Virtual body continuity during action observation affects motor cortical excitability.

Body ownership, the sense that the body belongs to oneself, can be altered by inducing body manipulations in Virtual Reality, such as by increasing the visual discontinuity between the avatar's hand and body. Body representation manipulations can also influence motor cortex excitability. We hypothesized that the degree of body continuity between one's body and the observed virtual body would affect ownership feelings and impact motor cortex excitability during action observation. Participants observed virtual hand movements from a first-person perspective with the virtual hand presented with different level of connection with their real hand; the virtual hand could be part of a full virtual body co-located with the real body (Full-Body condition), it could appear as connected to an upper limb visually discontinuous from the real body (Upper Limb condition), or the virtual hand appeared in isolation, fully discontinuous (Detached Hand condition). Results showed increased corticospinal excitability when body continuity is higher (Full-Body and Upper Limb). This effect was mediated by ownership and disownership feelings, supporting the relationship between body perception and motor system.