He focused on a particular segment of the hypothalamus known as the third interstitial nucleus of the anterior hypothalamus, which previous studies had shown to differ significantly between men and women.

In 2008, a new region with properties similar to that of BSTc in regards to transsexualism was found by Garcia-Falgueras and Swaab: the interstitial nucleus of the anterior hypothalamus (INAH3), part of the hypothalamic uncinate nucleus.

INAH3 is the short form for the third interstitial nucleus of the anterior hypothalamus, and is the sexually dimorphic nucleus of humanes.

A seminal paper by Simon LeVay found that the an interstitial nucleus of the hypothalamus INAH3 was found to be dimorphic according to sexual orientation not gender.

For the cell in the midbrain, see Rostral interstitial nucleus of medial longitudinal fasciculus.

The vertical gaze is controlled by the rostral interstitial nucleus of medial longitudinal fasciculus and the interstitial nucleus of Cajal.

The rostral interstitial nucleus of medial longitudinal fasciculus (riMLF) is a portion of the medial longitudinal fasciculus which controls vertical gaze.

Cell group B4 is located in the floor of the fourth ventricle, in the vicinity of the vestibular nuclei and abducens nucleus in the rat and in the caudal interstitial nucleus of the medial longitudinal fasciculus of the mouse.

The origin of the this uncrossed tract is in the interstitial nucleus of Cajal (related to the oculomotor nucleus) which is subsequently found in the Edinger-Westphal nucleus of the midbrain.