W2L2: Noradrenaline, Arousal, Anxiety and Decision-Making

noradrenaline: synthesis

get dopamine from tyrosine, amino acid converted into L-DOPA and then converted to dopamine then synthesised into noradrenaline (noradrenaline needs dopamine to be synthesised)

noradrenaline: function

regulates arousal, cognitive function, stress, flight-fight response, reward/addiction, memory consolidation, exploitation vs exploration

noradrenaline: breakdown

one additional synthesis step in adrenal gland results in hormone adrenaline (drives effects in body)

noradrenaline: adrenaline

from brainstem where noradrenaline is produced in locus coereleus innovates medulla of adrenal organs above kidneys which leads to release of adrenaline

monoamine oxidase

breakdown for monoamine enzymes (dopamine, serotonin, noradrenaline)`

noradrenaline: location

locus coeruleus (LC), hypothalamus, amygdala, neocortex

noradrenaline: locus coeruleus

during highest rates of neurotransmitter release neutrons fire after extremely positive or negative stimulus event (more salient the even the greater the arousal)

LC: high activity: 4 F’s

state of hyperarousal adapted for evolutionary important situations where individual or sexual fitness is involved

LC: high activity: stress

experienced when LC/NA activity is sustained due to environmental factors

LC: high activity: anxiety

brief intense episodes believed to reflect spikes of LC/NA activity due to triggers

noradrenaline: flow state

when own skill level and difficulty of task is well matched

noradrenaline: low levels of arousal/noradrenaline

bored, sleep, not challenging

noradrenaline: high levels of arousal/noradrenaline

anxiety, too hard

LC: moderate levels of activity

noradrenaline acts to consolidate decisions

exploration and exploitation

adaptive behaviour represents tradeoff between exploiting known sources of reward and exploring environment for alternative sources of reward

noradrenaline: behavioural selection

competition between two behaviours, burst of noradrenaline release tips balance in favour of a winner (increases strength of activating and inhibiting signals)

LC neurons: behavioural selection

neurons in LC fire when behavioural response is selected and executed, after they fire neutrons are inhibited allowing selected behaviour to be exploited

noradrenaline: behavioural selection: high arousal

larger burst of noradrenaline release tips balance in favour of winner with more strength

noradrenaline: LC neurons: during high arousal

larger response of neutrons in LC more noradrenaline released and longer following period of inhibition

LC neurons: low arousal

in absence of recent decisions or arousing events baseline levels of firing increase and more noradrenaline is released throughout brain forcing individual to seek other options and take exploration (find things to do), switching to a new decision

low levels of LC and NA release

tired, vague, poor performance

high levels of LC and NA release

restless, stressed, poor performance

noradrenaline: visual perception

helps consolidate perceptual representations + sensations (when visual stimuli is ambiguous helps choose one percept over another, revises as percept become clearer)

noradrenaline: pupil

pupil dilates when making decisions