The neuroscience of pessimism: Why some people always focus on the negative
Are you a glass half full or a glass half empty kind of person? Some people seem to inherently focus on the negative when faced with a decision-making situation, and new research from a team of MIT neuroscientists has identified exactly what region of the brain may be inducing these pessimistic decisions.
The researchers at MIT have been examining the neuroscience of decision making for several years. Previous work has revealed that cost-benefit decisions are mediated by a brain circuit that runs from the medial prefrontal cortex to a specific cluster of neurons located in the striatum. It was found that when this circuit is disrupted, an animal would be more likely to make a high-risk, high-reward decision such as traversing past unpleasant bright light for stronger chocolate milk, instead of a less-concentrated but easily accessible milk reward.
An interesting outcome of this prior research was that when the test animals were chronically stressed, they displayed similar high-risk, high-reward behavior, suggesting that risker decisions may be made under the influence of stress and anxiety. The researchers hypothesized that it is this process that may help explain how the stress of addiction can lead to substance abuse.
The new research set out to focus on the area of the brain where negative weighting is generated in the decision making process. The study focused on the caudate nucleus, a small structure making up part of the dorsal striatum, a component of the basal ganglia. The experiments stimulated the caudate nucleus in macaque monkeys with a small electric current.
The animals were presented with a decision, a reward of juice was paired with an unpleasant puff of air to the face – a simple cost-benefit decision. What degree of negative stimulus will the animal put up with to get the reward? The experiment intriguingly showed that when the caudate nucleus was stimulated the animals began to avoid choosing the reward, when previously they would have put up with the unpleasant stimulus.
"This state we've mimicked has an overestimation of cost relative to benefit," explains Ann Graybiel, senior author on the new research.
Essentially, the research reveals that pessimistic decision-making can potentially be tied to an overactive caudate nucleus. Graybiel is turning her focus to validating these findings in human subjects, working with patients suffering from anxiety and depression to find out whether abnormal activity in the caudate nucleus can be specifically seen during negative decision-making.
As well as offering a compelling insight into how our brains weigh positive or negative outcomes when making a decision, the research hopes to help direct scientists toward better treatments for people suffering from depression and anxiety. For some people with extreme neuropsychiatric disorders, a crippling pessimistic worldview can be overwhelming, and this discovery may help focus treatments on an area of the brain that can modulate those negative sensations.
The research was published in the journal Neuron.
Source: MIT News