Jean Piaget's theory suggests that cognitive development proceeds in discrete steps. The first is the sensorimotor period that happens in the first two years of life. In recent years it became clear, that it is necessary to have an intact and mature hippocampus for adequate memory formation, both in experimental animals and humans. In the present study, the morphological development of the human hippocampus was correlated with the developmental changes of intellectual development. Our results suggest that neuronal cell formation of the human hippocampus terminates several weeks before birth. In the dentate gyrus, a small number (less than 1%) of granule cells are still formed around birth. Immature granule cells migrate through the hilar region to their final position in the granule cell layer during the first six postnatal months. Light microscope studies of individual neurons indicate that connections between granule cells and their target neurons are not yet formed at birth. Such connections develop during the third postnatal year. If the development of the synaptic connections is damaged in experimental animals, the hippocampal function will be permanently impaired. Newborns may have basic synaptic circuits for memory formation, but the postnatal morphological changes suggest the significant modification of the hippocampal circuits happening continuously from the newborn age until late childhood. These changes may cause the phenomenon of the 'infantile amnesia'.
|Translated title of the contribution||Postnatal development of the human hippocampal formation|
|Number of pages||6|
|Journal||Lege Artis Medicinae|
|Publication status||Published - Aug 5 2000|
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