[Orientation and direction sensitivity of cells in subcortical structures of the visual system]

Since the work of Hubel and Wiesel, it is generally accepted that visual orientation and direction selectivity are achieved by processes in the visual cortex in the higher mammals. This view seems to require revision in views of more recent experimental finding that both relay cells in the lateral geniculate nucleus (LUN) and the ganglion cells in the retina do show some orientation and direction sensitivities. Such selective sensitivities in the LGN which are genetically determined and not affected by post-nated environment, would furnish a basis for further architectural fabrication in the visual cortex for orientation/direction detection. Relativiely segregated grouping in the LGN plays an important role in the formation of parallel processing pathways of the visual system. In the course of post-natal development of the visual system, the emergence of orientation/direction sensitive cells in the subcortical level would contribute to enhance intracortical mechanisms to achieve more refined orientation/direction detectability.