Magnetic stimulation of the human brain during phasic and tonic REM sleep: recordings from distal and proximal muscles

Abstract

During REM sleep, a powerful postsynaptic inhibition of spinal motoneurons induces a generalized muscle hypotonia. Despite this inhibition, it has been shown that by transcranial magnetic stimulation of the brain (TMS), muscle responses of normal amplitude can be evoked in small hand muscles of humans. Tonic innervation during sleep is different in postural vs. limb muscles, and the spinal inhibition differs during tonic vs. phasic REM episodes, Both phenomena may affect muscle responses to TMS. In this study, muscle responses of 14 healthy subjects were compared to TMS in abductor digiti minimi, lumbar erector spinae, trapezius, and diaphragm during phasic and tonic REM sleep. In all four muscles, the amplitudes of the muscle responses were extremely variable, ranging for example in trapezius from -100% to +473% as compared to wakefulness. There was no systematic difference between the muscles. Moreover, no differences were found for TMS during phasic REM events compared to tonic REM sleep. Thus, responses to TMS during REM sleep may be preserved, with a decreased or increased amplitude. As a likely explanation, the cortical excitability and/or the spinal inhibition fluctuates during REM sleep in humans.

Corticospinal excitability and sleep: a motor threshold assessment by transcranial magnetic stimulation after awakenings from REM and NREM sleep

“…This might explain the often reported great interindividual variability (Grosse et al. 2002; Stalder et al. 1995), as well as the large inconsistency of the findings.…”

“…(1987) reported, in a sample of only three subjects, that the amplitude of responses to magnetic stimuli was depressed during slow wave sleep (SWS) and enhanced or the same during REM sleep, the latter result suggesting an enhanced cortical excitability compensating for the spinal inhibition. On the contrary, Stalder et al. (1995) found decreased amplitude of motor evoked potentials (MEP) in REM sleep, and an even larger decrease in SWS.…”

“…These studies are undoubtedly limited by the fact that delivering one single suprathreshold magnetic stimulus easily awakes subjects, or lightens their sleep (Stalder et al. 1995).…”

Functional involvement of cerebral cortex in human narcolepsy

“…Recent research in animals and humans has shown that various sleep stage-dependent rhythmic oscillations of cortical, thalamic, and brainstem origin profoundly alter the excitability of cortical networks during NREM and REM sleep [1,2,5,10,12,27,28]. We hypothesise that changes in these circuits lead to cortical excitability changes in narcoleptic patients even during wakefulness.…”

Neurophysiologie der Kataplexie

“…Hy po kre ti ne sind im dor so la tera len Hy po tha la mus pro du zier te Neu ropep ti de mit ei nem ge mein sa men Prä kursor pep tid aus dem Hy po kre tin-1 und Hyder MEP-Bah nen vor zu lie gen. Die Un terdrückung von MEPs im REM-Schlaf [10,14,37] kann als wei te rer Hin weis für die feh len de As so zia ti on mit REM-Schlaf gewer tet wer den.…”