Fractal dimension analysis of states of consciousness and unconsciousness using transcranial magnetic stimulation
Comput. Methods Programs Biomed. July 1, 2019 J. R. D. Miras, F. Soler‐Toscano, S. Iglesias-Parro et al.
A measure combining fractal dimensions of brain activity—capturing both integration and differentiation of cortical responses—can distinguish conscious from unconscious states almost perfectly within individuals. In 18 healthy subjects, the Fractal Dimension Index (FDI) derived from high-density EEG after transcranial magnetic stimulation was significantly lower during non-REM sleep and sedation (with xenon or propofol) than during wakefulness. The index reflects how complex and differentiated the brain's spatiotemporal responses are to a perturbation. The findings suggest that tracking fractal dimensions of cortical dynamics offers a way to assess consciousness, with potential clinical applications for detecting awareness in patients.