Impaired passive maintenance and spared manipulation of internal representations in patients with schizophrenia

Working memory (WM) impairment is a core feature of schizophrenia (SZ), but the integrity of the various components of WM is unclear. After encoding, mental representations must be maintained in WM during the delay period. In addition to maintenance, manipulation of internal representation can occur in WM. It has been argued that manipulation of items in WM is more impaired than simple maintenance in SZ, but direct empirical data to support this claim have been mixed. Discrepant findings among studies might be explained by task parameters, specifically the degree to which the manipulation task places demands on encoding and maintenance processes. The present study set out to examine these components of WM in patients with SZ (n = 20) and demographically matched healthy controls (n = 19) using a spatial delayed response task (DRT) to measure maintenance processes and 2 mental rotation tasks (allocentric and egocentric) with no delay period or restriction on encoding time to measure manipulation processes. Consistent with previous findings, patients were impaired on the spatial DRT. However, patients performed equally well on the egocentric mental rotation task and were more accurate than controls on the allocentric mental rotation task as the required degree of rotation increased. These results indicated impaired maintenance and spared manipulation of representations in WM and suggest a pocket of cognitive function that might be enhanced in SZ.