15.5 - Early Biopsychological Research on Addiction

Question 1

explain the physical-dependence theory of addiction

Answer 1

dependence traps addicts. inn a vicious circle of drug. taking and withdrawal - so withdrawal symptoms are the reason why addicts continue to use

Question 2

What were early addiction treatment procedures modelled on?

Answer 2

The physical. dependence perspective - attempt to break the viciouscircle of drug taking by gradually withdrawing drugs from addicted individuals in hospital
- tend to relapse once they’re out

Question 3

what are the two reasons the fact that failure of detox as a treatment didn’t work is unsurprising

Answer 3

1. some highly addictive drugs (cocaine, amphetamines) dont really produce withdrawal distress
2. pattern of drug taking displayed by a lot of addicts involves an alternating cycle of binges and detox

Question 4

what are the primary reasons for a binge-detox patterns of drug use? (3)

Answer 4

1. weekend binges are compatible with their work schedule
2. not enough money to always have access
3. forced into it by repeated and unsuccessful efforts to. shake the habit

Question 5

Does physical dependence play a role in drug addiction?

Answer 5

yes, addicted individuals do sometimes consume to alleviate withdrawal, but most researchers no assume that the more important factor in addiction is the drugs hedonic effects

Question 6

what is intracranial self-stimulation (ICSS)?

Answer 6

phenomenon that humans and other species will administer brief bursts of weak electrical stimulation to specific brain areas

Question 7

Explain the Olds and Milner study on ICSS

Answer 7

argued that the specific brain sites that mediate self-stimulation are those that normally mediate the pleasurable effects of natural rewards - studied the self-stim of various sites to map the circuits that mediate pleasure experience

Question 8

What was initially assumed of ICSS?

Answer 8

that it was a unitary phenomenon - fundamental properties are the same across neural circuits

Question 9

what areas is ICSS mostly studied in? why?

Answer 9

septal or lateral hypothalamic stimulation
- self-stim in these areas is really really high, rats will press a. lever a thousand times per hour to stim. these sites and only stop when they’re exhausted

Question 10

What system plays an important role in ICSS

Answer 10

mesotelencephalic dopamine system - system of dopaminergic neurons that project from the mesencephalon (midbrain) into the telencephalon

Question 11

where do the neurons that compose the mesotelencephalic dopamine system mainly have their cell bodies? (2)

Answer 11

in the substantia nigra and the ventral tegmental area

Question 12

where do the axons of the neurons composing the mesotelencephalic dopamine system mainly project? (7)

Answer 12

pfc, limbic cortex, olfactory. tubercle, amygdala, septum, dorsal striatum, nucleus accumbens

Question 13

what is the nucleus accumbens

Answer 13

a nucleus of the ventral striatum

Question 14

where do most of dopaminergic neurons w cell bodies in the substantia nigra project?

Answer 14

into the dorsal striatum

- we call this section of the mesotelencephalic dopamine system the nigostriatal pathway

Question 15

where do the majority of the dopaminergic neurons w cell bodies in the ventral segmental area project?

Answer 15

various cortical and limbic cites, which we call the mesocorticolimbic pathway

Question 16

which section of the mesotelencephalic dopamine system is associated with parkinsons?

Answer 16

the nigrostriatal pathway, the degeneration of which is the cause of parkinsonism

Question 17

Is there an overlap between the mesocorticolimbic and nigrostriatal pathways?

Answer 17

yes, but they are for the most part distinct

Question 18

what are the four main pieces of evidence that the mesocorticolimbic system is very important in ICSS

Answer 18

1. many of the cites at which ICSS occurs are part of this pathway
2. ICSS is often associated with increased dopamine release in this pathway
3. dopamine agonists tend to increase ICSS and antagonists tend to decrease it
4. Lesions of the mesocorticolimbic pathway tend to disrupt ICSS

Question 19

what class of drugs are dopamines natural rewarding effects most associated with

Answer 19

stimulants

Question 20

what are the two primary paradigms for studying the rewarding effects of drugs

Answer 20

1. drug self administration paradigm

2. conditioned place preference paradigm

Question 21

explain the drug self administration paradigm

which type are most informative?

Answer 21

nonhuman animals press a lever to inject themselves through implanted cannulas (thin tubes), they learn to do so quickly if the drugs are associated with addiction in humans
- those where they are injected directly into certain brain structures

Question 22

explain the conditioned place preference paradigm

what is the main advantage

Answer 22

nonhuman animals receive a drug in the ‘drug compartment’ of a two compartment box

• during test phase, the sober animal is placed n the box, and the time it spends in the drug compartment is compared with the control compartment
• tend to prefer the drug compartment if they were given drugs humans get addicted to
• allows us to study animals when they are drug free, eliminating potential confounds of the drugs immediate effects

Question 23

What is an example of a study using these paradigms that implicated dopamine?
what does this suggest, specifically?

Answer 23

in rats, dopamine antagonists block the self administration of and conditioned preference for several different drugs, reduced the reinforcing effects of food
- dopamine signals something like reward value or pleasure

Question 24

which brain area seems to be most clearly related to the experience of reward ad pleasure?

Answer 24

the nucleus accumbens, and dopaminergic input to it from the ventral tegmental area

Question 25

what did most of the early studies on the nucleus accumbens and associated reward information study

Answer 25

the effects of stimulants

Question 26

what are the four findings from stimulant studies on the nucleus accumbens and the dopaminergic input to it from the ventral segmental area

Answer 26

1. lab animals self administered microinjections of addictive drugs directly into the nuceus accumbens
2. microinjections of addictive drugs the NA produced a conditioned place preference
3. lesions to the NA or ventral tegmental area blocked self administration of addictive drugs into general circulation and the development of conditioned place preferences
4. both the self admin of addictive drugs and the experience of natural reinforcers were associated with elevated levels of extracellular dopamine in the NA