1. Anatomy of the Limbic System and Thalamus Prof. Mujahid Khan
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6/15/2019

2. Objectives of the lecture:
At the end of the lecture, the students should be able to:
Describe the important relations of the thalamus.
Describe the subdivisions of the thalamus.
List the function and important connections of each of the thalamic nuclei.
Describe briefly the main effects in case of lesion of thalamus.
List the main nuclei and tracts of limbic system.
List the important connections between parts of limbic system
اسم ورقم المقرر – Course Name and No.
6/15/2019

3. The Limbic System
Limbic means border, so it’s a group of structures lie in the border zone between cerebral cortex and hypothalamus
The limbic system is believed to have a special role in emotion and behaviour: feeling, feeding, fighting, fleeing and mating
It is concerned with memory and with visceral and motor responses involved in defense and reproduction

4. The Limbic System The major component and connection:
1- Cingulate gyrus
2- Parahippocampal gyrus
3- Mammillary bodies
4- Anterior thalamic nucleus
5- Hippocampal formation
6- Amygdaloid body (nucleus)
7-Hypothalamus
8- Alveus, fimbria, fornix
9- Mammillothalamic tract

5. LIMBIC LOBE
The ring of grey matter on the medial aspect of each cerebral hemisphere, surrounding the corpus callosum
It includes:
The cingulate gyrus & the parahippocampal gyrus

6. The Hippocampal Formation
Ant
Location of Hippocampi (red)
Hippocampus
Dentate Gyrus
Parts of the Parahippocampal Gyrus
Subiculum
Post
Inferior view of ‘clear’ brain
Hippocampus
Parahippocampal gyrus
Subiculum
Parahippocampal gyrus

7. Hippocampus
Formed by a curved elevation of gray mater of the inferomedial part of the temporal lobe into the inferior horn of the lateral ventricle
Contains a layer of large, pyramidal shaped neurons (gray in illustration to the right), called the pyramidal cell layer. There are three regions of these cells: CA1, 2 and 3.
The pyramidal cells in CA1 are exceptionally sensitive to hypoxia and begin to die after only a few minutes. Pathologists term this region ‘Sommer’s sector’

8. Hippocampus: Afferents and Efferents
The hippocampus receives input from:
Adjacent inferior temporal cortex
Contralateral hippocampus (via the fornix)
The hippocampus sends fibres to:
Mammillary body of the hypothalamus (via the fornix)
The Mammillary body in turn
projects to the anterior thalamus
Mamillary body

9. Memory
Learning an association between two stimuli (e.g. face and name) requires an intact hippocampus
The hippocampus is also required for recalling the memory for a time after it is acquired

10. Hippocampus from unaffected individual
Hippocampus from patient with isolated bilateral hippocampal lesions
Note damage to CA1 region (between arrowheads). This patient exhibited both anterograde amnesia (inability to form new memories), and retrograde amnesia (inability to recall memories acquired before the onset of amnesia). As with most patients, the retrograde amnesia was temporally graded, that is the patient could recall remote events more easily than recent ones (often this extends to decades)

11. Hypothalamus
Serves as the main integrator of the autonomic and endocrine systems
Receives diverse inputs, including from:
Hippocampus
Visceral afferents
Somatosensory afferents
Input from the septal area (responsible for basic emotional drives)
Olfactory system
Hypothalamus

12. Hypothalamus Efferents of the hypothalamus reach:
Largest efferent bundle goes to the anterior thalamus
Vagal nuclei (parasympathetic)
Interomediolateral cell column of the spinal cord (sympathetic)
Sacral autonomic nucleus (parasympathetic)
Hypothalamus is also believed to participate in memory acquisition, subjective experience of emotions and, via the autonomic nervous system, the visceral manifestations of emotions

13. Amygdaloid Nucleus It resembles an almond
Partly anterior and partly superior to the tip of the inferior horn of lateral ventricle
Fused with the tip of the tail of the caudate nucleus
Unilateral or bilateral destruction of amygdaloid results in increased appetite and hypersexuality

14. Amygdala Found near the temporal pole, deep to parahippocampal gyrus
Inputs: Temporal cortex, septum and olfactory tract, brain stem
Outputs: Chiefly to the hypothalamus
Role in evaluating the significance of environmental events, and the association of environment events

15. Lesions associated with limbic lobe disorders
Temporal lobe epilepsy
Alzheimer’s disease
Schizophrenia

16. Thalamus Large egg shaped mass of gray matter
Two thalami situated on each side of 3rd ventricle
Thus form the lateral walls of the 3rd ventricle
Separated from hypothalamus by hypothalamic sulcus
May be connected to opposite thalamus by interthalamic adhesion (connection)

17. Thalamus
Thalamus has a narrow anterior end called tubercle of thalamus
The expanded posterior end, called pulvinar

18. Surfaces
4 Surfaces:
Superior
Inferior
Medial
Lateral S L M l

19. Relations Superior: lateral ventricle
Anterior: interventricular foramen
Lateral: Internal capsule
Medial: 3rd ventricle
Inferior: Subthalamus & Hypothalamus
Caudal: midbrain

20. Functions of the thalamus
Receives and analyses all the sensory information (except olfactory) from the body
Having extensive connections with the basal ganglia and the motor cortices, it plays a pivot role in voluntary motor activity
Connections with the limbic system makes it important in the control of mood, emotional and sexual behavior, and memory

21. Internal Organization
Thalamus is composed of grey matter, divided by two vertical sheaths of white matter called medullary laminae.
External medullary lamina:
Located laterally, separates reticular nucleus from the rest of the thalamic mass
Contains thalamocortical & corticothalamic fibers
Internal medullary lamina
Y- shaped band, divides thalamus into Anterior, Medial & Lateral nuclear groups
Contains:
Fibers connecting thalamic nuclei with one another
اسم ورقم المقرر – Course Name and No.
6/15/2019

22. Nuclear Groups Anterior nuclear group
Lateral nuclear group: Divided into:
dorsal &
ventral tiers
Medial nuclear group
Intralaminar nuclei
Reticular nucleus
Midline nuclei
اسم ورقم المقرر – Course Name and No.
6/15/2019

23. Functional Organization
The whole of the cerebral cortex receives input from the thalamus
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6/15/2019
2323

24. Based on their connection with the cerebral cortex, the thalamic nuclei are divided into:
Specific nuclei
Nonspecific nuclei
Specific nuclei:
Have well-defined sensory and motor functions
Have highly organized point-to-point connection with sensory & motor regions of cerebral cortex
Lie within the ventral group of the lateral nuclear group
Non-specific Nuclei:
Receive less functionally distinct afferent input
Connect with wider area of cortex, including associative and limbic regions
Include nuclei of the dorsal tier of lateral group, and whole of the anterior and medial group

25. Ventral anterior Ventral lateral Ventral posterior: Lateral geniculate
Lateral Nuclear Group, Ventral Tier
Ventral anterior
Ventral lateral
Ventral posterior:
(VPL)
(VPM)
Lateral geniculate
Medial geniculate
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6/15/2019

26. Ventral Anterior Nucleus
Influences motor activity
Ipsilateral
globus pallidus & substantia nigra
Motor cortex
Premotor & supplementary motor cortex

27. Ventral Lateral Nucleus
Influences motor activity
Ipsilateral
globus pallidus &
substantia nigra
Contralateral
dentate nucleus
Primary motor cortex
Primary motor cortex
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6/15/2019

28. Ventral Posterior Nucleus
Chief sensory relay station
General sensory afferents from the contralateral half of the Head & Neck (VPM) and Body (VPL)
Primary somatosensory cortex

29. Lateral Geniculate Body
Part of the Visual Pathway
Ipsilateral
temporal hemiretina
Contralateral
nasal hemiretina
Optic radiation to the primary visual cortex

30. Medial Geniculate Body
Part of the Auditory Pathway
Inferior colliculus
Auditory radiation to the primary auditory cortex

31. Lateral Nuclear Group, Dorsal Tier
Lateral Dorsal
Lateral Posterior
Pulvinar
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6/15/2019

32. Lateral dorsal nucleus Part of Limbic System
Hippocamus
Cingulate gyrus
Lateral posterior nucleus
sensory association cortex of parietal lobe
Pulvinar: Sensory association cortices of parietal, temporal & occipital lobes

33. Integrates emotion, thought, and judgment
Medial Nuclear Group
Integrates emotion, thought, and judgment
Mediodorsal nucleus & Nucleus reuniens
Hypothalamus, amygdala, other thalamic nuclei, prefrontal cortex
Prefrontal cortex & limbic structures

34. Anterior Nuclear Groups
Functionally part of the limbic system. Involved in control of instinctive drives, emotional aspect of behavior and in memory
3 parts:
Anteroventral
Anteromedial
Anterodorsal
اسم ورقم المقرر – Course Name and No.
6/15/2019

35. Intralaminar Nuclei Located within the internal medullary lamina
Function as activator of the cerebral cortex
Lesions reduce the perception of pain and level of consciousness

36. Reticular formation, spinothalamic & trigeminothalamic systems
Widespread regions of cerebral cortex, caudate & putamen of the basal ganglia

37. Reticular Nucleus
Regulates the activity of thalamus
Located between the external medullary lamina & the internal capsule
Collaterals of both Thalamocortical & Corticothalamic fibers
Other thalamic nuclei
اسم ورقم المقرر – Course Name and No.
6/15/2019

38. Thalamic Lesions
Cerebrovascular lesions or tumors of thalamus lead to:
Loss of sensation in the contralateral side of face and body followed by distressing discomfort, & burning and diffuse pain in the anesthetic areas (thalamic pain)
Thalamic syndrome: Abnormal voluntary movements (chorea or hemiballismus) with hemisensory disturbance

39. References
Clinical Neuroanatomy for Medical Students, Richard S. Snell-6th Edition.
Clinical Neuroanatomy and related neuroscience. M.J.T. FitzGerald, Jean Folan-Curran, Fourth Edition.
Crossman, AR and Neary D, Neuroanatomy: An Illustrated Colour Text.
Haines, DE, Neuroanatomy: An Atlas of Structures, Sections and Systems.
Agur, A. M. R. and A. F. Dalley Grant’s Atlas of Anatomy, 12th Edition. Lippincott, Williams & Wilkins, New York.
Moore, K. L., A. F. Dalley and A. M. E. Agur Clinically Oriented Anatomy, 6th Edition. Lippincott, Williams & Wilkins, New York.
Sadler, T. W Langman’s Medical Embryology, 9th Edition. Lippincott, Williams & Wilkins, New York.

40. THE END