Exploring the impact of ketamine on the experience of illusory body ownership.
BACKGROUND
Our sense of body ownership is profound and familiar, yet it may be misleading. In the rubber-hand illusion, synchronous tactile and visual stimulation lead to the experience that a rubber hand is actually one's own. This illusion is stronger in schizophrenia. Given the evidence that ketamine, a noncompetitive N-methyl-D-aspartate antagonist reproduces symptoms of schizophrenia, we sought to determine whether the rubber-hand illusion is augmented by ketamine.


METHODS
We studied 15 healthy volunteers in a within-subjects placebo-controlled study. All volunteers carried out two versions of the rubber-hand task, each under both placebo and ketamine infusions. In one task, they saw a rubber hand being stroked in synchrony with tactile stimulation of their real, hidden hand. In the other, stroking of the real and rubber hands was asynchronous. We recorded subjective changes in sense of ownership, as well as participants' ability to localize their hidden hand.


RESULTS
Ketamine was associated with significant increases in subjective measures of the illusion and in hand mislocalization. Although asynchronous visuotactile stimulation attenuates the strength of the illusion during both placebo and ketamine, there remained a significant illusory effect during asynchronous visuotactile stimulation under ketamine compared with placebo. The strength of the illusion during asynchronous visuotactile stimulation correlated with other subjective effects of the drug.


CONCLUSIONS
Ketamine mimics the perturbed sense of body ownership seen in schizophrenia, suggesting that it produces a comparable alteration in integration of information across sensory domains and in the subjective and behavioral consequences of such integration.
Department of Psychiatry, Brain Mapping Unit, University of Cambridge, Downing Site, United Kingdom.
Hannah L
HL
Morgan
Danielle C
DC
Turner
Philip R
PR
Corlett
Anthony R
AR
Absalom
Ram
R
Adapa
Fernando S
FS
Arana
Jennifer
J
Pigott
Jenny
J
Gardner
Jessica
J
Everitt
Patrick
P
Haggard
Paul C
PC
Fletcher
D000328:Adult; D001828:Body Image; D005260:Female; D006801:Humans; D007088:Illusions / Q000187:drug effects*; D007262:Infusions, Intravenous; D007649:Ketamine / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D008297:Male; D010552:Personality Assessment; D010775:Photic Stimulation; D010919:Placebos; D011434:Proprioception / Q000187:drug effects; D011569:Psychiatric Status Rating Scales; D011597:Psychomotor Performance / Q000187:drug effects; D055698:Touch Perception / Q000187:drug effects; D014796:Visual Perception / Q000187:drug effects
D010919:Placebos; D007649:Ketamine