Noradrenaline, Arousal, Anxiety, and Decision-Making

Flashcards covering the synthesis, anatomy, and functional roles of noradrenaline in arousal, stress, and decision-making, including the use of pupil dilation as a physiological marker.

What is the primary amino acid precursor for Noradrenaline synthesis mentioned in the notes?

Tyrosine, an amino acid found in food.

List the enzymes involved in the synthesis pathway from Tyrosine to Noradrenaline.

Tyrosine Hydroxylase (converts Tyrosine to DOPA), Amino Acid decarboxylase (converts DOPA to Dopamine), and Dopamine eta-hydroxylase (converts Dopamine to Noradrenaline).

What enzyme is responsible for the breakdown of Noradrenaline into an inactive metabolite?

Monoamine oxidase (MAO).

In which gland does the final synthesis step from noradrenaline to adrenaline occur?

The adrenal gland.

What is the approximate number of neurons in the Locus Coeruleus (LC) compared to the primary visual cortex (V1)?

The LC contains approximately $30,000$ neurons, whereas the V1 is estimated to have $280$ million neurons.

During which stage of sleep is Locus Coeruleus (LC) neuron firing silent?

Rapid eye movement (REM) sleep.

What are the '4 F’s' associated with high LC/NA activity?

Fight, Flight, Freeze, or Fornicate.

How is 'Anxiety' defined in the context of noradrenaline activity and clinical diagnosis?

Excessive, uncontrolled, and often irrational 'worry' requiring symptoms for $6$ months for diagnosis.

What characterizes a panic attack according to the lecture?

Brief intense episodes reflecting spikes of LC/NA activity triggered by random events, internal thoughts, or learned associations (PTSD).

Describe the relationship between stress/arousal and performance.

Optimal performance requires a balance; function is impaired with too little or too much stress (represented by an inverted U shape).

What is the difference between 'Exploitation' and 'Exploration' in adaptive behavior?

Exploitation involves using known sources of reward, while exploration involves searching the environment for alternative sources (food, water, sex, etc.).

How does noradrenaline (NA) affect the competition between two behaviors (Behavior A and Behavior B)?

A burst of NA release 'tips the balance' in favor of the winner by increasing the strength of activating and inhibiting signals, thereby consolidating the decision.

What happens to Locus Coeruleus (LC) neurons immediately after a behavioral response is executed?

The neurons are inhibited, allowing the selected behavior to be 'exploited'.

How does high arousal affect the period of inhibition following an LC neuron burst?

In high-arousal contexts, there is a larger burst of NA, and the following period of inhibition is longer, causing the chosen focus to dominate and inhibiting 'distracting' alternatives.

What effect do low baseline levels of LC activity have on behavior?

Baseline firing increases, adding 'noise/variability' to decisions and promoting a switch to new behaviors (exploration).

Which neurotransmitter induces pupil constriction, and how does Atropine affect this?

Acetylcholine (ACh) induces constriction; Atropine (Belladonna) causes dilation by blocking ACh muscarinic receptors.

What does pupil dilation reflect when measured in the dark?

It reflects noradrenaline levels released from the Locus Coeruleus.

What timing relationship was found between pupil diameter and perceptual switches?

Pupil dilation begins before the reported switch and peaks at approximately $1$ second after the switch.

What are the clinical uses of monitoring pupil dilation mentioned in the lecture?

Communicating with people who are minimally conscious or suffering from locked-in syndrome.

What is the theoretical implication of NA and the LC's role in perceptual and cognitive decisions?

They play the same role as they do in behavior: optimizing the balance between 'exploitation/stability' and 'exploration/flexibility'.