Intact implicit learning in schizophrenia.
OBJECTIVE
Schizophrenia impairs performance on explicit, but not implicit, memory tasks, indicating that conscious awareness at retrieval is a critical determinant of impaired memory. The authors investigated implicit learning, i.e., knowledge acquisition in the absence of conscious awareness, in patients with schizophrenia.


METHODS
An artificial grammar learning task was used to assess implicit learning in 48 patients with schizophrenia and 24 healthy comparison subjects. The subjects were first presented with letter strings that were generated according to the rules of a finite-state grammar paradigm. They were then required to indicate whether new letter strings were "grammatical," depending on whether or not the strings corresponded to the rules. IQ, working memory, explicit memory, verbal fluency, and speed of processing were also assessed.


RESULTS
Patients performed significantly worse than the comparison subjects on cognitive tasks that assessed episodic memory, verbal fluency, working memory, and speed of processing. In contrast, patients classified as being correct more grammatical than nongrammatical letter strings, and the magnitude of the difference was similar to that observed in healthy comparison subjects.


CONCLUSIONS
Implicit learning, as assessed with an artificial grammar learning task, is intact in patients with schizophrenia. Conscious awareness might be a critical determinant of memory impairment both at encoding and at retrieval.
Danion
J M
JM
INSERM Unité 405, Clinique Psychiatrique, Hôpitaux Universitaires de Strasbourg, 1 place de l'Hôpital-BP 426, 67091 Stranbourg Cedex, France.
Meulemans
T
T
Kauffmann-Muller
F
F
Vermaat
H
H
D000328:Adult; D000553:Ambulatory Care; D001245:Association Learning; D001364:Awareness; D003071:Cognition; D005260:Female; D006801:Humans; D007858:Learning; D008037:Linguistics; D008297:Male; D008568:Memory; D011939:Mental Recall; D008960:Models, Psychological; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D012559:Schizophrenia / Q000175:diagnosis*; D012565:Schizophrenic Psychology; D014706:Verbal Learning; D014888:Wechsler Scales / Q000706:statistics & numerical data