2.12 Limbic Brain Flashcards
What is the limbic brain
A number of different structures that may comprise several circuits underlying the complexity of emotional experiences that are associated with unique physiological responses.
Why is it described as the limbic brain not the limbic system
The functional relationship of these limbic areas have not been discovered yet (still lots of research ongoing), therefore it can not be described as the limbic system but instead the limbic brain.
What are the brain structures associated with the limbic brain
cingulate cortex, amygdala, hippocampus, nucleus accumbens, hypothalamus and insula
What do all the brain structures in the limbic brain have in common
They are all associated with emotions
Describe the current scientific understanding of mapping specific emotions to specific brain areas
It is very difficult to map specific behaviours to specific limbic brain areas, as although there are clear anatomical connections (with certain emotions being associated with activity in certain areas of the brain), the functional relationships are still not fully understood.
What is the amygdala
The amygdala is a complex of nuclei forming a bilateral structure that sits at the pole of the temporal node. The amygdala is associated with the emotion fear. There are many sensory inputs into the amygdala and outputs from it. There are complicated circuit loops with the amygdala projecting to the basal ganglia which projects to the hypothalamus and other parts of the limbic brain
Give research evidence for the connection of amygdala to the emotion fear
Studies removing the amygdala in monkeys caused an absence of fear, rage and aggression as well as a compulsion to be overly attentive to all sensory stimuli, this is Kluver-Bucy syndrome (similar symptoms have been seen in humans with temporal lobe lessions). Additionally, electrical stimulation of the amygdala in rodents caused anxiety, fear and aggression.
Describe the role of the hypothalamus in the limbic brain
The hypothalamus plays a complex role in emotional processing. Anatomically, the hypothalamus receives input from the nucleus tractus solitarus (lots of autonomic input from the periphery) and there is a strong tract between the two. Also it receives input from the olfactory cortex, retina, amygdala and hippocampus. It sends output to many areas affecting behaviour and physiological functions by modulating activity in the cerebral cortex, thus influencing limbic structures, autonomic output, and controlling hormone production by the pituitary gland.
Describe the role of the insula in the limbic brain
The insula is a bit of cortex nestled inside the brain and is loosely associated with the limbic brain. The anterior insula is a cortical centre for pain, the central insula is associated with language and the posterior insula is connected to the amygdala.
Describe the role of the nucleus accumbens in the limbic brain
The nucleus accumbens is a deep seated nucleus in the centre of the brain that has been experimented on for pain relief. The nucleus recieves dopaminergic projections from the ventral tegmental area and the release of dopamine in the nucleus accumbens mediates positive reinforcements of rewards. Stimulating the nucleus with electrodes has induced feelings of well being (hedonia). It recieves many inputs and has many outputs with both the limbic brain and higher brain areas.
What is the role of the hippocampus in the limbic brain
It is associated withe learning and memory, especially retrieval of emotional memories
