Hippocampus - Hippocampal Formation

Hippocampal Formation

Various sections of the hippocampal formation are shown to be functionally and anatomically distinct. The dorsal (DH), ventral (VH), and intermediate regions of the hippocampal formation serve different functions, project with differing pathways, and have varying degrees of place field neurons (Fanselow & Dong, 2009). The dorsal region of the hippocampal formation serves for spatial memory, verbal memory, and learning of conceptual information. Using the radial arm maze Pothuizen et al. (2004), found lesions in the DH to cause spatial memory impairment while VH lesions did not. Its projecting pathways include the medial septal complex, and supramammillary nucleus. The dorsal hippocampal formation also has more place field neurons than both the ventral and intermediate hippocampal formation (Jung et al., 1994). The intermediate hippocampus has overlapping characteristics with both the ventral and dorsal hippocampus (Fanselow & Dong, 2009). Using PHAL anterograde tracing methods, Cenquizca and Swanson (2007) located the moderate projections to two primary olfactory cortical areas and prelimbic areas of the mPFC. This region has the least amount of place field neurons. The ventral hippocampus functions in fear conditioning and affective processes. Anagnostaras et al. (2002) showed that alterations to the ventral hippocampus reduced the amount of information sent to the amygdala by the dorsal and ventral hippocampus, consequentially altering fear conditioning in rats.