Anatomical asymmetries in the human hippocampal formation
Department of Anatomy, Porto Medical School
Department of Anatomy, Porto Medical School
Department of Anatomy, Porto Medical School
Al. Hernâni Monteiro, 4200 Porto, Portugal
Résumé
Abstract
Unbiased stereological methods were used to evaluate whether in humans there are right/left asymmetries in the morphology of the hippocampal formation. The quantitative parameters analyzed were the volume of the layers, the total number of neurons and the mean neuronal volume. In the dentate gyrus, the estimations were carried out in the granule cell layer and in the polymorphic layer (hilus); in the hippocampus proper they were undertaken in the pyramidal cell layers of the CA1 and CA3-2 fields. The analyses were performed in glycolmethacrylate-embedded sections, sampled using a systematic random procedure, from six right and six left hippocampal formations. The volume of the layers was estimated by applying the Principle of Cavalieri; the total number of neurons in each layer was estimated by means of the optical fractionator; the mean somatic and nuclear volumes of the granule, hilar and pyramidal neurons were estimated by using vertical sections and the nucleator" method.
The right hippocampal formation contained 20% more granule cells and 14% more CA3-2 pyramidal neurons than the left. No right/left asymmetries were found in the number of hilar and CA1 pyramidal cells. The volume of the cell-containing layers and of the hilus was similar in the right and left hippocampal formations. Likewise, no right/left differences were detected in the mean somatic and nuclear volumes of the granule, hilar and pyramidal neurons.