Chapter 11: The role of the primate lateral terminal nucleus in visuomotor behavior

Abstract

This chapter discusses the role of the primate lateral terminal nucleus in visuomotor behavior. The neural pathways subserving the optokinetic reflex and its interaction with the vestibulo-ocular reflex (VOR) are not fully understood, but they are thought to involve the accessory optic system (AOS). In the cat and rabbit, the AOS consists of three terminal nuclei (lateral, medial and dorsal; LTN, MTN, DTN) distributed along the mesencephalic brainstem and the nucleus of the optic tract (NOT) located in the pretectum. Although the anatomical organization of the monkey AOS has received some attention, relatively little is known about the signals it carries. Recently, it is shown that single NOT units encode the direction of visual movement and that electrical stimulation of the primate NOT elicits a horizontal optokinetic nystagmus (OKN) with most of the classic features present in visually induced OKN. In addition to responding to full-field visual motion, many of the LTN units discharged to movement of a small spot. This ability to respond to small visual stimuli has also been reported in the primate NOT.