40 - Neurobiology of the Aging Brain

Abstract

This chapter discusses the age-related alterations occurring in the brain at cellular and subcellular levels. At variance with other organs, where the functional and structural units are repeated, the brain is a composite assembly of groups of cells with different metabolic features and functional tasks. A significant decrease in brain weight is a widely documented sign of aging. Widening of sulci and enlargement of ventriculi are also estimations accounting for age-related brain atrophy and are reported to progress according to the reduction in brain weight. Glial cells are very numerous, and in some parts of the brain, they outnumber the nerve cells by 10 to 1. Atheroma is the term used to define the caseous material, containing high amounts of lipids, found in plaque-like thickenings of the interior portion of the vessel wall. Fibrous streaks consist mainly of monocyte-derived macrophages that have entered the intima from the blood stream. The abundant presence of lipid droplets, mainly cholesterol ester, within the cytoplasm transforms these macrophages into foam cells. Cerebral atrophy is responsible for secondary changes of the artery wall that lead to pathological alterations of the aging brain.