title: Impaired visual hand recognition in preoperative patients during brachial plexus anesthesia: importance of peripheral neural input for mental representation of the hand.
abstract: BACKGROUND
  Perceptual illusions described in healthy subjects undergoing regional anesthesia (RA) are probably related to short-term plastic brain changes. We addressed whether performance on an implicit mental rotation task reflects these RA-induced changes in body schema brain representations. Studying these changes in healthy volunteers may shed light on normal function and the central mechanisms of pain.
  
  
  METHODS
  Performance pattern was studied in upper limb-anesthetized subjects on a left/right hand judgment task, which is known to involve motor imagery processes relating to hand posture. Three conditions were used: control (i.e., absence of deafferentation), RA (i.e., deafferentation), and vision (i.e., deafferentated limb exposed to view). To limit potential bias such as order effect, the control state was recorded in a randomized manner.
  
  
  RESULTS
  All subjects described perceptual illusions of their anesthetized limb. They were slower and less accurate on the task during RA compared with control. Response patterns were similar in all conditions, suggesting sensitivity of performance to arm/hand biomechanical constraints. Vision was associated with an increase in the proportion of correct responses and a reduction of the response times in hand judgment and was accompanied by disappearance of the lateralization of the underlying mental representations, which was identified during RA.
  
  
  CONCLUSIONS
  These results suggest the following: (1) the right/left judgment task involves mental simulation of hand movements, (2) underlying mental representations and their neural substrates are subject to acute alterations after RA, and (3) the proprioceptive deficit induced by RA is influenced by the subject's ability to see the anesthetized limb.
authors.affiliation: INSERM, Imagerie Cérébrale et Handicaps Neurologiques UMR 825, Toulouse, France. silva.stein@gmail.com
authors.forename: Stein
authors.initials: S
authors.lastname: Silva
authors.forename: Isabelle
authors.initials: I
authors.lastname: Loubinoux
authors.forename: Michel
authors.initials: M
authors.lastname: Olivier
authors.forename: Benoîmt
authors.initials: B
authors.lastname: Bataille
authors.forename: Olivier
authors.initials: O
authors.lastname: Fourcade
authors.forename: Kamran
authors.initials: K
authors.lastname: Samii
authors.forename: Marc
authors.initials: M
authors.lastname: Jeannerod
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Démonet
mesh_terms: D000328:Adult; D000577:Amides / Q000008:administration & dosage; D000704:Analysis of Variance; D000765:Anesthesia, Conduction / Q000379:methods*; D000779:Anesthetics, Local / Q000008:administration & dosage; D001917:Brachial Plexus / Q000187:drug effects*; D001921:Brain; D005260:Female; D006225:Hand; D006801:Humans; D007088:Illusions / Q000187:drug effects; D007600:Judgment / Q000187:drug effects; D008297:Male; D008606:Mental Processes / Q000187:drug effects*; D009407:Nerve Block / Q000379:methods; D010470:Perceptual Masking; D011300:Preoperative Care; D011930:Reaction Time / Q000187:drug effects; D021641:Recognition, Psychology / Q000187:drug effects*; D012016:Reference Values; D000077212:Ropivacaine; D013647:Task Performance and Analysis; D014796:Visual Perception / Q000187:drug effects*
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine