Increased cortical excitability after selective REM sleep deprivation in healthy humans: a transcranial magnetic stimulation study.
BACKGROUND
REM sleep has antiepileptogenic properties whereas, its loss is known to have a proconvulsive role. However, the mechanisms underlying the proepileptogenic effects of REM sleep deprivation are yet not fully understood. The aim of our study was to evaluate the effects of selective REM sleep deprivation (SRD) on cortical excitability in healthy subjects by means of transcranial magnetic stimulation (TMS).


METHODS
Ten normal subjects underwent three TMS sessions: (1) in baseline condition (BL), (2) after SRD by awakening them at each REM sleep onset and (3) after non-rapid eye movement sleep awakenings (NREM-A) as control for potential non-specific effects of interruptions. The TMS investigation included two protocols: (a) the evaluation of motor evoked potentials (MEPs) and silent period (SP) parameters, recorded in response to single pulse magnetic stimulation; (b) the evaluation of the time course of intracortical motor activity tested with paired-pulse TMS applied at inter-stimulus intervals of 1-10 ms.


RESULTS
After SRD the principal finding observed using single pulse TMS was a significant reduction in the duration of SP whereas, a reduction of intracortical inhibition was found, using the paired-pulse TMS. TMS parameters did not show significant changes after NREM-A with respect to BL.


CONCLUSIONS
SRD may influence cortical excitability with a reduction of inhibitory intracortical mechanisms, thus supporting the proconvulsant role of REM loss.
Department of Neurosciences, University of Rome Tor Vergata, Roma, Italy. fbplacidi@gmail.com
Fabio
F
Placidi
Silvana
S
Zannino
Maria
M
Albanese
Andrea
A
Romigi
Francesca
F
Izzi
Maria G
MG
Marciani
Maria G
MG
Palmieri
D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009433:Neural Inhibition / Q000502:physiology; D012016:Reference Values; D012892:Sleep Deprivation / Q000503:physiopathology*; D012895:Sleep, REM / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult