Summary: Study highlights how dopamine receptors shape motivation and decision-making.
Source: The National Institutes for Quantum and Radiological Science and Technology
Why do we act, even for routine goals? What drives us to exert effort, seek rewards, or accept risks? At the heart of these behaviors is the brain’s reward system—an evolutionarily conserved network that evaluates benefits and costs to guide action. Understanding how this system promotes or suppresses motivation is essential for tackling disorders such as depression, schizophrenia, and Parkinson’s disease, in which motivation and energy levels are often diminished.
People with these conditions frequently experience reduced willingness to work or persistent fatigue because their reward-processing circuits do not function normally. To develop better treatments, researchers study the neural mechanisms that compute cost–benefit trade-offs and control whether an individual will pursue a goal.
A research team led by Dr. Yukiko Hori at the National Institutes for Quantum and Radiological Science and Technology in Japan investigated how two major classes of dopamine receptors contribute to benefit- and cost-based motivation. Their results, published in PLOS Biology, reveal distinct and complementary roles for D1-like receptors (D1R) and D2-like receptors (D2R) in determining both the willingness to act for rewards and sensitivity to different types of costs.
“Patients often report that tasks feel too costly or that they lack the drive to act,” Dr. Hori explains. “To address these motivational disturbances, we need to understand how specific components of the dopaminergic system shape decisions about effort, delay, and reward.”
Dopamine (DA) is a critical neurotransmitter in motivation and decision-making. DA signals are transmitted through receptor proteins—primarily D1R and D2R—which initiate different intracellular pathways and thus may influence behavior in distinct ways. To map these effects, the researchers used macaque monkeys as a model of goal-directed behavior and combined pharmacological manipulations with brain imaging.
The team trained monkeys on two types of tasks: a “reward size” task that varied the amount of reward available, and “work/delay” tasks that varied either the required effort or the delay before receiving a reward. These designs make it possible to measure how perceived reward magnitude and different cost types affect the animals’ choices, refusal rates, and reaction times.
Dr. Takafumi Minamimoto, the study’s corresponding author, describes the approach: “We selectively reduced D1R or D2R signaling by administering receptor-specific antagonists and used positron emission tomography (PET) to quantify the degree of receptor blockade. Then we observed how these manipulations altered the monkeys’ motivation to perform tasks for varying rewards and costs.”
The behavioral data revealed several clear patterns. Blocking either D1R or D2R reduced how strongly larger rewards motivated the animals—both receptor types contribute to incentive motivation. Similarly, impairment of either receptor type increased delay discounting, meaning the animals were more likely to prefer smaller immediate rewards over larger delayed ones.
Crucially, the study found a dissociation between delay-related costs and effort-related costs. While both receptors influenced sensitivity to reward size and delay, increased workload discounting—devaluing rewards because of higher effort—was selectively associated with D2R blockade. In other words, D2R signaling plays a unique role in how effort costs reduce the motivational value of rewards.
When both receptor classes were blocked simultaneously, the combined effects were complex: the two blockades acted synergistically to increase delay discounting, but they produced opposing effects on workload discounting. These results suggest that D1R and D2R interact in nontrivial ways to shape cost–benefit computations and that they modulate different neural circuits for reward availability and energy expenditure.
Prof. Hori emphasizes the translational relevance: “Identifying the complementary contributions of D1R and D2R to cost–benefit evaluation advances our understanding of the neural basis of motivation. This knowledge may inform more targeted strategies to treat motivational deficits in psychiatric and neurological disorders by selectively modulating specific dopaminergic pathways.”
Overall, this study clarifies how distinct dopamine receptor subtypes influence three core aspects of motivated decision-making—reward sensitivity, delay discounting, and effort discounting—and highlights potential avenues for therapeutic intervention aimed at restoring healthy motivation.
About this motivation and neuroscience research news
Source: The National Institutes for Quantum and Radiological Science and Technology
Contact: Press Office – The National Institutes for Quantum and Radiological Science and Technology
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Original Research: Open access. “D1- and D2-like receptors differentially mediate the effects of dopaminergic transmission on cost–benefit evaluation and motivation in monkeys” by Yukiko Hori et al. PLOS Biology
Abstract
D1- and D2-like receptors differentially mediate the effects of dopaminergic transmission on cost–benefit evaluation and motivation in monkeys
Dopamine (DA) is known to play a central role in motivation, yet the distinct contributions of D1-like receptors (D1R) and D2-like receptors (D2R) to cost–benefit decision-making remained unclear. By combining pharmacological manipulation of DA receptors with positron emission tomography (PET) imaging, this study examined how varying degrees of D1R and D2R blockade affected benefit- and cost-based motivation in macaque monkeys.
The researchers found that blocking either D1R or D2R reduced the positive influence of larger rewards and increased delay discounting. Increased workload discounting, where higher effort reduced reward value, was selectively produced by D2R antagonism. Simultaneous blockade of both receptor types had a synergistic effect on delay discounting but opposing effects on workload discounting.
These findings offer fundamental insight into the distinct neurobiological mechanisms through which dopamine regulates benefit- and cost-based motivation, with important implications for understanding motivational alterations in neurological and psychiatric disorders.