On the basis of recent investigations some masses of grey matter lying in the region of the anterior perforated substance are now described as the ventral striatum. In Fig. 14.4 we see the anterior part
of the caudate and lentiform nuclei. Inferiorly, the two nuclei fuse to the form the fundus striati. Immediately below the fundus striati we see the olfactory tubercle (in the anterior perforated substance). More medially, we see a mass of grey matter called the nucleus accumbens. Note that this nucleus is closely related to the caudate nucleus (superolaterally) and to the septal nuclei medially. The ventral striatum consists of the nucleus accumbens and the olfactory tubercle.
A coronal section through the brain a little posterior to the plane of Fig. 14.4 is shown in Fig. 14.5. Note the anterior commissure running laterally just below the head of the caudate nucleus. It cuts through the globus pallidus. The part of the globus pallidus lying inferior to the anterior commissure is called the ventral pallidum. Identify the olfactory tubercle in Fig. 14.5. Medial to it there is a collection of neurons that form the basal nucleus of Meynert. In this figure the position of the nucleus accumbens is shown diagrammatically: it actually lies more anteriorly.
The reason for considering the nucleus accumbens and the olfactory tubercle as parts of the striatum is that their connections are very similar to those of the main part of the striatum (or dorsal striatum). These are shown in Fig. 14.6 which should be compared with Fig. 14.3.
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