Direct geniculo-extrastriate pathways: a review of the literature.

Abstract

The aim of this paper is to review the literature on direct geniculo-extrastriate pathways with special attention to 3D extrastriate visual areas. A literature review was realized using PubMed and Google Scholar. "Lateral geniculate nucleus", "geniculo-extrastriate pathways" and "white matter fiber tracts" were among the keywords used. Existence of geniculo-extrastriate connections was first hypothesized by the clinical observations of Riddoch's syndrome in patients with striate cortex (primary visual area, V1) lesions. Robust histological proof of geniculo-extrastriate pathways exists in monkeys. In humans, these pathways were tested through functional magnetic resonance imaging (fMRI), electro- and magneto-physiological paradigms. Conversely, only indirect proof of the connection between lateral geniculate nucleus and V5 exists. To our knowledge there were not any anatomical studies of geniculo-extrastriate connections in humans. Few human studies take interest in geniculo-extrastriate pathways. Only indirect proof of geniculo-extrastriate pathways exists in humans.