excellent ppt neuroanatomy of limbic system

1. Neuroanatomy of Limbic system
& memory
Presenter: Dr. Mestet Y.(neurosurgery
resident)
Moderator: Dr. Hagos B.( Consultant
Neurosurgeon)
7/24/2020 1

2. Outline
Introduction
Limbic system
Olfactory system
Memory
Clinical correlates
Reference
7/24/2020 2

3. Introduction
Limbic system: is a ring-like structure around
the upper end of brainstem and on the inferio-
medial surface of the cerebral hemispheres.
7/24/2020 3

4. Limbic lobe
• consists of subcalosal & cingulate gyrus,
isthmus, hippocampal formation,
parahippocampus, and uncus.
7/24/2020 4

5. Limbic Loop
• Anatomic substrates for the integrative
function of the limbic system.
7/24/2020 5

6. Functions of limbic system
• Homeostatic mechanisms
• Preservation of the species
• Emotional behavior and feeling
• Memory
• Matching up sensory input with autonomic-
endocrine drives and putting it into the context of
the situation
• Motivation
Different functions of the limbic system are not
distributed equally among its components.
7/24/2020 6

7. HIPPOCAMPAL FORMATION
• is an infolding of the parahippocampal gyrus
into the inferior horn of the lateral ventricle
• consists of three regions: hippocampus
dentate gyrus (fascia dentata), and subiculum.
• allocortex
7/24/2020 7

8. Hippocampus
7/24/2020 8

9. Afferent Hippocampus Connections
7/24/2020 9

10. Efferent Hippocampus Connections
7/24/2020 10

11. Entorhinal-hippocampal (internal)
circuit
7/24/2020 11

12. Papez (external hippocampal) Circuit
• It is a circular pathway that interconnects
important structures in limbic system.
• Concerned with memory.
7/24/2020 12

13. FUNCTION
• Memory: bilateral anterior temporal
lobectomies.
Lt vs Rt: like hemispheric asymmetries.
Anterior vs posterior: novelty vs familiarity
• No role in olfaction.
7/24/2020 13

14. Clinical correlates
• MTLE: anterior temporal lobectomy
• Seizure from hippocampus doesn’t become
generalized. Why?
• Alzheimer’s disease
• Korskoff syndrome
• Herpes simplex encephalitis
• Neurogenesis
7/24/2020 14

15. Amygdala
• Almond shaped group
of nuclei
• Relation:
• 2 nuclei: corticomedial-
central & basolateral.
7/24/2020 15

16. Afferent pathways
Cortical Subcortical
7/24/2020 16

17. Efferent pathways
• Stria terminalis sends fibers to the septal area
and hypothalamus before entering the medial
forebrain bundle and (downstream) the
central tegmental tract & bed nucleus.
• Ventral amygdalofugal pathway: synapse
within the nucleus accumbens
7/24/2020 17

18. Intra-Amygdaloid Connections
• extensive intranuclear and internuclear
connectivity between amygdalar nuclei.
• Most of the connections are glutamatergic.
• indicate extensive local processing of
information entering the amygdala before it
leads to the appropriate behavioral outcomes.
7/24/2020 18

19. Function
• Autonomic effects
• Orienting response
• Emotional behavior and food intake
• Facial expression
• Arousal response
• Sexual activity
• Motor activity
7/24/2020 19

20. Clinical correlates
• Kluver-Bucy syndrome
• Temporal lobe epilepsy
• The ‘What?’ pathway:
• Prosopagnosia
• Anxiety & phobia:
 Blood truama phobia
• Attack b/r from
 hypothalamus vs
 Amygdala vs
 sepal area
7/24/2020 20

21. Septal areaComponents
septum verum
nucleus accumbens
septi.
the bed nucleus of
stria terminalis
septal nuclei
Medial
Lateral
posterior
diagonal band of
Broca
septum pellucidum
7/24/2020 21

22. Afferents
 Amygdala
 Hippocampus
 Olfactory tract
 Brainstem
monoaminergic neurons
7/24/2020 22

23. Efferent projections
• Two chief efferent projections
stria medullaris
septohippocampal pathway: via fornix
rate & size of theta rhythm: Glutamatergic vs
cholinergic neurons
strength of theta rhythm in AD
7/24/2020 23

24. Function
• Provides interaction between limbic and
diencephalic structures.
Emotional behavior
Water consumption
Activity
Learning
Reward
Autonomic effects:
Septal syndrome
7/24/2020 24

25. Basal forebrain
• Extends from
Bifurcation of olfactory tract to infundibulum&
Midline to the amygdala .
• Abundant in cholinergic neurons
• Cholinergic neurons in septal nuclei & basal
nucleus of Meynert: LTP & ‘awake’ pattern on
EEG.
7/24/2020 25

26. Nucleus accumbens
• ‘’For feeling of high’’.
• Drugs of dependency
• Schizophrenia
7/24/2020 26

27. OLFACTORY SYSTEM
• Peculiarity of primary
afferent neurons:
1. somas at surface
epithelium.
2. axons enter to cortex
directly.
3. undergo continuous
turnover from basal stem
cells.
4. The pathway to the
cortical centers in the
frontal lobe is entirely
ipsilateral.
7/24/2020 27
Olfactory
epithelium
Olfactory
nerves
Olfactory bulb
Olfactory tract
Areas of
olfactory cortex

28. Cingulate cortex
• The anterior vs
posterior cingulate
cortex :
• Anterior cingulate:6
functional areas
7/24/2020 28

29. Reticular formation
7/24/2020 29

30. Memory
• depend on two distinct changes:
an electric membrane event of a temporary
nature and
a more stable, permanent change in the
chemistry of the nervous system.
DNA and RNA act as codes for synaptic
transmission for transforming short-term
memories into permanent stores.
7/24/2020 30

31. Neuroscience of long term memory
potentiation (LTP)
7/24/2020 31

32. Memory classification
7/24/2020 32

33. Types of Memory Loss (Amnesia)
(1) Retrograde
(2) Anterograde
(3) Global
(4) Modality-specific
(5) Permanent and
(6) Transient
7/24/2020 33

34. References
7/24/2020 34

35. 7/24/2020 35