Centre for Human Brain Health, University of Birmingham, Birmingham B15 2TT, UK; Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, UK; Turner Institute for Brain and Mental Health, School of Psychological Sciences, Monash University, VIC 3168, Australia.
School of Medical Sciences, University of Campinas, Campinas, SP 13083-970, Brazil.
Neuroimage. 2021 May 15;232:117840. doi: 10.1016/j.neuroimage.2021.117840. Epub 2021 Feb 9.
Functional connectivity (FC) of the motor network (MN) is often used to investigate how intrinsic properties of the brain are associated with motor abilities and performance. In addition, the MN is a key feature in clinical work to map the recovery after stroke and aid the understanding of neurodegenerative disorders. Time of day variation and individual differences in circadian timing, however, have not yet been considered collectively when looking at FC.
A total of 33 healthy, right handed individuals (13 male, 23.1 ± 4.2 years) took part in the study. Actigraphy, sleep diaries and circadian phase markers (dim light melatonin onset and cortisol awakening response) were used to determine early (ECP, n = 13) and late (LCP, n = 20) circadian phenotype groups. Resting state functional MRI testing sessions were conducted at 14:00 h, 20:00 h and 08:00 h and preceded by a maximum voluntary contraction test for isometric grip strength to measure motor performance.
Significant differences in FC of the MN between ECPs and LCPs were found, as well as significant variations between different times of day. A higher amplitude in diurnal variation of FC and performance was observed in LCPs compared to ECPs, with the morning being most significantly affected. Overall, lower FC was significantly associated with poorer motor performance.
Our findings uncover intrinsic differences between times of day and circadian phenotype groups. This suggests that central mechanisms contribute to diurnal variation in motor performance and the functional integrity of the MN at rest influences the ability to perform in a motor task.
运动网络（MN）的功能连接（FC）通常用于研究大脑的内在特性如何与运动能力和表现相关。此外，MN 是临床工作中的一个关键特征，用于绘制中风后的恢复情况，并帮助理解神经退行性疾病。然而，在研究 FC 时，尚未综合考虑时间变化和昼夜节律定时的个体差异。
共有 33 名健康、右利手的个体（13 名男性，23.1±4.2 岁）参与了研究。活动记录仪、睡眠日记和昼夜节律相位标志物（暗光褪黑素起始时间和皮质醇觉醒反应）用于确定早期（ECP，n=13）和晚期（LCP，n=20）昼夜表型组。在进行静息状态功能磁共振成像测试之前，进行了最大自主收缩测试，以测量等长握力的运动表现，测试时间分别为 14:00、20:00 和 08:00。
ECP 和 LCP 之间 MN 的 FC 存在显著差异，并且不同时间之间也存在显著差异。与 ECP 相比，LCP 中 FC 和表现的昼夜变化幅度更高，早晨的变化最为显著。总的来说，较高的 FC 昼夜变化幅度与较差的运动表现显著相关。
我们的研究结果揭示了不同时间和昼夜表型组之间的内在差异。这表明中枢机制有助于运动表现的昼夜变化，以及 MN 在静息状态下的功能完整性会影响完成运动任务的能力。
