Emotion Flashcards
What is emotion?
An emotion is feelings that we experience such as happiness, anger etc
What is meant by the manifestation of emotion?
It means what it looks like when you manifest your emotions for e.g.
- An exhausted person may have drooping eyelids
- An angry person may look all red
- A depressed person may have a sad face
What is meant by affective neuroscience?
The field of neuroscience with studies of emotion for e.g
- Neural basis of emotion and mood
- Mood as an emotion extended in time
How do we study depression in animal models?
- One way to test is the forced swim test
- You take a 5 litre beaker and fill it with water at a fixed temp
- You let the mouse swim in water for periods of 7-10 minutes
Describe how the forced swim test works
- Initially the mouse would like swimming so it would swim quite happily
- The mouse will eventually become fed up and try to escape the beaker
- But when it realises it can’t escape, it results in freezing like behaviour
- Where it will have just enough movement of its hind legs to keep its head above water
What do you measure during this type of experiment?
The time spent immobilised which is a proxy of a depressed like behaviour
What was found during these tests?
They found that morphine withdrawal mouses spent more time immobilised compared to the saline control
- This suggest that opioid abstinence mice expressed depressive like behaviour
What were some theories which were used to explain emotion?
- The James Lange theory suggested we experience emotions in response to physiological changes in our body
- So we feel sad before we cry, the crying is what induces this expression of sadness
What are some problems with this theory?
- It assumes that you have to cry in order to feel sad which is not necessarily true
- Since you can be crying full of happiness
- If a person suffered spinal injury or was paralysed and wasn’t able to express any emotion then this person will not be able to experience emotion
What is another theory used to explain emotion?
- Cannon Bard suggested we experience emotions independently from the emotional expression
- Emotions are produced when signals reach the thalamus either directly from sensory receptors or by descending cortical inputs
Briefly describe the James Lange and Cannon Bard theory side by side
- The James Lange theory: Emotion experienced in response to physiological changes in the body
- Cannon Bard theory: Emotions occur independent of emotional expression, no correlation to physiological state
Is the brain system responsible for emotions?
Broca’s lambic lobe
- Limbus (in Latin) means border
- Primitive cortical gyri that form a ring around the brain stem
What does the broca’s limbic lobe include?
- The parahyppocampal gyrus
- The cingulate gyrus
- The subcallosal gyrus
Describe the Limbic system
Broca’s limbic lobe
- Areas of brain forming a ring around corpus callosum: Cingulate gyrus, medial surface temporal lobe, hippocampus
- It was found that all these areas was involved in emotional processing
What is the Papez circuit?
- Papez figured out how the emotional processing takes place
- He came up with a circuit called the Papez circuit
How does the Papez circuit work?
- According to this circuit, once you respond to a stimulus, the emotional colouring takes place in the neurocortex
- This sends a connection to the cingulate cortex which deals with emotional experience
- The cingulate cortex is connected to the hippocampus via neurons
- The hippocampus is then connected to the hypothalamus via neurons called the fomix
- Emotions then get manifested in the hypothalamus which induces an endocrine or ANS response
How is the Papez circuit returned to the Cingulate cortex?
- Following the emotional expression, there is a circuitry consisting of neurons which project from the hypothalamus to the thalamus
- Then from the Thalamus to the cingulate cortex
How do scientists know that a specific area actually affects emotion?
- Found that the cortex is critical for emotional experience
- Hippocampus governs behavioural expression of emotion
- They lesions sections of the anterior thalamus and found that the lesions lead to spontaneous laughing or crying
What can the limbic system be defined as?
Involved in emotional processing
What does the limbic system also consist of?
- Cingulate Gyrus
- Parahippocampal structures
- Septal nuclei
- Amygdala
- Enthorinal Cortex
- Hippocampal complex: Dentate gyrus, CA1-CA4 subfields, Subiculum
What are the functions of the limbic system?
- Anatomically the limbic system appears to have a role in attaching behavioural significance and response to a stimulus, especially with respect to its emotional content
What does damage to the limbic system result in?
Leads to profound effects on the emotional responsiveness of the animal
What are the functions of the Cingulate gyrus?
- Role in the complex motor control
- Pain perception
- Social interactions as well as mood
What are the functions of the hippocampus?
- Primary function in memory
- Critical role in connecting certain sensations and emotions to these memories
What is the function of the amygdala?
Involved in learning and storage of emotional aspects of experience
What is a problem with the limbic system?
There are difficulties with single emotion system concept
- Divesity 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, Orion system is questionable
What were some previous theories of emotion based on?
- Early theories of emotion and limbic system was built on introspection and inference from brain injury & disease
- Studies of disease and consequences of lesions not ideal for revealing normal function
What are some basic theory of emotions?
- Nowadays you can assume that emotions are associated with distinct part of the brain
- For example, fearness was associated with increased levels of activity in the amygdala
- Sadness was associated with increased levels of activity in the prefrontal cortex
What is the role of the amygdala?
Has a critical role in fear, aggression & anxiety
Where is the amygdala found in the brain?
Situated next to the hippocampus
Describe the anatomy of the amygdala
- Consists of several subregions or sub nuclei
- 3 important nuclei are: Basolateral nuclei, Central nucleus, Corticomedial nuclei
- All have different roles in modulating emotions
Describe the inputs of the amygdala
- Recieves inputs from the neocortex: All lobes, including hippocampal and cingulate gyri
- Basolateral nuclei: recieves information from all sensory systems
- Corticomedial nuclei
- Central nuclei
Describe the outputs of the amygdala
Output to hypothalamus (region involved in expression of emotion):
- Stria terminalis
- Ventral amygdalofugal pathway
What research was used to investigate the role of the amygdala?
- Kluver Bucy syndrome done an experiment
- They removed the temporal lobe which involves the temporal cortex, Amygdala and hippocampus
What did they find in their experiment
They found:
- Good visual perception but very poor visual recognition
- Psychic blindness
- Oral tendencies
- Emotional changes (Reduced favour)
- Altered sexual behaviour
What happens to behaviour if the amygdala is removed (amygdalectomy)?
- Reduced fear
- Reduced aggression
- Hypersexuality
- Oral tendencies
- Reduced ability to recognise a fearful expression (can recognise happiness)
- Flattened emotions
What electrical stimulations take place once the amygdala is removed?
- Increased vigilance
- Anxiety
- Fear
- Aggression
What is one key factor that the amygdala is involved in?
Involved in forming memories of emotional and painful events
- Confirmed by fMRI and PET imaging
Briefly describe one concept of how the amygdala works
- The amygdala is involved in the integration of current stimuli with past experiences such as learned fear
- This is important in PTSD
Describe how the amygdala works in fear
Describe how the amygdala works in fear (PART 2)
Describe how the amygdala works in fear (PART 3)
What are the different types of aggression?
Multi faceted behaviour
- Kill for freedom (seen as positive aggression)
- Murderer
- Dominance
List the biological mechanisms of aggression?
- Endocrine mechanisms (Testosterone, castration)
- Brain mechanisms (Predatory aggression, Affective aggression)
Briefly describe predatory aggression under brain mechanisms
- Attacks made against a member of a different species to obtain food
- No sympathetic activity
Briefly describe Affective aggression under brain mechanisms
For show, threatening posture
- Social hierarchy
- High levels of sympathetic activity
- Amygdala important role related to social hierarchy
How do we know the amygdala is involved in aggression?
When you do a surgery to remove the amygdala, you get:
- Reduced aggressive behaviour
- Relief from anxiety
- Profound unpleasant side effects
Describe the role of the hypothalamus in aggression
In an experiment done on rats and cats, they carried out
- Removal of the cerebral hemisphere but not hypothalamus leading to sham rage
- Removal of both cerebral hemispheres + anterior hypothalamus led to sham rage as well
- Also removal of posterior hypothalamus led to no sham rage
- Found that electrical stimulation of hypothalamus leads to affective and predatory aggression
Describe what is led to aggressive behaviour
In response to a particular stimulus
- The cerebral cortex gets stimulated
- This sends signals to the amygdala
- This then sends a signal to the hypothalamus but there’s also direct connection to the PAG & Ventral tagmental area
- This finally leads to aggressive behaviour
What leads to predatory or affective aggression
Two hypothalamic pathways to brain stem involving autonomic functions
- Medial forebrain bundle -> Ventral tegmenal area leads to predatory aggression
- Dorsal longitudinal fasciculus -> Periaqueductal gray matter leads to affective aggression
Which neurotransmitter is involved in aggression?
Serotonin
What is the hypothesis regarding serotonin?
Serotonin deficiency hypothesis
- Aggression is inversely related to serotonergic activity
- 5 HT antagonist increase aggression levels
- Agonists of 5 HT1a or 5HT1B decrease anxiety and aggressiveness
- In humans also, reports of negative correlation between serotonin activity and aggression
