The Role of the Locus Coeruleus in Cellular and Systems Memory Consolidation

Synaptic plasticity, neuronal replay, and cross-regional communication are considered key physiological processes underlying memory consolidation. Both cellular and systems-level consolidation hypotheses are supported by extensive empirical evidence. However, presently, little is known about the temporal relations between local synaptic modifications and activity dynamics within extended neuronal networks supporting memory. The diffuse ascending neuromodulatory systems, with the locus coeruleus (LC) noradrenergic system being one of them, appear to be ideal candidates for bridging the cellular and systems mechanisms of memory consolidation. According to a canonical view, noradrenaline release from the terminal fields of LC neurons creates a window of heightened synaptic plasticity within a recently activated neuronal network. Importantly, this neuromodulatory input is critical at times of actual learning experience but also functions “off-line,” when experience-activated neuronal ensembles replay and protein-dependent synaptic modifications occur. Tracking the connectivity strength within learning-related large-scale networks combined with monitoring neuromodulatory activity and behavioral assessment of memory appear irreplaceable methodology for examining interactions between cellular and systems mechanisms of memory consolidation, which are both dependent on neuromodulation