Multifractal Spectrum Analysis of Heart Rhythm during Internally and Externally Operative Attention

Heart and brain are two most complex physiological structures of the human body and both continually interplay to mediate the human cognitive information processing. This paper identifies non-linear variations of heart rhythm acquired during internally and externally operative attention using multifractal analysis. To study internally and externally operative attention, fourteen healthy subjects performed the experiment designed as per Posner's spatial orienting paradigm. The multifractal spectrum width for the baseline and recovery session was observed as 1.35 ± 0.21 and 1.41 ± 0.14 (mean ± standard deviation) respectively, which reveals that the heart rhythm exhibit existence of long-range correlation and Gaussian spectrum shape. Moreover, for internally operative attention task, the subjects shown significant variation from baseline and recovery session with spectrum width 1.28 ± 0.21 and no change in multifractal spectrum shape. However, for the externally operative attention task, subjects shown significant variation from baseline, while insignificant variation from recovery session with spectrum width 1.31 ± 0.19 and no change in spectrum shape. Although for internally and externally operative attention task the multifractal-dimension analysis reveals that heart rhythm possessed fractal behaviour with reduced spectrum width and no change in shape of multifractal spectrum with respect to baseline and recovery session. Fractal variations of heart rhythm found to quantify internally and externally operative attention with respect to baseline and recovery session, which may support us to design robust braincomputer interfaces, accelerated sports and defense training paradigms.