Decision neuroscience

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Neuroscientists are trying to study the theories behind the operation of a larger-scale brain system with many interactive modules. However, they feel, it is unlikely to come across universal laws of decision-making

Decision neuroscience
We make a number of decisions every day, some right and some wrong. However, we are not as rational as we wish to be. We tend to make wrong decisions because our minds are laced with emotions. What goes on in our minds when we make decisions? What specific neuronal circuits in our brains are responsible for our thoughts and actions? Decision neuroscience tries to answer these questions. It investigates the neural basis of human decision-making.

The part of the brain linked to emotion is nucleus accumbens (nacc) — the peanut-sized area that becomes active when we expect a reward of a primary nature, such as water if we are thirsty. The other part of the brain linked to anxiety, anterior insula, lights up when a person sees disgusting, repulsive stimuli or when someone anticipates physical pain. According to researchers, if the emotional states of individuals are included in rational decision-making models, people take better financial choices.

Pure rational decision-making is difficult, if not impossible, as decisions are always coloured with the emotions of the person who is taking the decision. Neuroscientists say that people with damaged part of the brain responsible for emotional reactions are unable to decide; the rational mind dithers endlessly over the possible rational reasons. Extremely emotional decisions, on the other hand, can also lead us to trouble. Both ‘cold reasons’ and ‘hot emotions’ are needed to make a decision. A decision involves pulling up a memory and a value system and an emotional response.

Decision bridges neurobiology and cognitive science, neuroscientists say. The essence of the thinking during decision-making is mental simulation, says Daeyeol Lee of Yale University’s School of Medicine. Mental simulation means that “you are trying to predict the outcome before you take an action by using analogies of your previous experiences, or by observing and remembering the outcomes of other people’s behaviours”. We do mental simulations for many different actions before we actually make a choice.

Daniel Salzman of Columbia University’s school of medicine says that we tend to assign value to different options we observe. Some parts in our brain, being ‘perceptual system specialists’, place a value on what we see. The more common economic terms like “rewards” and “values” in the decision making process is a relatively new concept. It started about 10-15 years ago. Neuroscientists wanted to know how uncertainty about the reward or risk is represented in the brain and influences decision-making. They also wanted to find out how the brain handles the trade-off between the overall magnitude of the reward and how immediately one receives the reward.

Rewards are often the major parameter that affects decisions. They are thus manipulated in order to take decisions. Reward could be immediate or delayed. Neuroscientists want to understand how neurons represent rewards, and how information on rewards is integrated over time in order to reach a decision.

How do we value choices? Behaviour is very adaptive when we make decisions, says Xiao-Jing Wang of Yale University’s School of Medicine. “You can really watch how your choice behaviour adapts and changes from trial to trial, according to environment and task design, and such changes are reflected in the recorded activity of single neurons”. Wang also talks about reinforcement learning. It occurs when you are not explicitly taught what you are supposed to learn, but rather learn it by trial-and-error — by getting feedback about how well you predicted the outcomes of your behavioural choices. Non-invasive neuro-imaging techniques like PET and fMRI are normally used to read decision-related signals in the humans. These signals tell us a lot of things about the neural basis of decision-making.

According to some of the leading researchers, the driving questions in decision neuroscience are many. They want to understand the computations performed in different brain areas, how they are similar or different, how different areas communicate with each other, how the information is transformed as it moves around in the brain, how different variables come together and form a decision. As Wang says, a decision involves many processes. One needs to accumulate evidence for or against different choice options, evaluate their possible outcomes and risks and suppress certain learned responses and biases.

Thus, it is important to understand how different parts of the brain do different computations in a coordinated way. What neuroscientists are going to study in the coming years, says Wang, are the theories behind the operation of a larger-scale brain system with many interactive modules.

It is very unlikely to come across universal laws of decision-making. For Lee, brain is like a toolbox with random tools. You take out one particular tool to solve a specific problem. The problem is, how so many tools interact to solve an interrelated problem. “Since the design of the toolbox may not be completely rational, it may not be easy to come up with one set of equations for how the tools are collected in the first place”, says Lee. Another challenge for neuroscientists is to understand how the brain represents new situations in order to find out how the brain makes decisions about such new situations. Salzman says our brains are not big enough, and we don’t have requisite neurons to represent every situation that we might possibly encounter.

What about the practical application of decision neuroscience research? There are many. Research will lead us to understand the biological basis of mental disorders. It will tell us more about the mental disorders resulting from dysfunction of neural circuits, like how these dysfunctions produce different cognitive and emotional symptoms, and thereby, affect decision-making. It will tell us about the implications of treatment on neural network. Salzman says we don’t know enough about how those neural circuits work normally. What we need to understand is how cognition and emotion work in the brain to produce a decision, and how they become dysfunctional. We need to understand why different individuals make different decisions, and why they make different choices when they face the same decision. Are the differences due to genetic differences, or due to the differences in experiences and learning environments, or both?

When you try to do more than your mind can handle, decision fatigue sets in. When decision fatigue sets in, either you do nothing, or you take shortcuts and go wrong, or try to maintain status quo.

So don’t think too much. Having too much information is a plague. As they say, over-information generates cognitive stress. Often, too much thinking overwhelms our brain’s ability to synthesise all the facts, and thus, our ability to take decision gets distracted. We land up making bad decisions. When we’re distracted, we stop introspecting and listen to our emotional minds. Decisions in a happy state of mind are happy decisions. zz

(The writer is a biotechnologist and ED, Birla Institute of Scientific Research, Jaipur)

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