Transcranial direct current stimulation reconstructs diminished thalamocortical connectivity during prolonged resting wakefulness: a resting-state fMRI pilot study.

Reductions in the alertness and information processing capacity of individuals due to sleep deprivation (SD) were previously thought to be related to dysfunction of the thalamocortical network. Previous studies have shown that transcranial direct current stimulation (tDCS) can restore vigilance and information processing after SD. However, the underlying neural mechanisms of this phenomenon remain unclear. The purpose of this study was to investigate the neurocognitive mechanisms of tDCS following SD, by comparing changes in the brain network, especially the thalamocortical network, after tDCS and sham stimulation following 24 h of SD. Sixteen healthy volunteers were tested in a sham-controlled, randomized crossover design experiment. Resting-state functional magnetic resonance imaging was conducted during resting wakefulness and again after either active tDCS or sham stimulation to the right dorsolateral prefrontal cortex (1.0 mA, 20 min) immediately following 24 h of SD. Seed-based correlations and graph theory analysis were used to determine functional connectivity within the brain thalamocortical network. When tDCS was used, the functional connectivity of the thalamus with the temporal lobe and left caudate was higher than that when the sham stimulation was used. Analysis using graph theory showed that compared with sham stimulation, tDCS administration was associated with a significant improvement in not only the number of connections but also the global efficiency of the thalamus itself. Our study reveals a modulation of the activity of the intrinsic thalamus networks after tDCS. The effects may help explain earlier reports of improvements in the cognitive performance after anodal-tDCS.

Short-term memory deficits correlate with hippocampal-thalamic functional connectivity alterations following acute sleep restriction.

Acute sleep restriction heavily influences cognitive function, affecting executive processes such as attention, response inhibition, and memory. Previous neuroimaging studies have suggested a link between hippocampal activity and short-term memory function. However, the specific contribution of the hippocampus to the decline of short-term memory following sleep restriction has yet to be established. In the current study, we utilized resting-state functional magnetic resonance imaging (fMRI) to examine the association between hippocampal functional connectivity (FC) and the decline of short-term memory following total sleep deprivation (TSD). Twenty healthy adult males aged 20.9 ± 2.3 years (age range, 18-24 years) were enrolled in a within-subject crossover study. Short-term memory and FC were assessed using a Delay-matching short-term memory test and a resting-state fMRI scan before and after TSD. Seed-based correlation analysis was performed using fMRI data for the left and right hippocampus to identify differences in hippocampal FC following TSD. Subjects demonstrated reduced alertness and a decline in short-term memory performance following TSD. Moreover, fMRI analysis identified reduced hippocampal FC with the superior frontal gyrus (SFG), temporal regions, and supplementary motor area. In addition, an increase in FC between the hippocampus and bilateral thalamus was observed, the extent of which correlated with short-term memory performance following TSD. Our findings indicate that the disruption of hippocampal-cortical connectivity is linked to the decline in short-term memory observed after acute sleep restriction. Such results provide further evidence that support the cognitive impairment model of sleep deprivation.

Effect of Transcranial Direct Current Stimulation on Regional Homogeneity After Sleep Deprivation by fMRI / 中国医学影像学杂志

Purpose To observe the impact of sleep deprivation (SD) for 24 hours on human brain regional homogeneity (ReHo) by using functional magnetic resonance imaging (fMRI),and briefly discuss the intervening effect of transcranial direct current stimulation (tDCS) on ReHo after SD.Material and Methods Sixteen healthy individuals were enrolled,and self-controlled study were adopted.Resting-state fMRI scans were performed in wakefulness,after SD,and after tDCS (true or placebo stimuli).The ReHo analysis approach was employed to calculate the ReHo values of whole brain in different states.The differences between before and after SD,and between true and false tDCS after SD,were analyzed.Results Compared with wakefulness,SD mainly enhanced ReHo in brain regions of left precentral gyrus,right precentral gyrus,bilateral temporal lobe and thalamus,but decreased ReHo in brain regions of right precuneus,left superior occipital gyrus,limbic lobe and bilateral angular gyrus,superior frontal gyrus,middle frontal gyrus.Compared with placebo stimuli,the true tDCS enhanced ReHo in brain regions of bilateral precuneus,angular gyrus and right forehead,superior middle gyrus,but decreased ReHo in brain regions of the medial side of left frontal lobe,right precentral gyrus,parahippocampal gyrus,substantia nigra and bilateral temporal lobe,pons and so on.Conclusion SD can cause ReHo change in a large number of brain regions.The tDCS on the prefrontal cortex improves the brain regions with ReHo reduction caused by SD.The improved brain regions mainly include bilateral precuneus/posterior cingulate cortex.Therefore,tDCS on the prefrontal cortex can improve brain dysfunction caused by SD.

Changes in EEG approximate entropy of frontal lobes induced by sustained perform-ance / 军事医学

Objective To explore the effect of sustained performance on EEG approximate entropy (ApEn).Methods Fifty participants were divided into two groups according to whether they had undergone sustained performance .One day af-ter the sustained-performance group finished executing their task , the resting EEG of nine electrodes ( F3, Fz, F4, C3, Cz, C4, P3, Pz and P4) was acquired in two grups separately , and the ApEn of each electrode was calculated as well . Results The ApEn of F3 and Fz showed an evident decrease as well as randomness of spontaneous brain electrode activity in frontal lobes , especially in the left one .Conclusion The drop of ApEn and the asymmetry of frontal lobes might reflect participants′state of fatigue during sustained performance .

The Effect of Sleep Deprivation on Executive Control Function:an fMRI Study / 中国心理卫生杂志

Objective:To explore the impact of total sleep deprivation (TSD) on executive control function.Methods:Thirteen healthy young men completed visual Go/No-go task before and after the 36 hour sleep deprivation.Functional magnetic resonance imaging (fMRI) was carried out in these subjects 3 weeks apart.Results: The hit rate of Co/No-go task decreased (P