Temporal Stability of Higuchi's Fractal Dimension in EEG Signals of Healthy Individuals

The current study aims to evaluate the temporal stability of Higuchi's Fractal Dimension (HFD) in the electroencephalographic (EEG) signals of healthy individuals. HFD depends on a single tuning parameter, k_max, which indicates the time scale range in which fractality is analyzed. A k_max value that provides stable HFD values for healthy individuals is expected to allow easier detection of deviations in brain activity associated with neurological disorders. To identify the stable region, EEG signals from 15 healthy participants, recorded twice over a three-year period, were analyzed. HFD temporal stability at different k_max values was assessed using the intraclass correlation coefficient between sessions. We hypothesized that HFD stability would be highest at lower k_max values, as a smaller range of time scales of EEG signals are likely to provide clearer representation of the fractal nature. The results support our hypothesis, demonstrating that HFD stability is highest within the range of 6 < k_max < 14. This finding enhances the reliability of the HFD measure and its potential as a valuable tool to support clinical decisions.Clinical Relevance- The identified stable region of HFD in healthy individuals enhances the method's overall reliability, thereby improving also its potential to yield consistent results in detecting deviations associated with neurological disorders.