Cracking the Code of Motivation – ScienceDaily

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Our motivation to make an effort to achieve a goal is controlled by a reward system wired into the brain. However, many neuropathological conditions impair the reward system, decreasing the willingness to work. Recently, Japanese scientists experimentally manipulated the monkey’s reward system network and studied their behavior. They deciphered some critical missing pieces of the reward system puzzle that could help increase motivation.

Why do we do things? What convinces us to make an effort to achieve goals, no matter how mundane they are? What, for example, prompts us to look for food? Neurologically, the answer is hidden in the brain’s reward system – an evolutionary mechanism that controls our willingness to work or take a risk as a cost to achieve our goals and enjoy the perceived rewards. In people with depression, schizophrenia or Parkinson’s disease, the brain’s reward system is often impaired, leading them to a state of reduced motivation at work or chronic fatigue.

To find a way to overcome debilitating behavioral blocks, neuroscientists study the “anatomy” of the reward system and determine how it assesses the cost-benefit trade-off while deciding whether or not to continue with a task. Recently, Dr Yukiko Hori of the National Institutes for Quantum and Radiological Science and Technology, Japan, along with his colleagues, conducted a study that answered some of the most critical questions about motivation based on the benefits and costs of radiological systems. reward. The results of their study were published in PLoS biology.

Discussing what prompted them to undertake the study, Dr Hori explains, “Mental responses such as ‘feeling more expensive and being too lazy to act’ are often a problem in patients with mental disorders such as depression, and the solution lies in a better understanding of what causes such responses. We wanted to explore the mechanism of motivation disorders in the brain. “

To do this, Dr Hori and his team focused on dopamine (DA), the “neurotransmitter” or signaling molecule that plays the central role in inducing motivation and regulating behavior based on ‘a cost-benefit analysis. The effect of DA in the brain is transmitted through DA receptors, or molecular anchors that bind DA molecules and propagate signals through the brain’s neural network. However, since these receptors have distinct roles in DA signal transduction, it was imperative to assess their relative impacts on DA signaling. Therefore, using macaque monkeys as models, the researchers sought to decipher the roles of two classes of DA receptors – the D1-like receptor (D1R) and the D2-like receptor (D2R) – in human-based development. benefits and costs. motivation.

In their study, the researchers first trained the animals to perform “reward size” and “work / deadline” tasks. These tasks allowed them to measure how the size of the perceived reward and the effort required influenced task performance behavior. Dr Takafumi Minamimoto, the corresponding author of the study, explains: “We systematically manipulated the D1R and D2R of these monkeys by injecting them with specific receptor binding molecules that attenuated their biological responses to DA signaling. brain of the animals, the extent of receptor binding or blocking was measured. “Then, under experimental conditions, they offered the monkeys the opportunity to perform tasks for rewards and noted whether the monkeys accepted or refused to perform tasks and how quickly they responded to task-related signals.

Analysis of this data has uncovered intriguing information on the neurobiological mechanism of the decision-making process. The researchers observed that decision-making based on perceived benefits and costs required the involvement of both D1R and D2R, both to induce motivation (the process in which the size of the rewards inspired the monkeys to complete the tasks) and to increase the updating of delays. (the tendency to prefer immediate and smaller rewards to larger but delayed rewards). It has also become clear that DA transmission via D1R and D2R regulates the cost-based motivation process by separate neurobiological processes for the benefits or “availability of rewards” and the costs or “energy expenditure associated with the task”. However, workload discounting – the process of discounting the value of rewards based on the proportion of effort required – was exclusively related to D2R manipulation.

Professor Hori points out: “The complementary roles of two dopamine receptor subtypes that our study revealed, in calculating the cost-benefit trade-off to guide action will help us to decipher the pathophysiology of psychiatric disorders.” Their research brings hope for a future where, by manipulating the built-in reward system and improving motivation levels, the lives of many can be improved.


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