Role of the neocortex in consolidation of fear conditioning memories in rats

The aim of the present work was to investigate, by means of the reversible inactivation technique, the distinct roles of three neocortical sites, the Prefrontal (PFC), Frontal (FC) and Parietal (PAC) cortices, during memory consolidation of conditioned freezing to a tone, a defined conditioned stimulus (CS), and to the training context. Reversible tetrodotoxin inactivations were performed at increasing post-acquisition delays (0.25, 24 or 96 h). Retention testing was always performed 72 h after the inactivation procedure in order to avoid any possible influence on the retrieval phase. It was found that none of the three sites are involved in context freezing consolidation, but that FC and PAC are differentially involved in the consolidation of memory to the CS. FC inactivation was followed by retention impairment only when performed immediately after acquisition while PAC inactivation was followed by amnesia when performed both immediately after acquisition and 24 h later, but not when performed 96 h later. PFC inactivation was not followed by retention impairment at any of the employed delays. These findings show that some neocortical structures are involved in auditory-cued fear conditioning during the initial phases of the consolidation process.