2. The Dopamine Hypothesis

what is the key brain area implicated in addiction

the mesolimbic pathway

what is the mesolimbic pathway often referred to as

the reward pathway

what happens to the mesolimbic pathway when we engage in an activity that is rewarding

it is activated and causes pleasurable feelings which reinforce the behaviour and make us want to repeat the activity

what is the other risk that activates the reward pathway (not rewarding activities)

drugs also cause the reward pathways to activate

when was joutsa et al

2012

results (joutsa et. al 2012)

dopamine released in the mesolimbic pathway for both high reward and low reward tasks - dopamine released by the mere expectation of reward

3 strengths (joutsa et. al 2012)

shows the issues with addiction (biological reward), scientific (PET scans), high reliability

3 weaknesses (joutsa et. al 2012)

lack of protection from harm, androcentric, small sample size

where does the mesocortical dopamine pathway travel from and to

VTA to frontal lobe

Where is dopamine produced?

ventral tegmental area (VTA)

where does the mesolimbic pathway travel from and to

VTA to nucleus accumbens

what do addictive drugs do to the amount of dopamine released

they allow a rush of dopamine meaning the brain can more easily experience pleasure

how much more dopamine do addictive drugs provide compared to normal rewards

2-10 times more

what happens to someone's brain receptors if they become addicted to a substance

they become overwhelmed and as a result, the brain eliminates dopamine receptors and reduces the amount of dopamine produced naturally

what is the role of the hippocampus and the amygdala in maintaining addiction

they store information about environmental cues associated with the desired stimulus and so creates a conditioned response for when someone encounters those cues, this leads to a craving

how do D2 receptors link to addiction

they are compatible with dopamine

what did Volkow (1997) find about users of cocaine in relation to D2 receptors

in users of cocaine, there was a reduction in the number of D2 receptors and the amount of dopamine being released

what can high levels of dopamine caused by addiction do to the frontal cortex

it can alter the functioning f parts of the frontal cortex, the alterations remain present even after the addiction is no longer present

when was volkow’s study

1992

what did Volkow suggest changes to the frontal cortex cause

they alter attention to stimuli making an addict pay more attention to the stimulus and maintaining their addiction

results - glucose metabolism (Volkow 1992)

glucose metabolism was not significantly different between controls and cocaine abusers

results - metabolic activity (Volkow 1992)

cocaine abusers had significantly lower metabolic activity in left and right frontal regions

results - after 3-4 months (Volkow 1992)

decreases persisted after 3-4 months pf detoxification and were correlated with the dose and years of cocaine use

social implication - treatment (Volkow 1992)

future treatment should be centred around strengthening cognitive structures and processes

3 strengths (Volkow 1992)

demonstrates the long-term effects of addiction, scientific (PET scan), longitudinal (3 month follow up)

3 weaknesses (Volkow 1992)

small sample size, imbalance in group sizes, only 7 followed up

why can't dopamine alone explain addiction

not every addiction affects dopamine levels and dopamine's role is not only in addiction, it does many things throughout the brain

what "addictions" has dopamine been linked with (the unsexy truth about dopamine - guardian article)

cupcakes, firearms, cocaine

how likely is dopamine as an explanation (the unsexy truth about dopamine - guardian article)

not very likely as it is released in non-addictive behaviours as well as addictive ones

aside from being a "pleasure chemical" what other functions does dopamine have (the unsexy truth about dopamine - guardian article)

regulating movement, control of attention, regulates hormone release, stimulates the production of breast milk

what is the most accepted theory about the role of dopamine in the mesolimbic pathway (the unsexy truth about dopamine - guardian article)

it provides commentary on how well you are doing with temptations on offer and gives a surge of dopamine for success but also for a near-miss

what problems are there with the view that addiction can be explained solely by dopamine (the unsexy truth about dopamine - guardian article)

dopamine surges have been associated with sounds of battle for war veterans which is a negative association, especially for those with PTSD. even with dopamine blockers people can still be addicted to substances

how have the media misrepresented dopamine's role in addiction (the unsexy truth about dopamine - guardian article)

demonstrates the "dopamine is a pleasure chemical" concept as the sole reason suggesting that anything that causes a dopamine release is highly addictive

when was Olds study

1976

findings (Olds 1976)

rats gained reward despite shock - willing to receive a greater shock than a starving rat would for food

3 strengths for methodology of supporting studies for the dopamine explanation

longitudinal (Volkow 1992), scientific (Volkow 1992, Joutsa et. al 2012), high reliability (Joutsa et. al 2012)

4 weaknesses for methodology of supporting studies for the dopamine explanation

androcentric (Joutsa et. al 20120, small sample (Joutsa et. al 2012, Volkow 1992), imbalance in group sizes (Volkow 1992), use of animals (Olds 1976)

2 positive real-world applications for the dopamine explanation

treatment should be centred around strengthening cognitive processes, could prevent people taking drugs initially due to brain changes

1 other strengths for the dopamine explanation

determinist - lack of blame, feel less responsible, they can get help

3 other weaknesses for the dopamine explanation

dopamine levels don't increase in taking marijuana (Stokes et. al 2009) and alcohol (Yoder et. al 2007), reductionist - ignores differences in people, reductionist other factors influence addiction (dopamine blockers don't always stop addiction)