What is "habenular trigone"

The habenular trigone is a small depressed triangular area situated in front of the superior colliculus and on the lateral aspect of the posterior part of the taenia thalami.

It contains a group of nerve cells termed the ganglion habenulæ.

Fibers enter it from the stalk of the pineal gland, and others, forming what is termed the habenular commissure, pass across the middle line to the corresponding ganglion of the opposite side.

Most of its fibers are, however, directed downward and form a bundle, the fasciculus retroflexus of Meynert, which passes medial to the red nucleus, and, after decussating with the corresponding fasciculus of the opposite side, ends in the interpeduncular ganglion.