Alzheimer's disease-like features in resting state EEG/fMRI of cognitively intact and healthy middle-aged APOE/PICALM risk carriers

IntroductionGenetic susceptibility is a primary factor contributing to etiology of late-onset Alzheimers disease (LOAD). The exact mechanisms and timeline through which APOE/PICALM influence brain functions and contribute to LOAD remain unidentified. This includes their effects on individuals prior to the development of the disease. MethodsAPOE/PICALM alleles were assessed to determine the genetic risk of LOAD in 79 healthy, middle-aged participants who underwent EEG and fMRI recordings. The resting-state signal was analyzed to estimate relative spectral power, complexity (Higuchis algorithm), and connectivity (coherence in EEG and ICA-based connectivity in fMRI). ResultsThe main findings indicated that individuals at risk for LOAD exhibited reduced signal complexity and the so-called "slowing of EEG" which are well-known EEG markers of AD. Additionally, these individuals showed altered functional connectivity in fMRI (within attention related areas). DiscussionRisk alleles of APOE/PICALM may affect brain integrity and function prior to the onset of the disease