20. Wakefulness delta waves increase after cortical plasticity induction

Delta waves (Dw) during sleep are considered effectors of synaptic plasticity. During wakefulness Dw appear when brain lesions occur, but their functional meaning is not unanimously recognized. We aimed at testing whether Dw change after inducing cortical plasticity by intermittent theta burst stimulation (iTBS). Thirteen healthy subjects underwent iTBS on left primary motor cortex to induce long term potentiation (LTP) like phenomena. Five-minutes resting opened-eyes 32-channels EEG, right opponens pollicis motor evoked potentials (MEP) and alertness behavioural scales were collected before and up to 30 min after iTBS. Power spectral density (PSD) from delta to beta frequency bands of bilateral sensorimotor areas was calculated. iTBS induced a significant increase of both MEP amplitude and bilateral Dw (+87.5%) lasting up to 30 min after stimulation. No changes on behavioural scales were found. Our data showed that motor LTP induction during wakefulness, by means of iTBS, is accompanied by a large and enduring increase of Dw over sensorimotor areas. Present results evidenced that Dw own a prominent role in neural plasticity processes in the awake state.