It's a common scenario: you're on a diet, determined to give up eating cakes, but as you pass the cake counter, all resolve disappears… Now, scientists at the Wellcome Trust Centre for Neuroimaging at UCL (University College London) have shed light on the brain processes that affect our will power and make us act impulsively.
In a study published today in the Journal of Neuroscience, funded mainly by the Wellcome Trust, researchers led by Professor Ray Dolan have shown that increased levels of dopamine – a chemical in the brain involved in mediating reward, motivation, and learning through reinforcement, – make us more likely to opt for instant gratification, rather than waiting for a more beneficial reward.
People with attention deficit have high dopamine in their brains?
The research may help explain why people affected by conditions such as Attention Deficit/Hyperactivity Disorder (ADHD), characterised by high levels of dopamine in the brain, tend to show extremely impulsive behaviour. Similarly, it highlights why such behaviour can be a potential negative side-effect of L-dopa, a drug used to help alleviate the symptoms of Parkinson's disease.
This claim sounds a bit overly broad because anti-ADHD drugs like Adderall and Ritalin are believed by other scientists to work by raising dopamine in the prefrontal cortex (PFC) of the brain. When it comes to the brain what a neuortransmitter does depends on where it is.
L-dopa boosts dopamine in the brain and caused subjects in the study to go for more immediate rewards.
To test the effect of dopamine on decision-making, Professor Ray Dolan and colleagues carried out a test with 14 healthy volunteers under two conditions: once when given a small (150mg) dose of L-dopa, once when given a placebo. Under each condition, the subjects were asked to make a number of choices consisting of either a 'smaller, sooner' option, for example receiving £15 in two weeks, or a 'larger, later' option, such as receiving £57 in six months.
"Every day we are faced with decisions that offer either instant gratification or longer-term, but more significant reward," explains Dr Alex Pine, first author of the study. "Do you buy your new iPhone today or wait six months till the price comes down? Do you diet or eat that delicious-looking cake? Do you get out your books to study for a future exam or watch some more TV?"
All expermental subjects shifted toward instant rewards under the influence of L-dopa and dopamine. This result undermines the view that we can each fully understand our own desires and make rational choices thru introspection. We are puppets in the hands of eurotransmitters.
The researchers found that every subject was more likely to behave more impulsively – choosing the 'smaller, sooner' option – when levels of dopamine in the brain were boosted. . On the whole, the number of sooner options chosen increased by almost a third, although each subject varied on this measure.
Possibly the L-Dopa boosts brain dopamine in different brain areas as compared to anti-ADHD drugs. Anyone have some insights on this to offer?
If a drug can reduce our future time orientation it stands to reason that some other drug might be able to increase our future time orientation. Does Ritalin increase future time orientation of people who do not have attention deficit? Could one improve one's decision making about career and investments by using drugs to shift one's orientation toward bigger long term rewards?
|Share |||Randall Parker, 2010 June 29 10:35 PM Brain Free Will|