event-related functional magnetic-resonance imaging (fMRI) to identify brain regions responsive to changes in visual, auditory and tactile stimuli. Unimodally responsive areas included visual, auditory and somatosensory association cortex. Multimodally responsive areas comprised a right-lateralized network including the temporoparietal junction, inferior frontal gyrus, insula and left cingulate and supplementary motor areas. These results reveal a distributed, multimodal network for involuntary attention to events in the sensory environment. This network contains areas thought to underlie the P300 event-related potential and closely corresponds to the set of cortical regions damaged in patients with hemineglect syndromes.

This article argues that mirror neurons originate in sensorimotor associative learning and therefore a new approach is needed to investigate their functions. Mirror neurons were discovered about 20 years ago in the monkey brain, and there is now evidence that they are also present in the human brain. The intriguing feature of many mirror neurons is that they fire not only when the animal is performing an action, such as grasping an object using a power grip, but also when the animal passively observes a similar action performed by another agent. It is widely believed that mirror neurons are a genetic adaptation for action understanding; that they were designed by evolution to fulfill a specific socio-cognitive function. In contrast, we argue that mirror neurons are forged by domain-general processes of associative learning in the course of individual development, and, although they may have psychological functions, they do not necessarily have a specific evolutionary purpose or adaptive function. The evidence supporting this view shows that (1) mirror neurons do not consistently encode action "goals"; (2) the contingency- and context-sensitive nature of associative learning explains the full range of mirror neuron properties; (3) human infants receive enough sensorimotor experience to support associative learning of mirror neurons ("wealth of the stimulus"); and (4) mirror neurons can be changed in radical ways by sensorimotor training. The associative account implies that reliable information about the function of mirror neurons can be obtained only by research based on developmental history, system-level theory, and careful experimentation.