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PubMed1998

Feeding and vigilance behaviour of breeding ostriches (Struthio camelus) in a farming environment in Britain.

1. Vigilance and feeding behaviour of male and female adult breeding ostriches were recorded to determine feeding and scanning bout lengths, a time budget and the pattern of vigilance immediately after food was provided. 2. Males were more vigilant and fed for shorter periods than females immediately after concentrate food was delivered but not throughout the whole day. 3. Most interscan periods of males were below 40 s with a maximum of 90 s compared with most interscan periods of females lasting less than 70 s with a maximum of 160 s. 4. Gender differences in behaviour are attributed to increased male vigilance for predators and/or conspecifics, and increased female feeding required for egg production and greater opportunity to feed because of male vigilance.

Animals↗

PubMed2002

Age differences in perceived workload across a short vigil.

The main objective of this research was to investigate age differences in the perceived workload associated with the performance of a demanding, high event rate, vigilance task. Younger participants (n=26) aged 16 to 35 years (M=27.8) and older participants (n=24) aged 45 to 65 years (M=52.2) completed perceived workload scales (NASA-TLX) following a brief practice session (pretest) on the vigilance task, and then again following a test session (posttest) lasting nine minutes. In relation to the vigilance task, a statistically significant performance decrement was identified, but there was no evidence that performance differed according to age in respect to that decrement. However, a dissociation was found in relation to the perceived workload ratings: while no age differences were found in vigilance performance, the workload ratings revealed older participants to perceive a significantly greater increase in workload from pretest to posttest. These findings are considered theoretically in relation to the demands placed upon attentional resources, and their implications for both laboratory-based vigilance research, and workplace systems monitoring situations, are discussed.

Adolescent↗

PubMed1994

Monitor surveillance and vigilance of anesthesia residents.

BACKGROUND: Anesthesia residents take longer to detect changes in electronically monitored data during the induction phase of anesthesia during the maintenance phase. This study was performed to investigate the reasons for this delay and to validate a method of measuring vigilance. METHODS: The activity of ten residents was studied during 73 surgical procedures. Data were collected during three 15-min periods from each case: induction, starting with application of the electrocardiograph; maintenance, an arbitrary period between induction and emergence; and emergence, ending with detachment of the electrocardiograph. Vigilance was measured as the time taken to detect a change, from normal to abnormal, of an artificial parameter displayed on the physiologic monitor (response time). An observer simultaneously recorded each time that the resident looked toward the monitors. RESULTS: Vigilance to the monitor display was less during induction and emergence than during maintenance (P < 0.005). Residents spent less total time watching monitors during induction than during maintenance (P < 0.005), and the duration of each monitor observation was shorter (P < 0.0005). Anesthesia residents usually looked at the monitors several times before detecting the abnormal value. The measure of anesthesia vigilance correlated with independent measures of monitor watching time and frequency. CONCLUSIONS: The results suggest that during induction of anesthesia, which is a period of high anesthesiologist workload, residents glance toward monitors to gather data rather than scan displays. The results help to validate the method for measuring anesthesia vigilance.

Anesthesia↗

PubMed2005

Most obstructive sleep apnoea patients exhibit vigilance and attention deficits on an extended battery of tests.

Excessive daytime sleepiness, fatigue and altered attention are often experienced by obstructive sleep apnoea (OSA) patients. Although attentional problems are presumably responsible for part of the daytime functioning impairment in OSA, thorough investigation is unusual. Clinicians usually attribute these symptoms to somnolence. In clinical practice, only one isolated test is generally used to assess vigilance and attentional defects. It was hypothesised that most OSA patients exhibit a broad range of attentional deficits, beyond impaired maintenance of wakefulness, and a specific battery of tests is needed to correctly assess them. Three attentional tests were performed at 9:00, 11:00 and 13:30 h, measuring maintenance of wakefulness, sustained attention and divided attention. Twenty OSA patients (aged 51+/-12 yrs, apnoea/hypopnoea index 45+/-22 h) and 40 control subjects (aged 48.4+/-9.9 yrs) were tested. OSA patients performed significantly less well on the three tests than the controls at the three sessions. This battery of tests demonstrated that 95% of patients had vigilance and/or attentional impairment. Impairment patterns varied between patients. Vigilance is impaired in obstructive sleep apnoea patients over a wide range of attentional processes. Not only is their ability to remain awake in monotonous situations impaired but their ability to maintain attention in more stimulating conditions is also affected. A single test of vigilance is not sufficient and could underestimate impaired vigilance and attention in some patients.

Adult↗

PubMed2004

Performance vigilance task and sleepiness in patients with sleep-disordered breathing.

Altered vigilance performance has been documented in patients with sleep-related breathing disorders (SRBDs). Sleep fragmentation, sleepiness, respiratory disturbances and nocturnal hypoxaemia have been suggested as the pathogenesis of these deficits, yet it remains difficult to find a good correlation between performance deficits and the above factors. In the present study, which performance measure better characterised SRBD patients and the main factors implicated in these disturbances were examined. The study group consisted of 152 patients and 45 controls, all examined using a performance vigilance task and subjective sleepiness assessment. Speed and accuracy in the psychomotor vigilance task (PVT) were measured in patients and controls. Objective daytime sleepiness was assessed in the patient group using the maintenance of wakefulness test. In comparison with controls, PVT accuracy rather than speed seems to be affected in SRBD patients, with lapses and false responses significantly greater in patients with more severe objective sleepiness and higher apnoea/hypopnoea index. Although slowing and increased variability in reaction time were associated with shorter sleep latency in the maintenance of wakefulness test, subjective sleepiness, sleep fragmentation, nocturnal hypoxaemia and apnoea/hypopnoea index influenced mainly PVT accuracy. It is concluded that vigilance impairment, sleep fragmentation and severity of disease may partially and differentially contribute to the diurnal performance consequences found in sleep-related breathing disorders. Since the psychomotor vigilance task worsening is more marked in accuracy that in speed, measurement of lapses and false responses would better characterise the degree of diurnal impairment in these patients.

Adult↗

PubMed2000

The effects of signal salience and caffeine on performance, workload, and stress in an abbreviated vigilance task.

In 2 experiments, a 12-min computerized vigilance task was demonstrated to reproduce the vigilance decrement, high workload (NASA-TLX), and stressful character (Dundee Stress State Questionnaire) of vigilance tasks lasting 30 min or more. In Experiment 1, the abbreviated task was also shown to duplicate the signal salience effect, a major finding associated with long-duration vigilance tasks. Moreover, Experiment 2 showed that performance on the abbreviated task can be enhanced by caffeine - a drug that benefits long-duration tasks. This enhancement effect was limited to performance, however, suggesting that caffeine influences factors that control signal detection but not those that control task-induced stress. The results parallel those obtained with long-duration tasks and support a resource-depletion model of the vigilance decrement. The abbreviated task might be useful in situations in which long-duration tasks are precluded (e.g., performance assessment batteries, neuropsychological testing, and brain imaging).

Adolescent↗

PubMed1986

A new quantitative approach to the assessment of stages of vigilance as defined by spatiotemporal EEG patterning.

Electroencephalographically oriented research on vigilance needs valid measures for assessing the level of vigilance between wakefulness and sleep. When studying different psychologically, psychopathologically, and pharmacologically induced states, special attention has to be paid to minor alterations of the level of vigilance which are reflected, essentially, in topographical changes of alpha-activity (Stage A). Since vigilance is a dynamic process, brief fluctuations in the range of a few seconds must also be recorded. In our opinion existing methods of quantification do not fully meet these demands. We have, therefore, developed a relatively simple procedure which can be characterized as an attempt quantitatively to reconstruct visually, i.e., spatiotemporally defined patterns of vigilance. The usefulness of this method, which also has certain limitations, has been demonstrated in psychopharmacological studies.

Alpha Rhythm↗

PubMed1994

Covert orienting of attention controls vigilance decrement at low event rate.

Factors controlling sustained visual orienting were investigated by combining the paradigms of covert orienting and vigilance. Analysis suggests a close relationship between orienting of attention and vigilance which is dependent on the event rate during the vigilance task. At a low event rate both facilitatory and inhibitory effects of orienting are found. Vigilance decrement is related to the accumulation of inhibition over time, supporting Posner, et als 1984 theory. Invalid cues reduce the decrement. At a high event rate, however, neither facilitation nor inhibition effects are reliable, and vigilance decrement is related to limitations of the allocation of attentional capacity, supporting Parasuraman's multifactorial theory. The results suggest that facilitation and inhibition caused by orienting are important opposing mechanisms in visual attention, allowing the nervous system to control the distribution of attention both over visual space and over time.

Adolescent↗

PubMed1999

Health visitor screening versus vigilance: outcomes of programmes for detecting permanent childhood hearing loss in west Berkshire.

The Health Visitor Distraction Test (HVDT) screen for hearing was replaced in West Berkshire in 1989 with a vigilance programme incorporating a questionnaire. The detection of permanent congenital deafness (bilateral > 50 dB HL) for all children born since 1984 has been audited to compare the two regimes. Sixty-two cases met the criteria, giving an ascertainment of 1.0 per 1000. Performance was similar under the two systems for severe/profound losses (> 70 dB HL), but there was a longer tail of late-detected moderate losses (50-70 dB HL) under the vigilance regime. The sensitivity of the Health Visitor questionnaire in referring those with permanent hearing loss was very similar to that of the HVDT (39% compared with 42%). Coverage for the questionnaire was approximately 87%, but only 78% for the known cases. Referral rate was lower under the vigilance programme, at approximately 3%. The results suggest that a vigilance programme is likely to perform as well as the HVDT but no better. Despite subsequent modifications to the vigilance programme, the poor pickup of moderate losses probably indicates the limitations of parental and professional observation in detecting partial hearing problems. The evidence adds support to the recent recommendations for universal neonatal screening.

Age Distribution↗

PubMed2004

The role of memory representation in the vigilance decrement.

Working memory load is critically important for the overall level of performance on vigilance tasks. However, its role in a key aspect of vigilance-sensitivity decrement over time-is unclear. We used a dual-task procedure in which either a spatial or a nonspatial working memory task was performed simultaneously with a spatial vigilance task for 20 min. Sensitivity in the vigilance task declined over time when the concurrent task involved spatial working memory. In contrast, there was no sensitivity decrement with a nonspatial working memory task. The results provide the first evidence of a specific role for working memory representation in vigilance decrement. The findings are also consistent with a multiple resource theory in which separate resources for memory representation and cognitive control operations are differentially susceptible to depletion over time, depending on the demands of the task at hand.

Adolescent↗

PubMed2003

Effects of screen size and task difficulty on vigilance performance of older adults.

This paper describes an experiment to elucidate the effects of aging on vigilance performance with VDTs. In addition, the experiment was undertaken to evaluate whether the aging effects are affected by the degree of task difficulty and by the screen size of the VDTs. Forty healthy male volunteers were studied in two age groups of 20 participants. In the experiment, the participants were required to perform vigilance tasks, which were presented either on a conventional 17-inch display or a large-sized 110-inch display. The 60-minute task period was divided into three 20-minute phases assigning the tasks with two scenarios of different degrees of difficulty. Performance was measured using reaction time for detection and number of detection errors. The results pointed out three effects: (1) the performance of the vigilance tasks deteriorated more markedly among the older adults than among the younger adults; (2) the between-screen differences on the vigilance performance were significant for the older adults, but not for the younger adults; (3) the effect of screen size was amplified by increasing the degree of task difficulty. These data indicate that screen size and task difficulty have an effect on vigilance performance with VDTs of older adult.

Adult↗

PubMed1999

Families at the bedside: an ethnographic study of vigilance.

BACKGROUND: Vigilance, the close protective involvement of family members with hospitalized relatives, is a relatively recent phenomenon in the hospital setting. Before the 1960s, hospital visiting policies restricted the presence of family members at the bedside. Policies changed during the 1960s and 1970s when health care professionals recognized that parents' staying with their hospitalized children was beneficial for both the parents and the children. Vigilance later became a phenomenon that included family members staying with adult patients. METHODS: Two ethnographic studies were conducted to examine the meanings, patterns, and day-to-day experience of vigilance. Sixteen family members, described by the nursing staff as staying with the patient, participated in informal semistructured interviews. Participant observation was also used in data collection. RESULTS: Data analysis yielded 5 categories of meaning that describe the experience of vigilance: commitment to care, emotional upheaval, dynamic nexus, transition, and resilience. CONCLUSIONS: Managed care, shortened hospital stays, and cost containment make early involvement of the family in the patient's care imperative. An understanding of the family's needs and experiences is prerequisite to that involvement. The categories of meaning discovered in this research can help health care providers understand family members' experience of vigilance. The implications for the family physician include sensitization and awareness of family members' experiences and the developing of specific actions and interactions fostering a commitment to family-centered care that extends to the hospital setting.

Adolescent↗

PubMed1992

[Ketamine racemate or S-(+)-ketamine and midazolam. The effect on vigilance, efficacy and subjective findings].

Ketamine is a racemic mixture containing equal amounts of optical isomers that have almost identical pharmacokinetic properties but different pharmacodynamic effects. The S-(+)-isomer of ketamine has about twice the anaesthetic and analgesic potency of the racemic ketamine preparation and is judged to induce less psychic emergence reactions and to be followed by a more rapid recovery of vigilance. The present study was designed to assess whether the S-(+)-isomer of ketamine is superior to the racemic mixture in cardiovascular characteristics, emergence reactions and cognitive functions, and whether side effects may be reduced or prevented by administration of midazolam prior to injection of S-(+)-ketamine. METHODS. Following ethics committee approval and informed consent, 30 volunteers were randomly allocated in this double-blind study to three groups of 10 each. Group 1 received 2 mg/kg bw racemic ketamine, group 2, 1 mg/kg bw S-(+)-ketamine and group 3, 1 mg/kg bw S-(+)-ketamine after premedication with 0.1 mg/kg midazolam i.v. Cardiovascular changes, state of vigilance, cognitive performance, subjective mood and acceptance of anaesthesia were assessed by means of haemodynamic routine monitoring, electroencephalography (EEG), psychometric tests and interview. RESULTS. The increases in mean arterial pressure and heart rate following the injection of racemic ketamine and S-(+)-ketamine were identical and the differences from baseline values significant after both. Premedication with midazolam ensured stable haemodynamics after injection of S-(+)-ketamine. EEG analysis displayed the characteristic changes well known from ketamine anaesthesia for both racemic and S-(+)-ketamine. The vigilosomnoscript showed an identical profile of vigilance up to 30 min after injection of both drugs. The vigilance status after 125 min was less impaired by S-(+)-ketamine than by racemic ketamine. Psychological assessment showed a prompter recovery of visual attentiveness and sensorimotor performance in the S-(+)-ketamine group. Subjective mood was judged by the volunteers to be significantly better after S-(+)-ketamine, and volunteers found S-(+)-ketamine to be more acceptable than racemic ketamine. The frequency of dreams was the same after both drugs. No unpleasant dreams were reported after S-(+)-ketamine, but one of the volunteers who received racemic ketamine had uncomfortable dreams. Midazolam prevented any unpleasant emergence sequelae. On the other hand, the cognitive performance could not be restored to the baseline values until at least 240 min after injection of S-(+)-ketamine, because of the sedative effects of midazolam. DISCUSSION. These results suggest that S-(+)-ketamine offers the advantages of faster recovery of cognitive performance, greater acceptance by the volunteers and identical depth of anaesthesia after injection of half the dose compared with racemic ketamine. The clinical use of S-(+)-ketamine therefore seems to be justified. Premedication with benzodiazepines, e.g. midazolam, is essential. The dose to be administered, however, should be carefully selected in order not to abolish the positive effect of S-(+)-ketamine on vigilance by the sedative effects of the benzodiazepine.

Adult↗

PubMed1979

Vigilance of performance of mildly mentally retarded children.

The contribution of developmental factors to the vigilance performance of mildly mentally retarded children was investigated by comparing their vigilance performance with that of nonretarded children of the same CA and with younger nonretarded children of about the same MA. The retarded children showed an earlier and faster decline in vigilance performance than did the CA control group. This result was similar to that of Semmel (1965), but contrasted with that of Kirby, Nettlebeck, and Bullock (1978), who found no such difference in vigilance performance when comparing mildly mentally retarded and nonretarded adults. The MA control group performed in a similar way to the retarded children, suggesting that the more rapid decline in vigilance performance was largely a developmental phenomenon.

Adolescent↗

PubMed1980

[Study of vigilance after ingestion of zopiclone in comparison with nitrazepam and placebo (author's transl)].

Increasing importance is being given to the residual effects of hypnotics on the day following absorption; with zopiclone, a new hypnotic, we have studied vigilance 9, 12 and 15 hours after a single evening dose of 10 mg, on a double-blind basis in comparison with 10 mg of nitrazepam and a placebo. The assessment of vigilance is based on responses to self-rating questionnaires and psychometric tests. Twenty-one healthy subjects forming a homogeneous group as regards age, I.Q., and vigilance were included in this study. Each subject received the three products in random distributed order, with an interval of three months between each trial. The results of these tests reveal modifications which, particularly 9 hours after administration, reflect a modification in vigilance, appearing to be more marked with nitrazepam than with zopiclone. Thus, from the point of view of the residual effects of hypnotics on vigilance, it is possible to position the products tested in the following order: placebo -- zopiclone -- nitrazepam.

Arousal↗

PubMed1996

[Vigilance-decreasing effects of 2 plant-derived sedatives].

Previous studies on the efficacy of valerian extracts have given occasional hints of possible side effects involving impaired vigilance. Because of the currently insufficient knowledge about potential impairment of vigilance by plant-based sedatives, we have conducted a controlled study to assess the effects of two plant-based sleep remedies in comparison with flunitrazepam and placebo after single oral administration. Aim of the study was to derive recommendations concerning potential hazards in driving or operating machinery. Residual sedative effects (hangover) were examined in four groups of 20 healthy volunteers, receiving either tablets containing valerian and hops or syrup containing valerian only or flunitrazepam or placebo; furthermore, immediate sedative effects of the two plant preparations have been examined in comparison with placebo (three groups of twelve healthy volunteers). The tests included objective measurements of cognitive psychomotor performance as well as subjective questionnaires on well-being. Tolerability was assessed from spontaneous reports of side effects and a verbal inquiry at the end of the tests. We found that objectively measurable impairment of performance on the morning after medication occurred only in the flunitrazepam group, a finding which was even more pronounced in the subjective questionnaires. In addition, 50% of the volunteers in the flunitrazepam group reported mild side effects in the inquiry at the end of the tests, compared with only 10% from the other groups. The subjective perception of sleep quality was improved in all three medication groups, when compared to placebo. Examination of acute effects of the plant remedies 1 to 2 hours after administration revealed no changes in the more important lead variables; however, a very slight impairment of vigilance after taking syrup was statistically significant as well as a retardation in the processing of complex information for the tablets. The subjective perception of effects was more pronounced (shaky legs, feeling less active). In conclusion, the residual sedative effects (hangover) observed in some earlier studies cannot be confirmed for the recommended doses of the two plant-based sleep remedies which we have examined with respect to vigilance and cognitive performance. On the contrary: our findings show improved subjective self-assessment (more alert, more active, feeling better). Hangover effects on the following morning need not be a cause for concern, which is of particular interest to car drivers; however, a slight impairment of performance during the first few hours after ingestion should be anticipated. Impairment of vigilance on the morning after ingestion of benzodiazepines, frequently reported and confirmed by our results, constitutes a potential hazard. In this situation, plant remedies such as those examined in this study should be considered as viable alternatives.

Adult↗

PubMed1997

Effects of benzodiazepines, sleep and sleep deprivation on vigilance and memory.

Anterograde amnesia is one of the troublesome adverse effects of the benzodiazepines, especially when they are used as tranquillizers. Interestingly, benzodiazepines also produce retrograde facilitation. In this review, a unifying hypothesis concerning both the cognitive enhancement and the cognitive decrement is discussed: the decrease in vigilance or sedative-hypnotic properties of the benzodiazepines induces a superficial type of encoding and consolidation. This is expressed in anterograde amnesia. The shallower encoding also causes less retrograde interference and retrograde facilitation is the result. In this way also the positive effect of sleep on memory is explained. In a series of experiments, this hypothesis was investigated. Anterograde amnesia and retrograde facilitation was demonstrated after benzodiazepine intake in healthy, volunteers. It was striking that amnestic effects and retrograde facilitation were most prominent when memory was tested one week after drug intake. A decrease in vigilance was also obtained by sleep deprivation and an increase by the gavage of the central stimulant methylphenidate. The latter vigilance increasing drug did not change memory aspects. Also memory effects were hardly present in sleep deprived subjects with low levels of vigilance and the performance on memory tests were not changed. This jeopardizes the vigilance hypothesis of the memory effects of the benzodiazepines. However, amnesia under the influence of benzodiazepines was less for semantic related words than for unrelated words. This suggests that information might be stored without appropriate contextual cues. Only under special circumstances this information can be retrieved. It is further speculated that this storage costs less efforts leading to less retrograde interference and consequently retrograde facilitation.

Amnesia↗

PubMed2003

Fear of loss of vigilance: development and preliminary validation of a self-report instrument.

We describe the development and initial validation of the Fear of Loss of Vigilance Questionnaire (FLOVQ). Recent investigations indicate that individuals with nocturnal panic (NP) demonstrate increased anxiety and panic in response to meditative relaxation and imagined hypnosis, compared to those with daytime panic (DP) only, suggesting that NP individuals fear situations that involve a loss of vigilance (e.g., relaxation, fatigue and altered states of consciousness). The FLOVQ was designed to assess this construct and was tested in five non-clinical samples and one clinical sample. The 14-item instrument demonstrated good internal consistency and test-retest reliability. Non-clinical respondents who experienced NP endorsed greater fear of loss of vigilance than non-panickers; those who only experienced DP did not differ from the other groups. By contrast, on measures of trait and state anxiety, and anxiety sensitivity, both panic groups scored higher than non-panickers, suggesting that these latter measures were related to broader factors pertaining to a general tendency to panic versus a specific factor associated with NP. No group differences were found between NPs and DPs in either the non-clinical or the clinical sample, suggesting that fear of loss of vigilance may be a vulnerability factor for the development of NP and that the FLOVQ has more utility as a research rather than as a clinical instrument.

Adolescent↗