A zebrafish swims toward its intended target, but strong currents push it off course. Nevertheless, the tiny fish swims back to its original location, determined to finish its journey. How do animals know where they are in their environment, and how does this determine their subsequent choices? Scientists at Howard Hughes Medical Institute’s (HHMI’s) Janelia Research Campus discovered that the hindbrain--an evolutionarily conserved or “ancient” region in the back of the brain--helps animals compute their location and use that information to figure out where they need to go next. The new research, published in Cell on Dec. 22, 2022, uncovers new functions for parts of the “ancient brain,” findings that could apply to other vertebrates. The open-access article is titled “A Brainstem Integrator for Self-Location Memory and Positional Homeostasis in Zebrafish.”