People make risk-versus-reward decisions every day, whether making purchases or deciding how to travel to work. Despite the important role of risk in decision-making, neuroscience studies have focused on perceived reward. Furthermore, researchers have identified the regions of the cerebral cortex involved in gauging risk versus reward, but data for subcortical regions are ambiguous. However, Kerstin Preuschoff and colleagues at the California Institute of Technology in Pasadena wagered that they could determine the subcortical structures involved in gambling using functional MRI, which employs radio signals and magnetic fields to measure blood flow in the brain.

In the study, subjects bet $1 that either the first or second card in a deck of 10 would have a higher value. The reward probability and risk varied with each bet. The scientists believed that they eliminated confounding factors, such as varying complexity, learning, motivation and salience.

The scientists analyzed the period between the revelation of the first and second cards. In the Aug. 3 issue of Neuron, they reported that activity appeared in several subcortical brain regions that respond to the neurotransmitter dopamine. Of particular interest, the ventral striatum exhibited activity that initially corresponded to reward and later correlated with risk. Preuschoff said that it is the first brain region discovered that encodes both.

The researchers said that their results could apply to pathological conditions — such as gambling addiction, bipolar disorder and schizophrenia — that are associated with risky behavior.