New aspects of motion perception: selective neural encoding of apparent human movements.

Perception of apparent motion operates somewhat differently for objects and human figures. Depending on the interstimulus interval, the latter d may give rise to either perception of a direct path (i.e. biologically impossible) or indirect path (i.e. biologically possible). Here, PET was used to investigate whether a change in brain activity accompanies this perceptual shift. We found neural encoding of apparent motion to be a function of the intrinsic properties of the stimulus presented (object vs human) as well as the kind of human movement path perceived (biomechanically possible vs impossible). Motor and parietal cortex were only involved for possible motion which suggests that these regions are selectively activated to process actions which conform to the capabilities of the observer.