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Evidence for a differential contribution of early perceptual and late cognitive processes during encoding to episodic memory impairment in schizophrenia |
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| Authors: | Amity E. Green Paul B. Fitzgerald Patrick J. Johnston Pradeep J. Nathan Jayashri Kulkarni Rodney J. Croft |
| Affiliation: | 1. Monash Alfred Psychiatry Research Centre, Central Clinical School, Monash University and the Alfred Hospital, Australia;2. Department of Psychology and York Neuroimaging Centre, University of York, UK;3. School of Psychology &4. Counselling, Queensland University of Technology, Australia;5. School of Psychology and Psychiatry, Monash University, Australia;6. Brain Mapping Unit, Department of Psychiatry, University of Cambridge, UK;7. Illawarra Health &8. Medical Research Institute, University of Wollongong, Australia;9. School of Psychology, University of Wollongong, Australia |
| Abstract: | Objectives: Schizophrenia is characterised by significant episodic memory impairment that is thought to be related to problems with encoding, however the neuro-functional mechanisms underlying these deficits are not well understood. The present study used a subsequent recognition memory paradigm and event-related potentials (ERPs) to investigate temporal aspects of episodic memory encoding deficits in schizophrenia. Methods: Electroencephalographic data was recorded in 24 patients and 19 healthy controls whilst participants categorised single words as pleasant/unpleasant. ERPs were generated to subsequently recognised versus unrecognised words on the basis of a forced-choice recognition memory task. Subsequent memory effects were examined with the late positive component (LPP). Group differences in N1, P2, N400 and LPP were examined for words correctly recognised. Results: Patients performed more poorly than controls on the recognition task. During encoding patients had significantly reduced N400 and LPP amplitudes than controls. LPP amplitude correlated with task performance however amplitudes did not differ between patients and controls as a function of subsequent memory. No significant differences in N1 or P2 amplitude or latency were observed. Conclusions: The present results indicate that early sensory processes are intact and dysfunctional higher order cognitive processes during encoding are contributing to episodic memory impairments in schizophrenia. |
| Keywords: | Event-related potentials episodic memory encoding schizophrenia |