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THALAMUS
Epithalamus
Habenular Nuclei:
Thought to be involved in emotional and visceral
responses to odors.
Projects to septal nuclei (in thalamus):
Via stria medullaris thalami.
Projects to interpeduncular nucleus:
Via habenulointerpeduncular tract.
Epithalamus
Pineal Body
Secretes melatonin (hormone):
Regulates circadian rhythms.
Activity is modulated by light-dark cycle:
Via sympathetic inputs activated by
hypothalamic suprachiasmatic nucleus.
Calcification accrues with maturity.
Lesions associated with precocious puberty.
Thalamus
Is a large egg- shaped mass of gray
Matter that forms the major part of the
diencephalon.
Separated from hypothalamus via:
Hypothalamic sulcus (groove)
Other landmarks:
Optic recess
Infundibular recess
Pineal recess
It has a narrow and rounded anterior end
which forms the posterior boundary of the
Interventricular foramen.
 The posterior end is expanded and forms
the pulvinar which overhangs the inferior
colliculus.
 The inferior surface is continuous with the
tegmentum of the midbrain.

It is covered on its superior surface by a
thin layer of white matter, called the
Stratum Zonale and on its lateral surface
by another layer, the external medullary
lamina.
Thalamus
Commissures:
Habenular :
Above the pineal recess.
Posterior:
Below the pineal recess.
Thalamus
Functions:
Relays all sensory information except smell to
the cerebral cortex.
 Provides crude awareness of sensation.
 Plays a role in arousal and alertness.
 Plays a role in complex reflex movements.

Thalamus Anterior Nucleus
Concerned with certain emotions, attention
and memory.
Afferents: Mamillothalamic tract from the mamillary
bodies
Efferents: Cingulate gyrus
Connections of the ventral
group
In the ventral group there is the
a. ventral anterior
b. ventrolateral
c. ventral posterior nuclei.
Ventral anterior nucleus
Afferents: Globus pallidus , cerebellum
Efferents: 4,6 ( pre- and primary motor
cortex)
Ventrolateral Nucleus
Afferents: Cerebellum ( dentate nucleus),
Globus pallidus
Efferents: 4,6 ( pre- and primary motor
cortex)
Ventral posterior nuclei:
General sensations and taste.
It is divided into :
a. Ventral posteromedial nucleus
b. Ventral posterolateral nucleus
Ventral Posteromedial Nucleus
Afferents: Trigeminothalamic tract,
Solitariothalamic tract.
Efferents: Primary Somatosensory cortex
(3, 1, 2)
Ventral Posterolateral Nucleus
Afferents: Medial Lemniscus , Spinal
lemniscus
Efferents: 3,1,2
Connections of the Lateral
Group
Three nuclei are found here:
a. Lateral Dorsal
b. Lateral Posterior
c. Pulvinar
Their functions are not cleary understood.
Lateral Dorsal Nucleus
Afferents : Superior colliculus
Efferents: Cingulate gyrus
Lateral Posterior Nucleus
Afferents: Superior colliculus
Efferents: Superior parietal lobule (5, 7)
Pulvinar
Afferents: Superior Colliculus
Efferents: Extrastriate visual cortex (18, 19)
Connections of the medial
group
This contains a large Dorsomedial nucleus
and several smaller nuclei
Afferents: Prefrontal cortex
Efferents: Prefrontal cortex
It controls emotional states.
Damage results in decreased anxiety,
tension and aggression.
Others
Medial geniculate body:
Afferents: Inferior brachium from the inferior
colliculus
Efferents: Projects to primary auditory cortex in
temporal lobe. Areas 41, 42 ( Heschl's gyri or
Heschl's convolutions ).
Lateral geniculate body:
Afferents: Visual from the optic tract
Projects to primary visual cortex in
occipital cortex ( Area 17).
Thalamic reticular neurons
Modifies neuronal activity in the thalamus.
May be involved in:
Regulating sleep-wakefulness cycle and levels
of awareness.
They include:
a. Intralaminar
b. Midline
Intralaminar and midlineNuclei
Afferents: Brain- stem reticular formation,
spinothalamic tracts
Efferents: Pain information is sent to the
cingulate gyrus
Thalamic Pain
May occur as the patient is recovering from
a thalamic infarct.
The pain is spontaneous , often excessive
and occurs on the opposite side of the
body.
This sensation can be aroused by light touch
or cold and may fail to respond to powerful
analgesic drugs.
Abnormal involuntary movts
Choreoathetosis with ataxia may follow
vascular lesions of the thalamus.
Could be due to involvement of the
neighboring caudate and lentiform nuclei
Thalamic Hand
The wrist is pronated and flexed, the
metacarpophalangeal joints are flexed,
and the interphalangeal joints are
extended.
The fingers can be actively moved though
the movements are slow.
Due to altered muscle tone in different
muscle groups.