The reason for these individual differences is in the connections of a specific brain area, according to a study recently published in The Journal of Neuroscience. This work has involved researchers from the Bellvitge Biomedical Research Institute (IDIBELL) and the Department of Basic Psychology at the University of Barcelona Estela Cámara (now at the Institute of Cognitive Neuroscience, UCL, London) and Antoni Rodríguez Fornells (ICREA researcher). The research results provide new evidence on individual differences observed in how people can be more or less likely to seek rewards or pleasures or avoid negative or unpleasant situations.

The researchers studied the brain activity of 35 healthy volunteers while they played and bet to earn money. Before beginning the experiment, participants were asked to fill out standard questionnaires yielded information on their tendency to avoid losses or punishments (i.e. prone to anxiety) or sensitivity to seek rewards.

Participants were placed in front of a computer screen where two numbers appeared, 5 and 25, in white on black background, and were asked to select one of both numbers. Then, at random, one of the figures appeared, one in green and the other in red. If the selected number came in red, the participant lost the full amount of money expressed in euro cents, if it was green, the won.

Additionally, to learn how the brain reacts to unexpected gains and losses, in the ten percent of the tests the number 25 or 5 were changed by 125. Although these additional tests were unexpected, the magnitude of income remained virtually unchanged throughout the test.

Before starting, each player received from the researchers ten euros and was encouraged to earn as much money as possible. The experiment consisted in four blocks of 140 trials each one. At the end of each block, participants were informed of the amount that had been won. After finishing the experiment, the profits were distributed among participants.

While the volunteers were playing, the researchers assessed the brain activity using MRI. The study shows that the stimuli intensity of reward and punishment coming to the brain’s subcortical region responsible for processing them, called the nucleus accumbens (in the ventral striatum), is conditioned by the structural properties of the surrounding tissues.

Just as measurement and road capacity determines the amount of cars that can go from one city to another, the properties of white matter that connects various brain regions determines the amount of information flowing between these regions.

The authors have shown that people with greater sensitivity to anxiety and reward mechanisms differ in the brain white matter connections that surround the nucleus accumbens.

Addictive behaviours

This new evidence is important because provide new ideas about the strong relationship between brain structure, cognition and behaviour observed in potential situations that may lead to developing addictive behaviours such as pathological gambling or drug abuse.

The fact to understand the neurobiological bases governing these individual differences will help us to understand the causes of the behaviours and habits established throughout life, and make possible to develop appropriate intervention strategies.

In any case, these data raise important questions about how to build along the human development this relationship between brain structure and behaviour and, more important, where these individual differences arise.