Cortical excitability and sleep deprivation: a transcranial magnetic stimulation study

Abstract

The objective was to assess the changes in cortical excitability after sleep deprivation in normal subjects. Sleep deprivation activates EEG epileptiform activity in an unknown way. Transcranial magnetic stimulation (TMS) can inform on the excitability of the primary motor cortex. Eight healthy subjects (four men and four women) were studied. Transcranial magnetic stimulation (single and paired) was performed by a focal coil over the primary motor cortex, at the "hot spot" for the right first dorsal interosseous muscle. The following motor evoked potential features were measured: (a) active and resting threshold to stimulation; (b) duration of the silent period; (c) amount of intracortical inhibition on paired TMS at the interstimulus intervals of 2 and 3 ms and amount of facilitation at interstimulus intervals of 14 and 16 ms. The whole TMS session was repeated after a sleep deprivation of at least 24 hours. After the sleep deprivation, the threshold to stimulation (in the active and resting muscle), as well as the silent period, did not change significantly. By contrast, the paired stimulus study showed a significant (p<0.05) reduction in both intracortical inhibition and facilitation. Thus, TMS showed that sleep deprivation is associated with changes in inhibitionfacilitation balance in the primary motor cortex of normal subjects. These changes might have a link with the background factors of the "activating" eVects of sleep deprivation. (J Neurol Neurosurg Psychiatry 2001;71:809-812)

Increased cortical excitability after selective REM sleep deprivation in healthy humans: A transcranial magnetic stimulation study

“…However, an increase in cortical excitability induced by total sleep deprivation has been documented by some studies in healthy subjects [17,18,46] as well as in epileptic patients [20,21,47]. In particular, Scalise et al [18] reported a reduction of both SP duration and ICI after total sleep deprivation.…”

“…In the last decade, the effects of total sleep deprivation on human motor cortex have been explored by means of TMS in normal individuals with conflicting results, mainly due to partial different methodological protocols utilized [17][18][19]45]. However, an increase in cortical excitability induced by total sleep deprivation has been documented by some studies in healthy subjects [17,18,46] as well as in epileptic patients [20,21,47].…”

“…Recently, some studies documented an impairment of cortical excitability induced by total sleep deprivation in both healthy and epileptic subjects by using TMS [17][18][19][20][21]. To date, the effects of Selective REM sleep Deprivation (SRD) on cortical excitability have not been explored in humans.…”

Method for Assessing Brain Changes Associated With Gluteus Maximus Activation

“…3,7,17,32 Because surface electromyography (EMG) is used to measure changes in corticomotor excitability of the target muscle, TMS measures may also vary between test sessions, due to differences in electrode placement and/ or skin impedance. Though reliability of TMS has been established for upper extremity muscles such as the biceps and first dorsal interosseus, 17,[20][21][22] measurement error may be magnified when measuring corticomotor excitability of the gluteus maximus, a large muscle with a small M1 representational area.…”

New Perspectives in Transcranial Magnetic Stimulation: Epilepsy, Consciousness and the Perturbational Approach

“…It has been reported that corticospinal fibers are normally activated by magnetic stimulation, while motor excitability is decreased during different sleep stages [17,33]. In contrast, other authors [160] have observed that in normal subjects, 24 hours of sleep deprivation produce an increase in motor excitability as studied by TMS in two sessions, namely, before and after sleep deprivation. The different effects on motor excitability of sleep deprivation could be due to the differences in study methods and objectives.…”