Many important cell and fibre groups appear at this level of the neuraxis. One structure apparent in the telencephalon is the amygdala, involved in the regulation of emotion and memory. The thalamus is divided into two separate nuclei, two of which, the ventral posterior nucleus and the ventral lateral nucleus, are labelled. The thalamus provides much of the input to the cerebral cortex, with different thalamic nuclei projecting axons to different areas of the cortex. The ventral posterior nucleus, a part of the somatic sensory system, projects to the cortex of the postcentral gyrus. The ventral lateral nucleus and closely related ventral anterior nucleus (not shown) are parts of the motor system; they project to the motor system of the precentral gyrus. Visible below the thalamus are the subthalamus and the mammillary bodies of the hypothalamus. The subthalamus is a part of the motor system, while the mammillary bodies receive information from the fornix and contribute to the regulation of memory. Because this section also encroaches on the midbrain, a little of the substantia nigra ('black substance') can be seen near the base of the brain stem. The substantia nigra is also part of the motor system. Parkinson's disease results from degeneration of this structure.
Cortical white matter
Mammillary body
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