Search

Total sleep deprivation (TSD) is known to impair sustained attention. However, previously reported effects of TSD on response inhibition are mixed. We administered a "stop-signal" variation of the psychomotor vigilance test, which included 25% of trials requiring withholding of a response to assess response inhibition alongside sustained attention. Participants completed the task at baseline and after 34.5 h of wakefulness. Accuracy was not reduced during TSD. However, response times were significantly slower. A speed/accuracy trade-off allowed participants to effectively withhold responses on inhibition trials and conferred resilience of inhibitory control during TSD under conditions of relatively low time pressure.

Introduction Visual search is important in many operational tasks, such as passive sonar monitoring in naval operations. Shift work can contribute to fatigue and task performance impairment; in particular, backward rotating shift schedules have been shown to impair vigilant attention performance. However, the impact on visual search performance, above and beyond impaired vigilant attention, is unknown. We investigated the effects of two distinct shift work schedules using a visual search task with properties of real-life visual search performance. Methods N=13 adult males (ages 18–39) completed a 6-day/5-night laboratory study with an acclimation day, four simulated shift days, and a recovery day. Shift days involved either a 5h-on/15h-off backward rotating schedule (n=8) or a 3h-on/9h-off fixed schedule (n=5). The visual search task was performed once per shift at varying time of day depending on shift. Participants viewed search arrays where stimuli consisted of colored letters of different shapes. Over three trial blocks of 24 trials each, participants determined if a target was present or absent among 1, 5, 15, or 30 distractors. Similarity between targets and distractors was manipulated between blocks, such that targets differed from distractors by color only, shape only, or either color or shape but not both. For each distinct target feature block, and separately for presence or absence of a target, slopes of response times regressed against number of stimuli were calculated to quantify visual search rates. Mixed-effects ANOVA was used to analyze visual search rates by shift schedule and shift day. Results There were no significant effects of shift schedule (all p>0.30), shift day (all p>0.13), or their interaction (all p>0.22) on visual search rates. Conclusion Previous work showed degraded vigilant attention in the shift schedules considered here, especially in the backward rotating schedule, which may compromise operational performance. However, while our sample may have been too small to have adequate statistical power, we failed to identify specific impairments in visual search with statistical significance. It remains to be determined whether greater levels of fatigue, such as could be induced by total sleep deprivation, would reveal significant visual search deficits. Support (if any) Naval Postgraduate School award N62271-13-M-1228

Vigilant attention is a major component of a wide range of cognitive performance tasks. Vigilant attention is impaired by sleep deprivation and restored after rest breaks and (more enduringly) after sleep. The temporal dynamics of vigilant attention deficits across hours and days are driven by physiologic, sleep regulatory processes-a sleep homeostatic process and a circadian process. There is also evidence of a slower, allostatic process, which modulates the sleep homeostatic setpoint across days and weeks and is responsible for cumulative deficits in vigilant attention across consecutive days of sleep restriction. There are large inter-individual differences in vulnerability to sleep loss, and these inter-individual differences constitute a pronounced human phenotype. However, this phenotype is multi-dimensional; vulnerability in terms of vigilant attention impairment can be dissociated from vulnerability in terms of other cognitive processes such as attentional control. The vigilance decrement, or time-on-task effect-a decline in performance across the duration of a vigilant attention task-is characterized by progressively increasing response variability, which is exacerbated by sleep loss. This variability, while crucial to understanding the impact of sleep deprivation on performance in safety-critical tasks, is not well explained by top-down regulatory mechanisms, such as the homeostatic and circadian processes. A bottom-up, neuronal pathway-dependent mechanism involving use-dependent, local sleep may be the main driver of response variability. This bottom-up mechanism may also explain the dissociation between cognitive processes with regard to trait vulnerability to sleep loss.

Introduction Sustained attention is important for optimal neurobehavioral performance, but many biological and environment factors (e.g., circadian rhythm, distraction) may cause sustained attention deficits. Mastication (chewing) has been suggested to provide a countermeasure to sustained attention deficits. To investigate this, we conducted a randomized, within-subjects, cross-over study of sustained attention with a mastication condition and a control condition. Methods N=58 adults (ages 18–45; 38 females) completed a 5h in-laboratory study. Subjects entered the laboratory at 09:00. Following training on performance tasks, they had a 1h break before beginning the first of two test bouts at 11:00. Each test bout was 40min long and included subjective rating scales, the Sustained Attention to Response Task, and the Psychomotor Vigilance Test (PVT). Here we focus on PVT lapses of attention (RT > 500 ms), false starts, and mean reaction time (RT) as measures of sustained attention. In between test bouts, subjects had a 1h break inside the laboratory. During one of the two test bouts, subjects were instructed to chew a piece of gum at a steady, comfortable rate. Mastication activity was verified via electromyography (EMG). Half of the sample was assigned to the mastication condition during the first test bout, the other half during the second test bout. Results Controlling for order of conditions, there were no significant differences between conditions for PVT lapses (F1,56=0.40, P=0.54) or false starts (F1,56=0.10, P=0.80). Mean RT was higher in the mastication condition by 8.9±2.5ms (F1,56 =12.68, P Conclusion Using this test paradigm, we were unable to detect any significant improvement in PVT performance, although mastication resulted in a very small increase in mean RT. However, subjects were not sleep-deprived, distracted, or otherwise perturbed. A follow-up study under conditions of sleep deprivation and/or with longer task duration may provide further insight into the countermeasure potential of mastication. Support Mars Wrigley Confectionery, U.S., LLC

Introduction Stimuli with an emotional valence tend to produce better recognition from memory than neutral stimuli. Sleep loss is believed to increase reactivity to negative stimuli, as compared to positive stimuli, which may comparatively enhance subsequent recognition from memory for negative stimuli. We investigated the impact of total sleep deprivation (TSD) on recognition accuracy for words with different emotional valence using the Affective Item Source Memory Task (AISM). Methods N=14 adults (ages 21–39; 7 females) completed a 4-day in-laboratory study with 9h baseline sleep (22:00-07:00), 39h acute TSD, and 9h recovery sleep. The AISM was administered at 16:30 during baseline and after 34h TSD. During a 5min study phase, participants heard a list, twice, of 20 positive, 20 negative, and 20 neutral words spoken with a male or female voice. During an immediately subsequent 8min recognition phase, participants heard 120 words (50% new) and judged whether each word had been presented in the study list (item memory). For words judged to have been presented previously, participants indicated whether those were presented by a female or male speaker (source memory). Results Mixed-effects ANOVA showed effects of session (p Conclusion Sleep deprivation reduced item memory for words of all valence types. However, there was no comparatively greater impact on item or source memory for negative words nor any differential effect of TSD for different valences. Whether our results would hold with longer time intervals between task phases or an intervening sleep period remains to be determined. Support Jazz Pharmaceuticals