Toyoshima Michimasa, Yamada Kazuo, Sugita Manami, Ichitani Yukio
Institute of Psychology and Behavioral Neuroscience, University of Tsukuba, Tsukuba, Ibaraki, 305-8577, Japan.
Anim Cogn. 2018 May;21(3):345-351. doi: 10.1007/s10071-018-1171-5. Epub 2018 Feb 27.
The social environment is thought to have a strong impact on cognitive functions. In the present study, we investigated whether social enrichment could affect rats' memory ability using the "Different Objects Task (DOT)," in which the levels of memory load could be modulated by changing the number of objects to be remembered. In addition, we applied the DOT to a social discrimination task using unfamiliar conspecific juveniles instead of objects. Animals were housed in one of the three different housing conditions after weaning [postnatal day (PND) 21]: social-separated (1 per cage), standard (3 per cage), or social-enriched (10 per cage) conditions. The object and social recognition tasks were conducted on PND 60. In the sample phase, the rats were allowed to explore a field in which 3, 4, or 5 different, unfamiliar stimuli (conspecific juveniles through a mesh or objects) were presented. In the test phase conducted after a 5-min delay, social-separated rats were able to discriminate the novel conspecific from the familiar ones only under the condition in which three different conspecifics were presented; social-enriched rats managed to recognize the novel conspecific even under the condition of five different conspecifics. On the other hand, in the object recognition task, both social-separated and social-enriched rats were able to discriminate the novel object from the familiar ones under the condition of five different objects. These results suggest that social enrichment can enhance social, but not object, memory span.
社会环境被认为对认知功能有强烈影响。在本研究中，我们使用“不同物体任务（DOT）”来调查社会丰富化是否会影响大鼠的记忆能力，在该任务中，可以通过改变要记忆的物体数量来调节记忆负荷水平。此外，我们将DOT应用于一项社会辨别任务，使用不熟悉的同种幼体而非物体。断奶后（出生后第21天，PND），将动物饲养在三种不同的饲养条件之一：社会隔离（每笼1只）、标准（每笼3只）或社会丰富化（每笼10只）条件。物体和社会识别任务在PND 60进行。在样本阶段，让大鼠探索一个场地，其中呈现3、4或5种不同的、不熟悉的刺激物（通过网眼看到的同种幼体或物体）。在延迟5分钟后进行的测试阶段，社会隔离的大鼠仅在呈现三种不同同种个体的条件下能够区分新的同种个体和熟悉的同种个体；社会丰富化的大鼠即使在呈现五种不同同种个体的条件下也能识别出新的同种个体。另一方面，在物体识别任务中，社会隔离和社会丰富化的大鼠在呈现五种不同物体的条件下都能够区分新物体和熟悉的物体。这些结果表明，社会丰富化可以增强社会记忆跨度，但不能增强物体记忆跨度。
