Effects of sleep deprivation on cortical excitability: A threshold-tracking TMS study and review of the literature.

Objective: Insufficient sleep is linked to several health problems. Previous studies on the effects of sleep deprivation on cortical excitability using conventional transcranial magnetic stimulation (TMS) included a limited number of modalities, and few inter-stimulus intervals (ISIs) and showed conflicting results. This study aimed to investigate the effects of sleep deprivation on cortical excitability through threshold-tracking TMS, using a wide range of protocols at multiple ISIs.
Methods: Fifteen healthy subjects (mean age ± SD: 36 ± 3.34 years) were included. The following tests were performed before and after 24 h of sleep deprivation using semi-automated threshold-tacking TMS protocols: short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) at 11 ISIs between 1 and 30 ms, short interval intracortical facilitation (SICF) at 14 ISIs between 1 and 4.9 ms, long interval intracortical inhibition (LICI) at 6 ISIs between 50 and 300 ms, and short-latency afferent inhibition (SAI) at 12 ISIs between 16 and 30 ms.
Results: No significant differences were observed between pre- and post-sleep deprivation measurements for SICI, ICF, SICF, or LICI at any ISIs (p < 0.05). As for SAI, we found a difference at 28 ms (p = 0.007) and 30 ms (p = 0.04) but not at other ISIs.
Conclusions: Sleep deprivation does not affect cortical excitability except for SAI.
Significance: This study confirms some of the previous studies while contradicting others.
Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: ‘HT is a shareholder of QTMS Science Ltd., which licences the QTMSG-12 recording protocols used. Other authors have no potential conflict of interest to declare’.
(© 2023 International Federation of Clinical Neurophysiology. Published by Elsevier B.V.)