Lecture 18

Question 1

What is the function of the reticular activating system (RAS)?

Answer 1

• Filters sensory input and maintains alertness.
• Regulates cortical arousal, attention, and sleep-wake cycles.
• Damage can impair consciousness or cause coma.

Question 2

What are the four major dopaminergic pathways in the brain?

Answer 2

1. Nigrostriatal: Substantia nigra → dorsal striatum (movement)
2. Mesolimbic: VTA → nucleus accumbens, amygdala (reward, motivation)
3. Mesocortical: VTA → prefrontal cortex (executive function, learning)
4. Tuberoinfundibular: Hypothalamus → pituitary (hormone regulation)

Question 3

What is the role of dopamine in seeking circuitry?

Answer 3

• Drives “wanting” and effort to obtain rewards.
• Released in response to unexpected rewards or reward-predicting cues.
• Encodes reward prediction error and supports reinforcement learning.

Question 4

What is the role of the mesolimbic dopamine pathway?

Answer 4

• Projects from the ventral tegmental area (VTA) to the nucleus accumbens, amygdala, and septum.
• Drives reward, motivation, and reinforcement learning.
• Overactivity linked to addiction; underactivity linked to anhedonia.

Question 5

What is the role of the mesocortical dopamine pathway?

Answer 5

• Projects from the VTA to the prefrontal cortex and parietal areas.
• Supports complex executive functions: attention, working memory, behavioural flexibility, inhibition.
• Underactivity associated with schizophrenia and ADHD.

Question 6

How do dopamine and opioids differ in reward processing?

Answer 6

• Dopamine: “Wanting” – motivation to pursue rewards.
• Opioids: “Liking” – pleasure from receiving rewards.

Question 7

Where is serotonin produced and what are its functions?

Answer 7

• Produced in raphe nuclei (brainstem).
• Regulates mood, sleep, appetite, cognition, and pain.

Question 8

What is the role of 5-HT1A receptors in emotion?

Answer 8

• Inhibitory receptors in limbic areas (e.g., amygdala).
• Reduce anxiety by dampening emotional reactivity.

Question 9

What is the role of 5-HT2A receptors in emotion and perception?

Answer 9

• Excitatory receptors in the cortex.
• Influence perception, mood, and cognitive flexibility.
• Targeted by psychedelics (e.g., LSD, psilocybin) to enhance cortical plasticity.

Question 10

What is the role of noradrenaline in emotional regulation?

Answer 10

• Produced in the locus coeruleus (pons).
• Enhances arousal, attention, and stress response.
• Overactivation linked to panic and PTSD.