Evaluating aperiodic components of the spontaneous magnetoencephalograpic activity along AD continuum

Abstract Background The increase in life expectancy has resulted in a greater number of people developing disorders associated with aging such as Alzheimer’s disease. Mild Cognitive Impairment (MCI) is a prodromal stage that has been commonly assessed with the aim of finding biomarkers associated with the dementia progression. Previous literature has stated that MCI patients suffer a slowness of the basal oscillatory brain electrophysiological activity when compared to healthy controls. This slowness, reported with EEG and MEG, is mainly characterized by a diminished alpha power and enhanced theta and delta power. These results have been found when assessing the periodic component of the brain oscillations (i.e. evaluating the spectral power), whereas the aperiodic component has usually been ignored. Recently, researchers from UCSD have developed a toolbox (FOOOF) able to assess the aperiodic component of the spectral power, by computing the exponent of the 1/f‐like activity. This exponent is an aperiodic component that has been related to the integration of the underlying synaptic currents. Under this hypothesis, the exponent will be lower (flatter spectra) when the excitation‐inhibition (E/I) balance would reflect a higher excitation relative to inhibition, whereas the exponent will be higher (steeper spectra) when the E/I balance would reflect a higher inhibition relative to excitation. Method In this study, using a preexisting eyes closed resting state MEG database, we have assessed differences in the aperiodic exponent between healthy (N = 195) and MCI‐diagnosed (N = 79) individuals. To this end, we computed at the sources’ space (using a LCMV beamformer with a 1 cm spacing grid at MNI space) the exponent of the spectral power, and then performed a set of between groups statistics (ANCOVA with age as covariate) with a cluster‐based permutations methodology. Result In our results we observed an increased aperiodic exponent in the precuneus cortex of the individuals with MCI when compared to healthy participants. Conclusion This result would be indicating a decreased E/I balance, hypothetically due to an increased inhibition. Further investigation will be needed to clarify the relevance and implications of these results.