5. The limbic system, emotion, the hypothalamus, appetites Flashcards
What is the limbic system physically?
It’s a system of interconnected discrete structures within the brain and brain stem largely forming a ring around the corpus callosum
Name 8 functions that are controlled by the limbic system
- Eating / Drinking
- Fighting/killing
- Sex drive
- Enjoyment
- Fear / anxiety
- Autonomic preparation
- Memory formation and recall
- Expression of emotion
4 main functions of the limbic system?
- Emotions and drives via the amygdala
- Homeostasis and motivation (autonomic and
neuroendocrine) via the hypothalamus - Olfaction via the olfactory cortex
- Memory via the hippocampus
Cortical structures of the limbic system?
Corpus callosum Cingulate syrus mid brain edge Parahippocampal gyrus Temporal lobe Corbital and medial prefrontal cortex
Subcortical structures of the limbic system?
Cognitive area: Hippocampus Mammillary body Anterior nucleus of the thalamus Mammillothalamic tract Fornix
Emotional area: Amydgala Hypothalamus Ventral basal ganglia Anterior commissure Mediodorsal nucleus of the thalamus Optic chiasm
Position fo the amygdala?
Found at the anterior tip of the hippocampus.
Role of amygdala as part of the limbic system?
Provides an emotional component to experiences & memory, and the ability to recognise FEAR, others.
Provides an appreciation of INNATE (baby precipice) and LEARNED FEAR and has extensive connections with all cortical association areas allowing integrative function
What were the feat conditioning of little albert?
What was discovered?
Cruel experiments in which
little Albert was
conditioned with noise to
fear rats and rabbits
SOCIAL CONDITIONING of this sort however happens all the time in both the human and non-human primate worlds
We learn from, and fear to make, mistakes which have adverse effects
efferents and afferents of amygdala?
Most significant AFFERENTS are from FRONTAL, TEMPORAL AND PARIETAL lobes receiving cognitive information
Most significant EFFERENTS are to the HYPOTHALAMUS and LIMBIC cortex providing emotional cognisance, and visceral/homeostatic information
What is kluver-bucy syndrome?
Bilateral temporal lobe lesions in all mammals produce a range of symptoms known as Kluver- Bucy syndrome Symptoms: 1. Visual recognition impairments (visual agnosia) 2. Heightened sexual appetite (Hypersexuality) 3. Loss of fear and conditioning 4. Oral tendencies (Hyperorality) 5. Flattened emotions
What are the Ekman’s six types of universal facial expression?
Anger Fear Disgust Surprise Happiness Sadness
Lesions of human amygdala results in…
a loss of recognition of fear and anger in other peoples faces, these subjects however can usually recognise the other 4 Ekman emotion types (i.e. sad happy disgust surprise and anger).
Other modalities such as vocalisation can also be misunderstood
Result of electrical stimulation of amygdala (as well as the anterior hypothalamus & the PAG)?
causes anxiety, agitation and aggression in humans
Role of amygdala and unconscious reactions?
A fast sub-cortical route for visual information which connects to thalamus to the amygdala and thence to the hypothalamus
e.g. arachnophobics showing a skin conductivity reaction when seeing a camouflaged spider, BEFORE they are aware of what it actually is/
The main effector of the limbic system….
the hypothalamus
Hypothalamus afferents as part of the limbic system
Neocortex
Pain and sensory integration in brainstem nuclei
Spinal cord
Amygdala
Hypothalamus efferents as part of the limbic system?
—-> Neocortex –> Motivational strategies
–> Pain and sensory integration in brainstem nuclei –> Dulling pain and hunger
–> medulla –> Vomiting, respiration etc
–> Spinal cord –> Visceral motor function
–> Amygdala
–> ant. and post. pituitary –> Hormone release
What are the 3 main effects exerted by the hypothalamus?
1. Vegetative functions Cardiovascular regulation Thirst Appetites Temperature, blushing; pallor Sexual excitement
- Endocrine functions
Control over anterior pituitary gland hormone release through the connecting blood supply
3. Behavioural functions General level of activity up to and including ‘rage’ for pursuit of food, water, sex etc Ingestion/disinterest in/of food Fear and punishment behaviour Increased sexual drive
Describe the reward system within the limbic system
The mesolimbic dopamine system (or reward system) originates in the ventral tegmental area of the midbrain, and project via dopaminergic pathways to the:
1. medial prefrontal cortex (mPFC)
2. amygdala
3. Hippocampus
These then project to the nucleus accumbens via glutamatergic pathway
And then to the the ventral pallidum via GABAergic pathway
What is the basis of people with addition and the connection to the limbic system?
Drugs of abuse such as psycho stimulants (e.g. cocaine) opiates (e.g. heroin) , ethanol cannabinoids and nicotine are currently thought to have a final common dopaminergic pathway feeding into the limbic system
Role of anterior insular cortex?
Link to huntingtons?
Provides introspection which allows the interpretation of sensation as JOY or DISJUST
Patients with Huntington’s disease (a progressive frontal cortex degenerative disease) show IMPAIRMENT of VISUAL characteristics associated with DISGUST. The extent of the impairment is dependent of the amount of damage to the insular
Role of limbic system with pain recognition?
The limbic system interconnects with structures involved in pain and pain perception such as the PAG
The PAG is able to reduce activity in the ascending pain pathway, its effects are agonised by endorphins and so opiates.
PAG?
Periaqueductal in midbrain
How does the circumstance perception alter perception of pain?
The perception of pain is dependent on the perception of the circumstances.
Sadistically inflicted pain stimuli hurts MORE. Accidentally inflicted pain stimuli from a friend hurts less
E.g. The placebo effect of saline injections or a parental kiss to child wound can reduce pain.
Emotional relief of pain is blocked by nalaxone, so pain returns.