Chapter 12 Ratio of pyramidal cells versus non-pyramidal cells in the human frontal isocortex and changes in ratio with ageing and Alzheimer's disease

Publisher Summary This chapter presents a study that assesses the percentages of both the pyramidal neurons and the non-pyramidal cells in various layers of a defined prefrontal isocortical area of the human adult and it has the ultimate goal of examining whether changes of these percentages occur with ageing and in Alzheimer's disease. The neuronal constituents of the mammalian telencephalic cortex can generally be classified as either pyramidal neurons or non-pyramidal neurons. In general, pyramidal cells and the modified forms of pyramidal cells can be considered as projection neurons, while most non-pyramidal cells can be referred to as local circuit neurons. Lipofuscin pigment granules can frequently be encountered in nerve cells of the human adult. The size, shape, stainability, and pattern of distribution of these granules can serve as characteristics for the differentiation of various neuronal types forming the human brain. Pigmented nerve cells show a slight increase in the number of lipofuscin granules with age, but this does not change the typical pattern of pigmentation. The pigmentation of pyramidal cells and modified pyramidal cells differs considerably from that seen in the nonpyramidal neurons. After the demonstration of the correspondence of the pigment characteristics and the nerve cell type as seen in the Golgi preparation, a combined pigment, Nissl, preparation allow to quantitatively analyze the proportions of the various types of cortical constituents at light microscopical level and enables to study their pattern of distribution throughout various cortical layers.