Understanding retrosplenial amnesia: insights from animal studies.

Bilateral damage in the posterior cingulate region can induce anterograde amnesia. Identifying the potential contributions of the various areas within this heterogeneous region has, however, largely depended on animal research. Within the posterior cingulate region the retrosplenial cortex stands out by virtue of its dense interconnections with the hippocampal formation and anterior thalamic nuclei. Consistent with these connections is the finding from lesion studies in animals that the retrosplenial cortex is necessary for navigation and spatial learning, and that these functions occur in close conjunction with the hippocampal formation and anterior thalamus. Suggested functions include the creation and maintenance of scenes, linked to the switching between scenes based on different frameworks (e.g. egocentric versus allocentric). More fine-grain analyses suggest that there are functional distinctions between the subregions within the retrosplenial cortex, though these subregions are likely to then act as a coordinated unit. Other studies reveal that the retrosplenial cortex is highly sensitive to damage in distal sites, including damage to sites that do not have direct retrosplenial connections. The resultant retrosplenial dysfunctions, which include decreases in metabolic activity and a loss of plasticity, may contribute both to diencephalic and temporal lobe amnesias as well as to Alzheimer's disease.