Stereotaxic coordinates define positions in the brain along three axes:
- Anterior-Posterior (AP): measured from Bregma, positive values anterior (toward the nose), negative values posterior (toward the cerebellum)
- Medial-Lateral (ML): measured from the midline, increasing toward the ears; bilateral targets are written with ±, as in ±1.8 mm
- Dorsal-Ventral (DV): measured from the brain surface or skull, increasing in depth
In an adult mouse, a coordinate like AP -2.0, ML 1.5, DV 1.2 falls in the dorsal hippocampus. Structure positions relative to Bregma shift with age, sex, and strain, so atlas coordinates are adjusted for each study.