The Effects of Total Sleep Deprivation on the Generation of Random Sequences of Key-Presses, Numbers and Nouns

Instruction effects on randomness in sequence generation

Randomness is a fundamental property of human behavior. It occurs both in the form of intrinsic random variability, say when repetitions of a task yield slightly different behavioral outcomes, or in the form of explicit randomness, say when a person tries to avoid being predicted in a game of rock, paper and scissors. Randomness has frequently been studied using random sequence generation tasks (RSG). A key finding has been that humans are poor at deliberately producing random behavior. At the same time, it has been shown that people might be better randomizers if randomness is only an implicit (rather than an explicit) requirement of the task. We therefore hypothesized that randomization performance might vary with the exact instructions with which randomness is elicited. To test this, we acquired data from a large online sample (n = 388), where every participant made 1,000 binary choices based on one of the following instructions: choose either randomly, freely, irregularly, according to an imaginary coin toss or perform a perceptual guessing task. Our results show significant differences in randomness between the conditions as quantified by conditional entropy and estimated Markov order. The randomization scores were highest in the conditions where people were asked to be irregular or mentally simulate a random event (coin toss) thus yielding recommendations for future studies on randomization behavior.

Clinical Effect of Electroacupuncture on Acute Sleep Deprivation and Event-Related Potential Affecting the Inhibition Control of the Brain: Study Protocol for a Randomized Controlled Trial

Background

Acute sleep deprivation (ASD) can effect mood, attention, memory, alertness and metabolism. Especially, it is often accompanied by cognitive impairment of the brain. Acupuncture is safe and effective for improving cognitive function, but its underlying mechanism is not fully understood. In this study, an event-related potential (ERP) technique will be employed to measure the behavioral, cognitive, and physiological changes produced by electroacupuncture intervention after ASD.

Methods

We will recruit 60 healthy subjects. The participants will be randomly divided into a treatment group, a control group, a sham electroacupuncture group and a blank group, at a 1:1:1:1 ratio. The primary outcome will be determined by the change from baseline to 36 h in the MoCA score. The secondary results include the amplitude and latency of ERP N2 and P3, Go-hit rates, Go-RTs, No-Go-FA rates, the WCST, the Digit Span Subtest of the WAIS, the ESS score and FS-14. The 15 healthy subjects will not receive acupuncture treatment and ASD, but will receive EEG records and cognition functions test at the beginning and end of the experiment. Electroacupuncture intervention will be performed for 30 min once every 12 h, a total of three times. ERP measurements and other tests will be performed after baseline and ASD, and the statistician and outcome evaluator will be blinded to treatment allocation.

Discussion

This study is expected to investigate the effectiveness of electroacupuncture in improving cognition for ASD.

Trial Registration

ChiCTR2200055999.

The role of sleep deprivation and fatigue in the perception of task difficulty and use of heuristics

This study investigated the effects of sleep deprivation on perception of task difficulty and use of heuristics (mental shortcuts) compared to naturally-experienced sleep at home. Methods: Undergraduate students were screened and assigned through block-random assignment to Naturally-Experienced Sleep (NES; n=19) or Total Sleep Deprivation (TSD; n=20). The next morning, reported fatigue, perception of task difficulty, and use of “what-is-beautiful-is-good,” “greedy algorithm,” and “speed-accuracy trade-off” heuristics were assessed. Results: NES slept for an average of 354.74 minutes (SD=72.84), or 5.91 hours. TSD rated a reading task as significantly more difficult and requiring more time than NES. TSD was significantly more likely to use the greedy algorithm heuristic by skipping instructions and the what-is-beautiful-is-good heuristic by rating an unattractive consumer item with a favorable review as poor quality. Those in Total Sleep Deprivation who chose more difficult math problems made this selection to finish the task more quickly in findings approaching significance, indicating use of the speed-accuracy trade-off heuristic. Collapsed across conditions, self-reported fatigue predicted greater perceived difficulty in both the reading task and a visuo-motor task, higher quality rating for the attractive consumer item, and lower quality rating for the unattractive consumer item. Conclusions: Findings indicate sleep deprivation and fatigue increase perceptions of task difficulty, promote skipping instructions, and impair systematic evaluation of unappealing stimuli compared to naturally-experienced sleep.

Algorithmic complexity for psychology: a user-friendly implementation of the coding theorem method

Kolmogorov-Chaitin complexity has long been believed to be impossible to approximate when it comes to short sequences (e.g. of length 5-50). However, with the newly developed coding theorem method the complexity of strings of length 2-11 can now be numerically estimated. We present the theoretical basis of algorithmic complexity for short strings (ACSS) and describe an R-package providing functions based on ACSS that will cover psychologists' needs and improve upon previous methods in three ways: (1) ACSS is now available not only for binary strings, but for strings based on up to 9 different symbols, (2) ACSS no longer requires time-consuming computing, and (3) a new approach based on ACSS gives access to an estimation of the complexity of strings of any length. Finally, three illustrative examples show how these tools can be applied to psychology.

Inhibition of return, but not facilitation, disappears under vigilance decrease due to sleep deprivation

In this study, we assessed whether unspecific attention processes signaled by general reaction times (RTs), as well as specific facilitatory (validity or facilitation effect) and inhibitory (inhibition of return, IOR) effects involved in the attentional orienting network, are affected by low vigilance due to both circadian factors and sleep deprivation (SD). Eighteen male participants performed a cuing task in which peripheral cues were nonpredictive about the target location and the cue-target interval varied at three levels: 200 ms, 800 ms, and 1,100 ms. Facilitation with the shortest and IOR with the longest cue-target intervals were observed in the baseline session, thus replicating previous related studies. Under SD condition, RTs were generally slower, indicating a reduction in the participants' arousal level. The inclusion of a phasic alerting tone in several trials partially compensated for the reduction in tonic alertness, but not with the longest cue-target interval. With regard to orienting, whereas the facilitation effect due to reflexive shifts of attention was preserved with sleep loss, the IOR was not observed. These results suggest that the decrease of vigilance produced by SD affects both the compensatory effects of phasic alerting and the endogenous component involved in disengaging attention from the cued location, a requisite for the IOR effect being observed.

The effects of total sleep deprivation on semantic priming: event-related potential evidence for automatic and controlled processing strategies

There is general consensus that performance on a number of cognitive tasks deteriorates following total sleep deprivation. At times, however, subjects manage to maintain performance. This may be because of an ability to switch cognitive strategies including the exertion of compensatory effort. The present study examines the effects of total sleep deprivation on a semantic word priming task. Word priming is unique because it can be carried out using different strategies involving either automatic, effortless or controlled, effortful processing. Twelve subjects were presented with word pairs, a prime and a target, that were either highly semantically associated (cat…dog), weakly associated (cow…barn) or unassociated (apple…road). In order to increase the probability of the use of controlled processing following normal sleep, the subject's task was to determine if the target word was semantically related to the prime. Furthermore, the time between the offset of the prime and the onset of the target was relatively long, permitting the use of an effortful, expectancy-predictive strategy. Event-related potentials (ERPs) were recorded from 64 electrode sites. After normal sleep, RTs were faster and accuracy higher to highly associated targets; this performance advantage was also maintained following sleep deprivation. A large negative deflection, the N400, was larger to weakly associated and unassociated targets in both sleep-deprived and normal conditions. The overall N400 was however larger in the normal sleep condition. Moreover, a long-lasting negative slow wave developed between the offset of the prime and the onset of the target. These physiological measures are consistent with the use of an effortful, predictive strategy following normal sleep but an automatic, effortless strategy following total sleep deprivation. A picture priming task was also run. This task benefits less from the use of a predictive strategy. Accordingly, in this task, ERPs following the target did not differ as a function of the amount of sleep.

Implicit and explicit representations of hand position in tool use

Understanding the interactions of visual and proprioceptive information in tool use is important as it is the basis for learning of the tool's kinematic transformation and thus skilled performance. This study investigated how the CNS combines seen cursor positions and felt hand positions under a visuo-motor rotation paradigm. Young and older adult participants performed aiming movements on a digitizer while looking at rotated visual feedback on a monitor. After each movement, they judged either the proprioceptively sensed hand direction or the visually sensed cursor direction. We identified asymmetric mutual biases with a strong visual dominance. Furthermore, we found a number of differences between explicit and implicit judgments of hand directions. The explicit judgments had considerably larger variability than the implicit judgments. The bias toward the cursor direction for the explicit judgments was about twice as strong as for the implicit judgments. The individual biases of explicit and implicit judgments were uncorrelated. Biases of these judgments exhibited opposite sequential effects. Moreover, age-related changes were also different between these judgments. The judgment variability was decreased and the bias toward the cursor direction was increased with increasing age only for the explicit judgments. These results indicate distinct explicit and implicit neural representations of hand direction, similar to the notion of distinct visual systems.

The effects of stimulus degradation after 48 hours of total sleep deprivation

STUDY OBJECTIVES

To test the hypothesis that total sleep deprivation (TSD) slows stimulus detection and evaluation processes. Towards that end we manipulate degradation of the imperative stimulus, a manipulation well established to affect the processes of interest, in a delayed letter recognition (DLR) task and the psychomotor vigilance task (PVT), and predicted that after TSD the ordinary reaction time (RT) slowing effect of stimulus degradation would be increased. These hypotheses were only partially confirmed (see below).

DESIGN

Participants were exposed to 48 h of total sleep loss. The PVT and DLR were administered to the same participants. The PVT was administered 8 times -every 6 h from 12:00 on Day 1. The DLR was administered twice, at 09:00 of Day 1 and 48 h later.

SETTING

Participants were continuously monitored in a sleep laboratory.

SUBJECTS

26 healthy young adults enrolled. Due to dropouts and technical failures, the final n's were 20 for the DLR and 21 for the PVT.

MEASUREMENTS AND RESULTS

General linear mixed models were employed. In the DLR task there was no interaction between TSD and degradation on any variable. There was, however, a significant interaction between TSD and degradation on mean reaction time in the PVT (P = 0.01).

CONCLUSIONS

As in our previous reports, we observe the specificity with which total sleep deprivation affects cognitive processes. One aspect of visual processing, stimulus detection, was affected by total sleep deprivation and made a significant contribution to the performance impairments observed. Another aspect of visual processing, stimulus evaluation, remained unaffected after 2 days and nights of total sleep loss.

Associations between diurnal preference, sleep quality and externalizing behaviours: a behavioural genetic analysis

BACKGROUND

Certain aspects of sleep co-occur with externalizing behaviours in youth, yet little is known about these associations in adults. The present study: (1) examines the associations between diurnal preference (morningness versus eveningness), sleep quality and externalizing behaviours; (2) explores the extent to which genetic and environmental influences are shared between or are unique to these phenotypes; (3) examines the extent to which genetic and environmental influences account for these associations. method: Questionnaires assessing diurnal preference, sleep quality and externalizing behaviours were completed by 1556 young adult twins and siblings.

RESULTS

A preference for eveningness and poor sleep quality were associated with greater externalizing symptoms [r=0.28 (95% CI 0.23-0.33) and 0.34 (95% CI 0.28-0.39), respectively]. A total of 18% of the genetic influences on externalizing behaviours were shared with diurnal preference and sleep quality and an additional 14% were shared with sleep quality alone. Non-shared environmental influences common to the phenotypes were small (2%). The association between diurnal preference and externalizing behaviours was mostly explained by genetic influences [additive genetic influence (A)=80% (95% CI 0.56-1.01)], as was the association between sleep quality and externalizing behaviours [A=81% (95% CI 0.62-0.99)]. Non-shared environmental (E) influences accounted for the remaining variance for both associations [E=20% (95% CI -0.01 to 0.44) and 19% (95% CI 0.01-0.38), respectively].

CONCLUSIONS

A preference for eveningness and poor sleep quality are moderately associated with externalizing behaviours in young adults. There is a moderate amount of shared genetic influences between the phenotypes and genetic influences account for a large proportion of the association between sleep and externalizing behaviours. Further research could focus on identifying specific genetic polymorphisms common to both sleep and externalizing behaviours.

Alerting, orienting and executive control: the effects of sleep deprivation on attentional networks

Sleep deprivation alters attentional functions like vigilance or tonic alerting (i.e., sustaining an alert state over a period of time). However, the effects of sleep loss on both orienting and executive control are still not clear, and no study has assessed whether sleep deprivation might affect the relationships among these three attentional systems. In order to investigate the efficiency of the three attentional networks--alerting, orienting and executive control--within a single task, we used the Attention Network Test (ANT). Eighteen right-handed male participants took part in the experiment, which took place on two consecutive days. On the first day, each participant performed a 20 min training session of the ANT. On the second day, participants remained awake for 24 h during which time the ANT was performed once at 5:00 p.m. and once at 4:00 a.m. Results showed an overall slowing of reaction times in the nocturnal session, indicating a strong decrease in vigilance. Furthermore, sleep deprivation did affect attentional orienting and executive control. Results are consistent with the hypothesis that the tonic component of alerting interacts with both attentional orienting and executive functions.

Effects of sleep deprivation on dissociated components of executive functioning

STUDY OBJECTIVES

We studied the effects of sleep deprivation on executive functions using a task battery which included a modified Sternberg task, a probed recall task, and a phonemic verbal fluency task. These tasks were selected because they allow dissociation of some important executive processes from non-executive components of cognition.

DESIGN

Subjects were randomized to a total sleep deprivation condition or a control condition. Performance on the executive functions task battery was assessed at baseline, after 51 h of total sleep deprivation (or no sleep deprivation in the control group), and following 2 nights of recovery sleep, at fixed time of day (11:00). Performance was also measured repeatedly throughout the experiment on a control task battery, for which the effects of total sleep deprivation had been documented in previously published studies.

SETTING

Six consecutive days and nights in a controlled laboratory environment with continuous behavioral monitoring.

PARTICIPANTS

Twenty-three healthy adults (age range 22-38 y; 11 women). Twelve subjects were randomized to the sleep deprivation condition; the others were controls.

RESULTS

Performance on the control task battery was considerably degraded during sleep deprivation. Overall performance on the modified Sternberg task also showed impairment during sleep deprivation, as compared to baseline and recovery and compared to controls. However, two dissociated components of executive functioning on this task--working memory scanning efficiency and resistance to proactive interference--were maintained at levels equivalent to baseline. On the probed recall task, resistance to proactive interference was also preserved. Executive aspects of performance on the phonemic verbal fluency task showed improvement during sleep deprivation, as did overall performance on this task.

CONCLUSION

Sleep deprivation affected distinct components of cognitive processing differentially. Dissociated non-executive components of cognition in executive functions tasks were degraded by sleep deprivation, as was control task performance. However, the executive functions of working memory scanning efficiency and resistance to proactive interference were not significantly affected by sleep deprivation, nor were dissociated executive processes of phonemic verbal fluency performance. These results challenge the prevailing view that executive functions are especially vulnerable to sleep loss. Our findings also question the idea that impairment due to sleep deprivation is generic to cognitive processes subserved by attention.

Random noun generation in younger and older adults

We examined age-related changes of executive functions by means of random noun generation. Consistent with previous observations on random letter generation, older participants produced more prepotent responses than younger ones. In the case of random noun generation, prepotent responses are nouns of the same category as the preceding noun. In contrast to previous observations, older participants exhibited stronger repetition avoidance and a stronger tendency toward local evenness—that is, toward equal frequencies of the alternative responses even in short subsequences. These data suggest that at higher adult age inhibition of prepotent responses is impaired. In addition, strategic attentional processes of response selection are strengthened, in particular the application of a heuristic for randomness. In this sense response selection is more controlled in older than in younger adults.

Total sleep deprivation, chronic sleep restriction and sleep disruption

Sleep loss may result from total sleep deprivation (such as a shift worker might experience), chronic sleep restriction (due to work, medical conditions or lifestyle) or sleep disruption (which is common in sleep disorders such as sleep apnea or restless legs syndrome). Total sleep deprivation has been widely researched, and its effects have been well described. Chronic sleep restriction and sleep disruption (also known as sleep fragmentation) have received less experimental attention. Recently, there has been increasing interest in sleep restriction and disruption as it has been recognized that they have a similar impact on cognitive functioning as a period of total sleep deprivation. Sleep loss causes impairments in cognitive performance and simulated driving and induces sleepiness, fatigue and mood changes. This review examines recent research on the effects of sleep deprivation, restriction and disruption on cognition and neurophysiologic functioning in healthy adults, and contrasts the similarities and differences between these three modalities of sleep loss.

Individual differences in childhood sleep problems predict later cognitive executive control

STUDY OBJECTIVE

To determine whether individual differences in developmental patterns of general sleep problems are associated with 3 executive function abilities-inhibiting, updating working memory, and task shifting-in late adolescence.

PARTICIPANTS

916 twins (465 female, 451 male) and parents from the Colorado Longitudinal Twin Study.

MEASUREMENTS AND RESULTS

Parents reported their children's sleep problems at ages 4 years, 5 y, 7 y, and 9-16 y based on a 7-item scale from the Child-Behavior Checklist; a subset of children (n = 568) completed laboratory assessments of executive functions at age 17. Latent variable growth curve analyses were used to model individual differences in longitudinal trajectories of childhood sleep problems. Sleep problems declined over time, with approximately 70% of children having > or = 1 problem at age 4 and approximately 33% of children at age 16. However, significant individual differences in both the initial levels of problems (intercept) and changes across time (slope) were observed. When executive function latent variables were added to the model, the intercept did not significantly correlate with the later executive function latent variables; however, the slope variable significantly (P < 0.05) negatively correlated with inhibiting (r = -0.27) and updating (r = -0.21), but not shifting (r = -0.10) abilities. Further analyses suggested that the slope variable predicted the variance common to the 3 executive functions (r = -0.29).

CONCLUSIONS

Early levels of sleep problems do not seem to have appreciable implications for later executive functioning. However, individuals whose sleep problems decrease more across time show better general executive control in late adolescence.

Random number generation during sleep deprivation: effects of caffeine on response maintenance and stereotypy

Neurophysiological and functional imaging studies have demonstrated that frontal regions of the brain are particularly responsive to homeostatic sleep pressure. Previous neuropsychological studies indicate that sleep deprivation causes impairments in prefrontal cortical function. Random number generation (RNG) is thought to provide a sensitive index of executive functions that rely on the prefrontal cortex. The present study tested the hypothesis that sleep deprivation would impair RNG and that caffeine would mitigate this impairment. Healthy young men (n = 21) participated in two 40-h sleep deprivations 1 week apart. During each sleep deprivation period subjects received either caffeine or placebo according to a randomized, double-blind cross-over design, and they completed an oral RNG task at 3-h intervals. Comparison of test sessions at analogous times of day revealed that sleep deprivation was associated with significant drops in the number of responses, a threefold increase in the percentage of rule violations, 59% greater response redundancy and a 20% increase in stereotypy of adjacent response pairs. Sleep deprivation did not consistently alter counting tendency. Caffeine ameliorated the decrease in the number of responses but did not mitigate other deficits in RNG that arose during sleep deprivation. These findings are consistent with prior reports of diminished vigilance and increased perseveration during extended wakefulness. They support the conclusion that caffeine preserves simple aspects of cognitive performance during sleep deprivation, whereas caffeine may not prevent detrimental effects of sleep deprivation on some complex cognitive functions.