CHOLINERGIC MODULATION OF NETWORK DYNAMICS MEDIATES SWITCHING BETWEEN MEMORY ACTIVATION AND REACTIVATION MODES DURING DIFFERENT VIGILANCE STATES AND SUPPORTS FORMATION OF COMPLEX MEMORY REPRESENTATIONS

Neuromodulatory mechanisms in the brain control network dynamics, and can critically switch its function. Here we investigate the role of changing cholinergic levels during different vigilance states in modulating information processing during spatial tasks. ACh is a potent neuromodulator that is typically high during active waking and low during quiet wake and influences network dynamics via various synaptic and cellular mechanisms. We model the different vigilance states by modeling the effects of Acetylcholine concentrations through the M1 receptor pathway. Specifically, we simulate a complex maze run during which a rat traverses a maze composed of multiple junctions, represented spatially by activation of a network of excitatory neurons. We show that variations in ACh levels change the network-wide E/I balance driving distinct activation patterns in the network. Specifically, high ACh concentrations, associated with active waking, activate only local neuronal representations that code for spatially limited features of the memory. In contrast low ACh concentrations, associated with quiet waking, synchronously reactivate long-range paths representing an extended memory trace. This differential activation and subsequent consolidation of different memory features via spike timing dependent plasticity (STDP) allows for more efficient consolidation of the experienced trajectory as well as the formation of an alternative abstract representation of the memory trace. In all, our results indicate ACh may play a critical role in controlling interplay between online memory storage and offline consolidation during various vigilance states.