Complexity of everyday life heart rate dynamics and attentional control in healthy students.

Effective regulation of emotions requires the ability to voluntarily manage attention, i.e. attentional control (AC), which has been related to heart rate variability and vagal tone in laboratory based research. In this study, we calculated the correlation dimension (CD), the fractal-like properties (scaling exponents ?1 and ?2, and fractal dimension) and the sample entropy of heart rate time series obtained from ECG recordings (4 hours long each) taken from a sample of healthy students (n=47) during everyday activities. AC was assessed through a self-reported questionnaire. As expected, a linear positive correlation was found between AC scores and CD and entropy, but no associations were found between AC and ?1 and fractal dimension. The association between AC and ?2 was negative and marginally significant. No associations were found between AC and linear heart rate variability measures. These results show that nonlinear measures of long, everyday life, heart rate time series may provide useful information about the AC ability of healthy students.