The aging mirror neuron system: EEG activation during biological motion observation.

The human mirror neuron system may be an important mechanism for social cognition, such as for understanding other's actions and intentions. Healthy aging is associated with general cognitive declines and difficulties with these social cognitive abilities. However, the mirror neuron system has not yet been investigated in healthy aging. Sensorimotor mu desynchronization, composed of alpha and low beta activity, has been used as an EEG marker of the human mirror neuron system. We examined age-related differences in sensorimotor alpha and low beta activation across the pre-motor cortex, motor cortex and supplementary motor area during hand movement observation. Younger (18-35 years-old) and older adults (65+ years-old) completed a hand movement observation task. Initially, participants performed a 2-minute resting-state EEG as a reference period. Subsequently, participants watched different video clips (3s in duration) depicting either a static hand or various hand actions, such as locking a door or clicking fingers. For younger adults, we replicated previous findings of greater alpha and low beta desychronization across the sensorimotor cortex during hand movement observation compared to static hand observation. Interestingly, we found that this sensorimotor desynchronization was significantly greater for older adults compared to younger adults. Therefore, older adults activated their pre-motor cortex, motor cortex and supplementary motor area more than younger adults when they observed a hand action compared to when they observed a static hand. This study therefore suggests increased activation of the human mirror neuron system in older life.