1. Limbic System
Structure and Function

2. Outline
1) Neuroanatomy of the Limbic System
2) Circuits in the Limbic system
3) Functions of the Limbic System (plus HM and
Kluver-Bucy syndrome)
4) Memory and amnesia- coming soon!

3. Of rabid dogs and neuroanatomists

4. Where is it?
Limbic= border or edge (rim)
1) Medial aspect
2) Both Cortical and Sub-cortical structures
3) Involves parts of Frontal, Parietal and
Temporal lobes
4) Highly interconnected

5. Cortical Components
1) Frontal= Orbitofrontal and anterior cingulate
cortex
2) Parietal= Posterior cingulate cortex
3) Temporal= Parahippocampal cortex

7. Subcortical components
1) Hippocampus(partly)
2) Amygdala
3) Accumbens?
4) Septal and
Basal nuclei

9. Hippocampus
1) Intimately related to the ventricular system
2) Continuous with fornix- the output network
3) Fornix moves posterosuperiorly, and at the
splenium it curves forwards suspended by the
septum pellucidum.
4) Reach the mammillary body and septal nuclei
(of the hypothalamus)

12. Before we move on,
1) Where is the limbic system?
2) What are its cortical structures?
3) What are its subcortical structures?
4) Trace the course of the fornix

13. Amygdala and the rest
Amygdala= Collection of nuclei in the entorhinal
cortex, follows on from the tail of caudate
nucleus
Output= stria terminalis, runs on the ROOF of
inferior horn of the lateral ventricle (cf fornix)
Terminates in the hypothalamus and septal
nuclei

17. Finally
Accumbens nucleus= Terminal of mesolimbic
pathway
Septal nuclei= Under the septum pellucidum

20. Papez Circuit
START HERE

23. Amygdala connections

24. Functions of the Limbic System
1) Reward and punishment, via being involved
in memory and learning
2) The ‘survival police’

25. Action
Memory and
Evaluation
Reward or
punishment
Learning Emotion
Motivation

26. What do the bits and pieces do?
As we said before 3 cortical components:
1) Orbitofrontal Cortex- Behaviour mods to avoid a
future threat ie how to avoid negative stimulus.
Involved in OCD.
2) Cingulate cortex- Anterior in two bits= rostral ->
how to deal with pain, Caudal -> Quantify the
severity (objectification) of pain. Posterior ??
Visuospatial memory?
3) Parahippocampal gyrus- Learning and memory!

27. Understanding function through
dysfunction
The Famous case of HM:
Had medial temporal lobe’s removed -> lost all
his parahippocampal cortex and part of
amygdala on both sides.
Post- op: Severe anterograde amnesia with
preserved STM.

29. Lessons learned from HM
Hippocampus is very important for memory,
BUT not where memories are stored!
Further studies, tell us that it allows for easy
retrieval of memories and for proper transfer of
experience into LTM.
Also, not involved in learning or retrieving motor
skills.

31. Kluver Bucy Syndrome
Bilateral removal of amygdala in monkeys, made
them bonkers.
Further studies showed that: It complements
the hippocampus in labelling of experiences by
identifying their emotional component.

33. And finally,
Septal and Basal Forebrain nuclei:
Contain loads of Ach, project to the whole of the
cortex, and are lost in AD.
Their activity may allow strengthening of
synapses/ consolidation of memory.

35. So,
Hippocampus labels information wrt place &
date
Amygdala labels wrt to emotional component
Basal and septal nuclei consolidate the
information