Radiation Oncology, USA; Center for Integrative Neuroscience and Inflammatory Diseases, Eastern Virginia Medical School, Macon and Joan Brock Virginia Health Sciences at Old Dominion University, Norfolk, VA. 23507, USA.
Radiation Oncology, USA.
Life Sci Space Res (Amst). 2024 Nov;43:68-74. doi: 10.1016/j.lssr.2024.09.001. Epub 2024 Sep 19.
NASA's decision to resume manned deep space mission, first to the Moon and then Mars, necessitated a detailed assessment of the potential health effects that astronauts may experience on long-duration missions. Multiple studies suggest that there may be significant space radiation (SR)-induced impairment of neurocognitive processes, including advanced executive functions. However, given the multitude of SR-induced changes in the CNS, it is possible that completely different SR-induced sequelae will be induced in previously exposed individuals. Thus, current risk estimates are likely to be pertinent only for the early stages of a deep space mission, and even then only for astronauts that have no previous experience in space. In this study, rats that maintained high attentional set shifting (ATSET) performance after an initial exposure to 10 cGy of SR (either 250 MeV/n He or GCRsim), were exposed to an additional dose of 10 cGy GCRsim and their ATSET performance reassessed. The re-irradiated rats exhibited significant impairment of ATSET performance, however, the performance decrements differed in two important aspects from those typically observed after single exposures. First, the decrements were manifested when the rats were required to perform set shifting, specifically in the IDR and EDS stages of the ATSET test. Secondly, the main performance decrement was in a loss of processing speed, which in the IDR stage resulted in the re-irradiated rats taking 2-fold more time to solve the problem than did Sham rats. The functional consequence of this decrement was that compared to Sham rats, 20 % fewer SR-exposed rats solved the IDS and EDR problems within 20 s. These data suggests that prior SR exposure alters nature of ATSET impairments from that observed in radiation-naïve individuals. Risk estimates derived from studies that use radiation naïve rats may thus not fully reflect the incidence and nature of ATSET performance deficits that could occur over the entire duration of a mission to Mars, or in astronauts who return to deep space on multiple occasions. It would thus be germane to conduct in-flight monitoring for cognitive performance decrements observed in both radiation naïve and exposed rats during the mission, and ensure that the crew has sufficient overlapping skill sets to minimize the operational impact of these additional cognitive impairments.
美国国家航空航天局（NASA）决定恢复载人深空任务，首先是登月，然后是火星，这就需要对宇航员在长时间任务中可能经历的潜在健康影响进行详细评估。多项研究表明，空间辐射（SR）可能会对神经认知过程造成严重损害，包括高级执行功能。然而，鉴于中枢神经系统中存在大量的 SR 诱导变化，之前暴露于辐射的个体可能会出现完全不同的 SR 诱导后遗症。因此，目前的风险估计可能仅适用于深空任务的早期阶段，而且即使对于没有太空飞行经验的宇航员来说，也仅适用于早期阶段。在这项研究中，大鼠在初次接受 10 cGy SR（250 MeV/n He 或 GCRsim）照射后保持高注意力设置转换（ATSET）性能，然后再接受 10 cGy GCRsim 的额外剂量照射，并重新评估其 ATSET 性能。再次照射的大鼠的 ATSET 性能明显受损，但是，与单次照射后通常观察到的性能下降相比，这些下降在两个重要方面有所不同。首先，当大鼠需要进行设置转换时，特别是在 ATSET 测试的 IDR 和 EDS 阶段，会出现下降。其次，主要的性能下降是处理速度的下降，在 IDR 阶段，再照射的大鼠解决问题的时间比 Sham 大鼠长两倍。这种下降的功能后果是，与 Sham 大鼠相比，只有 20%的 SR 暴露大鼠在 20 秒内解决了 IDS 和 EDR 问题。这些数据表明，先前的 SR 暴露改变了 ATSET 损伤的性质，使其与辐射未受影响的个体所观察到的不同。因此，使用未受辐射的大鼠进行的研究得出的风险估计可能无法完全反映在火星任务的整个期间或多次返回深空的宇航员中可能发生的 ATSET 性能缺陷的发生率和性质。因此，在任务期间，对辐射未受影响和受影响的大鼠的认知性能下降进行飞行中监测，并确保机组人员具有足够的重叠技能集，以最小化这些额外认知障碍对操作的影响，这将是相关的。
