Structure & Function of the Limbic System Flashcards
What is the limbic system?
Anatomical concept
Group of cortical and subcortical nuclei on medial aspect of frontal/parietal/temporal lobes
All interconnected by cortico-cortical pathways
What is the blood supply to the limbic cortex in the frontal and parietal lobes?
Anterior cerebral artery
What is the blood supply to the limbic cortex in the temporal lobe?
Posterior Cerebral artery
What part of the limbic cortex does the middle cerebral artery supply?
Tip of the temporal lobe and orbital cortex
What cortices make up the limbic cortex in the frontal and parietal lobes?
Orbito-frontal cortex
Cingulate cortex
What cortex makes up the third part of the limbic cortex?
Parahippocampal cortex in the medial temporal lobe
What does the limbic system do?
- mediates sense of reward which you get from promoting survival (eating/drinking/sex)
- mediates sense of unhappiness/misery when decrease chance of survival (pain when injured/depressed when you fail)
What is the limbic system fundamentally involved in?
Memory processes
- to be rewarded/punished for something, it comes after the act so you have to remember the experience
What else is the limbic system involved in?
Learning - when an act is rewarded you tend to do it again vs. if it is punished you avoid doing it again
What are motivational processes?
Processes which link reward or punishment to changes in behaviour
What are emotional processes?
Subjective experience of motivational processes
Why do some smells make you feel hungry/nauseous?
Limbic system is intimately connected to the olfactory system
What is the association of the limbic system with the olfactory system?
Some smells are hard wired to pleasure/unpleasant emotions and don’t have to learn
What are reward circuits?
Neuronal circuits that are active when you have sensation of pleasure/joy/happiness
What are negative reinforcement circuits?
Essentially punishment circuits but cannot call them this
- neuronal circuits which are active when you are unhappy/depressed/in pain
When is the anterior cingulate cortex active?
During experience of pain/feelings of misery or depression
What is the pathway of pain/
Nociceptive pain info travels up lateral SPT
- goes to parabrachial nucleus to amygdala
- via anterior thalamic nucleus to anterior cingulate cortex and insula
What is the function of the anterior cingulate cortex?
Cortical area responsible for unpleasantness of pain and its depressing emotional consequences
What is the function of the prefrontal cortex?
Activated to do something about the pain you experience
What is cingulotomy?
cutting into anterior cingulate gyrus to disrupt fibres which pass rosro-caudally though it
- reduces emotional distress of pain
What is the function of the orbitofrontal cortex?
- anterior part of cingulate merges into it
- associated with behaviour when a threat is anticipated
- fits in with frontal love role as involved in planning future actions
- eg. actions to avoid pain
What happens if making a decision when a threat is anticipated is very difficult?
- no win situation
- unable to chosoe between actions so freezes
- prolonged pressure to make impossible choices = extreme stress
- release of stress hormones (cortisol and adrenaline)
- leads to sense of hopelessness and clinical depression