The thalamus, located in the upper part of the lateral wall of the third ventricle, serves as a major relay station for sensory information (except smell) and integrates motor functions, playing a crucial role in consciousness and emotional responses. It consists of two thalami connected by massa intermedia and is involved in specific projections to parts of the neocortex for sensory and motor processing. Damage to thalamic nuclei can lead to sensory and motor symptoms, including astereognosis, thalamic phantom limb, and Korsakoff's syndrome, which affects memory.

1. THALAMUS
DR. ANITA CHOUDHARY
PROFESSOR &H.O.D
R.D.G.M.C Ujjain

2. THALAMUS
 Location – upper part of
lateral wall of the III rd ventricle.
 Thalamus is a major relay station..all
general & special senses (except smell)
synapse in thalamus
 Integrating center for all inputs before relay
in CCx

3. Thalamus
 2 Thalami
 Egg shaped , cluster of nuclei
 Connected by mass of grey matter..massa
intermedia
 Anterior end is narrow
 Posterior end is broad…Pulvinar
 Internal medullary lamina divides thalami into
three parts- Anterior, Medial .Lateral

4. Nuclei of thalamus

5. Thalamic Nuclei – Functional
Classification
Non- Specific projection nuclei
RAS
inputs to
Thalamic Nuclei
Project diffusely to whole of neo cortex
Eg: Midline & Intralaminar nuclei

6. Connections

8. Functions
 Sensory Relay Center
Sensory impulse
Thalamus
(Thalamocortical
system)
Cerebral cortex

9. Specific Projection nuclei-Project to
specific part of neocortex
Medial & Lateral
Geniculate bodies
Relay auditory &
visual information
Auditory & Visual
areas of CCx
Posterio ventral
group
Relay somesthetic
information
Post central Gyrus
(sensory cortex)

10. Nuclei concerned with motor
control
Basal Ganglia cerebellum
Give in put to
Ventro lateral group of nuclei
Motor Cortex

11. Nuclei concerned with memory &
emotions
Mammilary bodies
give inputs to
Anterior group of nuclei
Limbic cortex
Recent memory & emotions

12. FUNCTIONS OF THALAMUS
 Center for Integration of sensory impulse
Thalamus integrates and modify the sensory
impulses
‘Functional gateway of cerebral cortex’

13. Crude center for perception of
sensations
 Discriminative
nature
Ability to recognize type
Location and other
details
is the function of
cerebral cortex
 Affective nature
Determine sensation is
pleasant or
unpleasant
is a role of thalamus

14. Center for integration of Motor
Functions
Basal Ganglion Cerebellum
Output
THALAMUS
Integrate Motor function
Cerebral Cortex

15. Role in Arousal and alertness
reactions
ReticularActivating System
Non-Specific
ascending
impulse
THALAMUS
Controls Consciousness and maintain alertness
& wakefulness

16. Role in emotional aspect of
behavior
 As it is a part of Limbic system (Papez circuit)
 Recent memory and Emotions
 Role in language –
Cortical and Sub-cortical connections
Speech

17. Center for Reflex activity-
All sensory fibers
Relay
Thalamus
Reflex Activity

18. Other functions…..
 Role in Synchronization of EEG
 Integration of visceral and somatic function
 Center for sexual sensation

19. THALAMIC SYNDROME
Disturbance of emotional response to
sensory experience
Cause : Blockage of thalamogeniculate branch
of posterior cerebral artery
 Damage of Ventro-posterior
lateral nuclei(VPL)
 Damage of Ventro- posterior
medial nuclei (VPM)

20. Symptoms & Signs -(opposite
side of body)
A. Sensory Symptoms : ( involvement of VPM)
 Astereognosis – due to loss of Tactile localization &
discrimination
 Thalamic Phantom Limb –
Closure of eyes
Loss of kinesthetic sensation
Person unable to locate position of limb in air

21.  Thalamic Over reaction :
Decrease Threshold for Pain, touch and
temperature- exaggerated & disagreeable
sensation
 Amelognosia – Illusion felt by patients that
his limb is absent

22. B. Motor Symptoms-
Involvement of VPL
 Ataxia, decrease muscle tone &
weakness (damage of cerebellar
afferent)
 Involuntary movements- chorea,
intention syndrome
 Thalamic hand/athetoid hand-
moderate flexion of hand at wrist
with increase hyperextension of
fingers

23. Korsakoff’s Syndrome
 Refers to lesion of MEDIODORSAL
NUCLEUS of thalamus
Characteristic feature:
 Difficult to remember new information

24. Frontal lobectomy
 Connection of dorsal nuclei of thalamus with
frontal lobe is surgically removed
 For relief of unbearable pain

25. THANK YOU