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PubMed2005

Caffeine maintains vigilance and marksmanship in simulated urban operations with sleep deprivation.

PURPOSE: The purpose of this study was to examine the effects of caffeine (CAF) on physical, vigilance, and marksmanship tasks in soldiers during a sustained 55-h field exercise. METHODS: There were 30 soldiers (23.6 +/- 4.5 yr, 81.8 +/- 10.3 kg) who were divided into a placebo (PLAC) and a CAF group. After a period of restricted sleep of 3 h during the first night, a period of sustained wakefulness began that ended at 11:00 of the third day. PLAC or CAF doses of 100 mg, 200 mg, 100 mg, and 200 mg were administered at 21:45, 23:45, 01:45, and 03:45, respectively. At 22:00 of day 2, subjects began two cycles of marksmanship, urban operations vigilance, and psychomotor vigilance (PVT) testing which ended at 06:00 of day 3. RESULTS: CAF maintained marksmanship vigilance at 85% throughout the second night as compared with PLAC, who significantly declined to 61.4 +/- 28.2% overnight. Marksmanship accuracy also decreased significantly in PLAC from 95.1 +/- 8.3% to 83.3 +/- 19.2%, but no change was observed in CAF. Urban operations vigilance decreased for both groups over the night, but the decrease was less for CAF (81.2 +/- 14.4% to 63.4 +/- 24.1%) compared with PLAC (77.6 +/- 19.2% to 44.0 +/- 30.2%). Reaction time and the number of major and minor lapses with the PVT significantly increased in PLAC but were unaffected in CAF. CONCLUSIONS: It was concluded that CAF was an effective strategy to sustain vigilance and psychomotor performance during military operations involving sleep deprivation.

Adult↗
PubMed1993

Vigilance and its disorders.

Vigilance has been defined as steady-state alertness-wakefulness. The right cerebral hemisphere, predominantly the right inferior parietal lobule and posterior parietal cortices, seems specialized for vigilance. Studies of the primary disorder of vigilance, a genetically determined condition, should provide a better understanding of the neurobiology of vigilance. Common causes of secondary hypovigilance (depression, learning disability, narcolepsy, and acquired focal right cerebral hemisphere brain lesions) explain the symptom complex of ADHD. If these specific entities producing hypovigilance are correctly identified, treatment is successful and with favorable outcome. The neuroanatomic substrate of lowered vigilance seems to be loss of modulating influence of the right cerebral hemisphere on the diencephalon and select brain stem nuclei. We propose that the right (more than the left) cerebral hemisphere is responsible for alertness and wakefulness (vigilance) with the reticular formation being accountable for sleep.

Adolescent↗
PubMed1999

Working memory and vigilance: evidence from normal aging and Alzheimer's disease.

Both single unit recording and neuroradiological studies suggest that frontal and executive processes are necessary for visual maintenance rehearsal. This observation is linked to the classic vigilance literature by the proposal that vigilance decrement is found when the subject is required to maintain a representation over a brief delay. Vigilance performance was therefore studied in a sample of elderly subjects who were tested over a 40-min period involving perceptual or memory-based tasks which were matched for initial level of performance. There was a significant interaction between task and delay, with only the memory-based task showing decrement. A second study used the same two tasks to investigate vigilance performance in patients suffering from probable Alzheimer's Disease. Over a 15-min delay period, an equivalent interaction effect occurred, again indicating substantially greater decrement for the memory-based task. The results are interpreted as consistent with a role for the executive processes of working memory in both visual rehearsal and vigilance performance.

Aged↗
PubMed2002

The effects of sleep debt on vigilance in young drivers: an education/research project in high schools.

The vigilance levels of a group of 59 students were assessed in the daytime (9:00-11:00 a.m.) and again early Sunday morning (2:30-5:00 a.m.), and were then compared. Data were collected at the students' schools. The differences in performance impairment associated with different Saturday night social activities and the effect of alcohol consumption were evaluated. Results indicate a vigilance decrease during the night, and this is greater in subjects who consumed more alcohol. Students who spent their Saturday night in a discotheque showed the most prominent nocturnal vigilance decrease, even when the effect of alcohol consumption is covaried. The effect of social activities on vigilance levels was also associated with different lengths of time spent awake and the different time in which subjects performed the vigilance task.

Accidents, Traffic↗
PubMed1989

Reading, spelling, and vigilance in attention deficit and conduct disorder.

A group of 51 male children, average age 9.1 years, presenting at a child psychiatric clinic because of attention and conduct problems were investigated for reading and phonetic spelling ability, vigilance, and intellectual level. Each child was given a DSM-III diagnosis prior to being tested. The Boder Test of Reading and Spelling patterns was used to obtain scores for reading age, number of syllables read correctly in the word list at the child's reading level, and number of phonetically correct syllables spelled in the known and unknown word lists, at and just above the child's reading level. A factor analysis with varimax rotation produced two significant factors, a Reading factor with high loadings for verbal and reading scores, aand a second Vigilance factor. Phonetic spelling ability loaded separately from reading into the Vigilance factor. The Vigilance factor was significantly related to the diagnosis of moderate and severe attention deficit disorder with hyperactivity (ADDH). The correlation of short-term working memory with vigilance in moderate to severe ADDH children is discussed.

Achievement↗
PubMed1995

Behavioral vigilance in rats: task validation and effects of age, amphetamine, and benzodiazepine receptor ligands.

An operant task for the measurement of sustained attention or vigilance in rats was characterized. The task requires the animals to respond to the presentation of visual signals (presented for 25, 50, or 500 ms) by operating one lever ("hits") and to the absence of a signal by operating the opposite lever ("correct rejection"). Incorrect responses ("misses" and "false alarms", respectively) were not rewarded. Performance in this task is a function of signal length, i.e., the shorter the signals the higher the number of misses. An increase in "background noise" by flashing the chamber houselight (at 0.5 Hz) impaired the animals' ability to discriminate between signal and non-signal events. Also flashing the houselight augmented the vigilance decrement observed for shortest signals. An increase in the event-rate also resulted in a vigilance decrement. Finally, the inability of the animals to time signals was examined by testing the effects of an increase in event asynchrony. In a second experiment, the performance of differently aged rats (6- and 20 month-old male BNNia/F344 rats) was studied. Compared to young animals, 20-month-old rats showed a decrease in their ability to discriminate between shortest signals (25 ms) and non-signal events but did not differ in their ability to correctly reject non-signal trials. Administration of the benzodiazepine receptor (BZR) agonist chlordiazepoxide (CDP; 3, 5, 8 mg/kg) resulted in an impairment of the animals' ability to discriminate between signal and non-signal events and, similar to the effects of age, this effect was exclusively due to an increase in the number of misses. CDP generally produced potent effects while affecting the aged animals to a greater degree. BZR-ligands with weak or "selective" inverse agonist properties (ZK 93426; beta-CCtB) did not affect vigilance performance. The BZR partial inverse agonist RU 33965 (0.1, 0.5 mg/kg) dose-dependently impaired vigilance performance. The administration of amphetamine (0.4, 0.8 mg/kg) also impaired performance, but these impairments were possibly based on effects unrelated to attentional mechanisms. The finding that performance in this task revealed the interactions between the effects of age and BZR agonists on attentional abilities further supports the validity of measures of performance generated by this task.

Aging↗
PubMed2004

Identifying target regions for vigilance improvement under hormone replacement therapy in postmenopausal syndrome patients by means of electroencephalographic tomography (LORETA).

RATIONALE: Daytime fatigue, which at the neurophysiological level is due to vigilance decrements, is a frequent complaint in postmenopausal women. OBJECTIVES: In a three-arm, 2-month, parallel group-design study, vigilance-promoting effects of a novel continuous combination (=Climodien 2/3) of estradiol valerate (EV; 2 mg) and dienogest (DNG; 3 mg) were compared with the effects of both EV alone and placebo in 55 insomniac, postmenopausal syndrome patients. METHODS: Low-resolution brain electromagnetic tomography (LORETA) was undertaken to identify the cerebral target regions of hormone replacement therapy. RESULTS: An omnibus significance test revealed Climodien to increase activity in 882 of 2,394 voxels in the alpha-2 band, followed by 733, 706, and 664 voxels in the beta-2, beta-1, and beta-3 bands, and 509 voxels in the delta band, whereas 2 mg EV alone did not produce a significant suprathreshold activity. Current density increased predominantly in the right hemisphere, which had already been described in the literature as the center of the vigilance system. In the fast alpha range, which plays a major role in the context of vigilance, increased activity was found in the right prefrontal, temporal, and superior parietal cortices, i.e., those brain areas of the right-sided fronto-parietal neuronal network that are responsible for sustained attention. A further activity increase was seen in the anterior cingulate gyrus associated with attentional control and conflict monitoring. The right temporal lobe showed increased current density in all frequency bands. CONCLUSIONS: Electroencephalographic tomography (LORETA) identified the right-hemispheric vigilance system as the target region of Climodien.

Arousal↗
PubMed2004

EEG-tomographic studies with LORETA on vigilance differences between narcolepsy patients and controls and subsequent double-blind, placebo-controlled studies with modafinil.

The aim of the present study was to identify brain regions associated with vigilance in untreated and modafinil-treated narcoleptic patients by means of low-resolution brain electromagnetic tomography (LORETA). 16 drug-free narcoleptics and 16 normal controls were included in the baseline investigation. Subsequently patients participated in a double-blind, placebo-controlled crossover study receiving a three-week fixed titration of modafinil (200, 300, 400 mg) and placebo. Measurements comprised LORETA, the Multiple Sleep Latency Test (MSLT) and the Epworth Sleepiness Scale (ESS) obtained before and after three weeks' therapy. Statistical overall analysis by means of the omnibus significance test demonstrated significant inter-group differences in the resting (R-EEG), but not in the vigilance-controlled recordings (V-EEG). Subsequent univariate analysis revealed a decrease in alpha-2 and beta 1-3 power in prefrontal, temporal and parietal cortices, with the right hemisphere slightly more involved in this vigilance decrement. Modafinil 400 mg/d as compared with placebo induced changes opposite to the aforementioned baseline differences (key-lock principle) with a preponderance in the left hemisphere. This increase in vigilance resulted in an improvement in the MSLT and the ESS. LORETA provided evidence of a functional deterioration of the fronto-temporo-parietal network of the right-hemispheric vigilance system in narcolepsy and a therapeutic effect of modafinil on the left hemisphere, which is less affected by the disease.

Adult↗
PubMed1988

The importance of the concept of vigilance for psychophysiological research.

The variety of meanings nowadays attached to the notion of "vigilance" essentially conceals H. Head's object in view when introducing the term more than half a century ago. It may be supposed that a major reason for the existing confusion is that Head failed to distinguish explicitly between "vigilance" as a force, i.e., a reorganizing power ("vital activity") on the one hand and as a system's state ("state of the nervous system") established by the action of the reorganizing power, on the other. We try to explain that the original intention of "vigilance" is compatible with recently elaborated proposals according to which living systems have to be regarded as organizationally closed. Rather than regarding an organism only alternatively, i.e., either as organizational closed (alive) or open (dead), "vigilance" implies a graduated description according to the state of order which has actually been realized by "vigilance".

Arousal↗
PubMed2005

Coots Fulica atra reduce their vigilance under increased competition.

Birds frequently interrupt feeding to scan their surrounding environment. Usually an inverse correlation between scan rate and flock size exists. The 'many-eyes' hypothesis suggests that more eyes are able to detect a predator earlier. Due to the 'dilution-effect' animals in larger groups experience 'safety in numbers', while the 'scramble competition' hypothesis suggests that individuals reduce their vigilance in larger groups since they compete for a limited amount of scarce resources. Here, I induced competition in natural coot populations. Coots preferred feeding on grass and were occasionally fed by passers-by at the study sites. However, this resource was scarce and coots experienced additional food as a very limited resource. I sampled coots prior and after an experimental treatment with an additional food supply. Correlations between vigilance rate (number of scans during 1 min of foraging), nearest neighbor distance and flock size existed before the experimental treatment but afterwards the correlation between vigilance and nearest neighbor distance faded. I found a significantly lower vigilance rate and nearest neighbor distance after inducing competition. This study provided experimental evidence for the 'scramble competition' hypothesis namely that individuals in groups lowered their vigilance when faced with competition for a limited amount of food resources given similar flock sizes.

Animals↗
PubMed2004

Mental effort affects vigilance enduringly: after-effects in EEG and behavior.

Vigilance is assumed to decline with sustained task performance. The EEG-effects during performance on mental tasks, however, cannot be ascribed indisputably to vigilance decline per se. During task performance itself, effects of information processing and vigilance decline may be confounded. In this study, effects of sustained mental effort were studied in the absence of specific information processing, after sustained information processing had taken place, namely after an effortful 70-min intelligence test. Vigilance was determined by means of EEG-measures in a rest condition. Furthermore, behavioral performance was assessed on two different tasks, the traditional Clock test and the SART. After mental effort, theta power in the EEG and errors on the SART were increased. Beta2 power, however, also appeared enhanced. We conclude that sustained mental effort produces an enduring decrease in vigilance, but that some active processing is enhanced at the same time. A second study replicated the EEG-results after mental effort.

Adult↗
PubMed2005

Antipredator vigilance in birds: modelling the 'edge' effect.

Many animals spend a large proportion of their time either foraging for food or watching out for predators (antipredator vigilance). There have been many theoretical and empirical studies investigating the trade-off between these two activities, especially in birds. Previous models of antipredator vigilance assume that all birds within the group spend the same amount of time feeding. However, many empirical studies have shown that individuals on the edge of flocks are more vigilant. Here we describe a vigilance model which investigates the effect of position on the birds' strategies by dividing the feeding area into an inner and outer region. The model examines how various parameters such as food availability and predation risk affect the strategies of individual birds according to whether they are in the inner or outer region. Our model predicts that birds in the outer group are always more vigilant than those in the inner region. Birds in the centre receive a higher payoff in each of the wide range of scenarios that we have considered, and so our model also indicates why dominant birds would choose to feed in the centre of the group; a prediction in accord with several empirical studies.

Algorithms↗
PubMed2001

Variations of the level of vigilance and of behavioural activities during simulated automobile driving.

During a monotonous activity, certain behaviours occur that are not necessary to the performance of the task. These are subsidiary or collateral activities. Our purpose was to find out if the number of these behaviours tends to increase during a monotonous and prolonged activity. A study was carried out with 17 subjects performing a 2-h car drive on the Vigilance Analysis Driving Simulator. An analysis of the drivers' behaviour and of their state of vigilance allowed us to confirm the existence of a relation between the occurrence of these behaviours and the variations of the level of arousal. In addition, we determined for all produced behaviours, those that preceded, those that coincided with, and those that followed low vigilance phenomena. These results were interpreted in terms of behavioural signs, precursory of low vigilance, indicative of low vigilance, or reactivating the driver.

Adult↗
PubMed2000

Decrease of vigilance assessed by EEG-mapping in type I diabetic patients with history of recurrent severe hypoglycaemia.

In Type I diabetic patients with history of recurrent severe hypoglycaemia, a more rapid decrease in vigilance (slowing of brain function) during hypoglycaemia in comparison to patients without history of such events was found. Our aims were: (1) to study EEG parameters of vigilance in non-hypoglycaemic state in representative groups of Type I diabetic patients with and without previous recurrent severe hypoglycaemia; and (2) to compare them with non-diabetic controls. A vigilance-controlled EEG mapping (10-20 system, significance probability maps) was performed in a non-hypoglycaemic state (blood glucose 4.0-10.0 mmol/l) in a group of 13 Type I diabetic patients with a history of recurrent severe hypoglycaemia and compared to that of 14 Type I diabetic patients without history of severe hypoglycaemia, matched for HbA1c, age and gender, and to age- and gender-matched non-diabetic controls. When compared to non-diabetic controls, hypoglycaemia patients demonstrated a reduction in absolute power in beta band (13-35 Hz) and slowing of centroid frequencies of beta and total frequency bands (1.3-35 Hz) (up to P < 0.01), whereas patients without history of severe hypoglycaemia showed only a borderline reduction of absolute power in delta (1.3-3.5 Hz) band. Deceleration in hypoglycaemia patients versus those without recurrent hypoglycaemia was most remarkable (P < .01) in centroid frequency of total frequency band. Patients with history of recurrent severe hypoglycaemia demonstrated in non-hypoglycaemic state significantly reduced vigilance when compared to the group without hypoglycaemia history and to the controls, as well. Lower vigilance may be at least in part responsible for impaired hypoglycaemia perception in these patients, but, as it resembles EEG patterns seen in pathologic ageing, it might also represent a consequence of recurrent episodes of severe hypoglycaemia.

Adult↗
PubMed2002

Hormone replacement therapy and vigilance: double-blind, placebo-controlled EEG-mapping studies with an estrogen-progestogen combination (Climodien, Lafamme) versus estrogen alone in menopausal syndrome patients.

UNLABELLED: The aim of the double-blind, placebo-controlled study was to investigate the effects of a continuous combined estrogen-progestogen treatment (Climodien, Lafamme) as compared with estrogen alone on vigilance in insomniac postmenopausal syndrome patients, objectified by EEG mapping. METHODS: In a 3-arm, 2-month parallel group design phase, patients received a combination of estradiol valerate 2 mg and the novel progestogen dienogest 3 mg (Climodien 2/3) or estradiol valerate 2 mg alone or placebo. In a subsequent open-label phase, all patients received estradiol valerate 2 mg+dienogest 2 mg (Climodien 2/2). EEG mapping was carried out before and after the 2-month double-blind phase as well as after the 2-month open-label treatment. RESULTS: As compared with placebo, Climodien 2/3 induced a marked and highly significant increase in absolute power in all frequency bands, specifically in alpha-2 activity. Moreover, a significant increase in relative alpha-2 power, a decrease in relative delta and beta power as well as an acceleration of the dominant frequency and of the delta and alpha centroids suggested a marked improvement in vigilance. In contrast, under estradiol valerate 2 mg alone, only a slight augmentation of alpha and attenuation of relative delta and beta power occurred, suggesting only a slight vigilance improvement as compared with placebo. Thus, dienogest 2 mg increased the estrogen effect, which was also confirmed by a statistical evaluation of the differences between Climodien 2/3 and estradiol valerate alone (augmentation of alpha-2, attenuation of relative beta, acceleration of the dominant frequency). Moreover, Climodien 2/2 also markedly increased alpha-2 power, decreased relative beta-2 power and accelerated the alpha centroid. Finally, comparing Climodien 2/3 with Climodien 2/2, there was even a dose-efficacy relation. CONCLUSIONS: Estradiol valerate 2 mg improves vigilance slightly, thereby confirming previous findings. The additional administration of dienogest does not minimize the effect of estrogen, but on the contrary increases it, which makes the combination superior to both placebo and estradiol valerate alone. Vigilance improvement may be of great therapeutic benefit to menopausal syndrome patients at a time when increased adaptability is needed to adjust to increasing sexual, marital, occupational and social difficulties known to occur specifically in this period of life.

Aged↗
PubMed1998

Sleep fragmentation and daytime vigilance in patients with OSA treated by surgical maxillomandibular advancement compared to CPAP therapy.

Impaired vigilance is a frequent daytime complaint of patients with obstructive sleep apnoea (OSA). To date, continuous positive airway pressure (CPAP) is a well established therapy for OSA. Nevertheless, in patients with certain craniofacial characteristics, maxillomandibular advancement osteotomy (MMO) is a promising surgical treatment. Twenty-four male patients with OSA (pretreatment respiratory disturbance index (RDI) 59.3 SD +/- 24.1 events/h) participated in this investigation. The mean age was 42.7 +/- 10.7 years and the mean body mass index was 26.7 +/- 2.9 kg/m2. According to cephalometric evaluation, all patients had a narrow posterior airway space, more or less due to severe maxillary and mandibular retrognathia. All patients except two were treated first with CPAP for at least 3 months and afterwards by MMO. Two patients only tolerated a CPAP trial for 2 nights. Polysomnographic investigation and daytime vigilance were assessed before therapy, with CPAP therapy and 3 months after surgical treatment. Patients' reports of impaired daytime performance were confirmed by a pretreatment vigilance test using a 90-min, four-choice reaction-time test. The test was repeated with effective CPAP therapy and postoperatively. Daytime vigilance was increased with CPAP and after surgical treatment in a similar manner. Respiratory and polysomnographic patterns clearly improved, both with CPAP and after surgery, and showed significant changes compared to the pretreatment investigation. The RDI decreased significantly, both with CPAP (5.3 +/- 6.0) and postoperatively (5.6 +/- 9.6 events/h). The percentages of non-rapid eye movement Stage 1 (NREM 1) sleep showed a marked decrease (with CPAP 8.2 +/- 3.6% and after MMO 8.2 +/- 4.4% vs. 13.3 +/- 7.4% before treatment), whereas percentages of slow wave sleep increased significantly from 8.0 +/- 6.1% before therapy to 18.2 +/- 12.8 with CPAP and 14.4 +/- 7.3% after MMO. The number of awakenings per hour time in bed (TIB) was significantly reduced after surgery (2.8 +/- 1.3), compared to both preoperative investigation (baseline 4.2 +/- 2.0 and CPAP 3.4 +/- 1.5). Brief arousals per hour TIB were reduced to half with CPAP (19.3 +/- 20.0) and after MMO (19.7 +/- 13.6), compared to baseline (54.3 +/- 20.0). We conclude that the treatment of OSA by MMO in carefully selected cases has positive effects on sleep, respiration and daytime vigilance, which are comparable to CPAP therapy.

Adult↗
PubMed2001

Slow release caffeine and prolonged (64-h) continuous wakefulness: effects on vigilance and cognitive performance.

Some long work or shift work schedules necessitate an elevated and prolonged level of vigilance and performance but often result in sleep deprivation (SD), fatigue and sleepiness, which may impair efficiency. This study investigated the effects of a slow-release caffeine [(SRC) at the daily dose of 600 mg] on vigilance and cognitive performance during a 64 h continuous wakefulness period. Sixteen healthy males volunteered for this double-blind, randomised, placebo controlled, two-way crossover study. A total of 300-mg SRC or placebo (PBO) was given twice a day at 21:00 and 9:00 h during the SD period. Vigilance was objectively assessed with continuous electroencephalogram (EEG), the multiple sleep latency tests (MSLT) and wrist actigraphy. Cognitive functions (information processing and working memory), selective and divided attention were determined with computerised tests from the AGARD-NATO STRES Battery (Standardised Tests for Research with Environmental Stressors). Attention was also assessed with a symbol cancellation task and a Stroop's test; alertness was appreciated from visual analogue scales (VAS). Tests were performed at the hypo (02:00-04:00 h, 14:00-16:00 h) and hypervigilance (10:00-12:00 h, 22:00-00:00 h) periods during SD. Central temperature was continuously measured and safety of treatment was assessed from repeated clinical examinations. Compared with PBO, MSLT showed that SRC subjects were more vigilant from the onset (P=0.001) to the end of SD (P < 0.0001) whereas some cognitive functions were improved till the thirty third of SD but others were ameliorated through all the SD period and alertness was better from the thirteenth hour of SD, as shown by Stroop's test (P=0.048). We showed that 300-mg SRC given twice daily during a 64-h SD is able to antagonize the impairment produced on vigilance and cognitive functions.

Adult↗
PubMed2002

[The vigilance paradigm in schizophrenia research - studies on the Continuous Performance Test (CPT)].

Deficits in vigilance/sustained attention of schizophrenic subjects have been a main topic of neuropsychological schizophrenia research for many years. The degraded stimulus Continuous Performance Test (ds-CPT) is the standard paradigm for measuring vigilance. Measurement of vigilance requires the observation of the course of perceptual sensitivity over time. The present review shows that from a theoretical point of view it is possible to show vigilance deficits (as a decrease of sensitivity) with the ds-CPT if certain conditions are given. However, only in a few schizophrenia studies the course of sensitivity over time was evaluated, while in most studies merely the level of sensitivity was analysed. Results presented in this review suggest that level and course of sensitivity are largely independent variables. Vigilance can be operationalised adequately only when considering the course of sensitivity over time. Therefore there still is a considerable need for research on the meaning of vigilance deficits for manifestation, course and treatment of schizophrenia.

Attention↗