A comparison of memory for verbal and non-verbal material in schizophrenia

Verbal memory impairment has been well explored in schizophrenia, but it is unclear whether findings relate to the type of material to be learned or the component process required by the memory task. Also, sparse data on non-verbal memory also open the question of how well schizophrenia patients encode this material. We tested whether episodic memory performance in schizophrenia varies as a function of stimulus material (verbal/non-verbal) and determined the integrity of various component memory processes. Memory tests that differ in stimulus material (words, California Verbal Learning Test, CVLT; designs, Biber Figure Learning Test-Extended, BFLT-E) yet produce similar memory component measures were used. Subjects were 28 neuroleptic-medicated inpatients with a diagnosis of chronic schizophrenia. Results showed that both verbal and non-verbal memory performance was impaired relative to age-matched controls. Learning and recall measures were most severely impaired, with memory storage problems and impairment in recognition memory evident. On the verbal task, the relative sparing of recognition memory suggested retrieval processes, in addition to encoding processes, were disrupted. On the non-verbal task, the deficits appeared more limited to encoding. Therefore, while the operational integrity of components such as encoding were compromised regardless of material, retrieval processes showed material-specific effects. To the degree verbal and non-verbal memory functions can be lateralized in the brain, these data support the possibility of deficits in both right and left hemisphere declarative memory systems in schizophrenia.