中国科技网9月21日报道（张微 编译）当你正开车经过一个十字路口时，交通灯突然变成红色。这时候你能及时踩刹车。

约翰霍普金斯大学的研究人员，与国家老龄化研究所的科学家们合作，已经找到了使大脑做出这类瞬间变化过程的神经细胞。在最新一期的《自然神经科学》杂志上，研究团队表明，当基底前脑的神经元被压制时，这些自我控制的能力就发挥作用了。

“这项研究发现了基底前脑神经元在控制行动方面的一个新作用，”约翰 霍普金斯大学心里和神经科学教授，米凯拉 加拉格尔和克里格-艾森豪威尔说。这项研究为聚焦于在一定的神经和精神条件下，影响大脑基本认知功能的回路研究的创新方法，开启了一扇新的大门。

快速阻止一种行为的能力对我们的日常生活非常关键——如果在过马路时，一辆汽车意外出现，那么我们能够立刻做出反应;在开会的时候，如果手机在口袋中震动，而不去看手机;当击球的时候，如果场地条件差就不要做摆动。更好地理解所谓反应性抑制，这个认识机制背后的原因，可以帮助患有神经状况疾病的人降低患病风险(这些人的控制能力减弱)，包括阿尔茨海默氏病和帕金森病，以及注意缺陷多动障碍和正常老化。

科学家们认为能够阻止计划好的行为发生的区域是基底神经节，大脑中的这个区域负责各种运动控制功能，包括启动一个动作或行为的能力。然而，这项研究表明，停止反应发生在基底前脑，大脑中最著名的调节睡眠的部分，也被公认为是一个阿尔茨海默氏病的早期神经退行性疾病发生的地点。

研究人员训练小鼠鼠玩一个游戏：如果小鼠听到一个音调后很快地移动，他们得到奖励。当一道光闪烁的时候，小鼠们停下来也会得到了奖励。在此期间，研究团队监测小鼠基底前脑的电信号。

研究人员训练小鼠快速移动来得到奖励。听到一个音调后，小鼠就会冲到一个新地点去喝蔗糖水。但是，当音调停止后接下来是一道闪光，小鼠们就会立刻停留在原地来获得奖励。换句话说，当闪光的时候，奖励规则相反，不是移动才能获得奖励，小鼠们不得不取消计划好的反应，停在原地不动才能得到奖励。

小鼠们完成任务后，研究团队监测了单个基底前神经元的活动。研究人员可以不用闪光而是用小的电脉冲刺激相同的神经元来阻止小鼠的移动。

“在实验室里，我们能够操纵这些神经元，造成小鼠停止他们的行为即使他们没有理由这样做，” 这项研究的主要作者杰夫瑞D. 梅瑟说，他作为霍普金斯大学的博士生参与了这项研究，现在是布朗大学的博士后。

“了解这些细胞是如何参与这种形式的自我控制行为，能够丰富我们正常大脑回路参与日常决策的相关知识，”他说，“并且对于未来治疗反应性抑制受损症状的疾病绝对是非常关键。”

How the brain can stop action on a dime

You're about to drive through an intersection when the light suddenly turns red. But you're able to slam on the brakes, just in time.

Johns Hopkins University researchers, working with scientists at the National Institute on Aging, have revealed the precise nerve cells that allow the brain to make this type of split-second change of course. In the latest issue of the journal Nature Neuroscience, the team shows that these feats of self-control happen when neurons in the basal forebrain are silenced.

"The study discovered a new role for basal forebrain neurons in the control of action," said Michela Gallagher, the Krieger-Eisenhower Professor of Psychology and Neuroscience at Johns Hopkins. "This work opens the door to novel approaches focused on this circuit in certain neurological and psychiatric conditions that affect basic cognitive functions of the brain."

The ability to rapidly stop a behavior is critical for everyday functioning—allowing people crossing the street to freeze if a car surprises them, to not reach for their phone when it vibrates in their pocket during a meeting or, in the case of a batter, to stop from swinging at a bad pitch. A better understanding of the cognitive mechanics behind what's known as reactive inhibition could help people suffering from neurological conditions where such control is diminished—everything from Alzheimer's disease and Parkinson's disease to attention deficit hyperactivity disorder and normal aging.

Scientists had assumed the ability to stop a planned behavior occurred in the basal ganglia, an area in the brain responsible for a variety of motor control functions including the ability to start an action or a behavior. This study demonstrates, however, that the stop response happens in the basal forebrain, a part of the brain best known for regulating sleep, but also recognized as a site for early neurodegeneration in Alzheimer's disease.

The researchers trained rats to play a game: If the rats quickly moved after hearing a tone, they got a treat. The rats were also rewarded if they stopped moving when a light flashed. All the while, the team monitored the rats for electrical signals in the basal forebrain.

The researchers trained rats to move quickly to get a treat. After hearing a tone, the rats would rush into a new port to lick sucrose water. But, when the tone was followed by a flash of light, the rats would have to immediately stay in place to get a treat. In other words, when the light flashed, the rule of reward reversed—instead of moving quickly to get reward, the rats had to cancel that planned response and stay still to get their treat.

While the rats performed the tasks, the team monitored the activity of individual basal forebrain neurons. The researchers were also able to get the rats to stop without using the flash of light by stimulating the same neurons with a small pulse of electricity.

"In the lab, we were able to manipulate these neurons, which caused rats to stop their behavior even though they had no reason to do so," said lead author Jeffrey D. Mayse, who conducted the research as a Johns Hopkins doctoral student and is now a postdoctoral fellow at Brown University.

"Understanding how these cells are involved in this form of self-control expands our knowledge of the normal brain circuits involved in everyday decision-making," he said, "and will be absolutely critical to developing future treatments and therapies for diseases and disorders with impaired reactive inhibition as a symptom."

来源：中国科技网