Pretectal Area - Location and Structure

Location and Structure

The pretectum is a bilateral group of highly interconnected nuclei located near the junction of the midbrain and forebrain. The pretectum is generally classified as a midbrain structure, although because of its proximity to the forebrain it is sometimes classified as part of the caudal diencephalon (forebrain). Within vertebrates, the pretectum is located directly anterior to the superior colliculus and posterior to the thalamus. Vertically, it is situated above the periaqueductal grey and nucleus of the posterior commissure.

Several nuclei have been identified within the pretectum, although their borders can be difficult to define and there has been debate over which regions should be included and their precise names. The five primary nuclei are: the olivary pretectal nucleus (OPN), the nucleus of the optic tract (NOT), and the anterior (APN), medial (MPN), and posterior (PPN) pretectal nuclei. The NOT consists of relatively large cells and is located between the superior colliculi. The OPN is located medial to the NOT and has a tail that extends between the NOT and PPN, which is ventral to the OPN. Two additional nuclei have also been identified: the posterior limitans (PLi) and the commisural pretectal area (CPA). While these two regions have not been examined to the same extent as the five primary nuclei, research has shown both the PLi and CPA to receive retinal input which suggests a role in processing visual information.