Accessory nuclei of optic tract

The accessory nuclei of optic tract, also called the terminal nuclei of the accessory optic system (AOS), are groups of neurons that receive visual information directly from the retina through accessory optic pathways.

In mammals, the main accessory optic nuclei are the:

• Dorsal terminal nucleus (DTN)

• Lateral terminal nucleus (LTN)

• Medial terminal nucleus (MTN)

The retinal neurons that project to these nuclei are particularly sensitive to the direction and slow movement of images across the retina. This allows the accessory optic system to detect movement of the visual surroundings.

The accessory optic nuclei are closely connected with the nucleus of the optic tract in the pretectal region. Although the nucleus of optic tract has similar functions and strong connections with the accessory optic nuclei, it is considered a separate nucleus.

Function

The main function of the accessory optic system is to help stabilise the visual image during movement. It contributes to optokinetic eye movements, including optokinetic nystagmus, and helps coordinate visual information with the vestibular system and cerebellum to produce compensatory eye movements.

The accessory optic system is therefore mainly involved in reflex control of eye movements and gaze stability, rather than conscious visual perception.