From gamblers playing blackjack to investors picking stocks, humans make a
wide range of decisions that require gauging risk versus reward. However,
laboratory studies have not been able to unequivocally determine how the
very basic information-processing “subcortical” regions of the brain
function in processing risk and reward. Now, Steven Quartz and colleagues at
the California Institute of Technology have created a simple gambling task
that, when performed by humans undergoing functional magnetic resonance
imaging (fMRI) of their brains, distinguishes the “gambling” structures in
the brain. Importantly, their findings tease apart the gambling function of
these brain structures from their functions in learning, motivation, and
assessment of the salience of a stimulus. In their research article
published in the August 3, 2006, issue of Neuron, published by Cell Press,
the researchers said their findings and experimental method could help in
understanding and perhaps treating aberrant risk-taking in disorders
including gambling addiction, bipolar disorders, and schizophrenia.

In their experiments, the researchers asked subjects to choose two cards
from a deck numbered one to ten. Before their choice, however, the subjects
were asked to bet $1 on whether the first or second card would be higher.
The fMRI imaging of the subjects’ brains during the gambling task could show
the researchers which areas of the brain activated during different parts of
the task. In fMRI, harmless radio signals and magnetic fields are used to
measure blood flow in brain regions, which reflects activity in those
regions.

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 that the second card would be
higher or lower.

Furthermore, the researchers divided that anticipatory period into two
subperiods. During a one second period immediately after the first card was
displayed, subjects were concentrating on expected reward, theorized the
researchers; and in the following six seconds before the second card, they
were assessing the risk revealed by the first card. The researchers based
this approach on studies by other researchers of such processes in primates.

Quartz and colleagues found they could distinguish brain regions that
specifically responded to either reward expectation or risk. Importantly,
these areas showed activity that increased with the level of expected reward
and perceived risk. The researchers found that the activation related to
expected reward was immediate, while the activation related to risk was
delayed.

These regions were part of the brain circuitry governed by the
neurotransmitter dopamine that is also involved in learning, motivation, and
salience. However, emphasized the researchers, the design of their gambling
task and analysis of their data ruled out involvement of these functions,
meaning that they had, indeed, isolated the “gambling” function of these
regions.

Of the practical implications of their findings, the researchers wrote that
“pathological behaviors ranging from addiction to gambling, as well as a
variety of mental illnesses such as bipolar disorder and schizophrenia, are
partially characterized by risk taking. To date, it is unknown whether such
pathological decision making under risk is due to misperception of risk or
disruptions in cognitive processes, such as learning, planning, and choice.

“For example, a bipolar subject during a manic episode may invest in a risky
business proposition either because they misperceive the risk to be lower
than it actually is, or because they accurately perceive the risk to be high
but may have impaired learning, attentional, working memory, or choice
processes.”

Previous research approaches had not been able to distinguish the processes
underlying such risky behavior, wrote the researchers. However, they wrote,
“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. 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.”

About the study:

The researchers include Kerstin Preuschoff, Peter Bossaerts, and Steven R.
Quartz of the California Institute of Technology in Pasadena, CA. This work
was supported by NSF Grant 0093757, the David and Lucile Packard Foundation,
and the Gordon and Betty Moore Foundation.