Limbic System Flashcards
Where is the limbic system?
Forms a ring around the corpus callosum
What are the general functions of the limbic system?
Emotion and motivation
Appetite
Endocrine
ANS
Where is the amygdala?
Tip of the hippocampus
What are the functions of the amygdala?
Emotional component of experiences and memory
Fear
What is fear conditioning?
We learn from and fear to make mistakes that have adverse effects
What are the afferents of the amygdala?
Frontal lobe
Parietal lobe
What are the main efferents of the amygdala?
Hypothalamus
Limbic cortex
What were the characteristics of the Macaque Monkeys that had their amygdala removed?
Lacked fear e.g. mated with inappropriate partners, stole food from superiors
Unusual tameness
What did Ekman recognise?
There are 6 universal facial expressions - anger, fear, surprise, disgust, happy, sad
What effect does loss of the amygdala have on facial recognition?
Unable to recognise facial expressions of fear and anger
What happens when you electrically stimulate the amygdala?
Anxiety, agitation, aggression
What causes Kluver-Bucy syndrome?
Bilateral temporal lobe lesions
What are the signs and symptoms of Kluver-Bucy syndrome?
Visual agnosia Hypersexuality Loss of fear and conditioning Hyperorality (putting things in mouth) Flattened emotions
Give an example of an unconcious fear reaction
Arachnophobes show a skin conductivity reaction to seeing camouflaged spiders, before they have consciously recognised that they are spiders
What are the functions of the hypothalamus?
Endocrine - controls anterior pituitary Thirst Hunger Temperature Sexual arousal CVS regulation
What is the name of the system responsible for the feeling of reward?
Mesolimbic dopamine system
Describe how the mesolimbic dopamine system works
Dopamine upregulates the ventral tegmental area which stimulates the Nucleus Accumbens
Nucleus Accumbens inhibits the Ventral Pallidum which removes its inhibition on the Mediodorsal thalamus setting off the reward loop
Name a structure that modulates pain by reducing activity in ascending pain pathways
Peri-aqueductal gray
Name substances that agonise the PAG
Opiates
Endorphins
What happens when you electrically stimulate the PAG?
Analgesia
What is nalaxone?
Opiod receptor blocker - used in heroin overdose
Give examples of placebos that can reduce pain
Saline injections
Parental kiss
What is the role of the ventromedial portion of the prefrontal cortex?
Goal setting, forward planning and ascribing meaning to perceptions
What happens to the ventromedial portion of the prefrontal cortex in depression?
Reduced mass and activity
What happens to the ventromedial portion of the prefrontal cortex in bipolar disorder?
Inactive during depressive periods
Overactive during manic periods
What happens to activity in the cingulate gyrus in depression?
Reduced
What happens to activity in the cingulate gyrus in bi-polar disorder?
Overactive during depressive periods
Underactive during manic periods
What is the proposed function of the cingulate gyrus?
Straddle between emotion and cognition
Which neurotransmitters have been implicated in depression?
Dopamine
NA
Serotonin
What happens to glucocorticoids in depression?
Unchecked production of glucocorticoids (no negative feedback)
Increased glucocorticoids affect expression of 5-HT receptors which could lead to depression
What is the role of the anterior insular cortex?
Interpretation of sensation as joy or disgust
What is the effect of a frontal lobotomy?
Disinhibition
Lack of forward planning
Lowered executive function
