The septo-hippocampal pathways and their relevance to human memory: a case report

The interaction between the septal region and the hippocampal formation appears indispensable for the maintenance of normal memory and learning mechanisms in humans. The disruption of some combination of septo-hippocampal pathways, especially the disruption of the "dorsal route", deteriorates explicit memory functions. The case of a 25-year-old male patient is presented who developed anterograde and to a certain extent retrograde amnesia following rupture and repair of an arteriovenous malformation in the atrium of the left ventricle. A left-sided lesion of the dorsal route involving the posterior cingulate bundle, the longitudinal striae (as part of the supracommissural hippocampus) and the fornix appeared responsible for his mnemonic deficits. The implications of these findings for the understanding of other clinical cases, particularly those with lesions of the septal region, the anterior and posterior singular gyrus/cingulate bundle and the fornix are discussed.