Explicit memory, repetition priming and cognitive skill learning in schizophrenia

Explicit memory and two forms of implicit memory, repetition priming and cognitive skill learning, were examined in twenty-four schizophrenic patients and twenty-four normal control subjects previously matched for sex, age, and educational level. Two explicit tasks, free recall and frequency monitoring, and two implicit tasks, word completion and the Tower of Toronto puzzle, a variant of the Tower of Hanoi puzzle, were selected. The performance of schizophrenic patients was impaired in both explicit tasks, whereas repetition priming was intact; in the Tower of Toronto puzzle, a deficit was observed in problem solving, but not in skill learning. This dissociation between explicit and implicit memory is not entirely consistent with the hypothesis of a deficiency in effort-demanding information processing. It could be better accommodated by a model of a disturbance in the internal representation of context.