The limbic system Flashcards
(20 cards)
What is emotion also known as?
Emotion is known as an ‘affect’
Emotional response = affective response; emotional disorders = affective disorder.
Define emotion.
A combination of psychological and physiological responses to a stimulus.
E.g. Physiological: crying (tears), smiling.
What is the normal emotional range and how can this be an issue?
We all have a range in which we are in our normal emotional state; there is no set value for happiness.
Individual: our emotional state varies from minute to minute; Population: averages may not show large variability.
Describe the types of emotions.
Emotions can be positive or negative and vary in intensity (arousal). Emotion is neither good nor bad, just an expression of a state an individual is in.
What are the reasons we should have emotion?
- Communication: We express our emotional state to communicate with each other.
- Aids memory: The impact of emotions can enhance memory encoding.
E.g. You remember what you had for lunch on your birthday but not the day before.
How is the brain linked to emotion?
There is no one discrete region for each emotion; emotions are underpinned by a network of interconnected neurons across various structures.
What is the history behind which structures of the brain are involved in emotion control?
Broca found structures around the brain stem (limbic). Papez linked emotion expression with ANS activation and hypothalamus involvement.
Papez stated that the limbic structures form the network connecting the hypothalamus and neocortex, known as the Papez Circuit.
What are the key structures of emotion?
- Neocortex = awareness.
- Cingulate gyrus.
- Hippocampus = stores information.
- Hypothalamus = physiological expression.
What is the evidence that supports the Papez Circuit?
- Lesions/tumors: Localized lesions in the anterior thalamus can lead to spontaneous laughter and crying.
- Neocortex: Evidence links orbitofrontal cortex activity with emotional states like pleasure.
E.g. Phineas Gage’s character changed after damage to the orbitofrontal cortex.
What is the current view regarding the Papez circuit?
Elements from the circuit are involved in emotional control but also in other functions.
E.g. Hippocampus is important in memory acquisition; changes in emotional expression can affect hippocampus volume.
What is the anatomical location of the amygdala?
There are 2 amygdalae, one in each hemisphere, located on the medial surface of the temporal lobe, adjacent to the hippocampus.
What is the amygdala composed of?
It is composed of multiple nuclei: corticomedial nuclei, central nucleus, and basolateral nuclei.
Why do we think the amygdala has a role in emotion?
- Experimental lesions: Temporal lobectomy in monkeys results in Kluver-Bucy syndrome, decreasing fear.
- Human evidence: Urbach-Wiethe disease affects the amygdala, leading to fearless behavior.
E.g. Individuals with epilepsy report strong emotions before seizures.
Why do we need emotional memory?
Emotional memory allows us to interpret sensory input and compare it with previous encounters.
Describe the emotional memory pathway.
A stimulus goes to the sensory cortex for interpretation, then to the amygdala. If the amygdala recognizes it as emotionally significant, it triggers a response involving the hypothalamus and brain stem.
This can lead to physiological changes and behavioral responses.
What determines aggression?
Many factors control aggression; the amygdala and hypothalamus are strongly linked to aggression, suggesting overlap with fear pathways.
How has the Papez Circuit been revised?
Papez’s circuitry has been revised to include structures like the hippocampus and amygdala, which are important for emotional control.
What is the clinical relevance of a dysfunctional amygdala?
Dysfunctional amygdala circuits are relevant for conditions like PTSD, depression, anxiety disorders, aggression, and autism.
How can we treat emotional disorders?
Treatment is complex due to unclear biology; options include psychosurgery and drugs.
E.g. Deep brain stimulation (DBS) and medications that manipulate neuronal activity.
Do the amygdalae in both hemispheres function in the same way?
There appears to be a degree of lateralization; the right hemisphere is specialized in recognizing emotions, which has implications for individuals with amygdala damage.
