An early marker for semantic memory impairment in patients with schizophrenia
Introduction: Semantic memory impairment is now a well-documented phenomenon in patients with schizophrenia. Nevertheless, the characteristics of this deficit and any early markers remain contentious. Methods: In this preliminary study, 12 schizophrenic patients underwent longitudinal assessment using a battery of semantic memory tests. Patient performance was compared to 12 matched controls. Using set criteria (derived from Warrington & Shallice, 1979), we examined whether the patients had a disorder affecting access to intact representations, or a degradation/loss of the representations themselves. The criteria were: consistency across time and modality, level of attribute information, and responsiveness to cueing. Finally, we compared patient naming for the same items across two naming tests (naming-to-description and picture naming) to determine cross-modality consistency. Results: As expected, normal controls outperformed the patients on all tests. Naming-to-description was the most significant differentiator between patients and controls. Patients were inconsistent across both time and modality, showed minimal attributional knowledge impairment, and improved significantly with cueing on two naming tests. Conclusion: The profile of results indicates an access-type semantic deficit in this cohort of patients with schizophrenic. Finally, on a naming-to-description task, the patients failed to name up to 20% of items that they could name to picture. This suggests that naming-to-definition may act as an early marker of semantic memory impairment.