The core of the brain arm pit

Nucleus interpeduncularis

The nucleus interpeduncularis is located in the bottom of the fossa interpeduncularis in the mesencephalon. The nucleus is usually included in the limbic system and receives the tractus habenulo-interpeduncularis/fasciculus retroflexus from the habenula nuclei.
An extensive signal flow emanates from the nucleus interpeduncularis to the rostral group of rafe nuclei.