Functional connectivity of the primary somatosensory cortex and its role during action observation

Researcher: Nikola Valchev, PhD

Thesis defense: 2014

During the observation of actions performed by other people, our brain activates a broad network of cortical areas. It is commonly believed that information is first processed by the visual system and then the “action observation” network calculates a mental simulation of the observed motor act. Ultimately this simulation helps us to extract information from the behaviours of other people, i.e. “understand” them. One area whose involvement in this network is not yet clear is the primary somatosensory cortex (SI) which is the main brain hub to process sensory stimuli. In two fMRI experiments we have shown that during action observation and also when the brain is at rest, SI communicates with brain regions that calculate mental simulations of actions. We have also shown in another behavioural experiment that after magnetically inhibiting the functioning of SI, participants are worse at estimating the weight of a box they observe while being lifted by a hand. These results suggest that while observing somebody act we simulate not only the motor act, but also the sensations involved in the action.
In one last experiment participants observed incomplete actions. Results showed that their expectations about the outcome and kinematics of the action influence their motor system. This interesting result can be interpreted as an indication that our brains do not only receive information from the outside world but also influence how we perceive the world. In a way “free will” is an illusion since our prior expectations influence what we see.