Real-time tracking of memory formation in the human rhinal cortex and hippocampus

A fundamental question about human memory is which brain structures are inv olved, and when, in transforming experiences into memories. This experiment sought to identify neural correlates of memory formation with the use of i ntracerebral electrodes implanted in the brains of patients with temporal L obe epilepsy. Event-related potentials (ERPs) were recorded directly from t he medial temporal Lobe (MTL) as the patients studied single words. ERPs el icited by words subsequently recalled in a memory test were contrasted with ERPs elicited by unrecalled words. Memory formation was associated with di stinct but interrelated ERP differences within the rhinal cortex and the hi ppocampus, which arose after about 300 and 500 milliseconds, respectively. These findings suggest that declarative memory formation is dissociable int o subprocesses and sequentially organized within the MTL.