Physiological fractals: visual and statistical evidence across timescales and experimental states.
Journal of the Royal Society, Interface June 1, 2020 Jeffrey J Kim, Stacey Parker, Trent Henderson et al.
Heart-rate variability (HRV) increases during compassion meditation, but the best timescale for measuring it and how the signal's stability changes over time remain unclear. Applying advanced time-series analyses to data from a two-week compassionate mind training intervention, the authors found that the pattern of HRV correlations across resting and meditation states was similar across multiple recording timescales, indicating a fractal-like property. After training, the HRV signal during compassion meditation became more highly correlated and less stochastic (variable) than before training, and the average difference between rest and meditation states decreased. These results offer new visual and statistical markers of HRV change across experimental states.