[Reading](/uploads/readings/Wise_and_Koob_2014_The development and maintenance of drug addiction.pdf)

Positive and Negative Reinforcement

  • Positive reinforcement occurs during the beginning of the development of an addiction
  • Negative reinforcement comes into play when tolerance (increasing reward thresholds) appears to develop into positive reinforcement

Agreements

They agree with each other about the early and late stages of addiction

  • Positive reinforcement leads to the initial repetition of drug taking that then becomes habitual, and eventually compulsive

Disagreements

  1. The time between early and late at which the diagnosis of addiction is considered
  2. The relative importance of positive and negative reinforcement
  3. The degree to which the specifics of negative reinforcement can be generalised across the range of addictive agents

Wise does not accept that dependent === addicted

Rather than development of the effects from negative reinforcements, reward selection may instead just be narrowing - a creature may raise the value of a certain value, and devalue other possible rewards - THOUGH, this does not attribute behaviours where stress-like responses were exhibited.

(Wise) Positive Reinforcement In Addiction - Issues of Cause and Consequence

When is something considered addictive?

There is no scientific definition to define addiction.

  • Should we use the word 'addiction' or 'dependence'
    • But does this help?
  • The word 'addiction' means different things to different people
    • The condition of addiction
    • The process of addiction

Opiate addiction causes users to progressively consume higher doses to maintain the effectiveness as experienced during initial drug taking.

Are the withdrawal effects of not taking opiates the reason for wanting to continue using opiates?

  • Continued use becomes required to avoid the withdrawal syndromes
  • Compulsive dug intake can develop before the development of physiological dependence
    • Rats will self-administer morphine without signs of tolerance or dependence, yet they will not self-administer the dug in locations where it does cause classic dependence signs
  • Whilst dependence theory was central to early theories, it did not explain the self-administation of psychomotor stimulants (cocaine, amphetamines)
  • Drug self-administration does not cause addiction
  • Rats and monkeys that learn to respond regularly to IV cocaine will likely take cocaine to the point of convulsion or death, many reached the point of feeling painful footshock.

Koob (?)

"Simple unfettered exposure to the drug (IV cocaine, amphetamines, heroin) is a sufficient condition for addiction in rats"

Do not generalise to other drugs, other routes of administration, doses, nor to humans.

Humans are smarter than rats - lab rats will continue to take a drug (once started on it), until they collapse.

Rats become addicted when its drug taking becomes regular, predictable and uninterrupted; rathr than hormonal. Addiction is therefore behavioural, a result of self-administration of drugs that more strongly elevate extracellular dopamine levels, and from the stamping in of memory traces associated. - Wise

Neuropharmalogical changes- Koob

Addition causes changes in the brain

  1. Changed by repeated drug exposure - drug-generated sensitisation of anti-reward

  2. Changed by the development of memory traces for the drug experience - that may cause cravings

The self-administration of addictive drugs cause brain and peripheral changes beyond those caused by passive receipt of the drug.

For smokers, the primary stimulus for craving is the thought of when the next cigarette will become available, rather than the time since the last one.

Addiction should therefore be related to the early signs of compulsive drug taking and the cravings associated with it, rather than the bodily consequences that develop after a long history of drug self-administration

(Koob) Negative Reinforcement in Drug Addiction - The Devil in the Dysphoria

Drug dependence requires the negative effects experienced through the absence of the drug.

Drug-generated sensitisation of the anti-reward

Negative reinforcement is required to enter addiction (Koob)

Dopamine is not the entire reward system, nor the crucial reward neurotransmitter - rather it is just one required component in addiction.

Addiction involves long-term, persistent dysregulation of the activity of neural circuits that mediate positive and negative reinforcement through

  • Decreased function of the brain reward systems that control natural rewards
  • Recruitment of brain stress/anti-reward systems that drive aversive states

Anti-reward

A concept developed by Koob and Le Moal (2008) that forms a general feature of biological systems, that are in place to limit reward. The body adapts to neutralise a drug's effect (inertia). Persistence of the opposing effects after the drug disappears produces adaptation..

Withdrawal is produced from the excessive activation of the body's reward and salience system that trigger neuroadaptive changes.

The anti-reward systems suppress dopamine and glutamate release via direct activation of stress-like/fear-like states in the extended amygdala, and the activation of dysphoric-like states in the ventral striatum and extended amygdala.

Drug seeking behaviour and addiction is the combination of decreases in reward neurotransmitter function and recruitment of anti-reward systems