a narrow band of white matter that crosses the midline of the spinal cord posterior to the central canal and posterior gray commissure (posterior white commissure [TA]) and anterior to the central canal and the anterior gray commissure (anterior white commissure [TA]). SYN: anterior white commissure [TA], commissura alba anterior [TA], commissura alba posterior [TA], ventral white column [TA], ventral white commissure [TA], commissura ventralis alba.