Human memory formation is accompanied by rhinal-hippocampal coupling and decoupling

In humans, distinct processes within the hippocampus and rhinal cortex supp ort declarative memory formation. But do these medial temporal lobe (MTL) s ubstructures directly cooperate in encoding new memories? Phase synchroniza tion of gamma-band electroencephalogram (EEG) oscillations (around 40 Hz) i s a general mechanism of transiently connecting neural assemblies. We recor ded depth-EEG from within the MTL of epilepsy patients performing a memoriz ation task. Successful as opposed to unsuccessful memory formation was acco mpanied by an initial elevation of rhinal-hippocampal gamma synchronization followed by a later desynchronization, suggesting that effective declarati ve memory formation is accompanied by a direct and temporarily limited coop eration between both MTL substructures.