Light modulates hippocampal function and spatial learning in a diurnal rodent species: A study using male nile grass rat (Arvicanthis niloticus).
Light modulates hippocampal function and spatial learning in a diurnal rodent species: A study using male nile grass rat (Arvicanthis niloticus).
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作者：
Soler JE;Robison AJ;Núñez AA;Yan L
光对认知功能的影响已在人类研究中得到充分证明，更明亮的照明可改善学龄儿童，健康成人和早期痴呆症患者的认知表现。然而，潜在的神经机制还没有得到很好的理解。本研究以昼夜活动的尼罗草大鼠（Arvicanthisniloticus）为动物模型，探讨了环境光对海马功能的影响。将草大鼠圈养在12：12小时的明亮-黑暗（brLD，1000 lux）或昏暗-黑暗（dimLD，50 lux）循环中。4周后，dimLD组在Morris水迷宫（MWM）任务中显示出受损的空间记忆。当将dimLD组转移到brLD条件下再持续4周时，其MWM性能的损害得到逆转。结果表明，照明条件以类似于在人类中观察到的方式影响草鼠的认知功能，因此明亮的光线比昏暗的光线更有利于认知性能。除了行为的变化，草大鼠在dimLD条件下表现出减少表达的脑源性神经营养因子（BDNF）在海马，最明显的是在CA 1分区。与brLD组相比，dimLD组CA 1顶树突中的树突棘密度也减少，并且减少主要是蘑菇和蘑菇棘的数量。当dimLD动物转移到brLD条件4周，海马BDNF和树突棘密度显着增加。结果表明，光强度不仅影响认知能力，而且还影响海马结构的可塑性。这些研究作为一个起点，以进一步了解环境光如何调节昼夜物种的神经元和认知功能。了解光对认知的影响有助于识别认知功能下降的风险因素，并有助于开发更有效的预防和治疗临床人群中的认知障碍。
The effects of light on cognitive function have been well-documented in human studies, with brighter illumination improving cognitive performance in school children, healthy adults and patients in early stages of dementia. However, the underlying neural mechanisms are not well understood. The present study examined how ambient light affects hippocampal function using the diurnal Nile grass rats (Arvicanthis niloticus) as the animal model. Grass rats were housed in either a 12:12hr bright light-dark (brLD, 1000 lux) or dim light-dark (dimLD, 50 lux) cycle. After 4 weeks, the dimLD group showed impaired spatial memory in the Morris Water Maze (MWM) task. The impairment in their MWM performance were reversed when the dimLD group were transferred to the brLD condition for another 4 weeks. The results suggest that lighting conditions influence cognitive function of grass rats in a way similar to that observed in humans, such that bright light is beneficial over dim light for cognitive performance. In addition to the behavioral changes, grass rats in the dimLD condition exhibited reduced expression of brain-derived neurotrophic factor (BDNF) in the hippocampus, most notably in the CA1 subregion. There was also a reduction in dendritic spine density in CA1 apical dendrites in dimLD compared to the brLD group, and the reduction was mostly in the number of mushroom and stubby spines. When dimLD animals were transferred to the brLD condition for 4 weeks, the hippocampal BDNF and dendritic spine density significantly increased. The results illustrate that not only does light intensity affect cognitive performance, but that it also impacts hippocampal structural plasticity. These studies serve as a starting point to further understand how ambient light modulates neuronal and cognitive functions in diurnal species. A mechanistic understanding of the effects of light on cognition can help to identify risk factors for cognitive decline and contribute to the development of more effective prevention and treatment of cognitive impairment in clinical populations.
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