Ume Eder Bat (A beautiful child) (popular song from Basque folklore) The aim of this monograph is to introduce the postnatal development of morphological features that are relevant to readers interested in the neurobiology and pathology of the hippocampal formation in terms of the complex phenomena that underlie the progressive anatomical and functional maturation of this brain region. This review focuses on the morphological aspects, while more detailed basic phenomena associated with neuronal maturation―which are undoubtedly also of great interest―are only marginally referred to, although a selection of behavioral and clinical aspects will also be briefly addressed in an attempt to illustrate real situations in different clinical specialties. The creation of this monograph is justified by the increasing importance and growing awareness shown in recent years of neurodevelopmental disorders in children. This awareness is leading to increasing refinement in clinical exami- tions of patients that may suffer from different neurodevelopment-related diseases, such as autism, epilepsy, memory disorders, etc. To the best of our knowledge, this work is the first comprehensive description of the postnatal changes in the hip- campal formation in its different constituent fields. Given the growing sensitivity and accuracy of neuroradiological examinations, particularly MRI, we also sought to offer a glimpse at the MRI aspects related to the development of the hippocampal formation in the human infant.
The postnatal development of the human hippocampal formation (HF) is subject of increasing interest due to its implication in important pathologies that hamper the normal development of children. In this work, the authors present a glimpse of the main events that constitute important milestones in the development and shaping of some of the most important psychological capabilities such as autobiographical memory. Although they examined some cases in the last trimester of gestation, their description starts at birth, around 40 gestational weeks. Serial sections with thionin for Nissl analysis revealed that all fields of the HF were present and identifiable at birth. However, the relative growth of the cortical mantle was much higher relative to the HF. The main structural changes took place during the first postnatal year, in particular in the dentate gyrus and in the entorhinal cortex. At subsequent ages, a growth in size was noted in all components of the HF. This growth was more evident at the body and tail of the hippocampus, as evidenced by measurements of the neuroanatomical series. In addition, the authors examined in some cases the MRI appearance of the HF at different postnatal ages obtained by post-mortem imaging. MRI neuroanatomical series provided anatomically identified landmarks useful for the MRI identification of different components of the HF during postnatal development.
