The Aperiodic Component of the Electroencephalographic Power Spectrum in Alzheimer’s Disease and Frontotemporal Dementia

Even though the potential of resting-state spectral electroencephalography (EEG) in the differential diagnosis of the conditions underlying dementia has long been investigated, past research has mostly focused on band-specific power differences. Aperiodic activity has only recently gained attention. This thesis aims to contribute to the clarification of the potential role of periodic and aperiodic EEG activity in differentiating between Alzheimer’s disease (AD) and frontotemporal dementia (FTD). Continuous resting-state EEG data of AD and FTD patients as well as of a healthy control (HC) group was decomposed into spectral and aperiodic components. The clinical groups had a lower aperiodic offset at right fronto-central electrodes compared to HC, but no differences were found in the exponent, nor between the FTD and AD patients. The clinical groups showed significantly higher non-adjusted as well as aperiodic-adjusted power in the lower frequency bands and lower power in the higher bands compared to HC, except for the gamma band, in which the reverse was found. The only difference between FTD and AD was a higher aperiodic-adjusted theta power at a central cluster in AD. Despite the absence of significant aperiodic differences between AD and FTD, classification performance substantially improved for these groups from a weak-to-moderate to a good-to-excellent classification when using a classifier trained on the aperiodic-adjusted power and parameters rather than the non-adjusted power. Spectral EEG may be a valuable tool in the differential diagnosis of AD and FTD, provided the aperiodic signal is explicitly considered.