Researchers at Kyoto University, Japan, have uncovered neurological insights into how depression and anxiety can influence our ability to make decisions
Every day, all of us are faced with a choice at some point. And when presented with two options, we naturally go into a state of weighing one up against each other. Do we get up early and run some errands, or lie in a bit longer? Do we have a nice healthy breakfast, or pick up a coffee and a croissant on the way to work? Do we go to bed a bit early and catch up on our sleep, or watch just one... more... episode?
Almost always, we opt for the choice that is easier, less disruptive, and offers up enough of a reward for the amount of effort it will take to obtain.
That is, unless we find ourselves in a negative state of mind. Research has shown that a condition like anxiety can make us less likely to want to expend effort for a reward, while depression makes us more likely to avoid making the decision entirely.
It might sound like a simple observation, but the connection between our decision making and our emotions is a complex relationship that we are still trying to understand fully.
Now, researchers in Japan have uncovered a possible window into this interconnection that could help advance our knowledge into how a negative mindset can influence our decisions.
Gathering data from studies into primates and rats, the researchers decided to investigate a specific area of the brain called the anterior cingulate cortex (ACC). The ACC sits in the centre of the brain and is thought to be involved in the relationship between emotions and rational thinking.
The team decided to test the theory of the ACC's role in decision making in monkeys, specifically macaques. The macaques were presented with a choice between combinations of rewards and varying levels of 'punishment', which in this case was a blast of air to the face.
The choices were represented visually on a screen and the monkeys made their selection using a joystick. Whichever choice they made would indicate to the researchers the level of risk the monkeys were willing to take for a reward.
Probing the brains of the macaques, the researchers discovered a set of localised brain cells within the ACC that would become activated or deactivated in line with the size of the reward or punishment for each choice. This area has been linked with both major depressive disorder and generalised anxiety disorder in previous research.
To see the weight of influence these cells could have on the monkeys' decisions, the team electrically stimulated them. Sure enough, the monkeys exhibited more negative decision making in response to the cells being stimulated, or activated. The team also discovered the therapeutic benefit of the common anti-anxiety drug diazepam – treating the macaques with the drug completely reversed this state of pessimism.
Once the area of the ACC was identified, the team went further to establish what other areas of the brain it could be influencing.
The monkeys were injected with a virus that would cause the brain cells of interest to create fluorescent proteins. As the virus spread, the proteins would begin emerging in other parts of the brain, revealing the pathways linking the ACC to other structures.
Interestingly, pathways were revealed between the ACC and an area called the prefrontal cortex, which is a part of the brain known to be responsible for higher thinking and reasoning.
Taking their findings, the team were then able to generalise their results to data from other studies into human brains.
"We are facing a new epidemic of anxiety, and it is important that we understand how our anxiety influences our decision making," said Ken-ichi Amemori, associate professor in neuroscience at Kyoto University. "There is a real need for a better understanding of what is happening in the brain here.
"It is very difficult for us to see exactly where and how anxiety manifests in humans, but studies in primate brains have pointed to neurons in the ACC as being important in these decision-making processes."
With the parallels the researchers recorded between the ACC's role in macaques compared with its role in humans, the team hope their findings can help develop pathway-specific treatments for neurological and psychiatric disorders, adds Amemori.
Read the full details of the study here.
Written by Marco Ricci
Editor and contributor for Talking Mental Health