Achterberg E J M, Burke C J, Pellis S M
Behavioural Neuroscience Division, Department of Population Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands.
Department of Neuroscience, University of Lethbridge, Lethbridge, Canada; Department of Pharmacology, McGill University, Montreal, Canada.
Behav Processes. 2023 Oct;212:104933. doi: 10.1016/j.beproc.2023.104933. Epub 2023 Aug 27.
Social play in rats is rewarding and important for the development of brain and social skills. There are differences in the amount of play behavior displayed among individuals, with earlier studies suggesting that, despite variation across trials, individual differences tend to be consistent. In the present study, juvenile Lister-hooded rats were paired with a different, unfamiliar same-sex partner on three days and based on the amount of play each individual initiated, it was characterized as a high, medium or low player. Using this categorization, we explored three features related to individual differences. First, we show that by increasing the number of test days from two, as was done in a previous study (Lesscher et al., 2021), to three, characterization was effectively improved. Secondly, while the earlier study only used males, the present study showed that both sexes exhibit a similar pattern of individual differences in the degree of playfulness. Even though low players consistently initiated less play than medium and high players, all rats varied in how much play they initiated from one trial to the next. Thirdly, we assessed two potential mechanisms by which the playfulness of one rat can modify the level of playfulness of the other rat (i.e., emotional contagion vs homeostasis). Analyses of individuals' contribution to the play of dyads suggest that rats consistently adjust their play behavior depending on the behavior displayed by the partner. Since this adjustment can be positive or negative, our data support a homeostatic mechanism, whereby individuals increase or decrease the amount of play they initiate, which results in the experience of an overall stable pattern of play across trials. Future research will investigate the neural bases for individual differences in play and how rats maintain a preferred level of play.
大鼠的社交玩耍对大脑和社交技能的发展具有奖励作用且至关重要。个体之间表现出的玩耍行为数量存在差异，早期研究表明，尽管各次试验存在差异，但个体差异往往具有一致性。在本研究中，幼年利斯特戴帽大鼠在三天内与不同的、不熟悉的同性伙伴配对，并根据每个个体发起的玩耍量，将其分为高、中、低玩耍者。利用这种分类，我们探索了与个体差异相关的三个特征。首先，我们表明，通过将测试天数从之前研究（Lesscher等人，2021年）中的两天增加到三天，分类得到了有效改善。其次，虽然早期研究只使用了雄性大鼠，但本研究表明，两性在玩耍程度上表现出相似的个体差异模式。尽管低玩耍者发起的玩耍始终比中、高玩耍者少，但所有大鼠在每次试验中发起的玩耍量都有所不同。第三，我们评估了两种潜在机制，即一只大鼠的玩耍性如何改变另一只大鼠的玩耍水平（即情绪感染与内稳态）。对个体在二元组玩耍中贡献的分析表明，大鼠会根据伙伴展示的行为持续调整自己的玩耍行为。由于这种调整可以是积极的或消极的，我们的数据支持一种内稳态机制，即个体增加或减少他们发起的玩耍量，从而在各次试验中产生总体稳定玩耍模式的体验。未来的研究将调查玩耍中个体差异的神经基础以及大鼠如何维持偏好的玩耍水平。
