The impact of sleep loss on sustained and transient attention: an EEG study

Total sleep deprivation effects on the attentional blink

The Attentional Blink (AB) is a phenomenon that reflects difficulty in detecting or identifying the second of two successive targets (T1 and T2) that are presented in rapid succession, between 200-500ms apart. The AB involves indicators of attentional and temporal integration mechanisms related to the early stages of visual processing. The aim of this study was to identify the effects of 24-h of sleep deprivation (total sleep deprivation, TSD) on the attentional and temporal integration mechanisms of the AB. Twenty-two undergraduate students were recorded during five successive days, in these three conditions: baseline (two days), TSD (one day), and recovery (two days). Each day, at around 12:00 h, participants responded to a Rapid Serial Visual Presentation task (RSVP) that presented two targets separated by random intervals from 100 to 1000ms. The attentional mechanisms were assessed by the AB presence, the AB magnitude, and the AB interval, while the temporal integration mechanisms were evaluated by lag-1 sparing and order reversal responses. TSD negatively affected the attentional mechanisms, which is expressed by an overall reduction in performance, an extended AB interval, and a reduced AB magnitude. TSD also negatively affected the temporal integration mechanisms, manifested by an absence of lag-1 sparing and an increase in order reversals. These results suggest that people are still able to respond to two successive stimuli after 24 h without sleep. However, it becomes more difficult to respond to both stimuli because the attentional and temporal integration mechanisms of the AB are impaired.

The evaluation of cEEGrids for fatigue detection in aviation

Operator fatigue poses a major concern in safety-critical industries such as aviation, potentially increasing the chances of errors and accidents. To better understand this risk, there is a need for noninvasive objective measures of fatigue. This study aimed to evaluate the performance of cEEGrids, a type of ear-EEG, for fatigue detection by analyzing the alpha and theta power before and after sleep restriction in four sessions on two separate days, employing a within-participants design. Results were compared to traditional, highly validated methods: the Karolinska Sleepiness Scale (KSS) and Psychomotor Vigilance Task (PVT). After sleep restriction and an office workday, 12 participants showed increased alpha band power in multiple electrode channels, but no channels correlated with KSS scores and PVT response speed. These findings indicate that cEEGrids can detect differences in alpha power following mild sleep loss. However, it should be noted that this capability was limited to specific channels, and no difference in theta power was observed. The study shows the potential and limitations of ear-EEG for fatigue detection as a less invasive alternative to cap-EEG. Further design and electrode configuration adjustments are necessary before ear-EEG can be implemented for fatigue detection in the field.

Effect of homeostatic pressure on daytime vigilance performance: Evidence from behaviour and resting-state EEG

Vigilance is highly sensitive to the time-of-day effect and goes through the daytime trough during the period of the post-noon dip. A midday nap could maintain individuals' vigilance at an optimal level. Thus, homeostatic sleep pressure is one of the main reasons for the post-noon dip in daytime vigilance. The current study focussed on the role of homeostatic sleep pressure in the diurnal variation of vigilance performance with normal circadian rhythms and the corresponding neural basis. With 34 healthy adults, we recorded the resting-state electroencephalogram activities and the following vigilance performance measured by psychomotor vigilance test in the morning, the no-nap mid afternoon, and the nap mid afternoon. The circadian process was controlled by measuring vigilance and resting-state electroencephalogram activities at the same time point in the nap and no-nap conditions. Homeostatic sleep pressure accumulated from morning to mid afternoon induced the declined vigilance performance and a global increase in resting-state delta, theta, alpha, and beta1 bands power, and a local increase in beta2 band power in the central region. Furthermore, the more the spontaneous beta2 power increased, the less vigilance declined from morning to mid afternoon. The current findings suggest that homeostatic sleep pressure increased cortical excitability but decreased cortical communication efficiency from morning to mid afternoon. In addition, the activity of the high beta waves probably reflected the compensatory effort to counteract the negative impact of the low arousal state on the following vigilance task by performing more action preparation in the no-nap afternoon.

Reduced Resting-State EEG Power Spectra and Functional Connectivity after 24 and 36 Hours of Sleep Deprivation

Total sleep deprivation (TSD) leads to cognitive decline; however, the neurophysiological mechanisms underlying resting-state electroencephalogram (EEG) changes after TSD remain unclear. In this study, 42 healthy adult participants were subjected to 36 h of sleep deprivation (36 h TSD), and resting-state EEG data were recorded at baseline, after 24 h of sleep deprivation (24 h TSD), and after 36 h TSD. The analysis of resting-state EEG at baseline, after 24 h TSD, and after 36 h TSD using source localization analysis, power spectrum analysis, and functional connectivity analysis revealed a decrease in alpha-band power and a significant increase in delta-band power after TSD and impaired functional connectivity in the default mode network, precuneus, and inferior parietal lobule. The cortical activities of the precuneus, inferior parietal lobule, and superior parietal lobule were significantly reduced, but no difference was found between the 24 h and 36 h TSD groups. This may indicate that TSD caused some damage to the participants, but this damage temporarily slowed during the 24 h to 36 h TSD period.

Total sleep deprivation impairs visual selective attention and triggers a compensatory effect: evidence from event-related potentials

Many studies have demonstrated the impairment of sustained attention due to total sleep deprivation (TSD). However, it remains unclear whether and how TSD affects the processing of visual selective attention. In the current study, 24 volunteers performed a visual search task before and after TSD over a period of 36 h while undergoing spontaneous electroencephalography. Paired-sample t-tests of behavioral performance revealed that, compared with baseline values, the participants showed lower accuracy and higher variance in response time in visual search tasks performed after TSD. Analysis of the event-related potentials (ERPs) showed that the mean amplitude of the N2-posterior-contralateral (N2pc) difference wave after TSD was less negative than that at baseline and the mean amplitude of P3 after TSD was more positive than that at baseline. Our findings suggest that TSD significantly attenuates attentional direction/orientation processing and triggers a compensatory effect in the parietal brain to partially offset the impairments. These findings provide new evidence and improve our understanding of the effects of sleep loss.

One night of 10-h sleep restores vigilance after total sleep deprivation: the role of delta and theta power during recovery sleep

A series of studies have demonstrated that impaired vigilance performance caused by total sleep deprivation could restore to baseline when recovery sleep is longer than the habitual sleep. However, it is unclear which factors on the recovery night affected the restoration of vigilance performance impaired by sleep deprivation. 22 participant's sleep electroencephalograms were recorded with polysomnography in 8-h baseline sleep and one-night 10-h recovery sleep following 36-h sleep deprivation. Participants completed a 10-min psychomotor vigilance task and subjective ratings after baseline and recovery sleep the following day. Objective vigilance and subjective ratings were impaired by sleep deprivation and recovered to baseline after one-night 10-h recovery sleep. Compared with baseline sleep, sleep depth increased with enhanced delta and theta power density, and sleep duration was also prolonged during recovery sleep. The vigilance performance difference between recovery and baseline sleep was taken as a behavioral index of the restoration of vigilance. The restoration of vigilance was correlated with the delta and theta power density of stage N3 in the frontal and central region during the recovery sleep. These findings indicated that one-night 10-h recovery sleep could restore the impaired objective vigilance and subjective ratings caused by sleep deprivation. The recuperative effect of vigilance relies on individual differences in sleep intensity. Individuals with higher sleep intensity in recovery sleep obtained better vigilance recovery.

Alcohol use severity and the neural correlates of the effects of sleep disturbance on sustained visual attention

Alcohol misuse is associated with sleep disturbance and cognitive dysfunction. However, the neural processes inter-relating the severity of alcohol use, sleep disturbance and cognitive performance remain under-investigated. We addressed this issue with a dataset of 964 subjects (504 women) curated from the Human Connectome Project. Participants were assessed with the Pittsburgh Sleep Quality Index (PSQI) and fMRI while identifying relational dimension pictures and matching dimension pictures (as a control) in alternating blocks. Imaging data were analyzed with published routines and the results were evaluated at a corrected threshold. Subjects showed lower accuracy rate and longer reaction time (RT) in relational than control blocks. The difference in RT between the two blocks (RT_Rel-Con) was driven primarily by the RT and correlated positively with performance accuracy of relational trials, suggesting that a more cautious response (i.e., longer RT_Rel-Con) improved accuracy. The severity of alcohol use, identified from principal component analysis of drinking metrics, was positively correlated with sleep disturbance. Further, whole-brain regression identified activity of the superior colliculus (SC) during relational vs. control blocks in positive and negative correlation with RT_Rel-Con and PSQI score, respectively. Mediation and path analyses demonstrated a significant model: more severe alcohol use → greater sleep disturbance → diminished SC activity → impaired performance. These findings support the influences of alcohol misuse on sleep and suggest neural correlates that mediate the relationship between sleep disturbance and altered sustained attention in young adults.

Intensity-Dependent Changes in Quantified Resting Cerebral Perfusion With Multiple Sessions of Transcranial DC Stimulation

Transcranial direct current stimulation (tDCS) to the left prefrontal cortex has been shown to produce broad behavioral effects including enhanced learning and vigilance. Still, the neural mechanisms underlying such effects are not fully understood. Furthermore, the neural underpinnings of repeated stimulation remain understudied. In this work, we evaluated the effects of the repetition and intensity of tDCS on cerebral perfusion [cerebral blood flow (CBF)]. A cohort of 47 subjects was randomly assigned to one of the three groups. tDCS of 1- or 2-mA was applied to the left prefrontal cortex on three consecutive days, and resting CBF was quantified before and after stimulation using the arterial spin labeling MRI and then compared with a group that received sham stimulation. A widespread decreased CBF was found in a group receiving sham stimulation across the three post-stimulation measures when compared with baseline. In contrast, only slight decreases were observed in the group receiving 2-mA stimulation in the second and third post-stimulation measurements, but more prominent increased CBF was observed across several brain regions including the locus coeruleus (LC). The LC is an integral region in the production of norepinephrine and the noradrenergic system, and an increased norepinephrine/noradrenergic activity could explain the various behavioral findings from the anodal prefrontal tDCS. A decreased CBF was observed in the 1-mA group across the first two post-stimulation measurements, similar to the sham group. This decreased CBF was apparent in only a few small clusters in the third post-stimulation scan but was accompanied by an increased CBF, indicating that the neural effects of stimulation may persist for at least 24 h and that the repeated stimulation may produce cumulative effects.

Dissociation of Subjective and Objective Alertness During Prolonged Wakefulness

BACKGROUND

Although the deterioration of subjective and objective alertness during prolonged wakefulness has been investigated rigorously, whether perceived sleepiness and fatigue are consistent with actual decrements in behavioral performance in the time course is still disputed. The present study examined the dissociation between decrements of subjective alertness and performance deficits during prolonged wakefulness of one night and explored the relationship between body temperature and the impairments of subjective and objective alertness.

PARTICIPANTS AND METHODS

Thirty-eight participants (27 females; age: 21.76 ± 2.37 years old) underwent prolonged wakefulness for one night at habitual bedtime (0:00-6:00 am). Participants completed a 10-min PVT to assess objective alertness, fatigue, and sleepiness ratings to assess subjective alertness every 2 hours, and body temperature was measured every hour during scheduled wakefulness.

RESULTS

Subjective alertness reflected a linear decline with time, but the magnitudes of objective performance deterioration increased significantly between 4:00 and 6:00 am. The increasing magnitudes of performance deficits were associated with the change of body temperature between 4:00 and 6:00 am.

CONCLUSION

These results indicate that the perceived degree of decline in alertness is temporally dissociated with the actual decline in objective vigilance with increased duration of wakefulness. The dissociation of magnitudes of subjective and objective alertness decrements mainly occurs between 4:00 and 6:00 am, and the changes of performance deficits have a relationship with body temperature.