The Density of Neurons in the Human Hippocampus

Abstract

The aim of this study was to determine the density and pattern of distribution of the neurons in the human hippocampus, and twenty-nine brains of healthy individuals were examined. The cells counted in each unit area were the pyramidal cells in the H-fields and the granule cells. Difference in density was found between all H-fields. The neuronal density was highest in the H2-fields. The density decreased through the transitional area H1-2 and H1, with the lowest density in H3. The neuronal density increased in all H-fields in the antero-posterior direction, while the granule cells decreased in density. In the individual brain there was a positive correlation found respectively between high and low cell density in the different H-fields. The pyramidal cell density decreased in persons more than 68 years old. No difference was found between neruonal cell density in the two sides of the brain. Sex did not influence the neuronal cell density.

Anteroposterior Hippocampal Metabolic Heterogeneity: Three-dimensional Multivoxel Proton1H MR Spectroscopic Imaging—Initial Findings

“…White matter axons in the alveus and fimbria not only ensheathe the hippocampus but also are interposed between its gray matter laminae. Second, the hippocampus is not histologically uniform, with an increase in the density of pyramidal cells and a decrease in the density of granular cells along its anteroposterior axis (21,22).…”

“…White matter axons in the alveus and fimbria not only ensheathe the hippocampus but also are interposed between its gray matter laminae. Second, the hippocampus is not histologically uniform, with an increase in the density of pyramidal cells and a decrease in the density of granular cells along its anteroposterior axis (21,22).Some spectroscopic heterogeneity already has been observed: A posterior-toanterior decrease in the NAA/(creatine ϩ choline) ratio along the hippocampus was seen in patients with medial temporal lobe epilepsy (bilaterally) and young control subjects (23). An NAA/creatine ratio decrease in control subjects and medial temporal lobe epilepsy (ipsilateral only) patients was reported but not specifically discussed by Hetherington et al (24).…”

Preservation of hippocampal neuron numbers in aged rhesus monkeys

“…Geinisman et al [15] extensively reviewed the data on neuronal numbers and densities in the hippocampus of aging subjects. Whereas some studies reported no age-associated loss in human hippocampal fields CA1-4 and the subiculum [10], other studies demonstrated a decrease of neuron numbers or densities in all or some of the hippocampal subfields or the dentate gyrus with advancing age [7,32,36,39]. Most, but not all, of these earlier studies made assumptions about size, shape, and distribution of the neurons, and for that reason these techniques are now designated as assumption-based counting techniques.…”

Changes in Cell Density within the Human Hippocampal Formation as a Function of Age

“…An increasing neuron population is not without precedent -Bayer et al [1982] note that, in rats, dentate gyrus granule cells continue to be produced during adulthood. In light of the reports by Shefer [1973,1977], Ball [1977] and Dam [1979], however, it appears less likely that such a proliferation of neurons is taking place within the human hippocampus in adulthood.…”

“…In histologic sections of human brains Dam [1979] observed a decreased number of neurons in the hippocampal regions of all brains beyond 68 years of age. The right side of the hippocampus was found to be equal in density to the left, and no sexual differences were observed.…”