Research reveals the neural mechanism for efficient decision-making in dynamic multi-value options

Recently, Nature Communications published an online research paper titled "The primate superior colliculus nucleus transforms absolute value information into classification choices in value-based decision-making".
The research was developed by the Chinese Academy of Sciences Brain Science and Intelligent Technology Excellence Innovation Center ( The decision-making research group of the Key Laboratory of Primate Neurobiology of the Chinese Academy of Sciences was completed
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The research developed a task of selecting among multiple options through eye movement based on reward value, and performed single-cell electrophysiological recording and electrical stimulation manipulation in the superior colliculus region of the midbrain
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The study found that the superior colliculus neuron not only encodes the absolute value of a single option itself, but also characterizes the decision threshold that changes flexibly with the total value of each option
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The researchers further used microcurrents to manipulate the activity of superior colliculus neurons, revealing the neural mechanism by which the superior colliculus transforms the absolute value of options into decision-making.
This work helps us understand how the brain makes efficient decisions in real life
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Although there has been a lot of research on how value is represented in different brain regions, there is still a lack of direct evidence on how value is transformed into the final choice
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Inspired by the optimal foraging theory, this research developed a multi-option eye movement foraging task on macaques (Figure A)
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Rhesus monkeys need to perform a series of scans in a visual stimulus array containing multiple options within a limited time, and obtain corresponding rewards by gazing at each option in turn
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Multiple targets in the task can have the same value, and their value combination changes dynamically during the foraging process (Figure B), so that we can separate the value signal and the eye movement decision signal at the neuron level, and study how the value representation is Varies with the combination of options
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The study has multiple findings in the superior colliculus nucleus of the brain (Figure C)
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The superior colliculus is one of the key brain areas for eye movement control in the brain
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The study found that the superior colliculus neuron first characterizes the absolute value of the next selected target in the eye movement decision-making process, and this characterization is not affected by the value of other options
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Before finally making the eye movement to complete the decision, regardless of the value of the selected target, the firing of the superior colliculus neuron has reached a decision threshold, and this decision threshold is regulated by the value combination of the alternatives
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The study shows that the dynamic multi-choice economic decision-making process can be realized with a simple mechanism: the brain determines the threshold of decision-making by integrating the value of each option; when different neurons in the superior colliculus represent the value of different options
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They compete with each other, and when one of the neurons is fired to the decision threshold, the corresponding option will be selected
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The fine microcurrent stimulation experiment supports this conjecture.
The closer the neuron firing is to the decision threshold, the more likely it is to be affected by the microcurrent stimulation and trigger the corresponding decision
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Under this decision-making mechanism, the absolute value representation that is not affected by other options ensures the stability of value preference and the efficiency of neuron’s value representation; while the dynamically adjustable decision threshold helps the brain to be flexible as the situation changes.
Decision-making
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This research provides direct neurobiological evidence for how the brain realizes efficient and flexible economic decision-making
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The study developed a new cognitive task of economic decision-making mechanism in primate model animals, and was the first to find that the absolute value of decision-making options can be represented in key sensory-motor brain regions
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The study also found that the decision threshold depends on the neural representation of contextual changes
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This research provides direct causal evidence for the neural mechanism that transforms value into decision-making actions in the upper colliculus, and has a profound impact on the understanding of the neural mechanism of economic decision-making
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The work was completed by Zhang Beizhen, a PhD student in the Center for Brain Intelligence Excellence, and Janis Ying Ying Kan, a PhD student in the Department of Biomedicine and Molecular Sciences at the Neuroscience Research Center of Queen's University in Canada, under the guidance of researcher Mike Dorris
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The research work was supported by researcher Xu Ninglong, postdoctoral fellow of the Center for Brain Intelligence Excellence, Duan Chunyu, researcher Yang Tianming, and doctoral student Zhang Zhewei
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The research work was funded by the Chinese Academy of Sciences
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(A) The task example of the multi-option eye movement foraging experiment
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The 4×4 visual stimulus array is composed of 3 color targets
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Each color represents a certain size of value
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The value is defined as the amount of juice divided by the gaze time required to obtain the reward
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When the macaque moves its eyes to a target and stares at the corresponding time, the color of the target will turn gray, and the macaque will get the corresponding amount of juice
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In this example, the target value decreases in the order of red to green to blue
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In the task, the association between color and value remains the same, but the position of the color point in the array is random
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(B) In this example task, as the macaque makes a series of choices, there are fewer and fewer high-value targets
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From top to bottom, the red target is selected first, then the green, and finally only the low-value blue target is left
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(C) Schematic diagram of the decision-making mechanism of Shangqiu
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Each peak represents a neuron, the height of the peak represents the activity of the neuron, and the color represents the color of the target represented by the neuron
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The dotted line is the decision threshold, and the realization represents the action threshold
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Neurons have stable value representations, flexible decision thresholds and fixed action thresholds
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The value representation of a certain color does not change with other options, and the decision threshold is determined by the overall value of each option
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(Left) At the beginning of the task, since the value of the red target is greater, the activity of the corresponding neuron is higher, and it is more likely to reach the decision threshold
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(Middle) After the red target is selected, the decision threshold is lowered, and the green neurons are more likely to win
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(Right) When only the blue option is left, the threshold is lower
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Source: Center for Excellence in Brain Science and Intelligent Technology, Chinese Academy of Sciences