These findings, based on functional magnetic resonance imaging (fMRI) of people's brains, distinguish the gambling function of the brain structures from their functions in learning, motivation, and assessment of the salience of a stimulus, according to a research group at the California Institute of Technology.

    The experimental method in their study may help understand and perhaps treat gambling addiction, bipolar disorders, and schizophrenia, the researchers say in the Aug. 3 issue of the journal Neuron.

    In the experiments, the testees were asked to choose two cards from a deck numbered one to 10 after they bet one dollar on whether the first or second card would be higher. Meantime, the researchers scanned the testees' brains with fMRI.

    The researchers concentrated their analysis on the "anticipatory period" between the display of the first and second card, since it was then that the subjects were able to judge from the number on the card the risk of whether they were likely to win or lose their bet.

    Earlier studies have shown that, during a one-second period immediately after the first card was displayed, subjects were concentrating on expected reward, and in the following six seconds before the second card, they were assessing the risk revealed by the first card.

    In the experiments, the researchers distinguished brain regions that specifically responded to either reward expectation or risk. Importantly, these areas showed activities that increased with the level of expected rewards and perceived risks.

    These regions were part of the brain circuitry governed by the neurotransmitter dopamine that is also involved in learning, motivation, and salience, according to the team led by Steven Quartz, an associate professor at the California Institute of Technology.

    The researchers noted, however, the design of their gambling task and analysis of their data ruled out involvement of these functions, meaning that they had isolated the "gambling" function of these regions for the first time.

    Of the practical implications of these findings, the researchers said that gambling addiction and a variety of mental illnesses are partially characterized by risk taking.

    To date, though, it is unknown whether such decision making under risk is due to misperception of risk or disruptions in higher cognitive processes such as learning, planning, and choice. Previous studies had not been able to pinpoint the underlying structure.

    "Since our task was designed to minimize the involvement of these high-level processes, in the future it may be utilized with clinical populations to determine whether alterations in risk perception accompany their changes in risky behavior," their paper said.

    "This may lead to a better understanding of the relative contributions of risk misperception versus cognitive impairments in these pathological cases, may suggest different treatment approaches, and may also gauge the impact on and the feedback from higher-level brain regions known to contribute to decision making." Enditem