2. As per:
Competency based Undergraduate curriculum 1
AN62.5: Describe boundaries, parts, gross relations, major nuclei, and connections of dorsal
thalamus, hypothalamus, epithalamus, metathalamus, and subthalamus.
Medical Council of India, Competency based Undergraduate curriculum for the Indian Medical Graduate,
2018. Vol. 1; pg 1-80.
Human Anatomy/Yogesh Sontakke 2
3. • Part of the brain that lies between the cerebral hemisphere and the midbrain.
• Cavity of the diencephalon is third ventricle.
• The diencephalon consists of pairs of:
• Thalamus
• Hypothalamus
• Metathalamus
– Medial geniculate body
– Lateral geniculate body
• Subthalamus
• Epithalamus
– Pineal body
– Habenular nuclei and commissure
– Posterior commissure
– Stria medullaris thalami.
DIENCEPHALON
4. • Thalamus (= chamber, in Greek) is a large avoid mass of grey matter
situated on each of the third ventricle, above the midbrain.
• Size:
– Length: 4 cm anteroposteriorly
– Width and vertical diameter: 1.5 cm
• Axis: The long axis of thalamus is oblique. It is directed backward and
laterally.
• Interthalamic adhesion: It is narrow band of grey matter that connects
both the thalami across the midline.
THALAMUS
5. • Sensory relay station: Thalamus is a sensory station for all impulses
except olfactory sensation.
• Pain and temperature perception: Thalamus is capable of poor
recognition of pian and temperature sensation.
• Extrapyramidal function: It conveys sensory inputs of cerebellum and
basal ganglia to motor cortex and influences motor activity.
• Maintenance of wakefulness and alertness through influencing ascending
reticular activating system.
FUNCTIONS OF THALAMUS
6. • Emotional behavior and recent memory: It play a role as a part of limbic
system in emotional behavior and recent memory mechanism.
• Autonomic control of viscera: It takes part in autonomic control through
the hypothalamus.
• Mood and emotional balance
• Personality and intellect of an individual.
FUNCTIONS OF THALAMUS
7. • Each thalamus has
– Two ends: Anterior and posterior
– Four surfaces: Superior, inferior, medial, and lateral
Ends of thalamus
Anterior end
• Narrow and rounded.
• Lies closer to the midline
• Forms the tubercle of thalamus.
• Forms the posterior boundary of interventricular foramen of Munro
Posterior end
• Expanded and known as pulvinar
• Overhangs the superior colliculus and its branchium.
External Features of Thalamus
8. Fig 11.1: Relations of thalamus (posterior view, coronal section of the brain)
9. Superior surface
It is free, convex, and covered by a layer of white matter. Its lateral part forms the
floor of the lateral ventricle.
Its medial part is covered by tela choroidea of the 3rd ventricle (that separates it
from the body of fornix).
Medial surface
It forms the part of the lateral wall of 3rd ventricle. It is covered ependyma.
It presents the interthalamic adhesion that connects the right and left thalami.
Inferior surface
It is continuous with the subthalamus. Posteriorly, it is free and forms the inferior
surface of pulvinar.
Lateral surface
It is flat and forms the medial boundary of the internal capsule.
Surfaces of thalamus
10. Fig. 11.2: Relation of thalamus with third ventricle (superior view, Note: overlying tela choroidea of third ventricle is
removed)
11.
12. Superior surface of thalamus is related to the body of the caudate nucleus laterally. Stria
terminalis and thalamostriate veins rubs between the thalamus and caudate nucleus.
Choroidal fissure: It lies between the fornix and the superior surface of thalamus. The tela
choroidea of the 3rd ventricle invaginates the lateral ventricle through choroid fissure.
Stria medullaris thalami separate superior surface from medial surface of thalamus.
Hypothalamic sulcus is a groove in the lateral wall of the 3rd ventricle. It extends from the
interventricular foramen to the cerebral aqueduct. It separates hypothalamus from the
thalamus.
Taenia thalami: It is a line of reflection of ependyma of 3rd ventricle from its lateral wall to its
roof.
Trigonum habenulae: It is a small triangular area between the posterior part of stria medullaris
thalami and superior surface of thalamus.
Some Interesting Facts
13. Fig. 11.4: Practice figure: Major afferent connections of thalamus (schematic representation)
14. Fig. 11.5: Practice figure: Major efferent connections of thalamus (schematic representation)
16. Grey matter of thalamus
They Y-shaped internal medullary lamina divides the thalamus into anterior, medial,
and lateral parts. Anterior part lies between the limbs of the ‘Y’ and medial and lateral
parts on either side of the stem of ‘Y’. The grey matter of the thalamus consists of
number of nuclei.
Note: The ventral part of thalamus lies inferiorly and dorsal part superiorly.
Internal Structure of Thalamus
17. Thalamus is mainly consisting of grey matter and a small layers of white matter.
White matter of thalamus
Thalamus contains small quantity of white matter as the following thin laminae:
1. Stratum zonulae on the superior surface
2. External medullary lamina on the lateral surface
3. Internal medullary lamina lies within the thalamus.
Internal medullary lamina is a vertical sheet of Y-shaped white matter that bifurcate
anterosuperiorly.
Internal Structure of Thalamus
18. The thalamic nuclei are as the nuclei of anterior medial, lateral, intralaminar, and reticular
nuclei (Table 12.1).
Thalamic Nuclei
Part Nuclei
Anterior part Anterior nucleus
Medial Part Medial dorsal nucleus (only one in humans)
Lateral part
Dorsal tier nuclei Lateral dorsal nucleus
Latera posterior nucleus
Pulvinar
Ventral tier nuclei Ventral anterior nucleus
Ventral lateral nucleus
Ventral posterior nucleus: ventral posterolateral (VPL) and ventral
posteromedial (VPM)
Other nuclei Medial geniculate body (MGB)
Lateral geniculate body (LGB)
Intralaminar nuclei
Centromedian nucleus (CM)
Midline nuclei
Reticular nucleus
19. Fig. 11.7: Practice figure: Thalamic nuclei (schematic representation, note: centromedian nucleus and VPM nucleus lies deep)
20. • The major connections and functions of thalamic nuclei are listed in Table 12.2.
Nucleus Afferent Efferent Functions
Anterior nucleus From mamillary body
(mammillothalamic tract)
To cingulate gyrus Associate with limbic system
Emotional behavior, recent memory
Medial nuclei From hypothalamus,
amygdala, other thalamic
nuclei
Prefrontal cortex Association or integration of visceral and
somatic activities
Personality of individual mood and feelings
Lateral dorsal group LD, LP, pulvinar Superior colliculus,
Pretectum
Cingulate gyrus, Parahippocampal
gyrus, Parietal, occipital, and
temporal lobes
Forms part of limbic system
Helps in sensory analysis by parieto-occipito-
temporal association cortex
Ventral posterolateral medial nucleus
(VPM)
Trigeminal lemniscus
Solitariothalamic tract
Postcentral gyrus Relay station for
Ventral posterolateral nucleus (VPL) Medial lemniscus
Spinal lemniscus
Postcentral gyrus Relay station for pain, temperature, touch,
proprioceptive sensation from whole body
except face and head
Ventral anterior (VA) nucleus Globus pallidus through
subthalamic fasciculus
Premotor area Relay station for striatal impulses modify
motor activity
Ventral lateral (VL) nucleus Cerebellum (dentato
thalamic)
Red nucleus (dentato-
rubrothalamic)
Motor and premotor areas Relay station for cerebellar impulses
Influences motor activity
Intralaminar nuclei (centramedian
and parafascicular nuclei)
Reticular formation Other thalamic nuclei and corpus
striatum
General awareness of painful stimuli
Sensory motor integration
Maintenance of arousal
Midline nuclei Reticular formation Hippocampus, Amygdala Part of limbic system
Memory
Arousal responses
Thalamic reticular nucleus (Lies
between external medullary lamina
and internal capsule)
Corticothalamic fibers Other nuclei of thalamus
Thalamocortical fibers
Regulation of interthalamic activity
21. Location of thalamic nuclei
1. Anterior thalamic nuclei are endorsed by the bifurcation of Y-shaped internal medullary lamina.
2. Medial thalamic nuclei lie medial to the internal meaty lamina. It consists of only dorsomedial
nucleus in humans.
3. Lateral thalamic nuclei lie lateral to the internal medullary lamina. They are divided into two
groups: dorsal tire and ventral tier group of nuclei.
– Dorsal tier (group) consists of lateral dorsal and lateral posterior nuclei and pulvinar.
– Ventral tier (group) consists of ventral anterior, ventral lateral, and ventral posterior nuclei.
4. Ventral anterior (VA) nucleus lies at the anterior pole of ventral group in between external and
internal medullary laminae. It extends anteriorly from reticular nucleus to ventral lateral nucleus
posteriorly.
Some Interesting Facts
22. Fig. 11.8: Location of thalamus (right medial view, sagittal section of the brain)
23. Location of thalamic nuclei
5. Ventral lateral nucleus (VL) lies between ventral anterior (VA) and ventral posterior (VP)
nuclei. It lies between lateral does (LD) nucleus superiorly and subthalamus inferiorly.
6. Ventral posterior nucleus lies behind the ventral lateral (VL) nucleus and anterior to
pulvinar. It lies inferior to the lateral posterior (LP) nucleus. The ventral posterior nucleus is
divided into ventral posterior medial (VPM) and lateral posterior lateral (VPL) nuclei.
7. Medial geniculate body (MGB) is a rounded elevation situated posterior on the inferior
surface of thalamus, separated from pulvinar by superior brachium.
8. Lateral geniculate body (LGB) is a small ovoid projection on the inferolateral aspects of
pulvinar. It lies lateral and anterior to the MGB.
Some Interesting Facts
24. Location of thalamic nuclei
9. Lateral dorsal nucleus (LD) is located on the anterior part of superior (dorsal) portion of
thalamus.
10. Lateral posterior (LP) nucleus lies on the middle part of the superior (dorsal) portion of
thalamus. It lies between the LD nucleus and pulvinar.
11. Pulvinar is the posterior most projecting part of thalamus. It overhangs the superior
colliculus of midbrain.
12. Intralaminar nuclei lie with the internal medullar lamina.
Some Interesting Facts
25. Location of thalamic nuclei
13. Midline nuclei of thalamus are located deep to the ependymal lining of thalamus. They
include paratenial nucleus, nucleus reuniens (located in interthalamic adhesion), rhomboid
nucleus, and paraventricular nucleus.
14. Reticular nucleus is a curved lamina that wraps around the lateral surface and anterior
ends of the thalamus. External medullary lamina separates the thalamus from the lateral
surface of thalamus.
Note: The nonspecific nuclei of thalamus do not receive inputs from ascending tracts.
They are connected with other diencephalic part of brain and with cortical association
areas of frontal and parietal lobes. They include anterior, dorsal medial, lateral dorsal,
lateral posterior nuclei and pulvinar.
Some Interesting Facts
26. Arterial supply
• Thalamus is supplied by the branches of the
1. Posterior communicating
2. Posterior cerebral
3. Posterior choroidal arteries
Venous drainage
1. Thalamostriate veins
2. Choroid veins of the 3rd ventricle
• These veins unite to form the internal cerebral vein.
Blood supply of Thalamus
27. Thalamic syndrome
Vascular lesions of thalamogeniculate branch of posterior cerebral artery results in thalamic
syndrome. It is characterized by the following features:
1. Hyperesthesia – exaggerated sensations.
2. Serve spontaneous pain on the opposite side body.
3. Emotional instability, that is, patient may laugh or cry without any reason.
4. Thalamic phantom limb, that is, patient is unable to locate the limb the eyes closed and
develops the illusion that the limb is lost.
5. Thalamic hand: It may occur in thalamic lesions. The opposite hand is involved. The
forearm is pronated, wrist flexed, metacarpophalangeal joint flexed and interphalangeal
joint extended.
Clinical integration
28. Thalamic pain syndrome (Dejerine Roussy syndrome)
It involves loss of sensation followed by progressive agonizing pain in the parts of
body where loss of sensation has occurred.
Thalamic syndrome shows
Allodynia – a painful sensation elicited from an innocuous stimulus on normal skin
Hyperpathia – an unusual and intense response to nociceptive stimuli
Dysesthesia – an abnormal sensation triggered by sense of touch.
Clinical integration
29. • It consists of
– Medial geniculate body
– Lateral geniculate body
Medial geniculate body (MGB)
• It is an oval elevation on the inferior
aspects of the pulvinar of thalamus and
lateral to the superior colliculus.
• It is connected with the inferior colliculus
by the inferior branchium.
• The cells of the medial geniculate body
are arranged in knee-shaped profile,
hence called geniculate (genu = knee).
METATHALAMUS
Fig. 11.9: Geniculate bodies (posterior view of brainstem)
30. Connections
• Afferent: From inferior colliculus through inferior branchium and some direct fibers of
lateral lemniscus.
• Efferent: Auditory radiation to the auditory area of the temporal lobe (areas 41 and 42).
Function
• It acts as relay station in the auditory pathway
Medial Geniculate Body
31. .
Lateral Geniculate Body
An oval prominence at the posterior end of optic
tract.
Lies on the inferolateral aspect pulvinar and
anterolateral to the medial geniculate body.
Structure:
– Neurons are arranged in 6 layers separated by
nerve fibers. The layers are numbered as layer 1
to 6 from ventral to dorsal.
– The layers 1, 4, and 6 receive fibers from the
nasal side of retina of the opposite side (crossed
fibers).
– The layers 2, 3, and 5 receive fibers from the
temporal side of the retina same side (uncrossed
fibers).
Fig. 11.10: Practice figure: Six layers (laminae) of the lateral
geniculate body and their afferent connections
32. .
Lateral Geniculate Body
Connections
Afferent: From the optic tract.
Efferent: Form optic radiation that passes
through retro-lentiform part of intern
capsule to the visual cortex (areas 17, 18,
and 19).
Functions
It is relay station on the visual pathway.
Clinical integration
Lesion LGB → contralateral homonymous
hemianopia
Fig. 11.10: Practice figure: Six layers (laminae) of the lateral
geniculate body and their afferent connections
33. Components:
1. Pineal body
2. Habenular nucleus and
commissure
3. Posterior commissure
EPITHALAMUS
Fig. 11.11 Epithalamus (right medial view, sagittal section
of the brain)
34. Pineal glands (Epiphysis
cerebri)
oSmall conical projection
between the two superior
colliculus of midbrain
oLies below the splenium of
corpus callosum.
Weight: about 100–200 mg
Shape: Flat, pine cone-
shaped (hence, named as
pineal gland)
EPITHALAMUS
Fig. 11.11 Epithalamus (right medial view, sagittal section
of the brain)
35. Pineal glands (Epiphysis
cerebri)
Pineal gland has a stalk that
divided into two laminae
1.Inferior lamina –
continuous with posterior
commissure
2.Superior lamina –
continuous with habenular
commissure.
EPITHALAMUS
Fig. 11.11 Epithalamus (right medial view, sagittal section
of the brain)
36. Pineal glands
Pineal recess: extension of
cavity of 3rd ventricle
between two laminae of
pineal gland
Nervus conorii: are
postganglionic sympathetic
fibers from the superior
cervical sympathetic
ganglion that supply the
pineal glands
EPITHALAMUS
37. Pineal glands
Structures
Consists of pinealocytes and
interstitial cells
Pinealocytes – chief cells of pineal
gland – secrete melatonin hormone
Interstitial cells – few cells support
the pinealocytes
Corpora areanacea or brain sand –
characteristic feature of pineal gland
– calcified concretions (deposits)
that increases with age.
EPITHALAMUS
38. Pineal glands
Functions
1. Secretion of melatonin that
inhibits secretion of
gonadotropins from
hypothalamus
2. Maintenance of circadian
rhythm (biological clock)
EPITHALAMUS
39. Habenular nucleus and Habenular
commissure
Habenular trigone
(habenula = little rein, in Latin) is
a small depressed triangular area
bounded superiorly by stria
medullaris thalami and superior
lamina of pineal stalk and
inferiorly by the superior
colliculus of midbrain and laterally
by pulvinar of thalamus.
EPITHALAMUS
40. Habenular nucleus and Habenular
commissure
Habenular nucleus – lies in the
habenular triangle – a part of
limbic system
Habenular commissure – fibers
that connects the habenular
nucleus of two sides across the
midline – lies in the superior
lamina of pituitary stalk.
Function: Form a part limbic
system and are responsible for
primitive visceral response to
basic emotional drives.
EPITHALAMUS
Fig. 11.13: Practice figure: Connections of habenular
nucleus
41. Posterior Commissure
Bundle of fibers that cross
the midline in the inferior
lamina of pineal stalk.
Contains fibers from
medial longitudinal bundle
interstitial nuclei, and
many other adjacent areas.
Exact function is not listed.
EPITHALAMUS
Fig. 11.11 Epithalamus (right medial view, sagittal section
of the brain)
42. Stria medullaris
– Bundle of fibers lying deep to
taenia thalami (ependyma if
3rd ventricle).
– Lies along the junction of
medial and superior surfaces of
thalamus
– Connects the septal nucleus,
basal nuclei of Meynert and
hypothalamus with habenular
nucleus
– Form a part of limbic system
Some interesting facts
43. Subthalamus consists of
1. Cranial extension of red
nucleus and substantia
nigra, subthalamic
nucleus, and zona incerta
2. Fasciculus retroflexes
3. Fasciculus lenticularis
4. Ansa lenticularis
5. Fasciculus subthalamics
6. Fasciculus thalamicus
Subthalamus
44. Subthalamic nucleus
Lens-shaped nucleus lying on the medial aspect of internal capsule
just above the substantia nigra
One of the extrapyramidal nuclei that modifies motor activity
Its lesion produces hemiballismus (involuntary uncontrollable,
violent jerky, movement of opposite side of the body)
Subthalamus
45. Zona incerta
Thin layer of grey matter between the subthalamic nucleus and
thalamus
Upward extension of brainstem reticular nuclei.
Subthalamus
46. Fasciculus lenticularis (lenticular fasciculus) – consists of fibers
of globus pallidus that passes through the internal to the
subthalamus nucleus.
Subthalamus
47. Ansa lenticularis – inferior bundle of fibers from globus pallidus
to thalamus and other subthalamic nuclei
Subthalamus
48. Thalamic fasciculus (Field H1 of Forel) – Group of fibers
extending from prerubral field to the thalamus. It also has some
fibers from fasciculus lenticularis and Ansa lenticularis
Subthalamus
