The limbic system Flashcards
What is the limbic system involved in
Pleasure
Pain
Learning
Memory
Where are the nuclei of the limbic system located
Medial aspect of frontal, parietal and temporal lobes
In simple organisms, what systems is the limbic system connected to
Olfactory and memory
What makes up the limbic system in the frontal and parietal lobes
Orbito-frontal cortex
Cingulate cortex
What makes up the limbic system in the medial temporal lobe
Parahippocampal cortex
What is the main blood supply to the limbic system
Anterior and posterior cerebral artery
What blood vessel supplies the tip of temporal lobe and orbital cortex in some people
Middle cerebral artery
When is the anterior cingulate cortex activated
Pain and depression
What does the caudal anterior cingulate register
The quality of pain (how bad on scale of 1-10)
What does the rostral anterior cingulate register
What actions to take to deal with the pain
Where does nociceptive information travel up
Lateral spinothalamic tract
Where does nociceptive information go once travelled up lateral spinothalamic tract
Parabrachial nucleus
Amygdala
Anterior thalamic nucleus
Anterior cingulate cortex and insula
What area of the brain is responsible for processing the unpleasantness of the pain and its emotional consequences
Anterior cingulate cortex and insula
What area of the brain is activated to ‘do something’ about the pain
Prefrontal cortex
What is a cingulotomy
Procedure of cutting the cingulate fibres to disrupt the fibres passing rostro-caudally reducing the emotional distress of pain
What % of people report improvement post cingulotomoy?
What % didn’t need painkillers anymore
72% report improvement
50% report reduction for need of painkillers
What is the orbitofrontal cortex involved in
Reacted to an anticipated threat (eg actions to avoid more pain)
How does the behaviours associated with orbitofrontal cortex differ in people with OCD
- In a difficult decision, person may be unable to respond to threat and ‘freeze’
- Prolonged pressure to make these choices00> OCD
When does the posterior cingulate cortex show activity
When recalling memories with emotional significance
Where do the parahippocampal gyrus lie
Medially and inferiorly on temporal lobe
What is the parahippocampal gyrus involved in primarily
Acquisition of new memories
What 2 structures are the subcortical parts of the limbic system
Hippocampus and amygdala
Where are the hippocampus and amygdala located
Walls of the inferior horn of lateral ventricles
What do the output fibres from the hippocampus form
The fornix
What shape does the fornix follow
Curves upwards and round and over the top of the third ventricle
Where does the fornix end up lying
Under the corpus collosum
How are the fornices attached to the corpus collosum
By the septum pullucidum
Where do the fornix axons end
In the septal nuclei and the mammillary body of the hypothalamus
Papez’s circuit is required for the formation of what
Memories
Describe the passage of information in the loop between the hippocampus and the limbic cortex
1) From cingulate cortex to parahippocampal gyrus
2) From parahippocampal gyrus to hippocampus
3) Along fornix to mamillary bodies of the hypothalamus
4) From hypothalamus to anterior thalamus
5) From anterior thalamus back to cingulate cortex
What is observed if there is damage to any structure in Papez’s loop
Deficits in recall from memory (recollective memory)
What are the mammilliary bodies important in
Include olfactory clues in memory of places
Is memory stored in the hippocampus
No
What are the current views of the hippocampus’ role in memory storage
- Labels new experiences with time and place they occured
- Transferring new memories to long term memories
- Learning new motor skills
What is anterograde amnesia
Loss of ability to store new experiences
What is Kluver-Bacy due to?
Bilateral removal of amygdala
What are the features of Kluver-Bacy syndrome?
Psychic blindness Oral tendencies Hypermetamorphosis Altered sexual behaviour Emotional changes
Where is the amygdala embedded?
In the anterior medial temporal lobe
What does electrical stimulation of the amygdala produce
Panic, fear and terror responses
What was the loss of fear seen in Kluver-Bacy monkeys attributed to
Removal of amygdala
What could be regarded as the command centre for the autonomic nervous system
Amygdala
2 main functions of the amygdala
Monitors and analyses sensory input
Activates fight/ flight response
Describe the steps that begin with the amygdala and end with sympathetic activation
Amydala— Hypothalamus— Reticular formation– (via reticulospinal tract)– Preganglionic sympathetic neurones– Sympathetic activation
What is seen if there is local bilatereal damage to the amygdala
Unable to identify fearful expression
What is seen if there is complete bilateral damage to the amygdala
Unable if face was sad or extremly sad (eg)
What brain structure is hypothesised to be damaged in autism?
Amygdala
Inputs from which lobe enable to amygdad to detect if stimulus is associated with pleasure or pain
Temporal
What makes up the ventral striatum
Accumbens nuclei
Septal nuclei
Basal nuclei
Where do septal nuclei lie
At the bottom of septum pellucidum
Merges into basal nuclei of meynert
What is the accumbens nuclei part of
a) anatomically
b) functionally
a) basal ganglia
b) limbic system
What does the accumbens nuclei receive fibres as part of?
The mesolimbic dopamine pathway
Where do fibres in the mesolimbic pathway project from and to
from the brainstem regions next to substantia nigra to the accumbens nuclei
What are the mesocortical and mesolimbic pathways
Part of a single diffuse system of dopamine neurones projectedd from VTA to limbic structures and to prefrontal limbic cerebral cortex
What happens if you block dopamine pathways in accumbens
Stops pleasure
What is the accumbens involved in
Initiation and termination of behaviours that trigger reward pathways
