title: Intracortical inhibition and facilitation upon awakening from different sleep stages: a transcranial magnetic stimulation study.
abstract: Intracortical facilitation and inhibition, as assessed by the paired-pulse transcranial magnetic stimulation technique with a subthreshold conditioning pulse followed by a suprathreshold test pulse, was studied upon awakening from REM and slow-wave sleep (SWS). Ten normal subjects were studied for four consecutive nights. Intracortical facilitation and inhibition were assessed upon awakening from SWS and REM sleep, and during a presleep baseline. Independently of sleep stage at awakening, intracortical inhibition was found at 1-3-ms interstimulus intervals and facilitation at 7-15-ms interstimulus intervals. Motor thresholds were higher in SWS awakenings, with no differences between REM awakenings and wakefulness, while motor evoked potential amplitude to unconditioned stimuli decreased upon REM awakening as compared to the other conditions. REM sleep awakenings showed a significant increase of intracortical facilitation at 10 and 15 ms, while intracortical inhibition was not affected by sleep stage at awakening. While the dissociation between motor thresholds and motor evoked potential amplitudes could be explained by the different excitability of the corticospinal system during SWS and REM sleep, the heightened cortical facilitation upon awakening from REM sleep points to a cortical motor activation during this stage.
authors.affiliation: Dipartimento di Psicologia, Università di Roma La Sapienza, Via dei Marsi 78, 00185 Rome, Italy. luigi.digennaro@uniroma1.it
authors.forename: Luigi
authors.initials: L
authors.lastname: De Gennaro
authors.forename: Mario
authors.initials: M
authors.lastname: Bertini
authors.forename: Michele
authors.initials: M
authors.lastname: Ferrara
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Curcio
authors.forename: Riccardo
authors.initials: R
authors.lastname: Cristiani
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Romei
authors.forename: Fabiana
authors.initials: F
authors.lastname: Fratello
authors.forename: Flavia
authors.initials: F
authors.lastname: Pauri
authors.forename: Paolo Maria
authors.initials: PM
authors.lastname: Rossini
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004558:Electric Stimulation / Q000379:methods*; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D017286:Polysomnography / Q000379:methods; D011930:Reaction Time / Q000187:drug effects; D012684:Sensory Thresholds / Q000502:physiology; D012894:Sleep Stages / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D014851:Wakefulness / Q000502:physiology*