Syntax and verbal working memory in schizophrenia: the role of language in facilitating serial recall

Abstract

OBJECTIVE: Deficits in verbal working memory have been consistently observed in schizophrenic patients, ranging from impairments in capacity, encoding to irregular semantic organisation.1 Deficits concerning syntax are less well-characterised. This study examined the role of simple syntactic structure (basis of the “sentence superiority effect”) in verbal memory,2,3 comparing patients and controls. METHODS: Patients with schizophrenia-spectrum disorders (n = 40) and healthy controls matched on age, sex, and education (n = 40) were administered an auditory serial recall task containing word lists with low semantic coherence and either syntactic structure (noun-verb-noun) or no structure. Other neurocognitive measures, symptom and social functioning of patients were also assessed. RESULTS: Three-way between-subjects ANOVA (version × list type × serial position) showed that patients had significantly worse performance overall, indicating a generalised verbal memory impairment. Significant interaction was found for list type × Group, demonstrating that healthy controls, but not patients, had superior performance in syntactic word lists. Further analysis of high-performing patients revealed that the interaction was not an artifact of poor verbal memory, but a selective deficit in syntactic facilitation. CONCLUSION: The findings support language-based accounts of verbal working memory, and suggest that semantics and syntax facilitate memory through distinct processes.4 Results show that schizophrenic patients have deficits in utilizing syntactic structure, implicating dysfunction in the procedural memory system, rooted in the frontal and parietal cortices and basal ganglia.