W10 - Emotion Flashcards
What is emotion?
- Emotional expression
– Animal and human studies - Emotional experience
– Human studies - Affective Neuroscience
– neural basis of emotion and mood
– (mood as an emotion extended in time)
How can you test for anxiety in rats?
Increase of anxiety-like behaviour following long-
term opioid abstinence
You can put a rat on an elevated cross like apparatus with one covered and protected segment and the other an open segment. Let the rat explore for a few mins and observe where it is most likely to explore in that time frame. Spends about 30% of the time in open arms.
If injected with a benziodiazepine drug, which is an anxiolitic drug, it would spend a lot more time in the open arms in comparison.
How do you test for depression in animal models?
Increase in depressive-like behaviour following
long-term opioid abstinence.
Forced swim test:
Take a 5L beaker and fill it with water.
Put the mouse in there and let it swim for 7-10 mins in the water.
At first, it would swim happily in the beaker. Then, after a while, it would get fed up and try to get out of the beaker. Once it realises it can’t, it will resort to a freezing behaviour, where it would only have just enough movement in the hind legs to keep the head afloat.
All antidepressant are tested using this forced swim test. These drugs should decrease the immobilised state of a mouse.
How do you measure expressions of emotions through sociability behaviour in mice?
Long-tem morphine abstinence abolishes social
preference.
This experiment needs a 3-chambered box with a connected door.
In two of the chambers, there needs to be cages.
In one of these cages, there needs to be another mouse, while the other one is empty.
You put the test mouse in the box and measure the time it spends socialising vs the time it spends alone.
They spend a lot more time in the social chamber because they are social animals.
In morphine absent mice, indifference was shown, where they spend an equal amount of time in both chambers, suggesting it was not interested in socialising.
What are the brain mechanisms of emotion?
- Emotions:
– Love, hate, disgust, joy, shame, envy, guilt, fear, anxiety, etc. - What defines emotions?
- Theories of emotion:
– James- Lange - We experience emotions in response to physiological changes in our body. Eg. when we cry, we get sad. Lots of holes in this theory.
– Cannon-Bard - We can experience emotions independently of emotional expression (dissociations)
– Emotions are produced when signals reach the thalamus either directly from sensory receptors or by descending cortical input
What are the James-Lange vs. Cannon- Bard theories?
- The James–Lange theory: emotion experienced in response to physiological changes in body
- The Cannon–Bard theory: emotions occur independent of emotional expression—no correlation with physiological state
Is there a brain system responsible for Emotions?
- Broca’s Limbic lobe
– Limbus (latin) means border
– primitive cortical gyri that form a ring around
the brain stem - Broca’s limbic lobe includes
– the parahippocampal gyrus
– the cingulate gyrus
– the subcallosal gyrus
What is the limbic system?
- Broca’s limbic lobe
– Areas of brain forming a ring around corpus
callosum: cingulate gyrus, medial surface
temporal lobe, hippocampus
Later discovered, all these areas are involved in emotional processing.
What are the limbic structures associated to the Papez circuit?
- Limbic structures, including cortex, involved in emotion
- Emotional system on the medial wall of the brain linking cortex with hypothalamus
When we respond to stimuli, the emotional colouring takes place in the Neocortex.
This is in connection to the Cingulate cortex - where emotional experience takes place.
This stimulus is propagated to the hippocampus.
This is connected to the Hypothalamus via a number of neurones called the fornix. Hypothalamus then expresses emotion.
The neurones then signal to the anterior nuclei of thalamus, which then circles back to the Cingulate cortex.
This means emotional experience triggers expression vise versa.
What is The Papez Circuit
- Cortex critical for emotional experience
- Hippocampus governs behavioural expression of emotion
– Rabies infection implicates hippocampus in emotion -> hyperemotional responses - Anterior thalamus
– Lesions lead to spontaneous laughing or crying. - Paul MacLean popularised the term limbic system.
– Evolution of limbic system allows animals to experience and express emotions beyond stereotyped brain stem behaviours.
What is the Limbic system as we define it?
- Cingulate gyrus
- Parahippocampal structures
- Septal nuclei
- Amygdala
- Enthorinal cortex
- Hippocampal complex
– dentate gyrus
– CA1-CA4 subfields
– subiculum
What is the function of the limbic system?
- Anatomically the limbic system appears to
have a role in attaching a behavioral
significance and response to a stimulus,
especially with respect to its emotional
content - Damage to the limbic system leads to
profound effects on the emotional
responsiveness of the animal - Cingulate gyrus
– role in complex motor control
– pain perception
– social interactions-mood - Hippocampus proper and
parahippocampal areas
– primary function in memory (critical role in
connecting certain sensations and emotions
to these memories) - Amygdala
– involved in learning and storage of emotional
aspects of experience
What is the limbic system by definition?
- Difficulties with the single emotion system
concept
– Diversity of emotions and brain activity
– Many structures involved in emotion - No one-to-one relationship between structure and function
– Limbic system: use of single, discrete emotion
system questionable
What are the Emotion Theories and Neural
Representations?
- Early theories of emotion and limbic system
built on introspection and inference from
brain injury and disease. - Studies of disease and consequences of
lesions not ideal for revealing normal
function. - More recent theories of emotion
– Basic emotion theories
– Dimension emotion theories
How do we measure neurological activity in our brain now?
We have scanners now where we can measure people’s brain activities while they feel a certain emotion.
In fMRI scanners, they found emotions are associated with distinct patterns of brain activity - signatures.
Eg. Sadness was more associated with activities of the prefrontal cortex.
Eg. Fear = More association with amygdala.
