Several factors alter the effects of sleep deprivation on RT and the performance of vigilance tasks. Long, simple, low-interest, self-directed RT tests are most affected by sleep loss (Wilkinson, 1965). The effects of sleep deprivation on RT are partially reversed when feedback is given, when the task is shorter or more difficult, or when a reward is used as an incentive to performance, suggesting that increased motivation or interest may at least partially offset the effects of sleep deprivation (Steyvers and Gaillard, 1993; Wilkinson, 1965). This motivational effect may be similar to the improvement in alertness performance that occurs when subjects know they are nearing the end of the task (final push effect) (Bergum and Lehr, 1963). The increase in RT is greater when there is a relatively long interval between a warning signal and the imperative stimulus, less so when the interval is short, suggesting that excitation or phasic alertness deteriorates rapidly in the event of sleep deprivation (Cochran, 1992). RT performance in sleep-deprived individuals during the night is slowed in sitting but normal in standing (Caldwell et al., 2002). The effects of sleep deprivation are complicated by the interaction of diurnal variation (circadian phase) with monotonic effects (duration of sleep deprivation), which is consistent with the two-process model proposed by Borbely (Achermann and Borbely, 2003; Babkoff et al., 1991; Cajochen, 1999). In addition, the effects of sleep deprivation on performance are not uniform, and there is significant variability between subjects who are likely to represent individual characteristics (Bonnet and Arand, 2005; Van Dongen, 2004). These are words that are often used in combination with vigilance. The effects of sleep deprivation on other cognitive tasks were less consistent than the effects on RT and alertness tasks. To some extent, this lack of consensus is due to different experimental conditions and study designs (duration of sleep deprivation, length of the test battery, difficulty of the task, etc.). For example, Stroop`s change in performance was influenced by the pattern of sleep deprivation (Beaumont, 2001; Binks et al., 1999; Herscovitch et al., 1980).

Variable effects on memory may be related to the difficulty of the task (Cajochen, 1999; Harrison et al., 2000; Humphrey, 1994; Linde and Bergstrom, 1992; McCarthy and Waters, 1997; Smith, 2002). Significant effects were also observed on Sternberg`s working memory task and correlated with decreased fMRI activation in several areas of the brain, particularly the bilateral parietal cortexes (Mu et al., 2005). Sleep deprivation effects on Raven matrices (Linde and Bergstrom, 1992), verbal fluency (Horne, 1988), the Tower of London (non-verbal planning) (Horne, 1988), the rhythmic serial auditory addition test (Martin, 1996) and Trails B (Martin, 1996) have been reported. The effects of sleep fragmentation on cognitive abilities are generally less pronounced than the effects of sleep deprivation, despite similar effects on MSLT scores (Cote, 2003; Kingshott, 2000; Philip et al., 1994; Stepansky, 2002). It was a huge structure of great weight, and only unusual honesty – and vigilance – in the construction had saved it from destruction. Excitation is another term used differently by different groups of scientists, but refers more systematically to the non-specific activation of the cerebral cortex in relation to sleep-wake states. While alertness, as we have defined it, conceptually distinguishes it from arousal, most vigilance research has actually looked at changes in arousal caused by the use of subjects who are sleep deprived, have trouble sleeping, or taking tranquilizers. This problem is exacerbated by the fact that relative sleep deprivation is common in the healthy population (Bonnet & Arand, 1995b; Levine et al., 1988) help healthy individuals become sleepy while performing a tedious, often tedious task. Therefore, the aspect of alertness, which is different from the excitement that a normally awake person needs to accomplish a task over a long period of time, has not been studied physiologically as well. Attention generally refers to more targeted activation of the cerebral cortex, which improves information processing (Mesulam, 1990; Mountcastle, 1978; Parasuraman, 1998; Posner & Petersen, 1990), but one aspect, sustained attention, is used interchangeably with the most common use of vigilance (Parasuraman, 1998b). While focused attention, divided attention and shifting attention, as well as executive control of attention are important, sustained attention is the aspect closely related to vigilance systems and the only aspect of attention discussed in detail.

Alertness is another term that overlaps with arousal, but specifically includes cognitive processing. Some researchers use the terms phasic and tonic alertness (Nebes & Brady, 1993; Posner and Petersen, 1990). Phasic alertness refers to the orientation response (Sokolov, 1963) and tonic alertness is used as a synonym for alertness and sustained attention. Often, the guard makes silent shouts that act as a “guardian song” to reassure the rest of the group that a person is on guard. [23] In response to a vocalizing sentinel, the flute player (Turdoides bicolor) reduces his own alertness, moves further away from the group and feeds in more exposed places, resulting in higher absorption of biomass. [24] Sleep deprivation at night and partial sleep deprivation at night are consistently associated with excessive daytime sleepiness, as measured by subjective indices and TMLS (Beaumont et al., 2001; Bonnet and Arand, 1995a, 2003; Carskadon und Dement, 1982; Gillberg et al., 1994; Roehrs et al., 1989; Rosenthal et al., 1993). Drowsiness increases in proportion to the total duration of sleep deprivation (Rosenthal, 1993). There may be different effects depending on the stage of sleep deprivation, since REM sleep deprivation does not alter MSLT levels (Nykamp et al., 1998). Sleep fragmentation (frequent brief disturbances at regular intervals) also increases subjective daytime sleepiness, alters mood and decreases LTSD times, even when total sleep duration is normal according to conventional methods of visual sleep assessment and even when awakenings are subclinical (i.e. Based on EEG changes only) (Bonnet and Arand, 2003; Cote et al., 2003; Kingshott et al., 2000; Levine et al., 1987; Martin et al., 1996; Stepansky, 2002).

Sleep interruptions can be as rare as every 10 minutes, but they still have an effect on LTSS levels (Stepanski, 2002). The effects of sleep deprivation are cumulative, up to one week and beyond partial sleep deprivation (Carskadon, 1981; Dinges et al., 1997; Van Dongen, 2003). These sample sentences are automatically selected from various online information sources to reflect the current use of the word “vigilance.” The opinions expressed in the examples do not represent the opinions of Merriam-Webster or its editors. Send us your feedback. Many physiological signals have been used to assess alertness and sustained attention, of which only a few are mentioned in this section. Overall, there is an increase in slow frequency activity on the EEG and a decrease in the amplitude of event-related potentials with decreasing vigilance. In addition, at maximum attention, certain frequencies of awakening, for example alpha, are attenuated. This was first described as a desynchronization related to events (Pfurtscheller and Aranibar, 1977). However, event-related attenuation may be a better term because synchrony has often not been measured directly and it has become clearer that the maximum alarm state is associated with synchronous activity recorded by the cortex, only at faster frequencies, such as gamma frequencies (Kaiser and Lutzenberger, 2004; Steriade et al., 1996). These gamma frequencies are difficult to reliably detect in the scalp EEG because the skull acts as a low-pass filter and the EMG artifact contains a lot of activity in the gamma frequencies.