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Why do some people find it so hard to change their minds even when faced with new facts? Scientists at MIT may have discovered an important clue hidden in our genes. According to a new study, a change in a specific gene can break a brain circuit responsible for helping us update our understanding of the world. When this system fails, the brain tends to stick to old ideas, ignoring what is actually happening.

The research focused on a gene called grin2a, which previous studies had linked to schizophrenia (精神分裂症). To test the gene’s exact role, researchers designed an experiment with mice. In the experiment, mice had to choose between two levers. One lever offered a small reward but required little effort, while the other gave a much larger reward but required more effort. As the test continued, the researchers made the large reward harder and harder to obtain.

Normal, healthy mice adapted quickly. They realized the task was no longer worth the extra effort and smoothly switched to the easier option. However, mice with the grin2a gene mutation struggled. They kept switching back and forth without a clear plan and took much longer to make a sensible choice. Their brains seemed unable to process the “update” that the situation had changed.

“Normal brains form a belief based on past experience, but they constantly adjust that belief using new sensory input,” explained Tingting Zhou, who led the study. “With this mutation, the brain weighs the old belief too heavily. It fails to use new information to correct the old view, so the mind becomes somewhat detached from reality.”

This brain pathway, which connects two key regions involved in decision-making, acts like a control center for flexible thinking. In a promising twist, when scientists used light-based technology to reactivate this specific circuit in the mice, the animals started behaving normally again and made smarter choices.

Scientists believe this brain circuit might be a common pathway for cognitive difficulties in many patients. The team is now working on finding drugs that could target this pathway to help improve thinking and decision-making in the future.

1.1.What was the main purpose of the experiment on mice?

A To cure mouse diseases.

B To test a gene’s function.

C To compare lever designs.

D To prove mice are smart.

解析：选B。B细节理解题。本题问老鼠实验的主要目的。原文第二段明确指出“To test the gene’s exact role, researchers designed an experiment with mice.”（为了测试该基因的确切作用，研究人员设计了老鼠实验），因此B项“测试基因的功能”正确。A项文中未提及治疗目标。C项“比较杠杆设计”将实验工具细节误作核心目的。D项“证明老鼠聪明”偏离科学探究本质。故选B。

2.2. How did mice with the grin2a mutation behave differently?

A They ignored the easier task entirely.

B They preferred the larger reward at first.

C They failed to form a consistent strategy.

D They stopped responding to any reward.

解析：选C。C细节理解题。根据文章第三段描述，正常小鼠能迅速调整策略转向更容易的选项，而突变小鼠则“kept switching back and forth without a clear plan and took much longer to make a sensible choice”，即它们犹豫不决，无法形成稳定、连贯的行为策略。因此选项 C “它们未能形成一致的策略” 是对原文的准确同义转述。选项 A 中的“完全忽视”过于绝对；选项 B 描述的是实验初期的普遍情况，并非突变导致的“不同”行为；选项 D 中的“停止对任何奖励反应”与原文“来回切换”相矛盾。故选C。

3.3. What does the brain circuit described in the text mainly function as?

A A storage unit for long-term beliefs.

B A monitor for physical effort levels.

C A center for updating existing views.

D A barrier against sensory interference.

解析：选C。C推理判断题。第四段指出正常大脑会 “adjust that belief using new sensory input”，但突变体无法更新。第五段称其为 “control center for flexible thinking”，故应推断为更新观点的中心。A 选项 “长期信念存储单元”、B 选项 “体力消耗监测器”、D 选项 “抵御感官干扰的屏障” 均不符合原文对该脑回路功能的定义，因此排除。故选C。

4.4.What is the significance of the study mentioned in the text?

A It confirms a new treatment for mental disorders.

B It identifies a neural basis for rigid thinking.

C It challenges previous findings on schizophrenia.

D It compares decision-making in two species.

解析：选B。B推理判断题。文章开篇提问“为何人难以改变想法”，结尾落脚于该神经回路是认知困难的 “common pathway”。B 选项准确概括：研究确定了僵化思维的神经基础。A项“Confirms a treatment”未发生（只是寻找药物阶段）；C项“Challenges”未提及；D项虽涉及人与小鼠，但研究目的不是“比较两个物种”，而是以鼠为模型。故选B。