In Parkinson's disease (PD), the identification of instrumental biomarkers is crucial to evaluate disease susceptibility and motor stage. We evaluated self-similarity of electrocortical activity as expression of brain signal complexity in untreated PD, to investigate its possible role as a neurophysiological biomarker. We analyzed the data of 34 untreated PD subjects and 18 group-matched controls who underwent standardized electroencephalography. A Welch's periodogram was applied to site-specific electroencephalographic signal epochs. To investigate self-similarity of electrocortical activity, the power law exponent β was computed for each selected coordinate. In both PD subjects and controls, β values at each coordinate increased with an antero-posterior gradient, changing from values around one in fronto-temporal sites to values around two among parieto-occipital sites. PD subjects presented overall lower β values among different sites compared to controls, with significant differences for the left fronto-temporal sites. Our findings suggest an increased level of fronto-temporal neuronal organization in untreated PD. We hypothesize a possible role of β as a neurophysiological biomarker for early untreated PD.
Keywords: Biomarker; Electrocortical complexity; Fronto-temporal electrocortical activity; Power law exponent β; Untreated Parkinson’s disease.