a white fiber bundle descending in the precommissural septum toward the base of the forebrain, immediately rostral to the lamina terminalis; this band consists of a horizontal limb [TA] (crus horizontale [TA]) and a vertical limb [TA] (crus verticale [TA]), and the cells associated with the band form the nucleus of the diagonal band [TA] (nucleus striae diagonalis [TA]); at the base, the bundle turns in the caudolateral direction; traveling through a ventral stratum of the innominate substance alongside the optic tract, it fades before reaching the amygdala. SYN: diagonal band [TA], stria diagonalis [TA].