Sensory and Motor Systems Research Group, Korea Brain Research Institute, 61, Cheomdan-ro, Dong-gu, Daegu, 41068, South Korea.
Division of Biology, Indian Institute of Science Education and Research Pune, Pune, Maharashtra, India.
Sci Rep. 2021 Oct 13;11(1):20350. doi: 10.1038/s41598-021-99456-w.
Behaviors driven by intrinsic motivation are critical for development and optimization of physical and brain functions, but their underlying mechanisms are not well studied due to the complexity and autonomy of the behavior. Songbirds, such as zebra finches, offer a unique opportunity to study neural substrates of intrinsic motivation because they spontaneously produce many renditions of songs with highly-quantifiable structure for vocal practice, even in the absence of apparent recipients ("undirected singing"). Neural substrates underlying intrinsic motivation for undirected singing are still poorly understood partly because singing motivation cannot be easily manipulated due to its autonomy. Also, undirected singing itself acts as an internal reward, which could increase singing motivation, leading to difficulty in measuring singing motivation independent of singing-associated reward. Here, we report a simple procedure to easily manipulate and quantify intrinsic motivation for undirected singing independent of singing-associated reward. We demonstrate that intrinsic motivation for undirected singing is dramatically enhanced by temporary suppression of singing behavior and the degree of enhancement depends on the duration of suppression. Moreover, by examining latencies to the first song following singing suppression as a measure of singing motivation independent of singing-associated reward, we demonstrate that intrinsic singing motivation is critically regulated by dopamine through D2 receptors. These results provide a simple experimental tool to manipulate and measure the intrinsic motivation for undirected singing and illustrate the importance of zebra finches as a model system to study the neural basis of intrinsically-motivated behaviors.
内在动机驱动的行为对于身体和大脑功能的发展和优化至关重要，但由于行为的复杂性和自主性，其潜在机制尚未得到很好的研究。鸣禽，如斑马雀，为研究内在动机的神经基质提供了一个独特的机会，因为它们自发地产生许多具有高度可量化结构的歌曲版本，即使在没有明显接受者的情况下（“无定向歌唱”）。无定向歌唱的内在动机的神经基质仍未得到很好的理解，部分原因是由于其自主性，歌唱动机不容易被操纵。此外，无定向歌唱本身就是一种内部奖励，这可能会增加歌唱动机，导致难以独立于歌唱相关奖励来衡量歌唱动机。在这里，我们报告了一种简单的程序，可以轻松地操纵和量化无定向歌唱的内在动机，而不受歌唱相关奖励的影响。我们证明，通过暂时抑制歌唱行为，可以显著增强无定向歌唱的内在动机，并且增强的程度取决于抑制的持续时间。此外，通过检查歌唱抑制后第一首歌的潜伏期作为独立于歌唱相关奖励的歌唱动机的衡量标准，我们证明了内在歌唱动机受到多巴胺通过 D2 受体的严格调节。这些结果提供了一种简单的实验工具，可以操纵和衡量无定向歌唱的内在动机，并说明了斑马雀作为研究内在动机行为神经基础的模型系统的重要性。
