A group of cells that fluoresce for dopamine and are distributed in clusters that, in the primate, are ventral and medial to the mammillothalamic tract of the hypothalamus; a few extend into the reuniens nucleus of the thalamus (Felten-1983). In the mouse A13 is located ventral to the mammillothalamic tract of the thalamus in the zona incerta (adapted from Brain Info). [ NLX:91101 ]