Department of Pharmacology and Physiology, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA.
Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, Child Health Institute of New Jersey, New Brunswick, NJ, USA.
J Neurosci Res. 2021 Sep;99(9):2046-2058. doi: 10.1002/jnr.24857. Epub 2021 May 28.
Digging behavior is often used to test motor function and repetitive behaviors in mice. Different digging paradigms have been developed for behaviors related to anxiety and compulsion in mouse lines generated to recapitulate genetic mutations leading to psychiatric and neurological disorders. However, the interpretation of these tests has been confounded by the difficulty of determining the motivation behind digging in mice. Digging is a naturalistic mouse behavior that can be focused toward different goals, that is foraging for food, burrowing for shelter, burying objects, or even for recreation as has been shown for dogs, ferrets, and human children. However, the interpretation of results from current testing protocols assumes the motivation behind the behavior often concluding that increased digging is a repetitive or compulsive behavior. We asked whether providing a choice between different types of digging activities would increase sensitivity to assess digging motivation. Here, we present a test to distinguish between burrowing and exploratory digging in mice. We found that mice prefer burrowing when the option is available. When food restriction was used to promote a switch from burrowing to exploration, males readily switched from burrowing to digging outside, while females did not. In addition, when we tested a model of intellectual disability and autism spectrum disorder that had shown inconsistent results in the marble burying test, the Cc2d1a conditional knockout mouse, we found greatly reduced burrowing only in males. Our findings indicate that digging is a nuanced motivated behavior and suggest that male and female rodents may perform it differently.
挖掘行为通常用于测试小鼠的运动功能和重复性行为。为了模拟导致精神和神经疾病的基因突变，已经开发出了不同的挖掘范式来研究与焦虑和强迫行为相关的行为。然而，这些测试的解释受到了确定小鼠挖掘背后动机的困难的影响。挖掘是一种自然的小鼠行为，可以专注于不同的目标，例如觅食、挖洞寻找庇护所、埋东西，甚至像狗、雪貂和人类儿童一样为了娱乐而挖掘。然而，当前测试方案的结果解释假设行为背后的动机通常认为增加挖掘是一种重复性或强迫性行为。我们想知道，在不同类型的挖掘活动之间提供选择是否会提高评估挖掘动机的敏感性。在这里，我们提出了一种区分小鼠挖掘和探索性挖掘的测试方法。我们发现，当有选择时，小鼠更喜欢挖掘。当通过食物限制促使它们从挖掘转向探索时，雄性小鼠很容易从挖掘转向在外面挖掘，而雌性则不会。此外，当我们测试一种智力障碍和自闭症谱系障碍模型时，即 Cc2d1a 条件性敲除小鼠，在大理石埋藏测试中表现出不一致的结果，我们发现雄性小鼠的挖掘行为明显减少。我们的研究结果表明，挖掘是一种复杂的动机行为，并且提示雄性和雌性啮齿动物可能以不同的方式进行挖掘。
