Emotion Flashcards
What is emotion?
- A feeling that is experience
- Personal for every person
Manifestation of emotions
- Other people can tell how you feel by your facial expressions
- Important to differentiate between the manifestation of emotion and the experience of your feelings/emotion
Describe how anxiety-like behaviour following long-term opioid abstinence can occur
- The maze the mice were put in had a cross like structure - partly covered and partly uncovered.
- The mouse prefers to be covered rather than exposed.
- Results: Morphine withdrawn animals spent significantly less time and entries in the open arms compared to saline withdrawn animals.
- This shows that prolonged withdrawal from morphine induces anxiety-like behaviour
- Consistent in humans
What are the two theories which define emotion?
James Lange
- We experience emotions in response to physiological changes in our body
Cannon Bard
- We can experience emotions independently of emotional expression
- Emotions are produced when signals reach the thalamus either directly from sensory receptors or by descending cortical input
- No correlation with physiological state
Brain systems responsible for emotion
- Broca’s Limbic Lobe
- > Primitive cortical gyri that form a ring around the brain stem
- > Includes: the parahippocampal gyrus, the cingulate gyrus, the subcallosal gyrus
Where is the limbic system and what is its function?
Areas of the brain forming a ring around corpus callosum: cingulate gyrus, medial surface temporal lobe, hippocampus. The limbic system allows animals to experience and express emotions beyond the stereotyped brain stem behaviours.
What is the Papez circuit?
According to Papez, the emotional colouring occurs in the neocortex.
- Sends signals to the cingulate cortex
- Signals passed via the hippocampus to the hypothalamus where expression of emotion takes place
- There will be activation of the ANS and endocrine system
- Hypothalamus will send signals to the cingulate cortex via the anterior nuclei of the thalamus. Experience of emotion will take place.
Which emotion theory is the papez circuit compatible with?
Both theories
Function of the cingulate cortex
Critical for emotional experience
Function of the hippocampus
Governs behavioural expression of emotion e.g. if an individual has rabies it affects the hippocampus and they become hyperemotional
Function of the anterior thalamus
Responsible for relaying the information from the hypothalamus to the cingulate cortex
Lesions of the anterior thalamus
Leads to spontaneous laughing or crying
Regions of the limbic system
- Cingulate gyrus
- Parahippocampal structures
- Septal nuclei
- Amygdala
- Enthorinal cortex
- Hippocampal complex
- > Dentate gyrus
- > CA1-CA4 subfields
- > subiculum
Function of the limbic system
The limbic system appears to have a role in attaching a behavioural 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
Function of areas of the limbic system
Cingulate gyrus
- Role in complex motor control
- Pain perception
- Social interactions - mood
Hippocampus proper and parahippocampal areas
- Primary function in memory
Amygdala
- Learning and storage of emotional aspects of experience
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
Emotion theories and neural representations
- Early theories of emotion and the limbic system where built on introspection and inference from brain injury and disease
- Studies of disease and consequences of lesions are not ideal for revealing normal function
- Studies have shown that different areas in the brain are associated with different emotions
- More recent theories of emotion
- > Basic emotion theories
- > Dimension emotion theories
Amygdala
- Critical structure for emotion in particular: fear and aggression, anxiety
- Found in the sagittal section of the brain
- Close to the hippocampus
- Right and Left Amygdala
- There are many subunclei: corticomedial nuclei, central nucleus and basolateral nuclei
Where does the amygdala receive information from?
- From the neocortex which includes the hippocampal and cingulate gyri lobe
- Basolateral nuclei which receives information from all sensory systems such as the corticomedial nuclei and the central nuclei
Where does the amygdala send output information to?
- Hypothalamus which is the region in the brain involved in expression of emotion
- Stria terminalis and ventral amygdalofugal pathway
Rhesus monkeys experiement
- Removal of the temporal lobe meant the animals had:
- > Psychic blindness meaning the animals were able to see objects but not identify what they are
- > Oral tendencies meaning to identify the objects in their mouth
- > Emotional changes: animals have reduced fear
- > Altered sexual behaviour - had hyperarousal
Amygdalectomy
Removal of the amygdala
- Reduce fear
- Reduce aggression
- Reduce ability to recognise a fearful expression (can recognise happiness)
- Flattened emotions
Electrical stimulation to the amygdala
- Increased vigilance
- Anxiety
- Fear
- Aggression
Which disorder is the amygdala activated in?
It is activated in those with post-traumatic stress disorder - involvement in giving emotional content to memories (fear conditioning).
Multi-facetted behaviour
Kill for freedom, murderer, power, dominance
Endocrine mechanism for aggression
Testosterone and Castration
What are the two types of brain mechanisms?
- Predatory aggression
- Attacks made against a member of a different species, to obtain food
- No sympathetic activity - Affective aggression
- For show, threatening posture/shows aggression but doesn’t actually act on it
- Social hierarchy
- High levels of sympathetic activity
- Amygdala important role in aggression related to social hierarchy
How can surgery reduce human aggression?
Amygdalectomy
Psychosurgery - now treatment of last resort
The results are:
- Reduced aggressive behaviour
- Relief from anxiety
- Profound, unpleasant side effects
Cat experiements of neural components of anger and aggression
- In an experiement conducted on cats, the removal of the cerebral hemispheres but not the hypothalamus showed behaviour of sham rage which is extremely angry, cat started hissing, opening its mouth showing its teeth.
- When the anterior hypothalamus was removed, the cats still has a sham rage.
- However, when the posterior hypothalamus was removed, the cats have NO sham rage.
Electrical stimulation of the hypothalamus
Leads to effective and predatory aggression showing that the hypothalamus plays a role in aggression as well
Elicited affective aggression
Stimulation of the medial hypothalamus just for show
Elicited predatory aggression
Stimulation of the lateral hypothalamus went for the kill
Two hypothalamic pathway to brain stem involving autonomic function
- Medial forebrain bundle -> ventral tegmental area; predatory aggression
- Dorsal longitudinal fasciculus -> periaqueductal gray matter; affective aggression
Serotonin and aggression
- Low levels of serotonin increases aggression
- Serotonin antagonists increase aggression and agonists decrease anxiety and aggressiveness
- Blocking serotonin receptors induces aggression
