Tegmentum

Lies below the Tectum. It's a collection of nuclei with movement-related, species-specific, and pain-perception functions.

Red nucleus
Controls limb movements.

Substantia nigra
Connects to the forebrain, and is important for initiating movements. Also produces dopamine for the dopaminergic system.

Destruction of the substantia nigra can lead to Parkinson's disease.

Periacqueductal gray matter
Contains circuits controlling species-specific behaviour.