Is persistent ketamine use a valid model of the cognitive and oculomotor deficits in schizophrenia?
BACKGROUND
Acute ketamine has been shown to model features of schizophrenia such as psychotic symptoms, cognitive deficits and smooth pursuit eye movement dysfunction. There have been suggestions that chronic ketamine may also produce an analogue of the disorder. In this study, we investigated the effect of persistent recreational ketamine use on tests of episodic and working memory and on oculomotor tasks of smooth pursuit and pro- and antisaccades.


METHODS
Twenty ketamine users were compared with 1) 20 first-episode schizophrenia patients, 2) 17 polydrug control subjects who did not use ketamine but were matched to the ketamine users for other drug use, and 3) 20 non-drug-using control subjects. All groups were matched for estimated premorbid IQ.


RESULTS
Ketamine users made more antisaccade errors than both control groups but did not differ from patients. Ketamine users performed better than schizophrenia patients on smooth pursuit, antisaccade metrics, and both memory tasks but did not differ from control groups.


CONCLUSIONS
Problems inhibiting reflexive eye movements may be a consequence of repeated ketamine self-administration. The absence of any other oculomotor or cognitive deficit present in schizophrenia suggests that chronic self-administration of ketamine may not be a good model of these aspects of the disorder.
Morgan
Celia J A
CJ
Clinical Psychopharmacology Unit, University College London, United Kingdom. c.morgan@ucl.ac.uk
Huddy
Vyv
V
Lipton
Michelle
M
Curran
H Valerie
HV
Joyce
Eileen M
EM
D000293:Adolescent; D000328:Adult; D003072:Cognition Disorders / Q000139:chemically induced* / Q000523:psychology*; D018691:Excitatory Amino Acid Antagonists; D005260:Female; D006801:Humans; D007361:Intelligence Tests; D007649:Ketamine; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D008875:Middle Aged; D009483:Neuropsychological Tests; D015835:Ocular Motility Disorders / Q000139:chemically induced* / Q000523:psychology*; D011597:Psychomotor Performance / Q000502:physiology; D011698:Pursuit, Smooth / Q000502:physiology; D012565:Schizophrenic Psychology; D013028:Space Perception / Q000502:physiology; D019966:Substance-Related Disorders / Q000523:psychology*; D014706:Verbal Learning; D055815:Young Adult
D018691:Excitatory Amino Acid Antagonists; D007649:Ketamine