Cambridge scientist shares world’s largest neuroscience prize for research on the brain’s reward system

The capacity to link reward to events and actions is the foundation of human and animal survival, and problems with the processing of reward lie at the heart of many neurological and psychiatric disorders.

The Brain Prize, awarded by the Lundbeck Foundation in Denmark, is worth €1 million.  Awarded annually, it recognises one or more scientists who have distinguished themselves by an outstanding contribution to neuroscience.  

The research of this year’s winners has far-reaching implications for understanding human behaviour, including decision-making, gambling, drug addiction, compulsive behaviour and schizophrenia.

Reward is essential to survival because humans and other animals need to learn to direct their decisions and their actions towards outcomes that will satisfy their needs, and away from danger.  This means that they have to learn which events in the environment predict future rewards and punishments. For instance, if you feel hungry and see a building with a sign ‘restaurant’, you are likely to enter because the sign predicts that your hunger will be reduced if you go inside.

The sense of reward is surprisingly complicated. It is influenced and determined by many things, such as taste and smell, as well as by fundamental motivations such as hunger or thirst. In turn, it influences choices, decisions and even attention. Many regions of the brain process information associated with reward, but one central linchpin for the regulation of learning and performance is a neurotransmitter (chemical messenger) in the brain called dopamine.

Thirty years ago, German-born Wolfram Schultz, professor of neuroscience now at the University of Cambridge, was studying learning in monkeys at the University of Fribourg in Switzerland. He developed methods for recording activity from neurons (nerve cells) that use dopamine to transmit information to other neurons.  He found that before learning, these dopamine neurons respond whenever a reward - fruit juice - is given to the monkey, but if the monkey is shown various visual patterns and has to respond to one of them in order to secure the reward, the pattern of response changes as the animal learns. The dopamine neurons now respond when the correct visual pattern appears, and the response to the reward itself disappears. If no reward is given, the activity of dopamine neurons actually decreases at the expected time after the visual signal; but if the reward is delivered at an unexpected time, the neurons respond to it.

“This is the biological process that makes us want to buy a bigger car or house, or be promoted at work,” said Schultz. Every time we get the reward, our dopamine neurons affect our behaviour.  “They are like little devils in our brain that drive us towards more rewards.”

Dopamine neurons play a ‘devilish’ role in drug addiction. “Addictive drugs generate, hijack and amplify the reward signal and induce exaggerated and uncontrolled effects of dopamine on the brain,” Schultz explained. 

British computational neuroscientist, Peter Dayan, director of the Gatsby Computational Neuroscience Unit, University College London, is recognised internationally as a leader in the rapidly developing field of computational neuroscience. When working at the Salk Institute in California, Dayan realised that the pattern of activity of dopamine neurons described by Schultz corresponds to a signal known - from the earliest days of artificial intelligence - as a ‘reward prediction error’.

This signal is the difference between the reward that is actually delivered and the reward that is predicted to be delivered.  Prediction errors sculpt our expectations and experience of the world.

“For example, imagine that you choose between restaurants based on predicting how good they are. Then, if the one you chose is better than expected, the positive prediction error allows you to update your prediction. Next time you are faced with a restaurant choice, you are more likely to pick the one that was better,” said Dayan.

This link between dopamine and prediction error was one of the spurs for an explosion of work using theoretical ideas and computational models to link artificial intelligence, economics, mathematics, engineering and statistics to swathes of results in psychology and neuroscience.

Professor Ray Dolan was born in the Irish Republic and is the director of the new Max Planck Centre for Computational Psychiatry and Ageing at University College London, and the Wellcome Centre for Neuroimaging. Dolan has been a leader in the development and use of methods for imaging the human brain, in order to understand the mechanisms of emotion, learning and decision-making. 

Through his pioneering application of mathematical models to brain imaging and behaviour, together with his discoveries on the action of dopamine and other neurotransmitters, he has shown how humans learn about reward and punishment and also how we learn about the preferences of other people.

Dayan and Dolan have worked collaboratively over the past decade to probe how reward learning impacts on complex human questions, including motivational drive, variation in happiness, and a propensity towards gambling. 

“One puzzling clinical problem is why some patients treated with drugs that boost dopamine function, for example in Parkinson’s disease, fall prey to pathological gambling. Our work has shown that this effect is, at least in part, due to dopamine amplifying an innate tendency to repeat activities that are rewarding,” said Dolan.

Schultz gratefully acknowledged the contributions of his many colleagues and collaborators, as well as the institutions and funding agencies that have supported his work, especially the University of Cambridge and the Wellcome Trust.  

“The Brain Prize is a fantastic reward for our research group. I can hear our dopamine neurons jumping up and down!” Schultz said.

Professor Sir Colin Blakemore, chairman of the Brain Prize selection committee said, “The judges concluded that the discoveries made by Wolfram Schultz, Peter Dayan and Ray Dolan were crucial for understanding how the brain detects reward and uses this information to guide behaviour. This work is a wonderful example of the creative power of interdisciplinary research, bringing together computational explanations of the role of activity in the monkey brain with advanced brain imaging in human beings to illuminate the way in which we use reward to regulate our choices and actions. The implications of these discoveries are extremely wide-ranging, in fields as diverse as economics, social science, drug addiction and psychiatry.”

The winners will share the prize of €1 million, which will be presented to them at a ceremony on 4 May in Copenhagen by His Royal Highness Crown Prince Frederik of Denmark.

Adapted from a press release by the Lundbeck Foundation.