Chapter 25 Atlas of the Human Forebrain^*

When the nervous system is discussed in terms of functional subsystems, as in the preceding chapters, it is sometimes difficult to envision how the various parts are related to the whole. Therefore an abbreviated atlas is provided here using the same philosophy as in Chapter 15, with a wide variety of forebrain structures and a few brainstem structures labeled.

Only major structures that are mentioned prominently in this book are indicated. In addition, to keep the number of labels manageable, cerebral sulci and gyri are generally left unlabeled, and a number of structures that appear repeatedly are not labeled every time they appear. Very abbreviated descriptions of labeled structures are provided; additional details can be found elsewhere in the text and in the glossary.

Figure 25-1 Planes of the sections shown in Figures 25-2 to 25-10.

Figure 25-2 Anterior horn of the lateral ventricle.

1. Corpus callosum (body). Commissural fibers interconnecting most cortical areas.

2. Anterior horn of the lateral ventricle.

3. Anterior limb of the internal capsule. Contains projections to and from prefrontal and anterior cingulate cortex, including those from the dorsomedial and anterior nuclei of the thalamus.

4. Insula. Includes gustatory and visceral cortex.

5. Lateral sulcus (sylvian fissure).

6. Anterior end of the temporal lobe (temporal pole). Limbic cortex.

7. Branches of the middle cerebral artery. Will emerge from the lateral sulcus and supply the lateral surface of the cerebral hemisphere.

8. Olfactory tract. Projections from the olfactory bulb to the piriform cortex and amygdala.

9. Anterior cerebral artery. Branches parallel the corpus callosum and supply the medial surface of the frontal and parietal lobes.

10. Gyrus rectus. Part of orbital frontal cortex; extensive limbic connections, particularly in circuits involving the amygdala.

11. Putamen. The part of the striatum with predominantly motor connections.

12. Caudate nucleus (head). The part of the striatum predominantly connected with association cortex.

13. Cingulate gyrus. Extensive limbic connections: anteriorly in circuits involving the amygdala, and posteriorly in circuits involving the hippocampus.

14. Claustrum. Reciprocal connections with cerebral cortex, poorly understood function.

15. Lenticulostriate arteries. Small perforating branches of the middle cerebral artery.

16. Nucleus accumbens. The part of the striatum with predominantly limbic connections.

17. Septal nuclei. Reciprocally connected with the amygdala, hippocampus, hypothalamus, and other limbic structures.

18. Projections from the anterior olfactory nucleus on their way to the anterior commissure.

19. Globus pallidus (external segment). Afferents from the striatum, efferents to the subthalamic nucleus and other parts of the basal ganglia.

20. Gray bridges between the putamen and caudate nucleus; part of the reason the striatum got its name.

21. Septum pellucidum. Paired membrane separating the two lateral ventricles.

Figure 25-3 Anterior commissure.

1. Corpus callosum (body). Commissural fibers interconnecting most cortical areas.

2. Junction between the anterior horn and body of the lateral ventricle.

3. Genu of the internal capsule. Contains projections to and from frontal cortex.

4. Insula. Includes gustatory and visceral cortex.

5. Lateral sulcus (sylvian fissure).

6. Internal carotid artery, just before it bifurcates into the anterior and middle cerebral arteries.

7. Optic chiasm, where optic nerve fibers from the nasal half of each retina decussate.

8. Optic nerve. Axons of retinal ganglion cells on their way to the lateral geniculate nucleus, superior colliculus, and a few other sites.

9. Branches of the middle cerebral artery. Will emerge from the lateral sulcus and supply the lateral surface of the cerebral hemisphere.

10. Putamen. The part of the striatum with predominantly motor connections.

11. Caudate nucleus (junction between the head and body). The part of the striatum predominantly connected with association cortex.

12. Choroid plexus adjacent to the interventricular foramen.

13. Stria terminalis. Efferents from the amygdala to the septal nuclei, basal forebrain, and hypothalamus.

14. Claustrum. Reciprocal connections with cerebral cortex, poorly understood function.

15. Globus pallidus (external segment). Afferents from the striatum, efferents to the subthalamic nucleus and other parts of the basal ganglia.

16. Globus pallidus (internal segment). Afferents from the striatum and subthalamic nucleus, efferents to the thalamus and midbrain reticular formation.

17. Basal forebrain. Includes the basal nucleus (of Meynert), groups of large cholinergic neurons that innervate most forebrain areas.

18. Column of the fornix. Efferents from the hippocampus to the septal nuclei, basal forebrain, and mammillary body.

19. Body of the fornix. Efferents from the hippocampus to the septal nuclei, basal forebrain, and mammillary body.

20. Anterior commissure. Commissural fibers interconnecting the temporal lobes, together with a few crossing olfactory fibers.

21. Olfactory tract. Projections from the olfactory bulb to the piriform cortex and amygdala.

22. Ventral pallidum. Limbic extension of the globus pallidus, with inputs from nucleus accumbens.

23. Reticular nucleus, covering the anterior (and lateral) surface of the thalamus. Afferents from the thalamus and cerebral cortex, GABAergic efferents to the thalamus.

24. Terminal (thalamostriate) vein, adjacent to the stria terminalis.

25. Interventricular foramen.

Figure 25-4 Anterior thalamus.

1. Corpus callosum (body). Commissural fibers interconnecting most cortical areas.

2. Body of the lateral ventricle.

3. Putamen. The part of the striatum with predominantly motor connections.

4. Insula. Includes gustatory and visceral cortex.

5. Lateral sulcus (sylvian fissure).

6. Amygdala. A collection of nuclei forming the core of one of the two major limbic circuits.

7. Optic tract. Axons of ganglion cells from half of each retina, on their way to the lateral geniculate nucleus, superior colliculus, and a few other sites.

8. Column of the fornix. Efferents from the hippocampus to the mammillary bodies.

9. Median eminence of the hypothalamus. Former attachment point of the infundibular stalk.

10. Third ventricle. The two portions indicated are separated by the interthalamic adhesion (massa intermedia).

11. Fibers that will cross in the anterior commissure, interconnecting the temporal lobes.

12. Posterior limb of the internal capsule. Contains projections to and from sensorimotor and parietal cortex, including corticospinal fibers and the somatosensory radiation.

13. Caudate nucleus (body). The part of the striatum predominantly connected with association cortex.

14. Transverse cerebral fissure. An extension of subarachnoid space, situated above the roof of the third ventricle and containing the internal cerebral veins.

15. Dorsomedial nucleus. Connections with prefrontal association cortex.

16. Anterior nucleus. Afferents from the mammillary body (via the mammillothalamic tract), efferents to the cingulate gyrus.

17. Terminal (thalamostriate) vein, adjacent to the stria terminalis.

18. Mammillothalamic tract. Projection from the mammillary body to the anterior nucleus of the thalamus. Part of the Papez circuit.

19. Lenticular fasciculus (passing through the internal capsule). Part of the projection from the internal segment of the globus pallidus to the thalamus.

20. Claustrum. Reciprocal connections with cerebral cortex, poorly understood function.

21. Ansa lenticularis. Part of the projection from the internal segment of the globus pallidus to the thalamus.

22. Interthalamic adhesion (massa intermedia).

23. Medial zone of the hypothalamus. At this level, includes the ventromedial and dorsomedial nuclei.

24. Lateral hypothalamic nucleus.

25. Location of the basal nucleus (of Meynert). Groups of large cholinergic neurons in the basal forebrain that innervate most forebrain areas.

26. Globus pallidus (internal segment). Afferents from the striatum and subthalamic nucleus, efferents to the thalamus and midbrain reticular formation.

27. Globus pallidus (external segment). Afferents from the striatum, efferents to the subthalamic nucleus and other parts of the basal ganglia.

28. Ventral anterior and ventral lateral (VA/VL) nuclei. Afferents from the cerebellum and basal ganglia, efferents to motor areas of cortex.

29. Reticular nucleus of the thalamus. Afferents from the thalamus and cerebral cortex, GABAergic efferents to the thalamus.

30. Body of the fornix. Efferents from the hippocampus to the septal nuclei, basal forebrain, and mammillary body.

Figure 25-5 Midthalamus; mammillary bodies.

1. Corpus callosum (body). Commissural fibers interconnecting most cortical areas.

2. Transverse cerebral fissure. An extension of subarachnoid space, situated above the roof of the third ventricle and containing the internal cerebral veins.

3. Body of the lateral ventricle.

4. Insula. Includes gustatory and visceral cortex.

5. Lateral sulcus (sylvian fissure).

6. Putamen. The part of the striatum with predominantly motor connections.

7. Caudate nucleus (tail). The part of the striatum predominantly connected with association cortex.

8. Inferior horn of the lateral ventricle.

9. Anterior end of the hippocampus, the core of one of the two major limbic circuits.

10. Choroid plexus in the roof of the third ventricle.

11. Third ventricle, the slit-shaped cavity of the diencephalon.

12. Uncus. The proximity of the surface of the uncus to the cerebral peduncle can cause clinical problems.

13. Amygdala. A collection of nuclei forming the core of one of the two major limbic circuits.

14. Posterior limb of the internal capsule. Contains projections to and from sensorimotor and parietal cortex, including corticospinal fibers and the somatosensory radiation.

15. Gray bridge between the putamen and caudate nucleus; part of the reason the striatum got its name.

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