The term VCA line refers to the vertical axis of the human brain in Talairach space. It passes through the caudal-most point of the anterior commissure in the midline as viewed by ventriculography. It lies in the mid-sagittal plane and is perpendicular to the bicommissural line, which in Talairach space passes through the most dorsal point of the anterior commissure and most ventral point of the posterior commissure in the mid-sagittal plane ( Talairach-1988 ). The Talairach coordinate system is widely used in human MRI studies. In other stereotaxic frameworks, particularly for research on the macaque, the origin is placed at the center of the anterior commissure with the bicommissural line passing through the center of the posterior commissure ( Bowden-2000 ); or the origin is located at the intersection of the interaural line with the mid-sagittal plane ( Paxinos-2000 ).