15.5 - Early Biopsychological Research on Addiction Flashcards
explain the physical-dependence theory of addiction
dependence traps addicts. inn a vicious circle of drug. taking and withdrawal - so withdrawal symptoms are the reason why addicts continue to use
What were early addiction treatment procedures modelled on?
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
what are the two reasons the fact that failure of detox as a treatment didn’t work is unsurprising
- some highly addictive drugs (cocaine, amphetamines) dont really produce withdrawal distress
- pattern of drug taking displayed by a lot of addicts involves an alternating cycle of binges and detox
what are the primary reasons for a binge-detox patterns of drug use? (3)
- weekend binges are compatible with their work schedule
- not enough money to always have access
- forced into it by repeated and unsuccessful efforts to. shake the habit
Does physical dependence play a role in drug addiction?
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
what is intracranial self-stimulation (ICSS)?
phenomenon that humans and other species will administer brief bursts of weak electrical stimulation to specific brain areas
Explain the Olds and Milner study on ICSS
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
What was initially assumed of ICSS?
that it was a unitary phenomenon - fundamental properties are the same across neural circuits
what areas is ICSS mostly studied in? why?
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
What system plays an important role in ICSS
mesotelencephalic dopamine system - system of dopaminergic neurons that project from the mesencephalon (midbrain) into the telencephalon
where do the neurons that compose the mesotelencephalic dopamine system mainly have their cell bodies? (2)
in the substantia nigra and the ventral tegmental area
where do the axons of the neurons composing the mesotelencephalic dopamine system mainly project? (7)
pfc, limbic cortex, olfactory. tubercle, amygdala, septum, dorsal striatum, nucleus accumbens
what is the nucleus accumbens
a nucleus of the ventral striatum
where do most of dopaminergic neurons w cell bodies in the substantia nigra project?
into the dorsal striatum
- we call this section of the mesotelencephalic dopamine system the nigostriatal pathway
where do the majority of the dopaminergic neurons w cell bodies in the ventral segmental area project?
various cortical and limbic cites, which we call the mesocorticolimbic pathway
which section of the mesotelencephalic dopamine system is associated with parkinsons?
the nigrostriatal pathway, the degeneration of which is the cause of parkinsonism
Is there an overlap between the mesocorticolimbic and nigrostriatal pathways?
yes, but they are for the most part distinct
what are the four main pieces of evidence that the mesocorticolimbic system is very important in ICSS
- many of the cites at which ICSS occurs are part of this pathway
- ICSS is often associated with increased dopamine release in this pathway
- dopamine agonists tend to increase ICSS and antagonists tend to decrease it
- Lesions of the mesocorticolimbic pathway tend to disrupt ICSS
what class of drugs are dopamines natural rewarding effects most associated with
stimulants
what are the two primary paradigms for studying the rewarding effects of drugs
- drug self administration paradigm
2. conditioned place preference paradigm
explain the drug self administration paradigm
which type are most informative?
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
explain the conditioned place preference paradigm
what is the main advantage
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
What is an example of a study using these paradigms that implicated dopamine?
what does this suggest, specifically?
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
which brain area seems to be most clearly related to the experience of reward ad pleasure?
the nucleus accumbens, and dopaminergic input to it from the ventral tegmental area
