week 10-noradrenaline

Question 1

Noradrenaline Synthesis

Answer 1

1.Tryrosine 
an amino acid 
found in food
2.dopa
3.dopamine
4.noradrenaline

Question 2

noradrenaline

Answer 2

Sympathetic nervous system
  (flight or fight)
 Arousal / Vigilance
 Anxiety
 Exploitation vs Exploration
 Reward / addiction
 memory consolidation
Very small area of the brain with very few neurons (~30,000). 
(In contrast the primary visual cortex V1 estimated to have 280million neurons).

Question 3

Locus Ceruleus (LC) - Neuron Firing

Answer 3

Highest rates rapidly follow a transient noxious or extremely positive stimulus/event (lots of NA released
Silent during rapid eye movement (REM) sleep (very little NA released).

Question 4

High LC/NA activity = 4 F’s

Answer 4

4F’s (Fight, Flight, Freeze or F… Fornicate)

State of Hyperarousal adapted for evolutionarily important situations where “individual” or “sexual fitness” is involved

Question 5

High LC/NA activity = Stress & Anxiety

Answer 5

High levels of LC/NA activity can lead to the following, depending on the trigger and duration

Stress: often experienced when LC/NA
Activity is sustained due to environmental
Factors (social, emotional, physical etc).

Anxiety: excessive, uncontrolled and
often irrational “worry” (diagnosis requires
symptoms for 6 months).

Panic attacks: brief intense episodes believed to reflect spikes of LC/NA activity triggered by

- apparently random events 
- internal thoughts 
- learned associations (PTSD)

Question 6

NA Function beyond arousal & 4F’s

Answer 6

At moderate levels of LC activity, Noradrenaline acts to consolidate decisions.

Adaptive behaviour represents a tradeoff between exploiting known sources of reward and exploring the environment for alternative sources of reward (food, water, sex etc).

Question 7

Exploitation vs Exploration

Answer 7

Indecision, inaction or constant changing decisions is BAD

………But inflexible, repetitive behaviour is also BAD. Balance is needed!!

Question 8

NA & Behavioural Selection

Answer 8

competition
Burst of NA release  
“tips the balance”
in favor of the winner. 
(Increases strength of activating & inhibiting signals)
Competition resolved 
Selection complete
Decision is “consolidated”

Question 9

LC neurons & Behavioural Selection

Answer 9

Neurons in the Locus Coeruleus (LC) fire when a behavioural response is selected and executed.

After they fire the neurons are inhibited allowing the selected behaviour to be “exploited”.

Question 10

NA & Behavioural Selection

Answer 10

The more “important,” “salient,” “arousing” one of the alternatives the bigger the burst of LC neurons and more NA released.

Question 11

NA & Behavioural Selection

in high arousal

Answer 11

Competition in 
“high-arousal” context
LARGER burst of NA release  
“tips the balance”
in favor of the winner with MORE STRENGTH 
Competition resolved 
Selection complete
Decision is “consolidated

Question 12

LC neurons & during high arousal

Answer 12

The larger the response of neurons in the Locus Coeruleus (LC), the more NA released & and the longer the following period of inhibition.

In highly arousing situations the chosen focus of attention/behaviour dominates more for longer .. “distracting” alternatives are inhibited

Question 13

LC neurons & during low arousal

Answer 13

In the absence of recent decisions or arousing events the baseline levels of firing increase and more NA is released throughout the brain.

Increased NA promotes a switch to a new decision, promoting “exploration” of alternative behaviors.

Question 14

LC-NA & Performance

Answer 14

Low levels of LC activity and NA release = tired, vague & poor performance.

High levels of LC activity and NA release = restless, stressed & poor performance.

Optimal performance requires moderate activity with large intermittent bursts

Question 15

NA & The Pupil

Answer 15

In the dark dilation reflects NA levels

- Noradrenaline is released from the Locus Coeruleus

Question 16

Measuring Pupil Diameter

Answer 16

Pupil diameter sampled at 1000/second

Stimulus presentation 5min continuous while subjects reported their perceptual switch with an immediate button press

Question 17

Other types of decisions

Answer 17

Pupil responses should be seen with
1) motor decisions
2) cognitive decisions?
Motor Decision-Instruction: “push a button when ever you feel like it during 10 seconds, if you push the button during the lucky 1 second you win money”

cognitive decision-Instruction: “Select a number WHEN it is presented and remember it until the end of the trial. If you select the lucky number you win money”

Question 18

mind reading

Answer 18

rock paper scissors challenge

Question 19

Clinical uses of pupil dilations

Answer 19

Using the same basic idea we recently showed it is possible to communicate with people that are minimally conscious or are suffering locked-in-syndrome using pupil dilation

Question 20

Experiment conclusions

Answer 20

Results
Pupil dilation accompanies a switches during perceptual rivalry

Pupil dilation can also be used as an index of cognitive decisions

Theoretical Implications
Noradrenalin and the locus coeruleus likely play the same role in perceptual and cognitive decisions, as they are believed to play in behaviour (optimizing a balance between “exploitation” / “stability” and “exploration” / “flexibility”).

Question 21

lecture summary

Answer 21

Noradrenaline (NA) is synthesized from foods containing tyrosine and released by neurons in the Locus Coeruleus (LC).

NA is important in increasing arousal during evolutionarily important events (4 F’s).

High levels of NA/LC activity is associated with stress, anxiety and panic attacks

NA helps to consolidate decisions and find an optimal balance between exploitation and exploration of the environment and cognitive or perceptual strategies.

Pupil dilation can be used as index of NA release in brain.