改变口味偏好?Nature拿小鼠“开刀”,解析背后机制
2018/06/04
味觉系统是我们品尝食物、建立口味喜好的基础。现在,来自于哥伦比亚大学Zuckerman研究所的科学家们以小鼠为模型,进行了一系列“改变其味觉偏好”的试验。他们通过控制大脑中的特定区域,使得小鼠厌恶甜食。


图片来源:Pixabay

这一研究以“The coding of valence and identity in the mammalian taste system”为题发表在《Nature》期刊。研究团队通过调控小鼠大脑杏仁核(amygdala)区域的开关,将品尝到的甜味转变成厌恶的味道,且让苦味变成令人满意的味道。这为理解、治疗包括肥胖和神经性厌食症等在内的疾病提供了新的策略。


doi:10.1038/s41586-018-0165-4

杏仁核

杏仁核附着在海马区的末端,是产生、处理情绪以及控制学习、压力等能力的重要区域。之前已有研究表明,杏仁核直接与大脑的味觉皮层相连。

在该研究中,科学家们重点验证了杏仁核对于味觉的作用。他们发现,跟味觉皮层一样,杏仁核存在感知甜味、苦味的不同区域。

改变味觉?


小鼠大脑杏仁核区域,负责甜味(绿色)、苦味(红色)的不同神经连接。(图片来源:Li Wang/Zuker Lab/Columbia's Zuckerman Institute)

随后,他们进一步提出设想:单独操控这些区域,并观察小鼠的行为变化。

结果让他们惊喜:当利用激光刺激技术人为地“打开”杏仁核中连接甜味区域的神经,小鼠对普通水的反应类似于吃糖。

此外,通过操纵相同类型的神经连接,研究人员甚至可以改变一种味道的感知质量,即把甜味变成一种让小鼠讨厌的味道,把苦味变成一种吸引小鼠的味道。

最后,当研究人员关闭杏仁核区域的神经连接(没有触及味觉皮层)后,结果显示,小鼠会照常进食,但是没有表现出对甜食的偏好或者对苦味的嫌弃。

“这就像你吃了一口曾经最喜欢的巧克力蛋糕,却没有从中得到任何乐趣一样。”研究人员解释道。

这些结果表明,大脑中复杂的味觉系统由“可单独分离、修改或者移除”的离散单元构成。

责编:艾曼

参考资料:

Sweet tooth? Brain-tinkering study makes sugar taste vile

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  • The coding of valence and identity in the mammalian taste system

    The ability of the taste system to identify a tastant (what it tastes like) enables animals to recognize and discriminate between the different basic taste qualities1,2. The valence of a tastant (whether it is appetitive or aversive) specifies its hedonic value and elicits the execution of selective behaviours. Here we examine how sweet and bitter are afforded valence versus identity in mice. We show that neurons in the sweet-responsive and bitter-responsive cortex project to topographically distinct areas of the amygdala, with strong segregation of neural projections conveying appetitive versus aversive taste signals. By manipulating selective taste inputs to the amygdala, we show that it is possible to impose positive or negative valence on a neutral water stimulus, and even to reverse the hedonic value of a sweet or bitter tastant. Remarkably, mice with silenced neurons in the amygdala no longer exhibit behaviour that reflects the valence associated with direct stimulation of the taste cortex, or with delivery of sweet and bitter chemicals. Nonetheless, these mice can still identify and discriminate between tastants, just as wild-type controls do. These results help to explain how the taste system generates stereotypic and predetermined attractive and aversive taste behaviours, and support the existence of distinct neural substrates for the discrimination of taste identity and the assignment of valence. Subscribe to Nature for full access:

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