title: Perception of actions performed by external agents presupposes knowledge about the relationship between action and effect.
abstract: We used the (14)C-deoxyglucose method to reveal changes in activity, in the lateral sulcus of monkeys, elicited by reaching-to-grasp in the light or in the dark and by observation of the same action executed by an external agent. Both visually-guided execution and observation of the same action activated the secondary somatosensory cortex, the ventral somatosensory area, the somatorecipient parietal ventral area, the retroinsula and the caudo-medial area of the auditory belt. These matching activations indicate that the somesthetic consequences of movements, generated bottom-up during action execution, may also be triggered top-down during action observation to represent the predicted sensory consequences of the perceived movement. The posterior granular part of insula found to be activated only for action execution and its anterior agranular part activated only for action observation may contribute to the attribution of action to the correct agent. Also, execution in the dark implicated all components activated by execution in the light but the retroinsula. In conclusion, activation of the somatorecipient parietal areas, not only for action-execution but also for action-observation, indicates that perception of actions performed by an external agent presupposes knowledge about the action-effect relationships, and that understanding others' actions consists of running off-line previously stored sensory-motor programs.
authors.affiliation: Institute of Applied and Computational Mathematics, Foundation for Research and Technology Hellas, Iraklion, Crete, Greece; Department of Basic Sciences, Faculty of Medicine, School of Health Sciences, University of Crete, P.O. Box 2208, GR-71003 Iraklion, Crete, Greece. Electronic address: vraos@med.uoc.gr.
authors.forename: Vassilis
authors.initials: V
authors.lastname: Raos
authors.affiliation: Institute of Applied and Computational Mathematics, Foundation for Research and Technology Hellas, Iraklion, Crete, Greece; Department of Basic Sciences, Faculty of Medicine, School of Health Sciences, University of Crete, P.O. Box 2208, GR-71003 Iraklion, Crete, Greece. Electronic address: savaki@med.uoc.gr.
authors.forename: Helen E
authors.initials: HE
authors.lastname: Savaki
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002250:Carbon Radioisotopes; D003847:Deoxyglucose / Q000008:administration & dosage; D005260:Female; D008253:Macaca mulatta; D009068:Movement; D011597:Psychomotor Performance; D013003:Somatosensory Cortex / Q000378:metabolism*; D014796:Visual Perception
chemical_list: D002250:Carbon Radioisotopes; D003847:Deoxyglucose
keywords: (14)C-deoxyglucose method; Action-simulation; Mental rehearsal; Reaching to grasp; Sylvian fissure