Resting State Cortical Electroencephalographic Rhythms in Alzheimer's Disease

Physiological brain aging is characterized by a loss of synaptic contacts and neuronal apoptosis that provoke age-dependent decline of cognitive functions. Neural/synaptic redundancy and plastic remodelling of brain networking, also secondary to mental and physical training, promotes maintenance of brain activity in healthy elderly for everyday life and fully productive affective and intellectual capabilities. However, age is the main risk factor for neurodegenerative disorders such as Alzheimer's disease (AD) that impact on cognition. Oscillatory electromagnetic brain activity is a hallmark of neuronal network function in various brain regions. Modern neurophysiological techniques including electroencephalography (EEG) can index normal and abnormal brain aging to facilitate non-invasive analysis of cortico- cortical connectivity and neuronal synchronization of firing, and coherence of rhythmic oscillations at various frequencies. The present review provides a perspective of these issues. It is concluded that discrimination between physiological and pathological brain aging clearly emerges at the group level, with applications at the individual level also suggested. Integrated approaches utilizing neurophysiological techniques together with biological markers and structural and functional imaging are promising for large-scale, low-cost and non-invasive evaluation of at-risk populations.