Reward and the brain Flashcards

1
Q

What is the background of reward and how it shapes behavior?

A
  • the pursuit of rewarding experiences drives behavior
  • early in life, behavior is driven by immediate reward: food
  • as we mature, more value is placed on long-term rewards: grades
  • reward-seeking is beneficial and helps to focus our attention and behavior
  • it can be maladaptive and lead to risky/poor decision making: excessive gambling, drinking, drug-taking
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2
Q

What is the brain reward pathway?

A

Mesolimbic dopaminergic pathway
Enters the Ventral tegmental area (VTA), and dopamine then goes into the amygdala and nucleus accumbens

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3
Q

What are endogenous ligands?

A

Neurotransmitters or hormones inside the body that bind to receptors (dopamine, acetylcholine, estrogen, cortisol)

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4
Q

What are exogenous ligands?

A

Drugs or toxins from outside of the body that bind to receptors (heroin, nicotine, THC)

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5
Q

How do drugs of abuse work?

A

Drugs have their effects by “tapping into” the brain’s naturally-existing reward circuitry
- increase neurotransmitter release
- block neurotransmitter reuptake
- alter neurotransmitter packaging in vesicles
- activate receptors

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6
Q

What did the Nuggets video show us about addiction?

A
  • it is usually seen as a choice, but it actually becomes a reliance
  • effects get smaller and smaller
  • usually seen as bad people but usually they are good people
  • bad effects increase and may not be noticed at first isolation
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7
Q

What is addiction?

A

A chronic, relapsing brain disease that is characterized by compulsive drug seeking and use, despite harmful or adverse consequences
- it is considered a disease because drugs change the brain structure and function
- the effects can be long lasting, if not permanent

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8
Q

Why do people take drugs?

A

environment (“norm”)
ease of access
social settings
genetics
- to feel good
- to feel better
- to do better
- prior medicinal use
- curiosity, and “because others are doing it”

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9
Q

What issues arise from drug use?

A
  • Drug use can quickly take over a person’s life
  • they require more and more drug to feel “normal”
  • formerly pleasurable activities become less pleasurable
  • they continue to seek out and take drugs, even with severe consequences
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10
Q

How does Dopamine change reward circuitry in the brain?

A

The brain adjusts to the overwhelming surges in DA by producing less and less of it, or reducing the number of receptors (downregulation)
- this alters the reward circuitry and the ability to experience pleasure is reduced
- this is also why the user is unable to enjoy things that previously brought them pleasure and feels lifeless and depressed
- Addicts need to take drug just to be able to elevate their DA levels back to normal levels

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11
Q

How are dendritic spines changed through drug use?

A
  • long-lasting changes
  • changes in spine density and branching in NAc
  • alterations in neurotransmitter release
  • altered receptor numbers and functioning
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12
Q

Who becomes addicted?

A
  • No single factor determines who will become addicted
  • environmental factors: home and family, peers and school, age at first use
  • certain characteristics or phenotypes can contribute to increased drug abuse vulnerability
  • Biological factors: prior stress history, character traits, sex, hormone state
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13
Q

What are some sex differences in drug taking?

A
  • 9 million women have used illegal drugs in the past year in the USA (40% of drug addicts are now women)
  • 3.7 million women in the USA have taken prescription drugs non-medically during the past year
  • among cocaine users 12-17 years old 51.5% are women, in the 18-25 age group 42% are women, for cocaine users 26 and older 38.8% are women
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14
Q

Is use a good indicator of addiction? (sex differences)

A
  • Time from first exposure to drug to chronic drug use is shorter for women
  • Females present for treatment sooner are consuming more cocaine than men
  • reasons for initiation of drug use are different for women vs. men:
    • women: self-medication for depression, stress, anxiety
    • men: risk-taking, in-group behavior
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15
Q

Why are there sex differences in addiction?

A

Influence of culture and society
influence of hormones
influence of developmental differences
combined influence of multiple factors

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16
Q

How do hormones affect sex differences in addiction?

A
  • Gonadal hormones act during early life and puberty to “organize” the brain
  • During adulthood hormones act on sexually differentiated brain structures to activate specific behaviors
17
Q

How do sex differences in addiction happen?

A
  • Males and females may exhibit sex differences in behavior because they secrete different hormones
  • Males and females may exhibit sex differences in behavior because males and females have different brains due to developmental influences
  • Males and females may exhibit sex differences in behavior because they secrete different hormones and because males and females have different brains due to developmental influences
18
Q

What has been found from using animal models to study addiction?

A
  • using operant response to look at drug taking behavior
  • female rats acquire drug taking faster than male rats
  • estradiol enhances cocaine intake in females but not males
  • estradiol enhances motivation for cocaine
  • estrogen enhances the behavioral response to cocaine in females
  • More females than males develop a preference for cocaine over food
  • Gonadectomy reduces the dopaminergic response to cocaine in females but not males
  • Estradiol acts directly in the stratum to rapidly enhance DA release in females but not males
19
Q

How does estrogen enhance the behavioral response to cocaine in females?

A
  • repeated administration of cocaine results in a progressive enhancement of the behavioral response associated with addictive behaviors and/or craving
  • females sensitize more and at a faster rate
  • estrogen enhances sensitization
20
Q

How does estradiol enhance striatal dopamine release?

A
  • Classical receptors take hours/days to have physiological effect
  • must be a different type of receptor that is responsive to estradiol in the striatum
    (the membrane-bound receptor seems to enhance DA downstream–> E binds to MB receptor)
  • estradiol inhibits GABA neurons
  • This leads to disinhibition of dopamine neurons and enhanced dopamine release
21
Q

What are some sex differences in reactions to drug taking?q

A
  • males show greater physical and motivational signs of withdrawal from alcohol than do females (ethanol withdrawal increases CORT release in males but not females)
  • Women show greater propensity to relapse for most drugs of abuse, with shorter periods of abstinence
    • They exhibit increase reactivity to internal (emotional) and external (drug-associated) cues
  • Some pharmacotherapies aimed to reduce the subsequent drug-taking work in men but not women