Although the hippocampus is responsible for recording new memories, growing evidence suggests that long-term memories undergo a process of consolidation and reside in the cerebral cortex. New research by scientists at the University of Arizona, in Tucson, investigating this shift provide an electrophysiological explanation of this process (Takehara-Nishiuchi K et al. Science. 2008;322:960-963).
In the study, rats learned during a 2-week training period to respond to a tone that consistently preceded a mild shock when they were placed in a square enclosure but not when they were in a circular enclosure (in which the tone occurred only intermittently). Late in this training period, electrodes in the medial prefrontal cortex began to record a higher rate of firing in some neurons after the tone sounded when the rat was in the square enclosure but not in the circular one.
Hildreth CJ. Consolidating Memories. JAMA. 2009;301(1):26. doi:10.1001/jama.2008.927