'tweenbrain

Noun

 * 1)  The region of the human brain, specifically the human forebrain, that includes the thalamus, the hypothalamus, the epithalamus, the prethalamus or subthalamus, and the pretectum.
 * 2) * 1931, Medicine: Tweenbrain & Stomach:
 * Deep within the brain is a biologically ancient section called the diencephalon or tweenbrain.
 * 1) * 2007, Robb S. Rehberg, Sports Emergency Care: A Team Approach
 * The brainstem constituents include the medulla oblongata, pons varolii, midbrain, and tweenbrain.