Seminar Series

How a desynchronized cortex and a synchronized hippocampus cooperatively form and retrieve memories

Brain oscillations have been proposed to be one of the core mechanisms underlying episodic memory. But how do they operate in the service of memory? Reviewing the literature a conundrum emerges as some studies highlight the role of synchronized oscillatory activity, whereas others highlight the role of desynchronized activity. In this talk, I will describe a recently published computational model that resolves this conundrum and parsimoniously shows how these two opposing oscillatory behaviours may cooperate in the service of memory. Building on empirical evidence, I will argue that the synchronization and desynchronization reflect a division of labour between a hippocampal and a neocortical system, respectively. Specifically, whereas desynchronization is key for the neocortex to represent information, synchronization in the hippocampus is key to bind information. I will then derive specific predictions that arise from this model about how the interaction between a synchronized hippocampus and a desynchronized neocortex is supposed to look like. These predictions will be assessed in a number of empirical studies ranging from non-invasive EEG and MEG data, invasive and non-invasive brain stimulation studies, and studies using intracranial recordings in human epilepsy patients. Together, these data support the notion that a desynchronized neocortex together with a synchronized hippocampus implement memory encoding and retrieval operations in the human brain.