Excitability and recruitment patterns of spinal motoneurons in human sleep as assessed by F-wave recordings.
Level 4 - case-series / case-control
Within-subject physiological study in healthy volunteers without a separate control group
PubMed 21717101 · doi:10.1007/s00221-011-2763-3
What was done
Ulnar nerve stimulation was performed to record F-waves from the first dorsal interosseus muscle in 22 healthy subjects during wakefulness, N2, N3 (slow-wave sleep), and REM sleep. At least 15 F-waves were recorded per vigilance state to assess F-amplitudes, F-persistence, F-conduction velocities, and F-tacheodispersion calculated via the modified Kimura formula.
What was found
The abstract reports qualitative directions of effect without numerical values. Spinal motoneuron excitability was significantly reduced in all sleep stages compared to wakefulness, as indicated by decreased F-persistence and F-amplitudes. F-tacheodispersion demonstrated a narrowed range of F-conduction velocities in all sleep stages, most prominently in REM sleep. Non-REM sleep showed significant reductions in maximal and mean conduction velocities with a trend toward lower minimal velocity, whereas REM sleep showed a further lowering of mean conduction velocity without shifts in minimal or maximal conduction velocities.
Why it matters
The study shows that supraspinal inhibition acts selectively across spinal motoneuron subpopulations depending on sleep stage, clarifying the neural mechanisms distinguishing non-REM muscle hypotonia from REM atonia.
Limits
The sample was small (22 healthy subjects) and the abstract presents no exact numerical data, effect sizes, or confidence intervals. Testing was limited to a single distal upper-extremity muscle pool, which may not generalize to axial, cranial, or lower-limb motoneuron populations.
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- supports Muscle paralysis (atonia) is most pronounced during rapid eye movement (REM) sleep.