The exposure model leshner 1997
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The exposure model – Leshner 1997. This is a different aspect of the biological approach – the notion that the illness involves lasting “damage” to the neural system. We may call the damage “Neuroadaption”. Question. Is enjoyment the cause of addiction ?

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The exposure model – Leshner 1997

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The exposure model leshner 1997

The exposure model – Leshner 1997

This is a different aspect of the biological approach – the notion that the illness involves lasting “damage” to the neural system. We may call the damage “Neuroadaption”


Question

Question

  • Is enjoyment the cause of addiction ?

  • Are we more likely to become addicted to something depending on how much pleasure it gives us ?

  • Or is it something more complex than that ?

30 plus film


Neuroadaptive effects in drug addiction

Neuroadaptive Effects in Drug Addiction

  • Normally we are not ruled by our reward system.

  • You may enjoy getting into a deep warm bath – but you don’t become addicted to it.

  • Events that activate the reward system without producing neuroadaptive changes (hot bath, cold orange juice etc )may lack the ability to produce addiction.

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How powerful is nicotine

How powerful is Nicotine?

  • With milder drugs we can measure the extent to which a dose of the drug shows an increase in brain activity.

  • If we compare nicotine to cocaine and other substances we find that nicotine does stimulate the reward system but not enough to make it highly addictive.

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The exposure model leshner 1997

A Comparison of the Effects of Cocaine and Mildly Psychoactive Substances on BSR, (brain-stimulation-reward)

From Bozarth, Pudiak, & KuoLee, 1997.

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The nicotine problem

The nicotine problem

  • Obviously there are numerous cases of addiction to the nicotine in tobacco

  • But nicotine’s action on “normal” brain reward systems is too weak to motivate this behavior

  • Something else must help nicotine to be more addictive in people who use it regularly – but what ?

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Neuro adaption

Neuro-adaption

  • Put simply, drugs like nicotine give pleasure, but at the same time they change the way your brain works so that in future you will need them more.

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So how does neuroadaption work

So how does neuroadaption work ?

  • Normalization.

    • Feeling bad if they don’t have it.

  • Sensitization

    • Living for the drug, enjoying it more

  • Punishment deficiency

    • They don’t care about what’s happening

  • Error detection

    • They don’t even understand what’s happening

  • Motivational toxicity:

    • Lose interest in other pleasures (food, family, even sex !)

  • Lets look at each of these in turn

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Normalisation the key to addiction

Normalisation: The key to addiction ?

  • Certain activities seem enjoyable because they stimulate phasic activity – you get a buzz while you are doing them.

    • Smoking

    • Alcohol

    • Drugs

    • Video Games

    • Gambling

  • But as your brain gets used to the high levels of phasic dopamine it begins to produce less dopamine overall

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Effects of chronic da activation

Effects of Chronic DA Activation

normal control

alcoholdependent

normal control

cocainedependent

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1 normalization tolerance

1) Normalization (Tolerance)

  • You have got used to the drug and without it you have lowered dopamine activity.

  • The feeling produced by the drug has become the normal baseline.

  • When you don’t have the drug you are feeling generally bad, so taking the drug gives you negative reinforcement by removed that hung over feeling.

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Reward hypersensitivity and the maintenance of drug use

Reward hypersensitivity and the maintenance of drug use

  • Kenney et al. (2006).

  • After chronic exposure to heroin rats showed an increased threshold in their brain reward system (dopamine) to activation by electrical stimulation compared to control rats who had not been exposed to heroin.

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Reward hypersensitivity and the maintenance of drug use1

Reward hypersensitivity and the maintenance of drug use

  • Suggests that chronic drug use is associated with a decrease in reward sensitivity (anhedonia, or depression).

  • Such anhedonia is believe to motivate drug use because drug use can quickly correct or improve this condition (negative reinforcement).

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Actual nicotine withdrawal symptoms

Actual Nicotine Withdrawal Symptoms

  • Psychological

    • Mood swings, loneliness, lack of concentration, emptiness, agitation, stress, anger, self-pity, and just general crankiness

  • Physical

    • Headaches - caused by your sinuses clearing out.

    • Shaking, sweating or feeling very cold.

    • Coughing, as your body is ridding itself of years of tar and built-up residues.

    • Insomnia.

    • Sour stomach or stomach pains..

    • Pains, sore gums, pains in chest... pains anywhere.

    • Tiredness and a general zapped feeling.

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2 sensitization

2) Sensitization

  • Sensitization, the patient recognises the buzz and looks forward to it, so this is positive reinforcement.

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3 punishment insensitivity

3) Punishment insensitivity

  • Why do people drink and smoke when they have had health warnings, experienced illness and seen the damage which their addiction is doing to their family?

  • How can a heroin addict fill a syringe with water from a public toilet, inject it into his arm and lie in the dirt waiting for their drug to kick in?

  • If they have a psychopathic personality for instance they simply may not care.

  • It may be that the drug itself can cause that attitude.

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Punishment insensitivity

Punishment insensitivity

  • Deroshe-Gamonet et al. (2004).

  • Rats were addicted to cocaine and then allowed to administer it to themselves but with a painful electric shock at the same time.

  • Those who were addicted to cocaine were less likely than non-addicts to reduce their response

  • This suggests that addicts become less sensitive to the negative consequences of taking the drug.

30 plus film


4 error detection

4) Error detection

  • Franken et al. (2007) measured the way in which addicts and non-addicts reacted when they made mistakes on a fast moving test

  • Cocaine addicts showed a reduced frontal negativity in response to errors (suggesting reduced neural sensitivity to errors) and showed less post-error improvement in performance.

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Error detection

Error detection

  • Franken’s work suggests that addicts may have less knowledge of the consequences of their behaviour, and so less ability to modify their behaviour.

  • In effect they don’t even understand what’s happening to them.

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Error detection1

Error Detection

The picture shows singer Amy Winehouse before and after becoming a regular user of hard drugs.

The question we have to ask ourselves is not does she realise what the drugs are doing – but does she care

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Error detection2

Error detection

  • In the world of celebrity we often see people who seem to be self-destructing but don’t seem able to see that they have a problem.

  • In “normal” life we can see something similar when drunks think they are being very funny – but everyone else thinks they are being rude or stupid.

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5 motivational toxicity

5) Motivational toxicity

  • Motivational toxicity: the reward from the drug takes the place of other things. You no longer get pleasure from football or shopping – only the drug matters.

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How addictive

How addictive ?

  • How many times have you heard people say that “heroin is more addictive than cannabis” or “coffee is more addictive than smoking”

  • Have you ever wondered how that can actually be measured ?

  • Various experiments with rats have been used to measure addiction.

  • In the example which follows you will see that a rat which is addicted to methamphetamine is willing to accept electric shocks just to get a fix of the drug

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The exposure model leshner 1997

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Motivational toxicity

Motivational Toxicity

  • Motivational toxicity describes a disruption of the motivational hierarchy.

    • The addicted person or animal is increasingly motivated by the drug

    • And less motivated by other rewards

  • In effect the creature is enslaved by the drug because nothing else matters any more

  • With drugs such as Heroin or Cocaine there is a very high level of motivational toxicity – in other words they are highly addictive.

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Dopamine activity da

Dopamine Activity (DA)

  • We can measure increases in the amount of dopamine released when the rats take different drugs, and use this as a guide to pleasure and addictive power

  • SEX leads to a 200% increase in dopamine

  • COCAINE - 300% increase in dopamine

  • METHAMPHETAMINE-1100% increase

  • This explains why rats (and people) will risk killing themselves to get more drugs - especially methamphetamine

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Progressive focusing of motivational energy on drug in this case cocaine

Progressive Focusing of Motivational Energy on Drug (in this case cocaine)

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Motivational toxicity1

Motivational Toxicity

  • This may help explain why human addicts frequently break social norms such as stealing from friends or family to support their habits.

  • Nothing else matters

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Example of motivational toxicity

Example of Motivational Toxicity

  • In August 2009 Scottish Courts heard the tragic case of baby Brandon Muir who was killed by his mother’s violent boyfriend.

  • His mother, Heather Boyd, was out at the time, working as a prostitute in order to buy heroin.

  • Motivational Toxicity - nothing else matters.

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If there is time

If there is time

  • Watch the film on electrified rats

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