Nucleus Accumbens

  • Lateral ventricle
  • Head of caudate
  • Internal capsule
  • External medullary lamina of the globus pallidus
  • Anterior commissure
  • Globus pallidus

The nucleus accumbens (Nac) is traced in the coronal plane. Tissue segmentation based on semiautomated algorithms that classifies each voxel as gray matter, white matter or ventricular CSF, is used for each slice in order to precisely define landmarks and delineate the borders of the NAc. Additional, axial viewing planes are used to aid in corroboration of NAc anatomy.

  1. The first slice containing the most rostral end of the ventral caudate-putamenal junction marks the anterior boundary of the NAc (internal capsule separate from white matter) (Fig. 1a and Fig. 1b). On slices rostrally with respect to the anterior commissure, the superior border of the NAc is demarcated by a line that connects the inferiormost tip of the lateral ventricle to the most ventral point of the internal capsule at the level of the ventral putamen. From this last point, a vertical line is drawn from the tip of the internal capsule down to the white matter thus defining the lateral border with the putamen (Fig. 1a).
  2. The medial border is identified by a line which includes all gray matter next to the white matter tract (olfactory radiation, radiation of the corpus callosum, olfactory tubercle) (Fig. 2a and Fig. 2b). Note that sometimes this medial white fiber tract appears to be discontinuous, in this case the two points of the fiber tract are connected at their shortest distance (Fig. 3a and Fig. 3b).
  3. Once the globus pallidus appears, the superior border is extended from the internal capsule to the lateral inferiormost tip of the external medullary lamina of the globus pallidus; then a vertical line is traced straight down to adjacent white matter (Fig. 4).
  4. Once the anterior commissure starts to decussate, a line is started from the junction of the internal capsule and the anterior commissure and then arced to the end point of the anterior commissure (Fig. 5). The last slice clearly containing the midline decussation of the anterior commissure demarcates the posterior boundary of the NAc.