Cerebral Correlates of Memory Consolidation During Human Sleep: Contribution of Functional Neuroimaging

Abstract

Abstract The brain dynamics in humans can be explored using a wide variety of non-invasive neuroimaging techniques: electroencephalography (EEG), magnetoencephalography (MEG), near infrared spectroscopy (NIRS), single photon emission tomography (SPECT), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI). This chapter focuses on the contributions of PET and fMRI. It concentrates on two main topics. First, the pattern of regional brain activity during sleep is consistent with the mechanisms described in animals at the microscopic systems level for the generation and maintenance of sleep states. This aspect is important because if sleep processes are similar in humans and in animals, the links between sleep and memory processes described in the latter are potentially valid in the former. Second, far from being fixed and stereotyped, regional brain function during sleep is modulated by the individual experience acquired during the previous waking period. The chapter presents evidence that these experience-dependent changes in regional brain activity are related to the amount of learning achieved by the subjects prior to sleep and also depend on the material to which the subjects have been exposed. These experiments provide the first experimental evidence in humans for a link between learning, as measured by behavioral methods, and the activity of neuronal populations during sleep.