Amplified Mnemonic Discrimination and Attenuated Generalization Are Associated with Positive Schizotypy

Abstract

Memory dysfunction has been first recognized in patients with schizophrenia over 100 years ago and it is considered to be a particularly pronounced symptom of the illness. According to the hippocampal dysfunction theory, memory impairments and positive symptoms of schizophrenia such as hallucinations and delusions might be attributable to an unbalance in the interplay of pattern separation and pattern completion neural computations. While the theory addresses alterations specifically related to schizophrenia, schizotypy (a personality construct that encompasses schizophrenia symptom-like traits) is increasingly considered to be a useful construct for conceptualizing the development and expression of schizophrenia. Behavioural studies in patients with schizophrenia have come to disparate findings when testing the hippocampal dysfunction theory and are not devoid of some of the limitations and confounds that are commonly encountered in schizophrenia research, such as small samples, and a possible modulating effect of medications on cognitive performance. The present study aims to reconcile this debate by investigating the relationship between positive schizotypy and lure discrimination index and false recognition of lures (putative behavioural indicators of pattern separation and completion, respectively) in a sample of healthy individuals (N=71) varying in terms of self-reported unusual experiences. Contradicting our expectations (which were based on patient studies), positive schizotypy in the healthy population was associated with enhanced mnemonic discrimination and attenuated false recognition of lures. The current study is the first ever to investigate pattern separation and pattern completion in relation to different schizotypy dimensions. We address possible underlying mechanisms that might cause a lower false recognition of lures (e.g. impaired ability to generalise) in schizotypy. Resemblance between positive schizotypy and schizophrenia could not be detected at the level of behavioural performance which can be interpreted in a theoretical framework of hippocampal neural computations . Uncovering the underlying mechanisms of this discrepancy awaits future research.