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It was recently demonstrated that the characteristics of EEG rhythms preceding a transcranial magnetic stimulation (TMS) of the motor cortex (M1) influence the motor-evoked potential (MEP) amplitude with a peculiar pattern, thus reflecting the M1 functional state. As physiological aging is related to a decrease in motor performance and changes in excitability and connectivity strength within cerebral sensorimotor circuits, we aimed to explore whether aging affects EEG-MEP interactions. Using MRI-navigated TMS and multichannel EEG, we compared the EEG-MEP interactions observed in healthy aged subjects with those observed in young volunteers. We divided the MEPs amplitude into two different subgroups consisting of "high" and "low" MEPs, based on the 50th percentile of their amplitude distribution. Then we analysed the characteristics of the pre-stimulus EEG from M1 and correlated areas separately for the "high" and "low" MEPs, comparing the two conditions. In both young and old subjects, significantly larger MEPs were evoked when the stimulated M1 was coupled in the beta-2 band with the homolateral prefrontal cortex. Conversely, only in young participants was the MEP size modulated when the M1 and homolateral parieto-occipital cortices were coupled in the delta band. The elderly didn't show this kind of pattern. Importantly, this coupling was significantly higher in elderly brains than in young brains, both for high and low MEPs. Our results suggest an age-related significant influence of time-varying coupling of spatially patterned EEG rhythms on motor cortex excitability in response to TMS., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Transient cognitive and behavioral stabilization of patients with Alzheimer's disease (AD) is the main goal of acetylcholinesterase inhibitor (AChEI) therapy. Response to treatment is variable and it is usually assessed clinically via neuropsychological scales. Functional neuroimaging could ideally permit the objective evaluation of the topographic correlates of therapy on brain functioning, but is expensive and little available on a large scale. On the other hand, neurophysiological methods such as transcranial magnetic stimulation (TMS) could offer an alternative, low-cost and risk free tool of assessing response to treatment in AD. Previous TMS studies have demonstrated hyperexcitability and asymptomatic motor cortex reorganization in the early stages of AD in patients with normal motor function. The aim of this study was to compare motor cortex functionality in 10 AD patients before and after long-term AchEIs therapy in order to monitor potential drug-related changes in cortical excitability and organization. Examined parameters of motor cortex physiology were found to be unchanged in patients with stabilized cognitive performance during the therapy. TMS, along with clinical, neuropsychological, and neuroimaging data, could be an inexpensive measure of biological progression in AD and it might supplement traditional methods to assess the effects of therapy., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)