Emotion Flashcards
Describe the experiment used to analyse anxiety-like behaviour in long term opioid abstinence?
Increase of anxiety-like behaviour following long-term opioid abstinence
We then assessed anxiety-related behaviour with the use of the elevated plus-maze.
This plus-shaped apparatus consisted of two open arms and two closed-arms and it was elevated 40cm from the floor.
This test measures the conflict between the natural tendency of mice to explore a novel environment versus the tendency to avoid exposed areas.
The animals were positioned in the centre of the apparatus and left to explore for 5 mins.
Anxiety-like behaviour was determined by calculating the amount of time spent and the number of entries each mouse made in the open and closed arms.
Morphine withdrawn animals spent significantly less time and entries in the open arms compared to saline withdrawn animals.
These data clearly show that prolonged withdrawal from morphine induces anxiety-like behaviour.
Consistent in humans
Describe the experiment analysing depressive-like behaviour following long-term opioid abstinence.
Increase in depressive-like behaviour following long-term opioid abstinence
The forced-swim test
Take a 5L beaker with water and let the mouse swim for about 10 minutes
Usually the rat or mouse will like swimming at first and then try to get out, realising it cannot it assumes a state of immobility
The morphine withdrawn mice got to the immobilised state quicker and spent much more time immobilised reflecting a depressive state
What defines emotion? (Theories)
Emotions:
- Love, hate, disgust, joy, shame, envy, guilt, fear, anxiety, etc.
What defines emotions?
LO Theories of emotion:
- James- Lange:
· We experience emotions in response to physiological changes in our body
- 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 is the difference between the two theories surrounding emotions?
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 Papez Circuit?
Limbic structures, including cortex, involved in emotion
Emotional system on the medial wall of the brain linking cortex with hypothalamus
The neocortex is responsible for emotional coloring
The cingulate cortex is where the emotional experience takes place
The cingulate cortex projects to the hippocampus, and the hippocampus projects to the hypothalamus by way of the bundle of axons called the fornix
At the hypothalamus emotions are manifested
Hypothalamic effects reach the cortex via a relay in the anterior thalamic nuclei
How do we know the Papez circuit is true?
Cortex critical for emotional experience
Hippocampus governs behavioral expression of emotion
- Rabies infection, destroyed hippocampal areas, implicates hippocampus in emotion -> hyperemotional responses
Anterior thalamus
- Lesions lead to spontaneous laughing or crying.
Paul MacLean popularized the term limbic system.
- Evolution of limbic system allows animals to experience and express emotions beyond stereotyped brain stem behaviors.
What are the functions 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
What are the functions of the cingulate cortex, hippocampus (and parahippocampal areas), and amygdala?
Cingulate gyrus
- role in complex motor control
- pain perception
- social interactions-mood
Hippocampus proper and parahippocampal areas
- primary function in memory but also maintains a critical role in connecting certain sensations and emotions to these memories
Amygdala
- involved in learning and storage of emotional aspects of experience
What role does the amygdala play in emotion?
Critical structure for emotion in particular
- fear and aggression, anxiety
What are the three areas of the amygdala?
The amygdala has 3 distinct areas:
- Basolateral nuclei - Central nucleus - Corticomedial nuclei
What are the structures and connections of the amygdala?
Receives input from neocortex
- All lobes, including hippocampal, and cingulate gyri
Basolateral nuclei
- Receives information from all sensory systems
Corticomedial nuclei
Central nuclei
Output to hypothalamus (region involved in expression of emotion) via two important pathways:
- Stria terminalis
- Ventral amygdalofugal pathway
What happens when we inhibit and excite the amygdala?
Amygdalectomy (humans)- does not happen anymore except for severe cases - Reduce fear - Reduce Aggression - Hypersexuality - Oral tendencies - Reduce ability to recognize a fearful expression (can recognise happiness) - Flattened emotions Electrical stimulation - Increased vigilance - Anxiety - Fear - Aggression
What are the different types of aggression?
Multi facetted behaviour (kill for freedom, murderer, power, dominance)
Underlined by endocrine mechanisms (especially testosterone, because following castration there is an associated reduction in aggression)
Brain mechanisms:
- Predatory aggression
· Attacks made against a member of a different species, to obtain food
· Not much vocalisation
· No sympathetic activity
- Affective aggression
· For show/dominance, threatening posture
· Social hierarchy
· High levels of sympathetic activity- amygdala plays an important role in aggression related to social hierarchy
What are the neural components of anger and aggression beyond the amygdala?
The hypothalamus and aggression
- Removal of cerebral hemispheres (cats) but not hypothalamus -> became extremely violent, exhibited a sham rage
- Remove both cerebral hemispheres + anterior hypothalamus -> sham rage remained
Also remove posterior hypothalamus -> No sham rage
Electrical stimulation of hypothalamus leads to affective and predatory aggression
