Motivation: The Limbic System - 16

Question 1

What is brain-reward self-stimulation (Intracranial self-stimulation)?

Answer 1

Interested in how the lateral hypothalamus is linked to reward. Experiments often missed the lateral hypothalamus and instead placed the electrode in adjacent regions which is heavily related to dopamine activation.

Question 2

What is deep brain stimulation used for?

Answer 2

Used as a therapeutic approach to treating refractory major depression (depression that does not respond to usual treatment). Electrodes in the brain to alleviate symptoms of depression. Brain stimulation also used in the treatment of Parkinson’s disease - reactivates parts of the brain.

Question 3

How is feeding linked to anticipation?

Answer 3

Newborns are homeostatic mechanisms (feed on need, only feed when hungry). This changes at 3-6 months: start feeding just before they go to sleep because they are anticipating nutrient deficits that will occur during the night. Seen in rats: just before daylight can see an increase in eating and drinking behaviour.

Question 4

How does learning effect eating?

Answer 4

Peter Holland tested cue-potentiated feeding in sated rats. Step 1: Pavlovian conditioning - cue is paired with food delivery when hungry. Step 2: Satiate with free feeding (taking away the drive to eat). Step 3: Play back to conditioned stimulus and it produces over eating. Birch et al. found evidence in children: when play certain music that is present during normal eating times will increase consumption and latency of food (eat quicker)

Question 5

How can you measure taste hedonics in humans and rats?

Answer 5

Berridge - taste reactivity procedure - closely monitor the mouth movement of rats and mice. If look at various species show similar mouth movements when they taste something sweet/sour. The brain system he studied was the mesolimbic dopamine system (has projects from the midbrain (VTA & substantia nigra), project neurons to the forebrain)

Question 6

What is the role of dopamine in reward?

Answer 6

If destroy dopamine in the brain animal will not eat or drink (become aphagic). However no difference in animals with or without dopamine in terms of liking: therefore wanting food is not the same as liking food. Come from two different brain systems. Wanting is related to dopamine, but this does not change the liking of food.

Question 7

What brain areas are involved in taste pleasure and feeding?

Answer 7

Liking is mediated by opiod, GABA and cannabinoid systems.