Thalamus and Hypothalamus

• The thalamus is a collection of subcortical grey matter and part of the diencephalon (along with the hypothalamus) involved in relaying information between different functional regions of the CNS.
• It borders the dorsal part of the third ventricle and functions as part of the lateral wall of the ventricle.

Thalamic nuclei

• There are three main types of thalamic nuclei: relay, association, and nonspecific nuclei.
  • Relay nuclei have very distinct inputs and outputs.
  • Association nuclei receive a majority of their input from the cortex and project fibers to other cortical regions.
  • Nonspecific nuclei broadly project to numerous cortical regions.

Relay nuclei

• Ventral posterior lateral (VPL) nucleus: Relay center for sensory information of the body. The output is to the postcentral (sensory) gyrus.
• Ventral posterior medial (VPM) nucleus: Relay center for sensory information of the face. The output is to the postcentral (sensory) gyrus.
  • The VPM is also the relay center for taste.
• Lateral geniculate body/nucleus (LGN): Relay center for vision. Receives input from the retina with output to the primary visual cortex via optic radiations.
  • Optic radiations from the upper visual world travel through the temporal lobe and optic radiations from the lower visual world pass through the parietal lobe.
• Medial geniculate body/nucleus (MGN): Relay center for hearing. Receives input from the inferior colliculi and projects to the primary auditory cortex.
• Ventral anterior (VA) nucleus: Conveys motor information from basal ganglia to the premotor cortex. It plays a role in the initiation of movement.
• Ventral lateral (VL) nucleus: Conveys motor information from both the cerebellum and basal ganglia to the primary motor cortex.