Reactivation in cortical and subcortical systems during consolidation of declarative memory - investigations in wakefulness and sleep

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After encoding, new memory traces are initially fragile and have to undergo a process of consolidation. These processes can occur at the synaptic level as well as on a systems level. Sleep has been shown to play an important role for several types of memory. One of the most influential theories states that during sleep, new memory traces are reactivated repeatedly and thus strengthened, reprocessed and transferred between different storage locations. Starting from this hypothesis, the present project aims to find brain mechanisms which underlie memory consolidation in human declarative memory. Based on previous studies, special attention will be given to a number of coordinated events occurring during sleep: the sleep slow oscillation, sleep spindles, hippocampal and locus coeruleus (LC) activity. Using a new task that allows to study the effect of sleep on memory more efficiently, questions of the influence of interference intervening between learning and recall will be addressed. EEG studies are planned to find signs of memory reactivation in ongoing brain activity during sleep after periods of intensive learning. Combined EEG/fMRI will be used to test current hypothesis of memory transfer between different brain regions during sleep. By means of pharmacological manipulation of the noradrenergic system and concurrent functional magnetic resonance imaging (fMRI), the contribution of the LC to memory consolidation will be investigated. Additionally, the impact of medications reducing noradrenergic activity on long‐term memory function will be examined.