W9L2 - Noradrenaline Flashcards
Noradrenaline Synthesis
Tyrosine > Dopa > Dopamine > Noradrenaline (Same as Dopamine)
What does Tyrosine Hydroxylase do
Synthesize tyrosine into DOPA
What does Amino Acid decarboxylase do
Synthesize DOPA into Dopamine
What does Dopamine β-hydroxylase do
Synthesize and break down Dopamine Enzyme
Noradrenaline Breakdown
1 additional synthesis:
Noradrenaline > Adrenaline (driven by hormone adrenaline)
Noradrenaline > Inactive metabolite
Noradrenaline > Inactive metabolite
Monoamine oxidase (MAO)
Noradrenaline alternative name
Norepinephrine
What does the norepinephrine do
- Sympathetic nervous system (flight/fight)
- Arousal/vigilance
- Anxiety
- Exploitation vs Exploraton
- Reward/Addiction (as in dopamine)
- Memory
What is the part of releasing norepinephrine
Locus Coeruleucs (LC)
Properties of Lcous Coeruleus (LC)
Very small area of brain with very few neurons (about 30,00)
One thing noradrenalien is MOST known for
Arousal. More NA = more arousal
During REM sleep, is NA released?
Silent = Little NA
Following a noxious/super positive event, is NA released?
Highest rates of NA released
4Fs in NA
Fight, Flight, Free or Fornicate
What is state of hyperarousal of NA adapted for:
Evolutionary aspect is NA important for individual or sexual fitness
What can high level of LC/NA lead to
- Stress and Anxiety
(Stress: sustained NA due to environmental factor)
(Anxiety: uncontrollable irrational worry for 6 months)
Panic Attacks: Brief intense episodes reflecting LC/NA Spikes
What is the function of stress. Explain
Inverted U shape. Optimal performance requires a balance.
At moderate levels of LC/NA activity, what does NA do
Consolidate decisions.
Explain moderate levels of LC/NA and its utility in evolution
Adaptive behaviour = Tradeoff between (1) EXPLOITING known sources of reward (2) EXPLORING environment for alternative reward sources
What is exploitation vs exploration. What kind of behaviour is best?
- Can choose one.
- Indecision / Inflexible is bad because we need balance
How does brain decide 2 behaviour
Burst of NA release “tips the balance” in favor of winner - increases strength of activation & inhibition of signals
When do LC neurons fire
When behavioural response selected & exectued (burst)
What happens after LC neurons
After response, neurons are inhibited (suppressed) to allow selected behaviour to be “exploited”
What affects the strength of burst of LC neurons
More Importance/Salience/Arousal = More NA burst
LC Neurons during high arousal
Bigger neuronal response = More NA + Longer inhibition
- In high arousal, chosen focus of attention dominates longer
LC Neurons during low arousal
Smaller neuronal response = Less NA + Shorter inhibition
- In low arousal, increased NA promotes a switch to a new decision, promoting “exploration” of alternative behaviors (firing more to add variability after)
How does LC release affect performance. What is the optimal performance. Compare low and high
Low levels of LC activity and NA release = tired, vague & poor performance (inattentive non-alert)
High levels of LC activity and NA release = restless, stressed & poor performance (distractible)
Optimal performance requires moderate activity with large intermittent bursts.
How does LC reflect pupil dilation
Pupil dilation is caused by Atropine and NA Causes Dilation.
How does NA solve perceptual ambiguity (depth perception)
NA consolidates information and tips balance in favour of winner
Is there a r/s between pupil diameter and timing of perceptual switch
Pupil dilates at the time of new percept (dilation begins before reported switch & pick at 1 sec)
How to measure pupil diameter in task
- Pupil diameter recorded during stimulus presentation.
- Subjects reported their perceptual switch with an
immediate button press
Task to distinguish pupil dilation between motor and cognitive decision: Results
Could predict based on pupil dilation which one they were going to pick. Pupil response by tracking.
What are the conclusion of pupil dilation and perception
1.) Pupil dilation accompanies a switches during
perceptual rivalry
2.) Pupil dilation can also be used as an index of cognitive decisions
What are the theoretical implications of research on pupils and perception
NA and LC likely play the same role in perceptual and cognitive decisions, as they are believed to play in behaviour (optimizing a balance between exploitation and exploration)
Clinical use of pupil dilation
Using pupil dilation, can communicate with people that
are minimally conscious or are suffering locked-in-syndrome
