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The sensorimotor cortical system undergoes structural and functional changes across the lifespan, some of these changes are physiological and parallel the normal aging while others might represent pathophysiological mechanism underlying some neurodegenerative disorders. Over the past decade numerous studies have been conducted to identify age-related changes in its functional properties. Here, we have used simultaneous electroencephalography (EEG) and transcranial magnetic stimulation (TMS) to study the effects of physiological aging on the excitability and the connectivity of the dominant hemisphere’s sensorimotor cortical system. To this end, we compared the TMS-evoked EEG potentials (TEPs) collected in healthy young individuals with the ones collected in healthy old individuals. We have shown that the TEPs are significantly affected by physiological aging and this phenomenon has clear spatio-temporal specificity. [ABSTRACT FROM AUTHOR]

It has been demonstrated that in young volunteers the characteristics of the ongoing EEG activity immediately preceding a TMS of M1 influence the following MEP amplitude. In this study we explored whether there is an effect of ageing on this EEG-MEP interactions. Then by means of a TMS-EEG experiment, the pre-stimulus EEG characteristics (coherence and spectral profile) of the stimulated M1 were analysed for “high” and “low” MEPs, classified according to the 50th percentile of their amplitude distribution and thus compared in the two groups. On the stimulated hemisphere the EEG coupling was observed more often in the high compared to the low MEP trials in both groups. The coupling in the beta2 band of the stimulated M1 with the ipsilateral prefrontal cortex was able to led to significantly larger MEPs both in young and old subjects. In contrast, the coupling in the delta band of M1 with the ipsilateral parieto-occipital cortices had an effect on the MEP’s size only in young subjects. Moreover, this coupling was significantly higher in elderly brain than in young brain both for high and low MEPs. These data provide evidence for an age-related influence of time-varying synchronization of EEG rhythms in determining M1 excitability. [ABSTRACT FROM AUTHOR]

Motor cortex hyperexcitability as a possible reflection of restorative plasticity is a well defined neurophysiological feature of Alzheimer’s disease (AD), probably related to its severity and progression. Vascular Dementia is the second most common type of dementia and it is mainly represented by an homogeneous subtype that is the Subcortical Ischemic Vascular Dementia (SIVD). To date, only few studies investigating motor cortex functionality in SIVD have been published and in none of them the TMS motor cortex mapping technique was used. The aim of this investigation was then test and better characterize neurophysiological features of motor cortex excitability and plasticity in SIVD by means of a TMS mapping study. Results showed that even though in SIVD the motor cortex was found to be hyperexcitable and functionally rearranged however the neurophysiological profile identified did not lead to a clear distinction between vascular and neurodegenerative dementia. On the other hand, in the examined population a significant direct correlation was seen between parameters associated to cortical excitability and those related to cortical plasticity, supporting the idea that cortical hyperexcitability can promote cortical plasticity and shading light on possible rehabilitative strategies. [ABSTRACT FROM AUTHOR]

Aim of this study is to investigate, for the first time by means of an EEG-TMS co-registration study, whether and how direct bidirectional connection between brain and hand prosthesis impacts on sensorimotor cortical topography. Within an experimental protocol for robotic hand control, a 26 years-old, left-hand amputated male was selected to have implanted four intrafascicular electrodes (tf-LIFEs-4) in the median and ulnar nerves of the stump for 4 weeks. Before tf-LIFE-4s implant (T0) and after the training period, once electrodes have been removed (T1), experimental subject’s cortico-cortical excitability, connectivity and plasticity were directly tested via neuronavigated EEG–TMS. The statistical analysis demonstrated a significant modulation of EEG activity between 30 and 100 ms post-stimulus for the stimulation of the right hemisphere. When looking at the individual latencies in that time range, significant differences between T0 and T1 condition at 30 ms, ms and 60 ms latencies were present. Finally, also a clear local decrement in N46 amplitude over C4 was evident. No differences between conditions were observed for the stimulation of the left hemisphere. The results of this study confirm the hypothesis that bidirectional neural interface could redirect cortical areas -deprived of their original input/output functions- toward restorative neuroplasticity. [ABSTRACT FROM AUTHOR]