![]() ![]() EEG and MEG TechniquesĮver since Berger reported temporal changes in electric potentials measurable on the scalp in 1929, EEG has been used for a direct and noninvasive measurement of brain cortical activity (i.e., electric potentials), not only in clinical practice but also in other fields such as basic research and industry. A major objective was to highlight the value of EEG and MEG in understanding the physiological mechanisms associated with brain aging. The signal complexity of EEG reflects the irregularity of wave shape and dynamics, and is influenced by healthy aging and associated with brain disorders such as AD. In this review, we will address neurocognitive aging from a neurophysiological perspective, focusing on oscillatory activity changes during the resting state, event-related potentials and stimulus-induced oscillatory responses during cognitive or motor tasks, the organization of brain functional networks, and changes in signal complexity. While fMRI, PET, and NIRS measure hemodynamic or metabolic changes that occur in response to brain activity, neurophysiological techniques such as EEG and MEG measure neural activity directly by detecting postsynaptic potentials in the cerebral cortex. Several methods have been applied to explore brain physiological and pathological aging, including functional magnetic resonance imaging (fMRI), positron emission tomography (PET), near-infrared spectroscopy (NIRS), electroencephalography (EEG), and magnetoencephalography (MEG). Since age is a major risk factor for Alzheimer disease (AD), issues related to pathological aging and its link to disease biomarkers will also be addressed. In the brain, aging is mainly associated with a decline in attention, memory, and other cognitive functions as well as an overall delay in the different steps of cognitive information processing: (i) input and coding, (ii) central processing, and (iii) decision of response and output. We also highlight the accumulating evidence on age-related EEG/MEG changes and biological markers of brain neurodegeneration, including genetic factors, structural abnormalities on magnetic resonance images, and the biochemical changes associated with Aβ deposition and tau pathology.Īging is a physiological process that affects all body tissues. This review addresses healthy and pathological brain aging from a neurophysiological perspective, focusing on oscillatory activity changes during the resting state, event-related potentials and stimulus-induced oscillatory responses during cognitive or motor tasks, functional connectivity between brain regions, and changes in signal complexity. However, the neurophysiological mechanisms underlying AD are not fully elucidated. ![]() It is well known that age is a major risk factor for Alzheimer’s disease (AD), and that synaptic dysfunction represents an early sign of this disease associated with hallmark neuropathological findings. Since electroencephalography (EEG) and magnetoencephalography (MEG) are able to measure neural activity directly with a high temporal resolution of milliseconds, these neurophysiological techniques are particularly important to investigate the dynamics of brain activity underlying neurocognitive aging. Several neuroimaging methods such as functional magnetic resonance imaging, positron emission tomography and near-infrared spectroscopy have been used to explore healthy and pathological aging by relying on hemodynamic or metabolic changes that occur in response to brain activity. Healthy aging is associated with impairment in cognitive information processing. ![]()
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