In 2010, 8% of the world's population was >65 years of age. The prevalence of dementia in 2015 was 47.47 million, while its incidence was at 7.7 million new cases each year i.e. translates to a new case every 4.1 seconds. Alzheimer's contributes to 60−70% of cases with dementia. The current global costs of care for dementia is US$ 604 billion/ year. One of the keep obstacles to better treatment outcomes and quality of life is late diagnosis. The present paper covers the role of EEG-based Alpha waves and event-related potential (ERPs) components as biomarkers of cognition and the changes in their features with aging, dementia, and Alzheimer's.