Unit 6 Flashcards
Is the limbic system a single structure?
no, its a phylogenetically ancient network of structres
What are the structures of the limbic sytsem involved in?
motivation and emotion
learning and memory
Where do the structures of the limbic system lie?
middle of the brain
hidden by cerebral cortex
What is the role of the hypothalamus?
regulating our physiological state
provoking emotions
What are physiological responses driven by?
autonomic and hormonal reactions
What do emotional responses involve in addition to autonomic and hormonal reactions?
conscious perception of emotions
-> often results in behaviour
When looking at the responses to emotional stimuli, what is the limbic sytsem responsible for?
integrating physiological, autonomic, hormonal and behavioural responses
The Papez cricuit
first neuroscientific theory
neural circuit responsible for expression of emotion
How does the Papez circuit work?
Nuclei in thalamus receive information
-> sent to sensory areas in cortex (for processing) and hypothalamus (prepares physiological response)
-> sent from hypothalamus to anterior nuclei of thalamus
-> sent to cingulate cortex
-> conscious experience of emotion
-> entorhinal cortex via cingulum
-> input to hippocampus
-> mamillary bodies via fornix
entorhinal cortex
extension of cingulate cortex next to hippocampus
Is the Papez circuit fully accurate?
no, oversimplified
-> gives framework
-> new regions added
What does the limbic system consist of?
limbic cortex
amygdala
hippocampus
mamillary bodies of hypothalamus
septum
What are important connections of the limbic system?
hypothalamus
anterior nucleus of thalamus
orbitofrontal cortex
olfactory bulb
What is the amygdala and what is it responsible for?
almond shaped structure in temporal lobe (anterior to the hippocampus)
processing emotions
What is most research on the amygdala concerned with?
fear and aggression
-> normally shown in animal subjects
-> occurs in many species
-> can be produced in controlled experiments
How many nuclei does the amygdala consist of and which nuclei are the most well-researched?
~ 12
lateral nucleus
basal nucleus
central nucleus
central nucleus
end of fear processing
-> produces response
sends information to hypothalamus and autonomic nuclei of brainstem
most important structre for expression of emotional responses
lateral nucleus
receives sensory information from thalamus, hippocampus and vetromedial prefrontal cortex
sends it to basal nucleus and dorsomedial nucleus of thalamus
important for learning
What does bilateral damage to the amygdala result in? (syndrome)
Klüver-Bucy syndrome
Klüver-Bucy Syndrome
previously agressive monkeys fail to show normal fears
-> hyperorality
-> picking up snakes or lit matches
-> characterised by excessive docility and hypersexuality
What does bilateral damage to the amygdala also cause in humans?
amnesia
aphasia
agnosia (disrupted recognition ability)
Example of Klüver-Bucy syndrome
40-y/o patient with status epilepticus developed syndrome
started eating paper towels, etc.
inappropriately touched other patients and was very docile
died from asphyxiation after stuffing mouth with surgical gaze
What are the structures mainly important for learning?
hippocampus
limbic cortex
what does the limbic cortex consist of?
medial temporal lobe
cingulate cortex
parahippocampal gyrus
entorhinal cortex
piriform cortex
perirhinal cortex
Where is the hippocampus?
next to amygdala in medial temporal lobe
What is the hippocampal formation?
composition of dentate gyrus, CA fields and subiculum
Dentate gyrus and CA fields (hippocampus proper)
formation of inter-locking Cs
How does the hippocampus recieve the sensory information which forms the basis of learning?
via entorhinal cortex
(receives information from amygdala, different parts of limbic system and association areas)
What is one of the main efferent pathways from hippocampal formation to other brain areas and how does it create the conscious perception of emotions?
Fornix
-> connect to mamillary bodies of hypothalamus
-> connect to anterior nucleus of thalamus
-> conscious perception of emotions
How is memory consolidation in association areas supposed to happen?
hippocampus sends information to entorhinal, perirhinal and parahippocampal cortex
-> send information to association areas
declarative (explicit) memory
conscious recollection of facts and events
What are semantic and episodic memory?
semantic: facts
episodic: experiences and events
What is memory consolidation?
process of comitting short-term memories to long-term memory
The role of sleep in the consolidation of memories
evidence suggests that it helps consolidate memory
How do we consolidate information into our LTM?
rehearsal process (time)
What else plays a role in commiting information to LTM and how was it discovered?
Flashbulb memories
-> emotionally significance of importance
How do highly emotional stimuli facilitate the consolidation of memory?
activate locus coeruleus (in reticular formation)
-> increases noradrenaline release in cortex and noradrenaline + dopamine release in hippocampus
Why is remembering highly emotional events beneficial?
useful for survival
Patient HM as proof for hippocampus not being the site of memory storage
had anterograde amnesia after hippocampus was removed
-> still access to many pre-existing memories
-> still able to learn non-declarative memories
-> hippocampus mainly responsible for forming declarative memories
non-declarative memories
memories that don’t require conscious recollection
Korsakoff’s syndrome
main symptom: anterograde amnesia
what causes Korsakoff’s syndrome?
high alcohol consumption
-> causes thiamine (B1) deficiency
-> causes cells that need high levels of energy to die (e.g. neurones)
brain- damage permanent
Thiamine deficiency
Thiamine: respinsible for metabolising carbohydrates, fats and amino acids
treateable
