title: Body schema and corporeal self-recognition in the alien hand syndrome.
abstract: OBJECTIVE
  The alien hand syndrome (AHS) is a rare neuropsychological disorder characterized by involuntary, yet purposeful, hand movements. Patients with the AHS typically complain about a loss of agency associated with a feeling of estrangement for actions performed by the affected limb. The present study explores the integrity of the body representation in AHS, focusing on 2 main processes: multisensory integration and visual self-recognition of body parts. Three patients affected by AHS following a right-hemisphere stroke, with clinical symptoms akin to the posterior variant of AHS, were tested and their performance was compared with that of 18 age-matched healthy controls.
  
  
  METHODS
  AHS patients and controls underwent 2 experimental tasks: a same-different visual matching task for body postures, which assessed the ability of using your own body schema for encoding others' body postural changes (Experiment 1), and an explicit self-hand recognition task, which assessed the ability to visually recognize your own hands (Experiment 2).
  
  
  RESULTS
  As compared to controls, all AHS patients were unable to access a reliable multisensory representation of their alien hand and use it for decoding others' postural changes; however, they could rely on an efficient multisensory representation of their intact (ipsilesional) hand. Two AHS patients also presented with a specific impairment in the visual self-recognition of their alien hand, but normal recognition of their intact hand.
  
  
  CONCLUSIONS
  This evidence suggests that the AHS following a right-hemisphere stroke may involve a disruption of the multisensory representation of the alien limb; instead, self-hand recognition mechanisms may be spared. (PsycINFO Database Record
authors.affiliation: Department of Psychology, University of Milan-Bicocca.
authors.forename: Elena
authors.initials: E
authors.lastname: Olgiati
authors.affiliation: Department of Psychology, University of Milan-Bicocca.
authors.forename: Angelo
authors.initials: A
authors.lastname: Maravita
authors.affiliation: Department of Psychology, University of Milan-Bicocca.
authors.forename: Viviana
authors.initials: V
authors.lastname: Spandri
authors.affiliation: Department of Psychology, University of Milan-Bicocca.
authors.forename: Roberta
authors.initials: R
authors.lastname: Casati
authors.affiliation: Department of Rehabilitation, Neuro-Motor Rehabilitation Unit, Carlo Poma Hospital.
authors.forename: Francesco
authors.initials: F
authors.lastname: Ferraro
authors.affiliation: Department of Rehabilitation, Physical Medicine and Rehabilitation Unit, San Gerardo Hospital.
authors.forename: Lucia
authors.initials: L
authors.lastname: Tedesco
authors.affiliation: Department of Neurosciences, Neurology and Stroke Unit, Niguarda Ca'Granda Hospital.
authors.forename: Elio Clemente
authors.initials: EC
authors.lastname: Agostoni
authors.affiliation: Department of Psychology, University of Milan-Bicocca.
authors.forename: Nadia
authors.initials: N
authors.lastname: Bolognini
mesh_terms: D000368:Aged; D055964:Alien Limb Phenomenon / Q000209:etiology / Q000503:physiopathology*; D001828:Body Image; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D021641:Recognition, Psychology / Q000502:physiology; D012678:Sensation Disorders / Q000209:etiology / Q000503:physiopathology*; D020521:Stroke / Q000150:complications*; D014796:Visual Perception / Q000502:physiology