Along with the whole organism, the functional capabilities of the brain gradually degrade upon aging, manifesting as declines in learning and memory, attention, decision-making capacity, sensory perception, and motor management. The aging brain exhibits significant indicative signs of impaired bioenergetics, weakened adaptive neuroplasticity and resilience, anomalous neuronal network activity, dysfunctional neuronal calcium homeostasis, accumulation of oxidatively modified molecules and organelles, and inflammation. Reduced number and maturity of dendritic spines in aging organisms, along with alterations in synaptic transmission, may indicate abnormal neuronal plasticity directly related to impaired brain functions. At worst, a neurodegenerative and cerebrovascular disease, which strongly damages the basic functions of the brain, may develop. Thus, age-associated alterations render the aging brain vulnerable to degenerative disorders including Alzheimer's and Parkinson's diseases, stroke, and various kinds of dementia. While currently there is no cure for these agerelated brain disorders, early detection by recognizing their symptoms can help slow the progression of the disease.