Browsing by Subject "Schizophrenia"

Goals. Schizophrenia is a neuropsychiatric disorder characterized with cognitive symptoms such as memory deficits and sleep disturbances. Sleep spindle (slow ~10Hz, fast ~13Hz) activity has been found to correlate with declarative and procedural memory performance. Having enough of spindles might not guarantee intact sleep-dependent memory consolidation, but their temporal coordination with neocortical slow oscillations (SOs) and hippocampal ripples (100-250Hz) needs to be considered. SOs temporally group thalamic spindle and hippocampal ripple activity thus creating coordinated brain activity that has been proposed to be responsible for the redistribution of recently encoded memories from temporary dependence on the hippocampus to longer term representation in the cortex. Synchronized SO-spindle activity has been observed to predict overnight memory consolidation. Abnormalities in sleep spindle parameters and synchronized SO-spindle activity have been proposed to explain memory performance deficits present in schizophrenia. The purpose of this review is to familiarize the reader with the current research on the relationship between sleep spindles and memory performance in schizophrenia, and to provide an understanding of the possible role of coordinated SO-spindle activity in this relationship. Methods. This integrated literature review was constituted of articles that build up an understanding of the basic mechanisms of sleep spindles and memory consolidation. The scope was then extended to cover articles concerning the synchronization of sleep spindles and slow oscillations, and its relation to memory performance in schizophrenia patients. Results and conclusions. Some studies observed reduced sleep spindle parameters such as sleep spindle number and density predicting less overnight improvement in memory performance in schizophrenia patients. Cortex-wide synchronized SO-spindle activity was found to predict overnight improvement in healthy controls but not in schizophrenia patients, whereas synchronized SO-spindle activity measured from local brain areas was observed to predict overnight improvement in patients. The result indicates that distributed SO-spindle synchrony could present a hallmark of impaired memory performance in schizophrenia patients.