“…Spectral indices of HRV have been used to assess the dynamics of the ANS, and it was suggested that the markers of parasympathetic and sympathetic activities are largely found in the HFs and LFs, respectively (Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology, 1996). The effects of sleep deprivation on HRV have been extensively studied, with different levels of success (Chua et al, 2012;Fogt, Cooke, Kalns, & Michael, 2011;Fogt, Kalns, & Michael, 2010;Glos, Fietze, Blau, Baumann, & Penzel, 2014;Nakano et al, 2000;Pagani et al, 2009;Vicente, Laguna, Bartra, & Bailón, 2016;Viola, James, Archer, & Dijk, 2008;Zhong et al, 2005). In general, these studies found that HRV alone has a limited potential to delineate the effects of sleep deprivation.…”