Action execution and observation network: the structural connectome supporting variable force detection

Social cognition has concerned itself with the study of the mirroring system, which supports a neural mechanism that enables action identification and understanding. The neurons of this system discharge both when an action is performed by an individual and also when an individual observes the same action while it is executed by another subject. The action execution-observation network (AEON) can be considered the neural correlate of the mirroring system because it combines the action execution network with the action observation one. The aim of this thesis is to study and characterize the structural substrate of the AEON in relation to force perception, by assessing the AEON structural connectome with its relative network measures derived using a graph theoretical approach. To functionally describe the AEON, four networks were derived from an fMRI study: AE zero and AE FRE for action execution, AO zero and AO FRE for action observation. Diffusion data from the Human Connectome Project dataset were instead used to perform a whole-brain-tractography, whose results where combined with the functional networks to create four connectomes. Graph theory measures were calculated to characterize the four networks and statistical comparisons between pairs of networks were performed. Our results showed that AO networks exhibited widespread connectivity with respect to AE networks. In particular, AO FRE displayed the highest number of connections and core regions. Its connectivity structure mirrored the one involved in action execution and also included areas that support mentalizing activity. These results support the complex structural substrate underlying the AEON, revealing that different connections between motor, somatosensory and associative regions characterize AE and AO networks also in relation to force perception. Key words: AEON; action execution; action observation; force perception; mirror neurons; connectome.