Electrophysiological markers and cognitive profile in aging: implications for screening and intervention

The aging process is associated to a complex ensemble of structural and functional changes. Focusing on the aging brain, the most reported modification has to do with the progressive atrophy of prefrontal cortices. The decrease in cortical volume is accompanied by a gradual (and greater) decrease of white matter density in anterior portions of the brain and by a progressive reduction of the functionality of the dopaminergic system. Those findings lead to the development of the frontal lobe hypothesis, which states that age-related cognitive and behavioral changes are due to the gradual decline of frontal brain structures. At the same time, functional data highlighted how older people show peculiar compensatory activity involving prefrontal regions when they are engaged in cognitive tasks, thus keeping acceptable performance levels notwithstanding neural losses. Within this scenario, the development of markers able to mirror and track functional decline across physiological and pathological aging processes is one of the most relevant challenges. Traditional paper-and-pencil assessment procedures, indeed, may not be sufficiently sensitive to discriminate small cognitive difficulties occurring, for example, in prodromal phases of degenerative diseases. Oscillatory and event-related electrophysiological measures, instead, are thought to be valuable candidates, them being sensitive to changes in cognitive and functional states, easy to record, non-invasive, and cheaper than alternative instrumental markers based on biochemical, metabolic or neuroimaging methods. Even though most of recent research focused on early pathological signs of Alzheimer Disease and/or Mild Cognitive Impairment, age has been classically associated to decrease in alpha band power and to progressive slowing of EEG rhythms even in healthy elderly people, as well as to prolonged latency of the N2 event-related component, lack of habituation of the P3a component, and reduced/later P3b deflections, mirroring information-processing and allocation of attention resources. In addition, in a recent study integrating cognitive-behavioral (standardized neuropsychological tests and computerized reaction times tasks) and electrophysiological (28-channels resting and taskrelated EEG-ERP) assessment in a sample of healthy old people, we observed relevant correlations between alpha reactivity during eyes open/closed resting and performances at a reaction times task, potentially marking differences in information-processing efficiency. Present and literature evidence point out the potential of EEG-ERP measures to help sketching a finer and more complete picture of cognitive-functional profile even in healthy elderly, and data on age-related changes of oscillatory cortical activity may be deemed as potential targets for future intervention via transcranial alternating current stimulation or neurofeedback techniques.