2. The Thalamus is a Scanner.
All information comes into the thalamus before being distributed to other parts of the brain. It’s sometimes called the scanner because it constantly scans the environment for information

3. Introduction- The Thalamus
Dorsal view
ventral view

4. (from Greek = bedroom, chamber)
The Thalamus
(from Greek = bedroom, chamber)
3.5cm in length,
1.5cm in width
80 % of the diencephalon
paired and symmetric part of the brain
There are 2 thalami,
one on each side of the 3rd ventricle, they are connected by the interthalamic adhesion

5. Introduction- The Thalamus
Insula
Internal
capsule
Lentiform
nucleus
Coronal Section

6. Coronal view

7. Thalamus
Dorsal View

8. Boundaries of the Thalamus
Anterior:
interventricular foramen
Posterior:
free pole of the pulvinar
Dorsal:
free surface underlying the fornix and the lateral ventricle
Ventral:
plane connecting the hypothalamic sulci

9. Boundaries of the Thalamus
Medial:
third ventricle
Lateral:
posterior limb of the internal capsule
Thalamus

10. Relations Dorsal: lateral ventricle Anterior: interventricular foramen
Medial: 3rd ventricle
Lateral: Internal capsule
Ventral: Subthalamus & Hypothalamus
Caudal: midbrain

12. Anatomic Divisions Internal medullary lamina
Thin sheet of myelinated fibers
Divides the thalamus into three major divisions, each containing specific nuclei:
Anterior
Medial
Lateral
Not included in these divisions are
The intralaminar nuclei
The Reticular nucleus

13. Anatomical Divisions Anterior Division Medial Division
Anterior nucleus
Medial Division
Dorsomedial Nucleus (DM)
Lateral Division
Dorsal Tier
Lateral dorsal (LD)
Lateral Posterior (LP)
Pulvinar
Ventral Tier
Ventral Anterior (VA)
Ventral Lateral (VL)
Ventral Posterior (VP)
Ventral posteriolateral (VPL)
Ventral posteriomedial (VPM)
Ventral posterioinferior

14. DORSAL
ANT.
POST.
VENTRAL

16. Posterior Anterior V A V L Pulvinar VPL LD LP
Internal medullary lamina
Interthalamic adhesion
Ant. Nucleus
Medial nucleus
Anterior LD
Posterior
V A LP
V L
Pulvinar
VPL
VPM
MGB
LGB .

17. Subdivision
Principal Nuclei
Common abbreviation
Ant. nuclear group
Med. nuclear group
Lat. nuclear group
Dorsal tier
Lateral dorsal LD
Lateral posterior LP
Pulvinar P
Ventral tier
Ventral anterior VA
Ventral intermediate VI
Ventral posterior VP
Ventral posterolateral
VPL
Ventral posteromedial
VPM
Ventral posterioinferior
VPI

18. Functional subdivision
According to function, the thalamus may be divided into three groups
1. Nonspecific relay nuclei
2. Association nuclei :DM,LD,LP & Pulvinar
3. Specific relay nuclei :MGB, LGB, VPL, VPM, VL VA, A
relay nucleus is one that receives input predominantly from a
single source, such as a sensory pathway or a cerebellar nucleus,
or from the basal nuclei.

19. Main Thalamic Nuclei and Their Major Connections
Anterior part
Contains the anterior thalamic nucleus
This nucleus receives hypothalamic input from the mammillary nucleus via the mamillothalamic tract
It receives hippocampal input via the
fornix (hippocampus).
It projects to the cingulate gyrus.
Function : associated with that of the limbic system and is concerned with emotional tone and the mechanisms of recent memory

20. Main Thalamic Nuclei and Their Major Connections
Lateral part
ventral anterior & ventral lateral nuclei
Motor relay nuclei associated with somatic motor system
VA receives from globus pallidus & S.nigra. Projects to supplementary motor area (6).
VL receives from cerebellar nuclei ( Dentate) & globus pallidus. Projects to primary (4) & supplementary (6) motor cortex.

21. Main Thalamic Nuclei and Their Major Connections
Lateral part
VL circuits:
Cerebral-cerbellar-cerebral
Cerebral-basal ganglia-cerebral
VL lesions would ameliorate contralateral tremor & rigidity in patients of Parkinson's disease

22. Main Thalamic Nuclei and Their Major Connections
Medial part
Contains the large Mediodorsal nucleus and several smaller nuclei
The Mediodorsal nucleus is reciprocally connected to the
Prefrontal cortex of the frontal lobe.
It has abundant connections with all other groups of thalamic nuclei
It receives input from
amygdaloid nucleus,
temporal neocortex, and
substantia nigra.

23. Main Thalamic Nuclei and Their Major Connections
Medial part
Function:
integration of a large variety of sensory information, including somatic, visceral, and olfactory information
relate this information to one’s emotional feeling

24. Main Thalamic Nuclei and Their Major Connections
Mediodorsal nucleus (dorsomedial nucleus)
Clinical correlate
When destroyed, the result is a memory loss
(Wernicke-Korsakoff syndrome).
It plays a role in the expression of affect, emotion, and behaviour (limbic function).

25. Main Thalamic Nuclei and Their Major Connections
Lateral part – Ventral tier VP
The ventral posterior nucleus
Recieves
general somatic afferent (GSA; pain and temperature) and
special visceral afferent (SVA; taste) pathways.
Contains three subnuclei

26. Main Thalamic Nuclei and Their Major Connections
Lateral part – Ventral tier
Ventral posterolateral (VPL) nucleus
Receives the spinothalamic tracts and the medial lemniscus (tactile discrimination, vibration, form recognition, joint and muscle sensation, proprioception).
Projects to the somatosensory cortex (postcentral gyrus - areas 3, 1, and 2).
These projections pass through the post. Limb of the internal capsule and corona radiata
Lesion results in contralateral loss of pain and temperature sensation, and loss of tactile discrimination in the trunk and extremities
VPL

27. Main Thalamic Nuclei and Their Major Connections
Lateral part – Ventral tier
Ventral posteromedial (VPM) nucleus
VPM
Receives the trigeminothalamic tracts.
Receives the taste pathway via the solitary nucleus and the parabrachial nucleus.
Projects to the somatosensory cortex (areas 3, 1, and 2).
These projections pass through the post. Limb of the internal capsule and corona radiata
Lesion results in contralateral loss of pain and temperature sensation, and loss of tactile discrimination in the head; results in ipsilateral loss of taste.

28. Main Thalamic Nuclei and Their Major Connections
Lateral part – Ventral tier
Ventral posteroinferior (VPI) nucleus
Receives vestibulothalamic fibres from the vestibular nuclei.
Projects to the vestibular area of the somatosensory cortex.
VPI

29. Main Thalamic Nuclei and Their Major Connections
Intralaminar nuclei
A groups of nuclei embedded within the internal medullary lamina
input from the brainstem reticular formation, and other thalamic nuclei, spinothalamic and trigeminothalamic tracts
efferent fibres to other thalamic nuclei which, in turn, project diffusely to the entire neocortex.
The nuclei are believed to influence the levels of consciousness and alertness in an individual – the level of activity of cerebral cortex

30. A A MD VA VL
VPL P
VPM
LGB
MGB

31. Blood Supply of the Thalamus 1.Posterior communicating artery
Gives rise to the
anterior thalamoperforating arteries

32. Blood Supply of the Thalamus 2.Posterior cerebral artery
Gives rise to:
posterior choroidal arteries.
posterior thalamoperforating arteries.

33. Thalamogeniculate artery
Thalamoperforating artery

35. Function of the Thalamus
Following removal of the cortex the thalamus can appreciate crude sensation.
However, the cerebral cortex is required for the interpretation of sensation based on past experience.

36. Functional Roles Sensory Motor Emotion/memory Vegetative
Thalamus has four basic functional roles:
Sensory
All sensory information (except olfaction) is relayed to the cortex via the thalamus
Motor
Motor system outputs from the basal ganglia and cerebellum are relayed by the thalamus
Emotion/memory
The thalamus is part of the Papez circuit and helps control some emotional and memory information going to limbic cortex (cingulate gyrus)
Vegetative
The thalamus has some intrinsic nuclei associated with alertness and arousal. Can be associated with disorders of consciousness

37. Functional Roles
Thalamus doesn’t just send information to the cortex. It receives cortical feedback
This signal helps regulate what is coming to the cortex
Cortical input is a feedback inhibition loop, letting the thalamus know that information has been received and inhibiting further relaying of the information

38. Thalamic Function Gateway to the cerebral cortex
Sorts, edits, and relays information
Afferent impulses from all senses and all parts of the body
Impulses from the hypothalamus for regulation of emotion and visceral function
Impulses from the cerebellum and basal nuclei to help direct the motor cortices
Mediates sensation, motor activities, cortical arousal, learning, and memory

39. Clinical considerations Thalamic syndrome (Dejerine and Roussy)
Is usually caused by occlusion of a posterior thalamoperforating artery!
Classic signs are:
Contralateral hemiparesis
Contralateral hemianesthesia
Elevated pain threshold
Spontaneous, agonizing, and burning pain (hyperpathia, Thalamic Pain Syndrome)
Athetotic posturing of the hand (thalamic hand).

40. Thalamic syndrome of Dejerine-Roussy
Stroke caused by occlusion of a branch of the PCA supplying the posterior and lateral thalamic nuclei.
Initially there is a contralateral hemisensory loss in the head and body.
Followed by dysesthesia (disagreeable sensation produced by ordinary stimuli), spontaneous intractable pain (thalamic pain) and emotional instability.
(axial CT scan)
Joseph Jules Dejerine
Gustave Roussy

41. This syndrome may include:
1.Spontaneous pain &
2.Evidence of emotional instability such as unprovoked laughing and crying

42. Thalamic Hand