Brain activity evoked by inverted and imagined biological motion.

Previous imaging research has identified an area on the human posterior superior temporal sulcus (STS) activated upon viewing biological motion. The current experiments explore the relationship between neural activity within this region and perceptual experience. Biological motion perception is orientation dependent: inverting point-light animations make them more difficult to see. We measured activity levels within this region as observers viewed inverted point-light animations. We also measured neural activity while observers imagined biological motion and compared it to that measured while observers viewed the animations. In both experiments we found that the BOLD response was modulated with perceptual experience. Viewing inverted biological motion activated posterior STS more than scrambled motion, but less than upright biological motion. Mental imagery of biological motion was also sufficient to activate this region in most of our observers, but the level of activity was weaker than during actual viewing of the motion animations.