title: Sleep and circadian rhythm disruption and recognition memory in schizophrenia.
abstract: Schizophrenia patients often show irregularities in sleep and circadian rhythms and deficits in recognition memory. Similar phenotypes are seen in schizophrenia-relevant genetic mouse models, such as synaptosomal associated protein of 25 kDa (Snap-25) point mutant mice, vasoactive intestinal peptide receptor 2 (Vipr2) knockout mice, and neuregulin 1 (Nrg1)-deficient mice. Sleep and circadian abnormalities and impaired recognition memory may be causally related in both schizophrenia patients and schizophrenia-relevant mouse models, since sleep deprivation, abnormal photic input, and the manipulation of core clock genes (cryptochrome 1/2) can all disrupt object recognition memory in rodent models. The recognition deficits observed in patients and mouse models (both schizophrenia-related and -unrelated) are discussed here in terms of the dual-process theory of recognition, which postulates that there are two recognition mechanisms-recollection versus familiarity-that can be selectively impaired by brain lesions, neuropsychiatric conditions, and putatively, sleep and circadian rhythm disruption. However, based on this view, the findings from patient studies and studies using genetic mouse models (Nrg1 deficiency) seem to be inconsistent with each other. Schizophrenia patients are impaired at recollection (and to a lesser extent, familiarity judgments), but Nrg1-deficient mice are impaired at familiarity-based object recognition, raising concerns regarding the validity of using these genetically modified mice to model recognition phenotypes observed in patients. This issue can be resolved in future animal studies by examining performance in different variants of the spontaneous recognition task-the standard, perirhinal cortex-dependent, object recognition task versus the hippocampus-dependent object-place recognition task-in order to see which of the two recognition mechanisms is more disrupted.
authors.affiliation: Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom.
authors.forename: Shu K E
authors.initials: SK
authors.lastname: Tam
authors.affiliation: Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Pritchett
authors.affiliation: Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
authors.forename: Laurence A
authors.initials: LA
authors.lastname: Brown
authors.affiliation: Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
authors.forename: Russell G
authors.initials: RG
authors.lastname: Foster
authors.affiliation: Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom.
authors.forename: David M
authors.initials: DM
authors.lastname: Bannerman
authors.affiliation: Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom. Electronic address: stuart.peirson@eye.ox.ac.uk.
authors.forename: Stuart N
authors.initials: SN
authors.lastname: Peirson
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D004195:Disease Models, Animal; D006801:Humans; D008568:Memory; D051379:Mice; D012565:Schizophrenic Psychology; D012890:Sleep
keywords: Familiarity; Mouse models; Neuropsychiatric disease; Novel object recognition; Recollection; Running wheel