Researchers have identified regions of the brain involved in deciding between effort and reward.

All actions require physical energy, but many studies on decision-making have a tendency to factor in external costs such as time or risks assessed. But because unwillingness to put in effort is one symptom common to many mental disorders, researchers sought to understand how the brain decides between effort and reward, helping shed more light on mental conditions.

For a study published in the Journal of Neuroscience, researchers worked with volunteers who had to make decisions based on varying levels of physical effort and monetary reward while hooked up to an MRI scanner. Unsurprisingly, they saw that low-effort, high-reward options were particularly favored.

They also discovered an activity pattern in three brain areas: the putamen, the dorsal anterior cingulate cortex (dACC) and the supplementary motor area (SMA). Analyzing the pattern and the brain areas further, the researchers observed that the putamen and SMA were particularly involved in effort assessment, while rewards are assessed in a different network within the ventromedial prefrontal cortex.

As if putting together results from different sources and finding a compromise, the dACC used one value to represent effort and reward assessment. Activity within the brain area was also associated with the level at which the study subjects' choice was guided by the kind of overall value perceived by the individual.

"There is not one single decision-making system in the brain but a set of them that are combined flexibly depending on the decision we are faced with," said Miriam Klein-Flügge, lead author for the study.

Identifying the system linked to effort, the researchers say that their work supports and adds to the results produced by earlier studies on decision-making. They also observed that the study subjects exhibited different levels of effort sensitivity and had varying neural activity, which suggests that it's possible for different people to have different balance levels between effort and reward systems.

While there is a need for further research to prove it, it may also be possible that some mental disorders are caused by acute imbalances in effort and reward systems in the brain, said Klein-Flügge.

Supported by the European Research Council and the Wellcome Trust, the study also involved the work of Sven Bestmann, Karl Friston and Steven Kennerley.

In another study, researchers identified personality types based on decisions made by individuals. According to them, there are four basic types of personalities: Optimists, Pessimists, Envious and Trusting. Of the four, Envious was the most common, manifesting in 30 percent of the subjects.

Photo: Moyan Brenn | Flickr

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