Effects of sleep deprivation on auditory and visual memory tasks.
ABSTRACT Probe recognition tasks have shown the effects of sleep deprivation following a full night of sleep loss. The current study investigated shorter durations of deprivation by testing 11 subjects for accuracy and response time every 2 hr. from 10 p.m. through 8 a.m. We replicated Elkin and Murray's auditory single-probe recognition task using the number triplets and added two visual tasks with number and shape triplets. Series of six stimuli were each followed by a probe, which was presented after 2.5 sec. as a short delay or 20 sec. as a long delay. Accuracy performance showed a significant decrease for the long delay beginning after 4 a.m. for the two visual tasks. Response times were significantly slower for the visual shapes task using the short delay. Visual tasks, especially shapes, may be more prone to disruption by sleep deprivation, given the visual information load and the briefness of iconic memory.
Chapter: Asthma in the Schools[Show abstract] [Hide abstract]
ABSTRACT: As other chapters in this text have illustrated, asthma is affected by a myriad of social and economic factors. It is also greatly influenced by factors in the physical environment of a person with asthma. As children spend a significant amount of time at school, the conditions at school are important for their asthma control. For example, they may experience asthma symptoms or exacerbations while at school and need to take medication. Moreover, they may need to use preventive medication before engaging in physical education activities or take steps to avoid other asthma triggers throughout the day. These precautions often require support from school administrators and assistance from school staff.12/2009: pages 229-244;
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ABSTRACT: The objective of this study is the development and evaluation of efficient neurophysiological signal statistics, which may assess the driver's alertness level and serve as potential indicators of sleepiness in the design of an on-board countermeasure system. Multichannel EEG, EOG, EMG, and ECG were recorded from sleep-deprived subjects exposed to real field driving conditions. A number of severe driving errors occurred during the experiments. The analysis was performed in two main dimensions: the macroscopic analysis that estimates the on-going temporal evolution of physiological measurements during the driving task, and the microscopic event analysis that focuses on the physiological measurements' alterations just before, during, and after the driving errors. Two independent neurophysiologists visually interpreted the measurements. The EEG data were analyzed by using both linear and non-linear analysis tools. We observed the occurrence of brief paroxysmal bursts of alpha activity and an increased synchrony among EEG channels before the driving errors. The alpha relative band ratio (RBR) significantly increased, and the Cross Approximate Entropy that quantifies the synchrony among channels also significantly decreased before the driving errors. Quantitative EEG analysis revealed significant variations of RBR by driving time in the frequency bands of delta, alpha, beta, and gamma. Most of the estimated EEG statistics, such as the Shannon Entropy, Kullback-Leibler Entropy, Coherence, and Cross-Approximate Entropy, were significantly affected by driving time. We also observed an alteration of eyes blinking duration by increased driving time and a significant increase of eye blinks' number and duration before driving errors. EEG and EOG are promising neurophysiological indicators of driver sleepiness and have the potential of monitoring sleepiness in occupational settings incorporated in a sleepiness countermeasure device. The occurrence of brief paroxysmal bursts of alpha activity before severe driving errors is described in detail for the first time. Clear evidence is presented that eye-blinking statistics are sensitive to the driver's sleepiness and should be considered in the design of an efficient and driver-friendly sleepiness detection countermeasure device.Clinical Neurophysiology 10/2007; 118(9):1906-22. · 3.14 Impact Factor
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ABSTRACT: Two Independent Sources of Short Term Memory Problems During Sleep Deprivation: A commentary on Wee et al. Sleep deprivation accelerates delay-related loss of visual short-term memories without affecting precision. Adrienne M. Tucker, Ph.D. Research Institute Psychology, University of Amsterdam, Amsterdam, the Netherlands Accidents related to sleep loss are estimated to cost billions of dollars annually,1 yet the effects of sleep deprivation (SD) on aspects of cognition have yet to be unraveled. For example, short term memory (STM) plays a vital role in the performance of a wide range of tasks such as decision making and problem solving.2 During sleep loss, STM performance is slower and less accurate with large individual differences in the magnitude of impairment3-8 yet the underlying mechanism(s) for these performance changes are not clear. In this issue of SLEEP, Wee and colleagues9 take a model-based approach to understanding cognitive performance by fitting quantitative mathematical parameters which are theorized to reflect latent cognitive processes. Theoretically, this approach allows one to disentangle the multitude cognitive processes contributing to a single behavioral output variable such as reaction time (RT) or accuracy.10 Another way to isolate cognitive processes is via parametric manipulations, which place increasingly greater difficulty on a given process of interest (such as a requirement to remember 1, 3, or 6 letters).11 These approaches allow more specific conclusions to be drawn and can help pinpoint which of the following processes underlie the STM deficits seen during SD: memory encoding, memory maintenance, memory retrieval and/or a more general deficit in basic perceptual and attentional processing. Below I summarize what is known about the effects of SD on these specific processes from the study by Wee and colleagues9, as well as previous approaches involving cognitive modeling, parametric task manipulation, and neuroimaging. Memory Maintenance: Wee et al.9 tested 19 healthy young participants twice in a counterbalanced order, once after sleep and once after a night of SD. Three colored squares were presented and at a delay of either 1 or 10s; subjects were cued to retrieve the square presented at the identified location by selecting the matching color from a wheel including 180 choices. Bayes’ probabilistic model was used to separate the response error distribution into three parts: one representing precision of target items, one representing distractor items, and one representing random guesses. The model parameter reflecting random guesses increased as a function of SD and delay, which suggests that participants were more likely to drop items from STM during sleep loss (i.e., that participants had a harder time maintaining items in STM). Intriguingly, two studies using a parametric approach have also reported selective deficits in working memory maintenance in SD, as well as one other model-based analysis described further below.12-14 In this issue of SLEEP, Wee et al. also found that SD subjects were more likely to erroneously report a non-target item.9 SD did not affect the model parameter reflecting the precision of remembered items, however, which suggests that encoding quality is not impacted for those items that are successfully maintained. Memory Encoding: Rakitin et al. investigated the effects of 48h SD on a letter recognition task where the difficulty of encoding the probe was manipulated by randomly scrambling either 0%, 25%, or 50% of the image’s pixels.15 Contrary to prediction, there was no interaction between SD and degradation. In line with the result reported by Wee et al.9, this suggests that stimulus encoding is not primarily responsible for the working memory deficits seen. Memory Retrieval: In other studies, the difficulty of memory retrieval was manipulated by using memory set sizes of one, three, or six letters. After two nights of sleep loss there was no interaction between SD and memory set size on either RT or accuracy suggesting that working memory retrieval was not impaired.16 Another study used a similar task, also after two nights of sleep loss. In this task the memory probes were manipulated such that 50% that were not in the current set were in the set previous; this recency places an additional proactive interference demand on retrieval. Again, there were no interactions between SD and set size nor between SD and recency, providing even stronger evidence that memory retrieval is not greatly impacted by sleep loss.17 Basic perceptual and attention processing: Converging evidence suggests that decrements in basic perceptual and attention processing contribute to STM impairment during SD. First, sleep-deprived subjects show failures to respond on STM tasks similar to the attentional lapses seen in the Psychomotor Vigilance Test (PVT)18-23 Second, more complex STM tasks which are more attentionally engaging – and thus put lesser demands on endogenous attentional control – are better preserved during sleep loss.24-26 Third, SD participants have a harder time maintaining attention in the face of distracting items presented during working memory tasks.27-28 Finally, some brain regions (e.g., occipital and parietal cortex) identified in neuroimaging studies implicate deficits in basic perceptual and attentional processing.7, 29-33 Notably, after 53-57h of SD, rTMS to facilitate left upper middle occipital cortex in BA19 (a region involved in perceptual processing) was shown to significantly decrease RT on a delayed letter recognition task.34 That is, facilitating a brain region involved in perceptual processing was able to at least partially restore performance, suggesting that perceptual processing deficits underlie some of the STM impairment seen during SD. Later this finding was replicated.35 Two sources of STM impairment: Intriguingly, two independent sets of neural correlates of working memory impairment during SD have been dissociated.36 Further, basic attentional versus working memory maintenance deficits have been dissociated using computational modeling.14 The effects of SD on STM were investigated using a letter string recognition task across lags of 0-4 trials. A computational model based on Atkinson was used to estimate three parameters representing attention, working memory span, and encoding. In line with the report by Wee et al.9, SD significantly reduced attention and working memory span parameters, but it did not reduce the encoding parameter. Specifically, SD reduced working memory span by 38%--a large effect (ƞ2=0.21). This was reflected in a significantly greater drop in accuracy with lag (or delay), reflecting trouble maintaining items in working memory span. The effect on attention was slightly more than half that of working memory span (ƞ2=0.13) and the change in these two parameters was not correlated with each other. Indeed, individual differences in the profile of cognitive impairment were of such a degree that some individuals were selectively vulnerable to attention decrements while others were selectively vulnerable to working memory span decrements. Summary: Behavioral, cognitive modeling, and neuroimaging results converge to suggest that deficits in short term memory during sleep deprivation arise from decrements in basic attentional and perceptual processing as well as decrements in memory maintenance, while memory encoding and retrieval processes seem to be relatively spared. Thus, the study by Wee et al.9 adds further evidence to the conclusion that there are at least two independent ways that short term memory deficits can occur during sleep deprivation: one related to basic attention and perceptual processing; and the other related to memory maintenance. Individuals can experience deficits in one or both processes when sleep deprived. More studies that use quantitative modeling as reported by Wee et al.9 can help provide a greater understanding of the underlying mechanisms responsible for the effects of sleep loss on STM. REFERENCES 1. Dinges DF. An overview of sleepiness and accidents. J Sleep Res 1995;4:4-14. 2. Baddeley AD & Hitch GJ. Working memory. Psychol Learn Motiv 1974;8:47-89. 3. Frey DJ, Badia P, & Wright KP. Inter‐and intra‐individual variability in performance near the circadian nadir during sleep deprivation. J Sleep Res 2004;13:305-315. 4. Van Dongen HPA, Baynard MD, Maislin G & Dinges DF. 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Luber B, Stanford AD, Tucker A, Nguyen T, Rakitin BC, Habeck C, Basner R, Stern Y. & Lisanby SH. fMRI-guided rTMS in the remediation of sleep deprivation-induced performance deficits in a working memory task. Sleep In Press. 36. Choo WC, Lee WW, Venkatraman V, Sheu FS & Chee MW. Dissociation of cortical regions modulated by both working memory load and sleep deprivation and by sleep deprivation alone. Neuroimage 2005;25:579-587.Sleep 01/2013; 36(6):815-7. · 5.10 Impact Factor