Episodic memory is the time machinery that allows us to mentally travel back in time in order to relive past experiences, often in great sensory detail. These memories are highly associative and very information rich, but how are these memories coded in human brains? Any mechanism accounting for episodic memory must accomplish at least two functions: to build novel associations, and to represent the information constituting the memory.
Neural oscillations, regulating the synchrony of neural assemblies, are ideally suited to accomplish these two functions, but in opposing ways. On the one hand, neurophysiological work suggests that an increase in synchrony strengthens synaptic connections and thus forms the basis for associative memory. Information theory, on the other hand, suggests that decreased synchrony is necessary to flexibly express information rich patterns in a neural assembly. Therefore, a conundrum exists as to how oscillations code episodic memory. The aim of this project is to propose and test a new framework that has the potential to reconcile this conflict. This framework assumes that both synchronized and desynchronized neural behaviour cooperatively code episodic memories in the human brain but play different roles. In a nutshell, synchronization is believed to bind information in the episodic memory system, whereas desynchronization represents this information. Thereby, synchronization is the “glue” that holds memories together, whereas desynchronization represents the content of these memories.
In this ERC funded project Dr Hanslmayr and his team will test this hypothesis in a series of complex experiments involving invasive and non-invasive electrophysiological imaging techniques and brain stimulation.