TOPIC 2- 22. The limbic system, the dentate gyrus and the hippocampus

A group of cortical and subcortical structures

- that are involved in memory formation and emotional life

What is the limbic system?

Because the region of the brain - which was believed to be responsible for emotions and memory - formed a physical border between the cerebrum and the hypothalamus

Why was it called the limbic system?

Border, edge

What does limbus mean?

1. Memory formation

2. Affective (emotional) life

What is the limbic system involved in?

- Feeding = satiety and hunger

- Fighting = emotional response

- Forgetting = memory

- Family = sexual reproduction and maternal instinct

- Fornicating = sexual arousal

What is the functions of the limbic system?

- Cingulate gyrus

- Indusium griseum

- Septum pelludicum

- Paraterminal gyrus

- Mammillary bodies

- Olfactory bulbs

- Anterior thalamic nucleus

- Hippocampus

- Parahippocampal gyrus

- Amygdala

- Uncus

What are the limbic structures? Grey matter

Thin layer of grey matter that covers the surface of the corpus callosum

What is the indusium grisium?

- Fornix

- Mammillothalamic tract

- Stria medullaris thalami

- Stria terminalis

- Anterior white commissure

What are the limbic structures? White matter

- The olfactory system

- The spinothalamic system

What are the main afferents to the limbic system?

The papez circuit is an important connection between limbic structures

- and is involved in control of emotional expression and memory

What is the papez circuit?

Hippocampus --(1)--> Mammillary body --(2)--> Anterior thalamic nucleus --(3)--> Cingulate gyrus of the cortex --(4)--> Parahippocampal gyrus ---> Hippocampus

(1) = Fornix

(2) = Mamillothalamic tract

(3) = Thalamocingular tract

(4) = Cingulum

Explain the neural circuit of papez

Formation and storage of new memories

- Related to memory and emotions

What is the function of Papez circuit?

Connection between septum pellucidum, hypothalamus and habenular nuclei

What is stria medullaris of thalamus a connection between?

Connection between Amygdala and hypothalamic and septal areas

What is stria terminalis a connection between?

Adaptation to stressful situations (Increased HR, and increased release of stress hormones)

Function of stria terminalis?

Involved in learning and explicit type of memory

- Does not store information but activates other areas involved in information processing and learning

Function of hippocampus?

If the hippocampus is damaged, we loose access to out memory storage

What happens if the hippocampus is damaged?