The limbic system in Alzheimer's disease. A neuropathologic investigation

The morphologic alterations of Alzheimer's disease, presenile and senile dementia, have conventionally been associated with the cerebral cortex; however, it is clear that other areas of the brain, notably the hippocampus and amygdala, are involved as well. These structures, together with others such as the fornix, cingulate gyrus, septal nuclei, and mamillary bodies, constitute the limbic system, which has been recognized as the anatomic substrate of memory, emotion, and learning. Disturbances in these modalities are central to the clinical expression of Alzheimer's disease; therefore, the limbic system was studied in its entirety in 9 patients with Alzheimer's disease and in 3 elderly individuals with Down's syndrome, in whom identical morphologic lesions were present. The findings disclose that the limbic system is regularly involved in Alzheimer's disease, to a severe degree and in a distinctively patterned distribution.