Do or do not: your ability to learn differently when older depends on dopamine

Dopamine crystals

If you’re anything like me, you may work overtime for bonus pay or not speed to avoid a traffic fine, but you probably find it harder to give up cake for the sake of your health or to start going to the gym to avoid getting fat. We are hard-wired to approach things that are rewarding and avoid things that are punishing, so we can easily learn to do something for a reward or avoid doing something to escape punishment.

It’s much harder to refrain to get a reward or act to avoid a loss. Yet this could save your life: for many people the automatic to an unexpected car is to freeze (inaction to avoid loss), even though the better reaction would be running (action to avoid loss). Overcoming such hard-wired learning patterns to do things differently is known as “flexible learning” and new research suggests that some adults may get better at it thanks to the way our brains handle the chemical signal dopamine.

Supported by a Wellcome Trust grant, researchers from UCL and Otto-von-Guericke-University Magdeburg University in Germany, asked a group of 65 and 75 years olds to either press a button or stop themselves pressing a button to either gain £1 or avoid losing £1, depending on which of 4 abstract patterns they were shown (they were given their winnings of £5-£15 in real money at the end). Sure enough, the participants found it easier to learn to act (‘go’) for a win and to refrain (‘no-go’) to avoid loss: a learning asymmetry. 

The interesting thing came when they looked at who was able to learn the correct responses to the other patterns – requiring the subjects to ‘go’ to avoid a loss and ‘no-go’ to get the money. Those who were better that this could overcome the learning asymmetry and were therefore better at flexible learning. MRI brain scans showed that these people had more neurons in areas of the brain responsible for the production and transport of dopamine, a chemical signal in the brain involved in reward, pleasure and thrill-seeking. Those who weren’t as good at flexible learning had fewer neurons in these brain regions.

The researchers found a similar pattern of responses in younger adults they had studied – good at simple ‘go’ for reward, ‘no-go’ to avoid loss learning but weak at flexible learning. But their brain scans showed that unlike in older people, for younger adults there wasn’t a correlation between being good at flexible learning and having more dopamine neurons.

The findings could have wide-reaching implications because the dopamine signalling system is involved in many ageing-related issues, including Parkinson’s disease. “The amount of dopamine in our brain declines as we age,” says Dr Rumana Chowdhury, first author on the study. “Our findings suggest that this dopamine decline impacts on the ability to flexibly learn in older age”. Prior research has shown that the dopamine system is important in learning to make a response (‘go’ learning). But the new study shows that it is also involved in flexible learning, regardless of whether the action needed is ‘go’ or ‘no-go’.

This raises the possibility of influencing this type of learning by the manipulating the dopamine system, for example using drugs, says Chowdhury. There are also implications for medical treatments. Medication for Parkinson’s disease normally increases dopamine in the brain, so patients with the disease may learn differently while on their medication, something doctors might consider when assessing the side effects of such drugs.

Reference

• Chowdhury R, Guitart-Masip M, Lambert C, Dolan RJ, & Düzel E (2013). Structural integrity of the substantia nigra and subthalamic nucleus predicts flexibility of instrumental learning in older-age individuals. Neurobiology of aging, 34 (10), 2261-70 PMID: 23623600

Image credit: Spike Walker, Wellcome Images