The connectional anatomy of the temporal lobe.

The idea of a temporal lobe separated from the rest of the hemisphere by reason of its unique structural and functional properties is a clinically useful artifact. While the temporal lobe can be safely defined as the portion of the cerebrum lodged in the middle cranial fossa, the pattern of its connections is a more revealing description of its functional subdivisions and specific contribution to higher cognitive functions. This chapter provides an historical overview of the anatomy of the temporal lobe and an updated framework of temporal lobe connections based on tractography studies of human and nonhuman primates and patients with brain disorders. Compared to monkeys, the human temporal lobe shows a relatively increased connectivity with perisylvian frontal and parietal regions and a set of unique intrinsic connections, which may have supported the evolution of working memory, semantic representation, and language in our species. Conversely, the decreased volume of the anterior (limbic) interhemispheric temporal connections in humans is related to a reduced reliance on olfaction and a partial transference of functions from the anterior commissure to the posterior corpus callosum. Overall the novel data from tractography suggest a revision of current dual stream models for visual and auditory processing.