There is growing awareness that repeated mild traumatic brain injury (r-mTBI) can cause deficits in learning and memory performance, however there is still a paucity of preclinical data identifying the extent of these deficits. Epidemiological data shows that juveniles are at high risk to sustain r-mTBI, and these injuries may cause significant changes in cognitive abilities, as they occur during a period where the brain is still maturing. This is particularly true for the hippocampus, a brain region important for learning and memory processes. R-mTBI during the juvenile period may disrupt functional capacity of the hippocampus, and thus the normal development of cognitive processes associated with this structure. To examine this issue we used a model of awake closed head injury (ACHI) and administered 8 impacts over a 4 day period to juvenile male and female rats (P25-28). A neurological assessment was preformed after each impact, and anxiety and learning related behaviours were examined 1 and 7 days after the last impact. Our results indicate that r-mTBI was associated with sensorimotor deficits in the acute phase immediately after each procedure. R-mTBI also reduced the capacity for hippocampal-dependent learning for at least 7 days post-injury, but did not result in any long-lasting changes in anxiety-related behaviours.

中文翻译：

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反复轻度脑外伤后幼年大鼠海马认知障碍

人们越来越认识到，反复轻度创伤性脑损伤（r-mTBI）会导致学习和记忆能力缺陷，但仍缺乏确定这些缺陷程度的临床前数据。流行病学数据显示，青少年遭受 r-mTBI 的风险很高，而且这些损伤可能会导致认知能力发生显着变化，因为它们发生在大脑尚未成熟的时期。对于海马体来说尤其如此，海马体是一个对学习和记忆过程很重要的大脑区域。青少年时期的 R-mTBI 可能会破坏海马体的功能，从而破坏与该结构相关的认知过程的正常发展。为了研究这个问题，我们使用了清醒闭合性头部损伤 (ACHI) 模型，并在 4 天内对幼年雄性和雌性大鼠进行 8 次撞击 (P25-28)。每次撞击后均进行神经学评估，并在最后一次撞击后 1 天和 7 天检查焦虑和学习相关行为。我们的结果表明，r-mTBI 与每次手术后急性期的感觉运动缺陷相关。 R-mTBI 还降低了受伤后至少 7 天的海马依赖性学习能力，但并未导致焦虑相关行为发生任何持久的变化。