24. Sensorimotor cortex excitability and connectivity in Alzheimer’s disease: An EEG-TMS co-registration study

Several experimental studies have shown that, nevertheless motor symptoms are late events in the natural history of Alzheimer’s disease (AD), neuropathological progression in the motor cortex parallels that in other brain cortices generally considered more specific targets of the aggression. In the last years we have clearly demonstrated that motor cortex excitability is enhanced in AD since the early stages of the disease and this is probably related to its severity and progression. To further investigate, for the first time without peripheral or attentional confounding effects, the neurophysiological hallmarks of motor cortex functionality in AD we used here transcranial magnetic stimulation (TMS) combined with electroencephalography (EEG). We then demonstrated that in mild AD, despite the lack of clinical manifestations, the sensorimotor system is strongly hyper-excitable and its connectivity is deeply rearranged with the recruitment of additional neural sources, the activation of reverberant circuits and their integration in the distributed excitatory network subtending sensorimotor functions.