Limbic System

Question 2

What are the main functions of the limbic system, the amygdala and the hippocampal formation?

Answer 2

• Control of memory and emotion
• coordination of some autonomic responses
• the amygdala controls emotions
• the hippocampal formation is involved with formation of memories, specifically short-term

Question 3

What are the following structures?

What is significant about their relationship with the limbic system?

Answer 3

The olfactory tract is involved with the limbic system

smell can trigger emotions, memories and autonomic nervous system responses

the olfactory bulb and olfactory tract are outgrowths of the telencephalon - olfaction is the only sensory system to bypass the thalamus on the way to the cerebral cortex

Question 4

What are the following structures?

Answer 4

Question 5

What is the isthmus?

Answer 5

A narrowing of the cingulate gyrus where it is continuous with the parahippocampal gyrus

Question 6

What is the uncus?

Answer 6

The parahippocampal gyrus hooks upon itself anteriorly to form a bump called the uncus

Question 7

Where is the cingulate gyrus located?

Answer 7

Below the cingulate sulcus and above the corpus callosum

Question 8

What is meant by HOME to remember the limbic structures?

Answer 8

H - Homeostasis

• performed by the hypothalamus
• e.g. blood pressure, heart rate, production and release of hormones

O - Olfaction

• paraolfactory area

M - Memory

• hippocampus

E - Emotions

• amygdala

Question 9

Which developed first, the limbic system or the neocortex?

Answer 9

The limbic system is phylogenetically older and was present before the brain developed

the neocortex evolved later in development and is responsible for higher order functions

Question 10

What is the cingulum?

Answer 10

The cingulum is underlying the cingulate gyrus

it receives information from pre-frontal, parietal, occipital and temporal gyri

it is involved in the formation of memories and emotions

Question 11

What kind of subcortical white matter fibre type is the cingulum?

Answer 11

Association fibres

these white matter fibres interconnect regions of one hemisphere with the limbic lobe and the hippocampus

Question 12

What is the role of the limbic system?

Answer 12

The limbic system is concerned with the regulation of drive and affective behaviour and plays a crucial role in memory and learning

Question 13

What parts of the limbic system are concerned with emotions and memory?

Answer 13

Amygdala - emotional brain:

• emotional and motivational aspects of behaviour
• e.g. pain, pleasure, rage
• provides emotional component to the learning process

Hippocampus - associated with memory

Question 14

What is the amygdala?

Where is it found and what is its main function?

Answer 14

It is an almond shaped nuclear complex (collection of cell bodies) in the medial temporal lobe

it is located deep to the uncus

it is mainly involved in emotions and behaviour

Question 15

What is the primitive role of the amygdala?

How can we control this?

Answer 15

The primitive role is important for species preservation

e.g. feeding, drinking, sex, nurturing, need for survival

we have control of the amygdala due to the neocortex allowing us to rationalise and acquire context, whereas animals do not

Question 16

What is the hippocampal formation (hippocampus)?

Where is it found and what is its main role?

Answer 16

Nuclear complex (nerve cell bodies) in the medial temporal lobe

it is found deep to the parahippocampal gyrus

it is mainly involved in memory

Question 17

What happens if there is a lesion in the hippocampal formation?

Answer 17

Lose the ability to form new memories

the hippocampal formation is mainly involved in formation of short term memories, so it is difficult for a single lesion to affect long term memories

Question 18

Where is the cingulum?

What are the landmarks of the limbic system?

Answer 18

Landmarks are the bumpy regions we can see in the brain as they have something underneath them

the cingulum is a bundle of association fibres bringing information from the cortex and towards the limbic system

Question 19

What are the connections associated with the limbic system?

Answer 19

Stria terminalis:

• connects the amygdala to the hypothalamus

Fornix:

• connects the hippocampus to the hypothalamus
• they both follow the curves of the lateral ventricles

Question 20

What does the fornix connect to?

Answer 20

The fornix connects the hippocampus to the mammillary bodies of the hypothalamus

connecting to the hypothalamus immediately triggers functions of the hypothalamus, such as autonomic responses

emotions and memories can trigger autonomic responses e.g. increased heart rate

Question 21

What 3 structures does the amygdala link with?

Answer 21

• Unprocessed visual, auditory, somatosensory, gustatory and olfactory stimuli

Cortex - cingulate & parahippocampal gyri:

• Processed visual, auditory, somatosensory, gustatory and olfactory stimuli
• the majority of the connections reaching the amygdala

Nuclei of autonomic nervous system:

• brainstem and hypothalamus
• this involves emotions triggering increased HR, salivation, BP etc.

Question 22

What is the difference between unprocessed and processed stimuli reaching the amygdala?

Answer 22

Unprocessed stimuli:

• minor direct projections where the sensory systems connect directly with the amygdala
• before information is processed in the neocortex, a few fibres reach the amygdala and trigger an emotional response

Processed stimuli:

• information from what we see is sent via the visual cortex, processed and sent to the visual association cortex to give it meaning
• information is given meaning and context before being sent to the amygdala
• context means the emotion is not as powerful

Question 23

What is the outflow tract of the amygdala?

Answer 23

Stria terminalis

this is a band of fibres that runs along the ventricular surface of the thalamus (in lateral ventricle)

Question 24

Label the features of the hippocampal formation

What is their appearance like?

Answer 24

Dentate gyrus:

• strip of grey matter with a tooth-like appearance

Hippocampus proper:

• has a seahorse appearance in coronal section

the hippocampal formation forms the floor of the inferior horns of the lateral ventricles

Question 25

Where is the hippocampus located in coronal section?

Answer 25

Question 26

What does the fornix contain? Where does it lead to?

Answer 26

The fornix contains the main efferent fibres of the hippocampus it follows a C-shape over the thalamus to reach the hypothalamus some fibres reach the mammillary bodies

Question 27

Label the components of the fornix and hippocampus

Answer 27

Question 28

What is the hippocampal commissure?

Answer 28

There is a hippocampus in each hemisphere the hippocampal commissure allows for communication between fornices on both sides of the brain

Question 29

How long is the hippocampus? Where does it end?

Answer 29

It is about 5 cm long it narrows and ends near the splenium of the corpus callosum

Question 30

Where are the mammillary bodies located?

Answer 30

Posterior to the optic chiasma and infundibulum

Question 31

Label the planes of dissection

Answer 31

Question 33

What is the role of the circuit of papez? What structures are involved?

Answer 33

Reinforcement of emotion, memory and olfaction with each other for survival responses it is a **closed, bidirectional** circuit: * hippocampus * fornix * mammillary bodies * anterior thalamic nuclei * cingulate gyrus * hippocampus

Question 34

What are the stages involved in the function of the Circuit of Papez?

Answer 34

Question 35

What is the main function of the hippocampal formation?

Answer 35

**Short term memory** * vital for the formation of new memories and learning * damage leads to an inability to recall recent events (short term memory) and learning * memories of distant past and intelligence remain intact if there is a lesion

Question 36

What inputs does the hippocampal formation receive? WHat is the outflow tract?

Answer 36

The hippocampus receives all types of information (inputs) via the cingulum it receives information from many areas including the cingulate gyrus and other cortical areas the fornix is the major outflow tract it connects the hippocampus to the hypothalamus and septal area

Question 37

Where do fibres travel once they have reached the mammillary body from the hippocampus?

Answer 37

Fibres ascend to the anterior nucleus of the thalamus fibres then project to the cingulate gyrus they are then distributed to cortical areas including pre-frontal, posterior parietal and temporal association via the cingulum

Question 39

What happens in the hippocampus when specific items of information are important to remember?

Answer 39

When specific items of information are important to remember, these items are rehearsed repeatedly until they are permanently stored in the areas of the cortex associated with long-term memory

Question 40

What is the endocrine function of the hippocampal formation?

Answer 40

* It has inputs to the hypothalamus - modulatory role * hypothalamus is connected to the pituitary gland

Question 41

What is the definition of memory? What are the 4 different types of memory?

Answer 41

The mental capacity to ***encode***, ***consolidate***, ***store*** and ***retrieve*** information * sensory memory * working memory * recent memory * remote memory

Question 42

What is sensory memory? How long does it last for?

Answer 42

Information perceived from the senses which is usually sent to working memory it is quick and short-lived (in 2 seconds we understand what we see, hear, etc.) it is visual, auditory or haptic

Question 43

What is working memory and where is it stored?

Answer 43

Occurs in the **hippocampus** Information we hold on to as we learn it has the capacity to manipulate information and give privilege to what information is held in the brain It has limited capacity so it can only hold a few items at the same time, but can prioritise this information

Question 44

What ways can help the working memory deal with and store new information?

Answer 44

* Chunking information * linking information with things we already know - e.g. acronyms

Question 45

What is recent memory? Where is it stored?

Answer 45

If working memory is consolidated enough, it can become long-term memory the recent memory is found in the **hippocampus**

Question 46

What is consolidation?

Answer 46

When you take new memories from the hippocampus and bring them into the neocortex for permanent storage not all recent memories can be consolidated

Question 47

What is remote memory and where is it found?

Answer 47

Remote memory is long term memory it is stored in the neocortex

Question 48

What is retrieval? What is retrieval practice?

Answer 48

The ability to recall information stored in the neocortex or hippocampus by bringing it back to working memory the strength of pathway determines the efficiency of retrieval retrieval practice involves constant review of material

Question 49

Answer 49