PVT reaction time

Figure 1 Individual PVT reaction times (msec) for a representative subject undergoing 88 hr (3.67 days) of total sleep deprivation. Reaction times are from the 10-min visual PVT test bouts at 20 00 on each day of deprivation at 12, 36, 60, and 84 hr of sustained wakefulness. Reaction times after presentation of each stimulus are represented by black bars. Blank spaces between reaction times represent false starts (errors of commission). Reaction times > 500 msec are termed performance lapses, or lapses in attention. After 12 hr of wakefulness, reaction times were comparable across the test bout, with no false starts. At 36 hr of wakefulness, there were occasional lapses in attention (RT > 500 msec), with some false starts near the end of the test bout. After 60 hr awake the frequency of performance lapses was increased a few minutes into the performance bout. At 84 hr of sustained wakefulness, there were significantly more lapses of attention, with RTs > 8000 msec, and a greater incidence of false starts. (From Ref. 44.)...

Figure 2 Mean PVT reaction times (log msec sem) across 40 hr of total sleep deprivation. Data from the first 10 min of a 20-min visual PVT performance bout—high workload—are represented by the closed squares data from the entire duration of a 10-min visual PVT performance bout—low workload—are represented by the open squares. The reaction time data (log transformed) were compared between the two groups using a mixed-model (workload by time awake) ANOVA. Reaction times during the first 10 min of the high-workload performance tests were significantly higher than those in the low-workload performance tests (F9 456 = 19.87, p <. 001). In addition, a decrease in reaction times across the 40 hr of wakefulness was evident in both workload groups (F9>456 = 2.17, p < 0.003). (From Doran et al., 2000.)...

Figure 3 Mean PVT reaction times (msec) and false starts (errors of commission) during 88 hr of total sleep deprivation and 88 hours of sleep deprivation with two 2-hour nap opportunities each day. Subjects in the total sleep deprivation (TSD) group (n = 13) are represented by the open circles. Subjects in the 88-hr sleep deprivation plus two 2-hr nap opportunities (NAP) group (n = 15) are represented by the closed squares. Nap opportunity periods were at 02 45-04 45 and 14 45-16 45 each day. The top panel illustrates mean reaction times ( s.e.m.) for each test bout across the experimental protocol. Subjects in the NAP group demonstrated little variation in reaction times across the experimental period, while subjects in the TSD group experienced significant impairment in performance, reflected in the increasing reaction times as time awake increased, with circadian variation in performance capability evident. The bottom panel illustrates mean number of errors ( s.e.m.) per test bout across the experimental protocol. A similar pattern of performance degradation in this variable was evident for both the NAP and TSD groups. (From Ref. 44.)...

Figure 5 Least-square regression lines fit for the linear relationship between mean and standard deviation of PVT reaction times (msec). Data are from n = 13 subjects undergoing 88 hr (3.67 days) of total sleep deprivation. This figure illustrates that while all subjects experienced a decline in neurobehavioral performance on the PVT, as illustrated by increased reaction times when responding to the visual stimuli, there is a significant degree of interindividual variability in the magnitude of neurobehavioral impairment, evident by the differing lengths of the lines fit to the data. (From Ref. 44.)...

Figure 7 PVT reaction times prior to the first uncontrolled sleep attack during total sleep deprivation. Fourteen subjects completed 42 hr of total sleep deprivation and completed a 20-min PVT every 2 hr (represented by the closed circles) 19 subjects completed 88 hr of total sleep deprivation and completed a 10-min PVT every 2 hr (represented by the open circles). The number of test bouts (up to 30) prior to an uncontrolled sleep attack (failure to respond for 30 sec on the PVT) is represented on the bottom abscissa, with time prior to the sleep attack (up to 6 min) represented on the top abscissa. In both subject groups a progressive decline in performance on the visual PVT was evident within minutes of an uncontrolled sleep attack on console. This study also demonstrated an increase in subjective sleepiness (measured using the Stanford Sleepiness Scale) in the test bouts prior to the one in which the first sleep attack occurred. Taken together, these findings suggest that even a very sleepy subject cannot fall asleep while performing computerized tasks without some levels of awareness. (From Ref. 95.)...

The Walter Reed Army Institute of Research s Department of Behavioral Biology has developed a field-deployable version of a commercial Psychomotor Vigilance Task (PVT) that has been widely used in sleep research. The software runs on handheld PDAs running the Palm Operating System (Palm OS). It is modeled after the simple reaction time task of Wilkinson and Houghton,57 as modified by Dinges and Powell.58 The Palm OS version incorporates additional stimulus, feedback, control, and data options developed by Dr. Thome. In laboratory studies, performance on the PDA task has been shown to be sensitive to time-on-task fatigue effects, sleep deprivation, and circadian variation.18 Field studies have utilized the PVT to measure the efficacy of caffeine gum as a sleep loss countermeasure. 

Due to the high barrier, it is safe to assume that the induction time is much shorter (by a factor of e Pvt) than the reaction time (1/T) so that the time dependence on the right hand side of Eq. 13 may be ignored. Then, noting that the derivative of a step function is a Dirac delta function, and using detailed balance one finds the desired formula ... 

Psychomotor vigilance task performance is exquisitely sensitive to lapses as classically defined by Bills (39), Warren and Clarke (37), Bjemer (41), and Williams et al. (43). Figure 1 displays consecutive individual reaction times during a 10-min PVT task from a single subject at 12, 36, 60, and 84 hr of wakefulness during an 88-hr total sleep deprivation protocol (44). After 12 hr of wakefulness, responses were maintained at a fast and consistent level. In contrast, much longer responses become evident in PVT trials undertaken as time awake increased. The lapses (conventionally defined at RT > 500 msec) demonstrated not only... 

The MSLT has been performed in patients with UARS, and abnormal results have been reported, but the test is often borderline normal, equating well with the complaint of fatigue. No systematic study of cognitive function has been performed in UARS patients, and investigation of mental lapses using tests such as the psychomotor vigilance task (PVT), a reaction-time test, is also lacking. But reevaluation of subjects treated with nasal CPAP demonstrated that sleep efficiency and MSLT scores improve (28). 

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