The course of semantic memory dysfunction in first-episode schizophrenia

Abstract

BACKGROUND: Semantic memory dysfunction has been investigated in schizophrenia using the categorization task. Early data in chronic patients suggestive of an outward shift in category boundary (Chen et al, 1994) has been contentious. This study investigated categorization in first episode schizophrenic patients followed up for a period of three years. METHODS: We studied categorization longitudinally in 37 first episode patients (schizophrenia, schizophreni form psychosis and schizoaffective psychosis). Patients were required to make a categorization decision. Exemplars were either typical, atypical, borderline, related, or unrelated in relation to the category (5 conditions). We derived the following measures based on the reaction time data (borderline shift, borderline peak, false relatedness effect and typicality effect). Longitudinal changes were analyzed with repeated measure ANOVA. The relationships between categorization measures, clinical and cognitive variables were also explored. RESULTS: Semantic categorization was anomalous at presentation (ANOVA: group x condition interaction, df=4, F=4.8, p=0.001). The anomaly normalized following treatment. By year one, the performance was similar to normal control. There was little longitudinal change over the second and third years. At presentation, typicality effect, borderline peak, over-inclusiveness and overall speed were related to negative symptoms, borderline shift was related to visual memory, overall speed was related to verbal fluency. At stabilization, over-inclusiveness was related to both positive and negative symptoms. At three year follow-up borderline shift was correlated with positive symptoms while borderline peak was related to negative symptoms. CONCLUSIONS: Semantic memory abnormalities are detectable during the first episode schizophrenia. They normalized following symptomatic recovery and remained stable for the first three years. Borderline shift appears to be related to positive symptoms whereas borderline peak is related to negative symptoms. Reference: Chen EYH et al (1994) Semantic memory is both impaired and anomalous in schizophrenia, Psychological Medicine, 24, 193–202.