ANATOMY OF THE MEDIAL TEMPORAL-LOBE

The medial temporal lobe concept is an example of neurojargon rich in clinical and behavioral meaning, but sparse in neuroanatomical meaning except for topography. Like the concept of anterior speech area, many know roughly where it is located and roughly what its functional corr elates are, but not a lot else. At least three anatomical entities qua lify as components of the medial temporal lobe. These include the amyg daloid body, the hippocampal formation, and the parahippocampal cortic es that cover them superficially and are visible on the external surfa ce of the hemisphere. For the greater part of this century, topographi cal observations, dissection, and descriptive data from passive staini ng methods have formed the principal source of information about the a natomy of the medial temporal lobe. However, in the past two decades m uch new information has emerged from experimental neuroanatomical stud ies in nonhuman primates and from neuropathological studies in humans. With magnetic resonance imaging (MRI), previous neuroanatomical detai l, which earlier may have seemed like descriptive minutia, has now com e alive and assumed substantial relevance in neurological and psychiat ric diagnosis. Some of the emerging concepts as they relate to the neu roanatomy of the primate brain are highlighted and summarized here.