ABO and Alzheimer disease: Nevertheless, the unique EEG spectral signature of hippocampal soluble Aβo obtained here using electrodes at the surface of the cerebral cortex shows a translational potential as a biomarker of preclinical and/or prodromal stages of AD, when soluble Aβo begin to accumulate before amyloid plaque deposition, tau pathology, brain structure alterations, and cognitive deficits emerge.