title: Wakefulness delta waves increase after cortical plasticity induction.
abstract: OBJECTIVE
  Delta waves (DW) are present both during sleep and in wakefulness. In the first case, DW are considered effectors of synaptic plasticity, while in wakefulness, when they appear in the case of brain lesions, their functional meaning is not unanimously recognized. To throw light on the latter, we aimed to investigate the impact on DW exerted by the cortical plasticity-inducing protocol of intermittent theta burst stimulation (iTBS).
  
  
  METHODS
  Twenty healthy subjects underwent iTBS (11 real iTBS and nine sham iTBS) on the left primary motor cortex with the aim of inducing long-term potentiation (LTP)-like phenomena. Five-minute resting open-eye 32-channel EEG, right opponens pollicis motor-evoked potentials (MEPs), and alertness behavioral scales were collected before and up to 30 min after the iTBS. Power spectral density (PSD), interhemispheric coherence between homologous sensorimotor regions, and intrahemispheric coherence were calculated for the frequency bands ranging from delta to beta.
  
  
  RESULTS
  Real iTBS induced a significant increase of both MEP amplitude and DW PSD lasting up to 30 min after stimulation, while sham iTBS did not. The DW increase was evident over frontal areas ipsilateral and close to the stimulated cortex (electrode F3). Neither real nor sham iTBS induced significant modifications in the PSD of theta, alpha, and beta bands and in the interhemispheric coherence. Behavioral visuo-analogic scales score did not demonstrate changes in alertness after stimulations. No correlations were found between MEP amplitude and PSD changes in the delta band.
  
  
  CONCLUSIONS
  Our data showed that LTP induction in the motor cortex during wakefulness, by means of iTBS, is accompanied by a large and enduring increase of DW over the ipsilateral frontal cortex.
  
  
  CONCLUSIONS
  The present results are strongly in favor of a prominent role of DW in the neural plasticity processes taking place during the awake state.
authors: Dipartimento di Neurologia, Università Campus Biomedico di Roma, Rome, Italy. Electronic address: gianni.assenza@gmail.com.
authors: G
authors: G
authors: Assenza
authors: Dipartimento di Neurologia, Università Campus Biomedico di Roma, Rome, Italy; Multimodal Functional Imaging Laboratory, Biomedical Engineering Department and Montreal Neurological Institute, McGill University, Montreal, Canada.
authors: G
authors: G
authors: Pellegrino
authors: Dipartimento di Neurologia, Università Campus Biomedico di Roma, Rome, Italy.
authors: M
authors: M
authors: Tombini
authors: Dipartimento di Neurologia, Università Campus Biomedico di Roma, Rome, Italy.
authors: G
authors: G
authors: Di Pino
authors: Dipartimento di Neurologia, Università Campus Biomedico di Roma, Rome, Italy.
authors: V
authors: V
authors: Di Lazzaro
mesh_terms: D000328:Adult; D003700:Delta Rhythm / Q000502:physiology*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D017774:Long-Term Potentiation / Q000502:physiology; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D014851:Wakefulness / Q000502:physiology*; D055815:Young Adult
keywords: Delta band; Delta waves; EEG; MEP; Plasticity; Sleep; Synaptic homeostasis hypothesis; TMS; iTBS