1. The document describes the anatomy and functions of the thalamus. 2. It is a midline paired structure located within the brain that relays sensory information (except smell) between the brainstem and cerebral cortex. 3. The thalamus has several nuclei that receive sensory information from different pathways and project to specific areas of the cerebral cortex, functioning as a relay for sensory integration.

5. Transverse section thro’ upper part of pons
Sup.Cereb.Peduncle
Mid.Cereb.
Peduncle
Main.sens.N.Trig.
Lat.Lemn.
(Cochlear N. to Inf.Colliculi)
Spinal.Lemn.
(ant.&Lat spinothalmic tracts)
Pain, Temp, Crude touch
Trig.Lemn.
(Chief sens.& spinal N.)
Pain & Temp – face
Proprioception – Muscles of Mast.
Medial.Lemn.
(Gr. & Cun. N.)
Touch,vibration
poprioception0
MLF – integrates 3, 4, 6, 8 cranial nerves

6. DIENCEPHALON
Pars Dorsalis
Hypothalamic sulcus
Pars Ventralis
01.Thalamus (Dorsal thalamus)
02.Metathalamus – Med Gen. Body
- Lat. Gen. Body
03.Epithalamus - Pineal body
- Habenular Nuclei
- Habenular Commissure
- Post. Commissure
- Stria Medullaris Thalami
01.Subthalums (Ventral Thalamus)
– Sub-thalamic Nucleus
- Zona Inserta
02.Hypothalamus -

7. Thalamus = Gk - inner room
Midline paired structure within brain
Between cerebral cortex and brain stem
(Both in location & neurological connections)
Sends fibres out to cerebral cortex in all directions
FUNCTIONS
Relay of sensation (Except olfactory system)
Spatial sense
Regulation of consciousness
Regulation of sleep
and alertness
Main largest product of embryonic diencephalon
Great sensory gateway to cerebral cortex
Damage to thalamus can lead to permanent coma

8. Two thalami on each side of slit like cavity of 3rd ventricle
3 cms length x 1.5 cms breadth
Long axis 30 deg. oblique to midline
Interthalamic adhesion

9. Cingulate gyrus
Corpus CallosumBody of caudate
nucleus
TT
Hypothalamus
Stria Terminalis
Thalamostriate Vein
Third Ventricle

10. External features
Two ends
1. Anterior end – Tubercle of Thalamus
2. Posterior end – Pulvinar – Overhangs
Med & Lat.Gen.Bodies
Sup.Colliculi & their brachia
Surfaces
01.Sup. Surface – Lat. Part forms central part of lat. Vent.
Med. Part is covered by tela choroidea
of 3rd ventricle.
02.Inf. Surface - Ant. part fused with subthalamus
- Post. part free – inf. part of Pulvinar
03.Med. Surface – Greater part of Lat. wall of
3rd ventricle
04.Lat. Surface - Med.boundary of Post. Limb of
internal capsule
Subthalamus

11. Thalamus
Internal capsule
Cad. Nucleus
Lat.Ventricle
Lat.Ventricle
Cad. Nucleus
Optic radiation
Lateral surface of Thalamus – Medial boundary of Post. Limb of Int.Capsule

12. Stria medullaris Thalami
or Habenular stria
Taenia Thalami
Stria Terminalis
Thalamostriate vein
Body of caudate
nucleus

13. WHITE MATTER - THALAMUS
Stratum Zonale
External Medullary
Lamina
Internal Medullary
Lamina

14. Nuclei of Thalamus
Anterior Nucleus
Hypothalamus
Medial Dorsal
(Large)
Medial Ventral
(Small)
Lateral Dorsal
Lateral Ventral
LD, LP, Pulvinar – Dorsal Tier nuclei
VA, VL, VPL, VPM – Ventral Tier nuclei
VPL
VPM
CMN
ILN
PVN
EXT.Med.Lam
Ret.N
LGB
MGB
Stratum Zonale
MEDIALLATERAL

15. Functional group nuclei
1. Specific
2. Non-specific
3. Reticular
1. Specific - Input from certain specific ascending tratcs
Project specific cortical areas
Ventral tier, Med & Lat. Geniculate bodies
Ventral Posterior Nucleus:
VPM
VPL
Nucleus Afferent Efferent Relay station
VPM Trigeminal lemniscus
Solitariothalamic tract
Post central gyrus
(3,1 & 2)
Impulses from face & head
Taste buds
VPL Medial lemniscus
Spinal lemniscus
Post central gyrus
(3,1 & 2)
Exteroception (Pain,Tocuh
& Temp) Proprioception
from whole body except
face & head

16. Functional group nuclei
1. Specific group -
Nucleus Afferent Efferent Relay station
Ventral
anterior
Globus pallidus
(subthalamic fasciculus)
Premotor cortex
area 6 & 8
Striatal impulses
Ventral
lateral
Cerebellum
(dentato-rubro-thalamic
fibres)
(Dentato-thalamic fibres)
Motor & premotor
areas
Area 4 & 6
Cerebellar impulses
MGB Auditory fibres from
Inferior Colliculus
Primary auditory
area 41 & 42
Auditory impulses
LGB Optic tract Primary visual
cortex area 17
Visual impulses

17. Functional group nuclei
2. Non - Specific group
Do not receive afferents from ascending
Tracts, but have abundant connections with
other diencephalic nuclei. Project to cortical
association areas in frontal & parietal lobes.
Nucleus Afferent Efferent Relay station
Anterior
nucleus
Mamillothalmic tract
(Mamillary body)
Cingulate gyrus Attention & Recent
memory
Medial
dorsal
Other thalamic nuclei &
Hypothalamus
Prefrontal area Mood & Emotional
balance
Lateral
dorsal
Ventral tier of thalamic
nuclei
Precuneus &
Cingulate gyrus
Integrate sensory
information
Lateral
posterior
Ventral tier of thalamic
nuclei
Superior parietal
lobule
Integrate sensory
information
Pulvinar Ventral tier of thalamic
nuclei
Association areas
in parietal, occipital
& temporal lobes
Correlates visual &
auditory information with
other sensations

18. Functional group nuclei
3. Reticular nuclei
Reticular nucleus,
Intralaminar nuclei &
Median nuclei
(Paraventricular nucleus)
Connected with Reticular formation
Nucleus Afferent Efferent Relay station
Reticular Brain stem reticular
formation
Whole of cerebral
cortex
Forms part of reticular
activating system (RAS)
Intralami
nar &
Centro
median
Brain stem reticular
formation
Other thalamic
nuclei & Corpus
striatum
Involved in awareness of
painful stimuli at thalamic
level

19. Dorsal nerve root
N. of spinal tract of Trig. nerve
NG & NC
Sup. Sens. N. of Trigeminal
Dentate Nucleus
Sup. Cereb. Peduncle
MB
Hypothalamic Nuclei
Caudate N.
Prefrontal cortex
Cingulate gyrus
Somesthetic sensory area
(3, 1, 2)
Parietal cortex
Inferior parietal lobule
RN
Spinal lemniscus
(Spinothalamic tract)
Trigeminal lemniscus
Medial lemniscus
VPM
VPL
VPL
Anygdaloid body
Main connections
of Thalamus

20. Premotor cortex
Area 6
Motor cortex
Area 4
Sensory cortex
Area 3,1,2
Superior parietal lobule
Parietal,
Temporal
Occipital cortex
RN
Trigeminal lemniscus
Solitariothalamic tract
Medial lemniscus
Spinal lemniscus
Globus pallidus
Cingulate gyrusCingulate gyrus
Subthalamic fascilulus
Connections of ventral
and lateral group nuclei

21. Functions of Thalamus
1. Sensory integration relay station for all sensory pathways
(Except olfaction)
2. Capable of recognition of pain, thermal & tactile sensations
3. Influences voluntary movements through basal ganglia &
cerebellum – cerebral cortex – cortico-nuclear / cortico-spinal pathways
4. Through ascending activating system – maintains state of wakefulness
and alertness
5. Impulses received from hypothalamus projected o prefrontal &
cingulate gyrus – Determination of mood
6. Recent memory and emotions
7. Influences electrical activity of cerebral cortex (EEG)

22. METATHALAMUS
1. Medial Geniculate body – Relay station for auditory pathway
2. Lateral Geniculate body – Relay station for visual pathway
1. Medial Geniculate body
Afferents – Through lateral lemniscus – inferior colliculus
- brachium of inf. Colliculus
Efferents - Geniculocortical fibres project as auditory radiation
thru’ sublentiform of int. capsule to primary auditory
area in temporal lobe of cerebral cortex (41 & 42)
Auditory radiation
Inferior thalamic radiation
Midbrain
Pulvinar

23. METATHALAMUS
1. Lateral Geniculate body – Relay station for visual pathway
Afferents – Lateral root of optic tract – retinal fibres of both eyes
(temporal fibres of same side & nasal fibres of opposite
side)
Efferents - Geniculocalcarine fibres project as optic radiation trhu
sublentiform part of int. capsule to visual cortex of
occipital lobe (17, 18 & 19)
Optic radiation
Posterior thalamic radiation
Midbrain
Pulvinar
6 layers (laminae) of LGB
& their afferents
1,4,6
Retina of
opp.side
1
4
6
2,3,5
Retina of
same side
2
3
5

24. Sensory fibres are mostly thalamocortical fibre, radiate from thalamus
In different directions to reach wide spread areas of cerebral cortex
Constitute – thalamic radiations
Sup. Thal. Radiation
(Ventral tier to frontal & parietal lobes)
Inf Thal. Radiation
(Auditory radiation)
Post.Thal.radiation
(Opticradiation–
Geniculo-calcarinetract)
Ant.Thal.radiation
(Ant&Dorsomed.N.toFrontallobe
Ant.Thal.
Radiation
Sup.Thal.
Radiation
Post.Thal.
Radiation