Contextual Fear Conditioning Selectively Increases Levels of Arc and c-Fos Proteins in the Dorsal, but not the Ventral Hippocampus.

The hippocampus plays an important role in contextual fear-conditioning and exhibits functional specialization along its dorso-ventral axis. The dorsal hippocampus (DH) is primarily involved in spatial and contextual processing, whereas the ventral hippocampus (VH) modulates affective and emotional components of memory. Although these regions are functionally interconnected, their differential neuronal temporal dynamics during contextual fear conditioned (CxFC) memory consolidation and retrieval remain unclear. In this study, we examined the selective engagement and activity-dependent changes during the early phase of CxFC memory consolidation and retrieval in the DH and VH. Mice were subjected to fear-conditioning, and freezing behaviour was assessed during baseline, training, and testing sessions as a measure of fear memory. The levels of Arc and c-Fos proteins in the DH and VH were measured at 0, 1, 3, and 5 h. The freezing response increased significantly during testing compared to the baseline day. The level of Arc and c-Fos proteins significantly increased in the DH but not in the VH during the training and testing days. Arc levels in the DH showed a time-dependent increase, peaking at the 1st hour, and remaining significantly elevated through the 5th hour on conditioning and post-conditioning days, with no corresponding changes observed in the VH. Similarly, c-Fos levels in the DH increased significantly at 1