The Diencephalon

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The auditory system | Main Anatomy Index | The hypothalamus

Last updated 30 March 2006

The Diencephalon

  1. The epithalamus, which included the pineal gland and nearby structures;
  2. The thalamus (G. inner chamber);
  3. The subthalamus;
  4. The hypothalamus.


Borders of the Diencephalon

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The Epithalamus


Pineal Gland

Retina --> one or more relays in hypothalamus --> intermediolateral column of spinal cord --> preganglionic sympathetic fibres --> postganglionic neurons of the superior cervical ganglion --> pineal gland




Habenulointerpeduncular Tract


Stria Medullaris Thalami

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The Subthalamus

  1. Inferior to the thalamus;
  2. Lateral to the hypothalamus;
  3. And medial to the basis pedunculi and internal capsule.


Subthalamic Nuclei


Zona Incerta

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The Thalamus

  1. Anteriorly to the interventricular foramen;
  2. Superiorly to the transverse cerebral fissure;
  3. Inferiorly to the hypothalamic sulcus;
  4. And posteriorly it overlaps the midbrain.


Overall Pattern of Thalamic Connections

  1. Their topographical locations in the thalamus;
  2. And the pattern of their connections with the cerebral cortex.
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Topographical Subdivisions of the Thalamus

Click here for a schematic diagram of the thalamus.


Internal Medullary Lamina


Medial Group of Thalamic Nuclei


Lateral Group of Thalamic Nuclei

  1. The large pulvinar;
  2. The lateral posterior nucleus (LP);
  3. And the lateral dorsal nucleus (LD).
  1. The ventral anterior nucleus (VA);
  2. The ventral lateral nucleus (VL);
  3. And the ventral posterior nucleus (VP).


Other Thalamic Nuclei

  1. The lateral geniculate nucleus (visual system) and medial geniculate system (auditory system) are located posterior and a bit ventral to the VPL/VPM.
  2. The internal medullary lamina, a certain locations, splits and encloses groups of cells.
  3. The external medullary lamina is a 2nd curved sheet of myelinated fibres that cover the lateral surface of the thalamus.
  4. The midline nuclei of the thalamus are a thin layer of cells that covers part of the medial surface of the thalamus.


Functional Subdivisions of the Thalamus

Specific Relay Nuclei


Association Nuclei


Non-specific Nuclei

  1. The basal ganglia;
  2. The cerebellum;
  3. The brainstem reticular formation;
  4. And the spinothalamic and spinoreticulothalamic fibres (carrying information about dull, aching pain).


Subcortical Nuclei

Table derived from Nolte (1993) The Human Brain 3rd Ed. Table 7, p. 259 and Dr. Robinson UNSW Neuroanatomy (ANAT 2007) Lecture Handout, 31 August 1998.

Type Name of Nucleus Major Input Major Output Function
Specific Relay Lateral geniculate Optic tract Primary visual cortex (area 17) Vision
Medial geniculate Inferior colliculus and lateral lemniscus Primary auditory cortex (areas 41, 42) Hearing
Ventral posterolateral Medial lemniscus, spinothalamic tract Primary somatosensory cortex (areas 1-3) Pain, temperature, touch, proprioception (body)
Ventral posteromedial Trigeminothalamic tracts and solitary nucleus Primary somatosensory cortex (areas 1-3) Pain, temperature, touch, proprioception (head)
Ventral lateral Dentate nucleus, substantia nigra, globus pallidus Primary motor cortex (area 4), premotor cortex (area 6) Initiation of movement
Ventral anterior Globus pallidus, substantia nigra Premotor cortex (area 6) and prefrontal cortex Planning of movement
Anterior Hippocampus (fornix), mammillothalamic tract Cingulate gyrus Emotion and memory (limbic)
Association Pulvinar Retina, superior colliculus, secondary visual cortex (areas 18, 19) Parietal-occipital-temporal association cortex Vision recognition(?)
Lateral posterior Superior colliculus (**unknown**) Parietal association cortex **Unknown**
Lateral dorsal Hippocampus (fornix) Cingulate gyrus Memory (limbic)
Dorsomedial Spinothalamic tract, amygdala & Entohinal cortex Prefrontal cortex Emotional response to pain and memory
Non-specific Part of ventral anterior Other thalamic nuclei(?) Prefrontal cortex  
Centromedian Reticular formation, spinothalamic, trigeminothalamic tracts Frontal and parietal lobes, caudate nucleus and putamen Alertness and response to pain
Subcortical Thalamic reticular All thalamic nuclei and cortical regions All thalamic nuclei Attension


Blood Supply of the Thalamus

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The Internal Capsule

  1. The thalamocortical and corticothalamic fibres;
  2. The corticopontine, corticobulbar and corticospinal fibres pass through the internal capsule and then the cerebral peduncles;
  3. And the fibres projection from the cerebral cortex to the various nuclei of the extrapyramidal system (e.g., the putamen and caudate nucleus).


Shape of the Internal Capsule

  1. The anterior limb is the portion between the lenticular nucleus and the head of the caudate nucleus;
  2. The posterior limb is the portion between the lenticular nucleus and the thalamus;
  3. The genu the portion at the junction of the above 2 parts and is adjacent to the interventricular foramen;
  4. The retrolenticular part is the portion posterior to the lenticular nucleus;
  5. The sublenticular part is the portion inferior to the lenticular nucleus.

This table was contributed by David Boshell.

Portion Description Origin Destination
Anterior Limb Anterior thalamic radiation
  • Anterior nucleus
  • DM
  • Cingulate gyrus
  • Prefrontal cortex
Genu Relays to motor areas
  • VA
  • VL
  • Premotor cortex
  • Primary motor cortex
Posterior Limb
  1. Motor pathways:
    • Corticospinal tract
    • Corticobulbar tract
  2. Somatosensory relays
  1. Motor cortex
  2. VPL/VPM


  1. Motor pathways:
    • Spinal cord
    • Brainstem
  2. Somatosensory relays:
    • Primary somatosentory cortex
  • Association relay
  • Optic radiation
  • Pulvinar
  • LGN
  • Association cortex
  • Visual cortex
  • Optic radiation
  • Auditory radiation
  • LGN
  • MGN
  • Visual cortex
  • Auditory cortex


The Hypothalamus

Click here to go to "The Hypothalamus".

  1. Interconnections with various components of the limbic system;
  2. Outputs which influence the pituitary gland;
  3. Interconnections with various visceral and somatic nuclei.


Extent of the Hypothalamus


Subdivisions of the Hypothalamus

  1. The anterior region, is above the optic chiasm;
  2. The tuberal region, is above the tuber cinereum;
  3. And the posterior region is above and including the mammillary bodies.

Nolte (1993) The Human Brain, An Introduction to its Functional Anatomy 3rd Ed. Mosby-Year Book, Inc., St. Louis, Missouri, USA. Table 8, p. 265.

Region Medial Area Lateral Area
Anterior Medial preoptic nucleus
Supraoptic nucleus
Paraventricular nucleus
Anterior nucleus
Suprachiasmatic nucleus
Lateral preoptic nucleus
Lateral nucleus
Part of supraoptic nucleus
Tuberal Dorsomedial nucleus
Ventromedial nucleus
Arcuate (infundibular) nucleus
Lateral nucleus
Lateral tuberal nuclei
Posterior Mammillary body
Posterior nucleus
Lateral nucleus
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Michael Tam (c) 1999