Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, United States.
German Aerospace Center (DLR), Cologne, Germany.
Front Neural Circuits. 2022 Mar 2;16:784280. doi: 10.3389/fncir.2022.784280. eCollection 2022.
The altered vestibular signaling and somatosensory unloading of microgravity result in sensory reweighting and adaptation to conflicting sensory inputs. Aftereffects of these adaptive changes are evident postflight as impairments in behaviors such as balance and gait. Microgravity also induces fluid shifts toward the head and an upward shift of the brain within the skull; these changes are well-replicated in strict head-down tilt bed rest (HDBR), a spaceflight analog environment. Artificial gravity (AG) is a potential countermeasure to mitigate these effects of microgravity. A previous study demonstrated that intermittent (six, 5-mins bouts per day) daily AG sessions were more efficacious at counteracting orthostatic intolerance in a 5 day HDBR study than continuous daily AG. Here we examined whether intermittent daily AG was also more effective than continuous dosing for mitigating brain and behavioral changes in response to 60 days of HDBR. Participants ( = 24) were split evenly between three groups. The first received 30 mins of continuous AG daily (cAG). The second received 30 mins of intermittent AG daily (6 bouts of 5 mins; iAG). The third received no AG (Ctrl). We collected a broad range of sensorimotor, cognitive, and brain structural and functional assessments before, during, and after the 60 days of HDBR. We observed no significant differences between the three groups in terms of HDBR-associated changes in cognition, balance, and functional mobility. Interestingly, the intermittent AG group reported less severe motion sickness symptoms than the continuous group during centrifugation; iAG motion sickness levels were not elevated above those of controls who did not undergo AG. They also had a shorter duration of post-AG illusory motion than cAG. Moreover, the two AG groups performed the paced auditory serial addition test weekly while undergoing AG; their performance was more accurate than that of controls, who performed the test while in HDBR. Although AG did not counteract HDBR-induced gait and balance declines, iAG did not cause motion sickness and was associated with better self-motion perception during AG ramp-down. Additionally, both AG groups had superior cognitive performance while undergoing AG relative to controls; this may reflect attention or motivation differences between the groups.
微重力导致前庭信号改变和躯体感觉卸载,从而导致感觉重新加权和适应冲突的感觉输入。这些适应变化的后效在飞行后表现为平衡和步态等行为受损。微重力还会导致液体向头部转移,大脑在颅骨内向上移位;这些变化在严格的头低位卧床休息(HDBR)中得到很好的复制,这是一种太空飞行模拟环境。人工重力(AG)是减轻微重力影响的潜在对策。先前的研究表明,在 5 天 HDBR 研究中,间歇性(每天 6 次,每次 5 分钟)每日 AG 治疗比连续每日 AG 更有效地对抗直立不耐受。在这里,我们研究了间歇性每日 AG 是否也比连续给药更有效地减轻 60 天 HDBR 对大脑和行为的影响。参与者(= 24)平均分为三组。第一组每天接受 30 分钟连续 AG(cAG)。第二组每天接受 30 分钟间歇性 AG(6 次 5 分钟;iAG)。第三组不接受 AG(Ctrl)。我们在 HDBR 之前、期间和之后收集了广泛的感觉运动、认知和大脑结构和功能评估。我们观察到,在 HDBR 相关的认知、平衡和功能性移动变化方面,三组之间没有显著差异。有趣的是,在离心机中,间歇性 AG 组报告的晕车症状比连续组轻;iAG 的晕车水平没有高于未接受 AG 的对照组。他们在 AG 后的幻觉运动持续时间也比 cAG 短。此外,在接受 AG 的同时,两组每周进行 paced auditory serial addition test;他们的表现比在 HDBR 中进行测试的对照组更准确。虽然 AG 没有抵消 HDBR 引起的步态和平衡下降,但 iAG 不会引起晕车,并且在 AG 减速期间与更好的自我运动感知相关。此外,在接受 AG 时,两组的认知表现都优于对照组;这可能反映了两组之间的注意力或动机差异。