Visuospatial memory and learning in first-episode schizophreniform psychosis and established schizophrenia: a functional correlate of hippocampal pathology?

BACKGROUND: Despite a number of studies that have indicated impaired memory function in patients with schizophrenia, there have been few that have used a sensitive measure of right medial temporal lobe pathology. Given the reported findings of reduced hippocampal volume in schizophrenia, we used a theoretically sensitive test of the right medial temporal lobe to determine the nature of the visuospatial memory deficit in the disorder.
METHODS: Seventy-six patients (37 with a first-episode schizophreniform psychosis, and 39 with established schizophrenia) were compared with 41 comparison subjects on a number of tests of visuospatial memory. These included spatial working memory, spatial and pattern recognition memory and a pattern-location associative learning test.
RESULTS: Both patient groups displayed recognition memory deficits when compared to the comparison group. However, only those patients with established schizophrenia (of 9 years duration on average) were impaired on the associative learning test.
CONCLUSIONS: The results indicate either a progressive decline in visuospatial associative learning ability over the course of the disorder, or that poor visuospatial associative learning is a marker for poor prognosis. In addition, these results have implications for our understanding of the role of the right medial temporal lobe in the pathophysiology of schizophrenia.