Did I say that word or did you? Executive dysfunctions in schizophrenic patients affect memory efficiency, but not source attributions

Abstract

Introduction. Schizophrenic patients have difficulties in recognising previously presented verbal information and identifying its sources. The antecedents of these recognition and source misattributions are, however, largely unknown. The current study examined to what extent schizophrenic patients’ lack of memory efficiency, their memory errors, and their source misattributions are related to neurocognitive deficits (i.e., executive dysfunctions).

Methods. 23 schizophrenic patients and 20 healthy controls were administered an adapted version of the Deese/Roediger-McDermott (DRM) task from which parameters of memory efficiency, memory errors, source misattributions, and two-high threshold measures were derived. Furthermore, two neurocognitive tasks tapping executive functions were administered: the Wisconsin Card Sorting Test (WCST) and the Behavioural Assessment of the Dysexecutive Syndrome (BADS). Using multiple linear regression analyses, we examined whether these neurocognitive measures predicted various memory parameters.

Results. Patients with schizophrenia showed poorer memory efficiency and were more prone to make internal-external source misattributions with high confidence. However, they did not more often falsely recognise critical lure words than controls. Executive dysfunctions predicted memory efficiency, but not source misattribution performance.

Conclusion. Our findings provide further evidence that schizophrenic patients’ memory impairments are intimately related to fundamental neurocognitive deficits.

Acknowledgements

This study was supported by a grant from the Dutch organisation for scientific research, N.W.O., grant number 452-02-006. We would like to thank Drs Mesotten and Bryon, psychologist Michael Hilderson, and other staff members of both psychiatric hospitals for their help with the data collection. We would like to thank editor Professor Anthony David, reviewer Dr Ayana Gibbs, and one anonymous reviewer for their constructive comments on the earlier versions of this manuscript.

Notes

¹WCST categories completed was left out of the regression analyses, because this variable strongly correlated with the other WCST scores (r > .80, p<.001), indicating multicollinearity.

²A negative correlation was found between misses and false alarms of critical lure words when both samples were pooled (r = –.49, p<.001, two-tailed), thereby underscoring this possible explanation.