Perceptual priming in schizophrenia evaluated by word fragment and word stem completion

Abstract 

Implicit memory seems to be preserved in schizophrenia as a whole, but dissociations between conceptual and perceptual tasks and between accuracy and reaction time measures have appeared. The present research has revealed some methodological limitations in many studies to date that are focused on the study of perceptual implicit memory in schizophrenic patients using accuracy measures. The review of these studies revealed that limitations are related to an inadequate definition of performance and priming measures, a lack of control over the characteristics of the stimuli, and the absence of information on the experimental procedures used in data collection. Moreover, the task used in these studies is word stem completion, a task that makes use of perceptual and conceptual processes. In the experiment reported here we use a pure perceptual implicit task and stimuli selected from a normative database to measure perceptual implicit memory in schizophrenic patients. Their performance was compared with that of normal participants. Thirty-two schizophrenic patients and 30 healthy control participants were administered a word fragment completion task. Direct comparison between the two groups yielded similar results in priming, suggesting that perceptual implicit memory is preserved in schizophrenia.

Keywords: Implicit memory, Schizophrenia, Cognitive deficit, Priming, Word stem completion, Word fragment completion