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The academic code in “milk tea”! A post-90s doctor skipped the second review and directly procured the “admission ticket” in the top journal

Just as a wine expert compares aged wine, your brain is also “grading” each sip of milk tea. However, the brain has a unique grading criteria: If the sweetness of the current milk tea doesn’t reach the “peak” in your memory, the dopamine neurons will light up. This “dopamine judge” hidden deep in the brain is the key factor that makes us addicted to snacks.

 

This is a study of Zhenggang Zhu published on Science. The reviewers highly recognized the creativity and preciseness of this study, making the editorial office skip the second review and directly pre-accept the paper, which is a rare situation in top journal.

 

Neurological code of “hedonic eating”

 

Zhenggang Zhu’s study stems from a group of irritable mice. At that time, he joined the team of Shumin Duan, an academician of Chinese Academy of Sciences, and the team found substantia innominata neurons in the brain of mice can switch the animals’ social status during a study, which made Zhenggang Zhu realize that there may be a “switch” existing in the brain to precisely control motivated behaviors.

 

Subsequently, Zhu headed to the University of California, San Diego to further explore motivated behavior. The common life question, “Why is delicious food so irresistible?”, guided Zhu to the core arena of “hedonic eating”.

 

A breakthrough emerged in Sternson’s laboratory. The team found that neurons surrounding the locus coeruleus activate the reward center through a “dual braking system”, with dopamine cells continuously reinforcing the craving for delicious tastes.

 

Zhu pointed out that dopamine is not only “a molecule of pleasure” but more like a “deliciousness calculator”: It can predict pleasure and compares current experiences with the “best taste” in memory in real-time. This “hedonic contrast effect” explains why home-cooked meals seem bland after Michelin-starred cuisine and reveals the neural mechanism behind the “binge eating-dieting”cycle in dieters.

 

“Serendipity” is a charm of scientific research

 

During studies, the team simulated “full-sugar” and “half-sugar” milk tea with high and low concentration of sugar water. When mice alternately drank them, the dopamine activity induced by half-sugar was surprisingly negative, indicating the brain’s “disappointment” due to the experiential gap. After artificially stimulating neurons to full-sugar levels, the feeding time of mice on half-sugar matched that on full-sugar, proving that dopamine can directly “fabricate” pleasure.

 

Another surprise came from research on a popular weight-loss drug. At low doses, the drug suppresses dopamine secretion and reduces food intake. However, when the dose doubles, neuronal activity rebounds, causing appetite to return. This explains why some weight-loss drugs are effective in the early stage but trigger binge eating in the late stage. The team accordingly proposed a therapy targeting and inhibiting specific circuits, opening new avenues for obesity treatment.

 

How the brain constructs the “ladder of desire” 

 

The research progress was not smooth. In 2020, Zhu obtained a postdoctoral position at the Howard Hughes Institute but had his trip to the US delayed due to the pandemic. The net year, the laboratory relocation and equipment reconstruction took over a year. During this period, key experiments were halted owing to laboratory approval issues.

 

In his view, challenges and opportunities are always intertwined. “Being forced to pause was actually an opportunity, allowing us to deeply examine existing findings,” he recalled.

 

He thought the ultimate goal of neuroscience is not to “control the brain” but to understand how humans are driven by desires and how to transcend them. In the future, he plans to combine application with the understanding of intelligence to create a more precise “map of motivated behavior”.


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