Spatial working memory deficits in schizophrenia: Relationship with tardive dyskinesia and negative symptoms

Objective: This study examined the interrelationship between negative sympt oms, orofacial tardive dyskinesia, and specific neurocognitive processes, p articularly those involved in memory and executive function, in patients wi th schizophrenia. Method: A set of computerized neurocognitive tasks, the Cambridge Neuropsyc hological Test Automated Battery, was used to assess executive and memory f unction in 54 hospitalized patients with chronic schizophrenia. Analysis of covariance was used to examine differences between groups with or without the topographical syndromes of orofacial tardive dyskinesia and between gro ups with high or low negative symptom scores. Principal-components and path analyses were used to examine further the influence of negative symptoms a nd orofacial tardive dyskinesia on performance on tests of memory and execu tive function. Results: Both orofacial tardive dyskinesia and negative symptoms were signi ficantly and independently associated with deficits on measures of spatial working memory span derived from principal-components analysis, but only or ofacial tardive dyskinesia was associated with deficits on measures of spat ial working memory strategy. Both were also associated with impairment on t he delayed-matching-to-sample task, a test of memory. These associations we re not explained by deficits in global intellectual function. Path analysis suggested that the relationships between the clinical symptoms and perform ance on the delayed-matching-to-sample task were mediated entirely through their relationship with the spatial working memory measures. Conclusions: in schizophrenia, orofacial tardive dyskinesia and evident neg ative symptoms are relatively independent markers of compromise of the cere bral systems that mediate spatial working memory. Candidate neural circuits include the frontal-striatal-thalamic systems, particularly those involvin g the dorsolateral prefrontal cortex.