Measuring mimicry: general corticospinal facilitation during observation of naturalistic behaviour

• Published in: The European journal of neuroscience 2017-07, Vol.46 (2), p.1828-1836
• Main Authors: Schaik, J. E., Sacheli, L. M., Bekkering, H., Toni, I., Aglioti, S. M.
• Format: Article
• Language: English
• Subjects: Adult; Arousal; Arousal - physiology; Behavior; Bouncing; Cognition; Electromyography; Evoked potentials; Evoked Potentials, Motor - physiology; Feet; Female; Foot; Hand - physiology; Humans; Imitative Behavior - physiology; Leg; Leg - physiology; Magnetic fields; Mimicry; Motion Perception - physiology; Motor Activity - physiology; Motor Cortex - physiology; Motor evoked potentials; Motor task performance; Muscle, Skeletal - physiology; Pyramidal tracts; Pyramidal Tracts - physiology; Rubbing; sensorimotor arousal; Sensorimotor system; Social interactions; Spatial discrimination; Stimulation; Transcranial Magnetic Stimulation; Young Adult
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/ejn.13618

Mimicry of others' postures and behaviours forms an implicit yet indispensable component of social interactions. However, whereas numerous behavioural studies have investigated the occurrence of mimicry and its social sensitivity, the underlying neurocognitive mechanisms remain elusive. In this study, single‐pulse transcranial magnetic stimulation was used to measure corticospinal facilitation during a naturalistic behaviour observation task adapted from the behavioural mimicry literature. Motor evoked potentials (MEPs) in participants' right hands were measured as they observed stimulus videos of a confederate describing photographs. MEPs were recorded while confederates were and were not carrying out hand and leg behaviours that also differed in spatial extent (i.e. large behaviours: face rubbing and leg crossing; small behaviours: finger tapping and foot bouncing). Importantly, the cover task instructions did not refer to the behaviours but instead required participants to focus on the confederates' photograph descriptions in order to later perform a recognition test. A general arousal effect was found, with higher MEPs during stimulus video observation than during a fixation‐cross baseline, regardless of whether or not the confederate was carrying out a behaviour at the time of the pulse. When controlling for this general arousal effect, results showed that MEPs during observation of the larger two behaviours were significantly higher than the smaller two behaviours, irrespective of effector. Thus, using a controlled yet naturalistic paradigm, this study suggests that general sensorimotor arousal during social interactions could play a role in implicit behavioural mimicry. Corticospinal facilitation was measured during a naturalistic interaction adapted from the behavioral mimicry literature. Motor evoked potentials during observation of confederates – both while the confederates were and were not performing behaviours – were higher than during baseline. Moreover, observation of large behaviours led to increased MEPs, regardless of somatotopy. This socially enhanced corticospinal facilitation may contribute to the production of behavioral mimicry.