Lecture 15 Review Flashcards
What is motivation? Describe the different types of motivation
motivation is the reason for our behavior
- drive reduction - reduce need
- hedonic - increase pleasure
- homeostatic - we do things in order to maintain homeostasis in our bodies
What are reinforcers and how do they affect motivation?
reinforcers are stimuli that alter the probability of behavior
- positive = increases behavior
- negative = decreases behavior
stimuli associated with rewards also control behavior
- both come together to form incentives = things we are wiling to work for
What are the neural bases of motivation?
In the hypothalamus, there are structures for homeostatic and non homeostatic regulation of motivation
- Nucleus accumbens
• major target of limbic structures
• serves as an interface between limbic structures and motor systems
How does homeostatic regulation work?
When a change that alters conditions away from homeostasis occurs, we are motivated to do things that limit or reverse the change
Describe the short-term regulation of feeding and energy
Short term
- Low energy increases feeding and high energy decreases feeding
- glucostatic hypothesis
• glucose levels are key targets in short term regulation of E
- high glucose levels activated insulin receptors in the brain that contribute to feeding regulation
Describe the long term regulation of energy
body weight is usually stable around a set point but will change due to long term changes in feeding
- lipostatic hypothesis: fat levels are a key target in long term regulation of energy. amount of adipose tissue controls feeding by releasing leptin, which inhibits feeding
How does the hypothalamus affect feeding?
Lateral hypothalamus - hunger center, - lesions causes decreased feeding Ventromedial hypothalamus - satiety center - lesion causes increased feeding hypothalamus acts as a neural regulator of feeding motivation
Where is the arcuate nucleus and what is its function?
- part of the hypothalamus that is sensitive to insulin and leptin (glucose and fat)
- NPY/AgRP neurons are inhibited by leptin and insulin
- aMSH/CART neurons are activated by leptin and insulin
Why is the PVN important to feeding?
It projects to
- anterior pituitary which regulates endocrine system
- brainstem/spinal cord, which regulates the ANS
If you inject
- NPY/AgRP it decreases metabolic activity
- aMSH/CART it increases metabolic activity
How does the lateral hypothalamic area affect feeding?
it contains projections to the limbic system, motor system, and cerebral cortex
if you inject
- AgRP/NPY is stimulates feeding behavior
- aMSH/CART it decreases feeding behavior
Describe the role of ghrelin in feeding. What is its pathway?
Ghrelin is released from the stomach and serves as an orexigenic (hunger signal)
- NPY neuron has a ghrelin receptor, releases NPY to activate eating behavior
What is the nucleus accumbens?
connects the limbic system to the motor system
- driven by dopamine
What controls the VTA?
hypothalamic peptides
How does dopamine interact with VTA and the nucleus accumbens?
Dopamine increases during anticipatory phases of appetitive behavior and aversive behavior
- VTA neurons are activated under initial reward incentive learning prediction
- The major target of the VTA dopamine neurons are in the nucleus accumbens
- mesolimbic dopamine is crucial for reinforcement and operant behavior
• reward projection signal
Describe the limbic motor interface for the NAC and how it is organized
- multiple inputs with topographical organization
- outputs to dorsal striatum for motor function
- subregions of the NAC are topographically encoded
• different parts are simulated during appetitive and aversive stimuli
What is the mesocorticolimbic system’s relationship with dopamine?
Dopamine mediates changes in motivational/goal-directed behavior
What is the mestostriatal system’s relationship with dopamine?
it mediates changes in habitual responding
How does serotonin relate to food reward?
- there are increases of 5HT in the lateral hypothalamus during the anticipation and consumption of food
- it seems to be important with the hedonic aspects of goal-oriented behavior
What is non-homeostatic motivation? What is an example
motivation that is not based on maintaining homeostasis within the body
ex. sexual motivation
Describe the hormonal control over the male sexual behavior
Castration abolished all sexual behavior, but testosterone can help (only castration)
Describe the hormonal control over the female sexual behavior
- cyclic changes in gonadal steroids (estrogen and progesterone) are controlled by HPG
- hormones interact with social settings to determine sexual behavior
What is the role of 5HT and DA in sexual behavior?
- Dopamine is elevated during sex but falls after ejaculation
- 5HT elevated only following ejaculation
How do drugs affect the brain?
- They act on neurons by altering neurotransmission at receptors
- action in brain requires the drug to be able to cross the blood brain barrier
- common action of drugs is to impact dopamine by altering uptake via transporter
What are the neuroadaptions associated with repeated drug use?
Creates homeostatic changes that are typically opposite of the effect of the drug
- tolerance: adaptation opposes drug effects
- withdrawal - absence of the drug
some effects of the drugs increase with repeated exposure - sensitization
Describe the positive theory of drug addiction
-addicts seek drug in order to experience positive effect of drug
- sensitization to the incentive value
• they want drugs more and more with repeated exposure, despite their tolerance to drugs effects
Describe the negative theory of drug addiction
- dependence can be physical and motivational/emotional
- addicts seek the drug to prevent negative consequences of being free
• e.g. avoid rug withdrawal syndrome
•withdrawal symptoms can be continued, can be triggered by cues and lead to relapse
Describe the hedonic theory of drug addiction
- it is a cycle of binding and withdrawal effects
- this includes anhedonia, or reward suppression
• results in preoccupation with drug taking
