Showing papers on "Vigilance (psychology) published in 1994"

Combined spatial and temporal imaging of brain activity during visual selective attention in humans.

Abstract: VISUAL–SPATIAL attention is an essential brain function that enables us to select and preferentially process high priority information in the visual fields1,2. Several brain areas have been shown to participate in the control of spatial attention in humans3–5, but little is known about the underlying selection mechanisms. Non-invasive scalp recordings of event-related potentials (e.r.ps) in humans have shown that attended visual stimuli are preferentially selected as early as 80–90 ms after stimulus onset6,7, but current e.r.p. methods do not permit a precise localization of the participating cortical areas. In this study we combined neuroimaging (positron emission tomography) with e.r.p. recording in order to describe both the cortical anatomy and time course of attentional selection processes. Together these methods showed that visual inputs from attended locations receive enhanced processing in the extrastriate cortex (fusiform gyrus) at 80–130 ms after stimulus onset. These findings reinforce early selection models of attention8–10.

Effects of Attention Training on Information Processing in Schizophrenia

Abstract: This study evaluated the impact of a cognitive retraining intervention designed to enhance the attention skills of schizophrenia patients. The dependent variables included measures of perceptual sensitivity and sustained vigilance derived from a visual continuous performance test, as well as visual span of apprehension and world-list recall. Sixteen subjects received approximately 15 hours of repeated practice with computer-mediated vigilance tasks. Seventeen subjects were assigned to a no-treatment control group. All subjects were rated on measures of negative and positive symptoms before treatment. Despite improved performance on the training tasks, no significant changes on the outcome measures were observed following treatment. Thus, it is suggested that cognitive rehabilitation interventions with schizophrenia patients stress the teaching of behavioral strategies that bypass deficits, rather than remediating deficiencies in basic abilities, such as attention.

Vigilance in African Mammals: Differences Among Mothers, Other Females, and Males

Abstract: The time devoted to eating, vigilance (or scanning), walking and aggression was studied in one-minute focal animal samples as a function of sex, age, and motherhood for several African animals including African elephant, Burchell's zebra, Cape buffalo, Defassa waterbuck, impala, and Uganda kob. Between 24 and 45 percent of the variation in vigilance behavior was accounted for by location (center or edge of herd), sex, age and whether a female had young. Time of day entered the linear multiple regression models for two species, and surprisingly group size did not enter any of the linear multiple regression models in 1993. In general, females with young were more vigilant than their young or females without young. There were few gender differences in vigilance among animals without young, except that male zebra, wildebeest and waterbuck were more vigilant than females. Animals on the edge of herds devoted more time to vigilance than intermediate or central animals (regardless of sex or age class). Although there was no relationship between group size and vigilance in 1993 when all herds were considered, there was a decrease in vigilance with increasing herd size for impala and kob for herds less than 50. Moveover, herd size and vigilance were negatively correlated in our 1984-1985 study, due partly to differences in group sizes. In 1984-1985 animals were not migrating, and were in relatively small, discrete groups, whereas in 1993 some species were migrating in large herds that stretched for several km. We suggest that in 1993 herd size was above a threshold where increases in group size can lead to further decreases in vigilance. Under these circumstances, location in the herd becomes paramount: Outside animals can be directly exposed to attack. Consequently animals on the edge devote more time to vigilance than central animals.

Ontogenetic variations in auditory arousal threshold during sleep

Abstract: Developmental variations in auditory arousal thresholds during sleep were investigated in four groups of normal male subjects--children, preadolescents, adolescents, and young adults. Arousal thresholds were determined during NREM and REM sleep for tones presented via earphone insert on a single night following two adaptation nights of undisturbed sleep. Age-related relationships were observed for both awakening frequency and stimulus intensity required to effect awakening, with awakenings occurring more frequently in response to lower stimulus intensities with increasing age. Although stimulus intensities required for awakening were high and statistically equivalent across sleep stages in nonadults, higher intensity stimuli were required in Stage 4 relative to Stage 2 and REM sleep in adults. These results confirm previous observations of marked resistance to awakening during sleep in preadolescent children and suggest that processes underlying awakening from sleep undergo systematic modification during ontogenetic development.

Methylphenidate and information processing. Part 1: Differentiation between responders and nonresponders; Part 2: Efficacy in responders.

Abstract: Part 1 of this study attempted to discriminate clinical responders and nonresponders to methylphenidate (MPH) on the basis of neuropsychological deficit profiles. Part 2 addressed the question to what extent MPH might ameliorate these deficits. Hyperactive clinical responders (n = 30) and nonresponders (n = 28) to MPH, were compared to normal controls (n = 27) on selective and sustained attention tasks and on conventional psychological and neurological measures. The responders took part in a randomized double-blind placebo-controlled crossover study. They ingested a placebo (PL) or MPH (0.3-0.6 mg/kg/day) during 4 weeks, and were then tested. After crossover, another period of 4 weeks was concluded by a second test series. Compared to controls, both responders and nonresponders showed attention deficits in encoding, memory search, and decision operations, as well as in focused and sustained attention, vigilance, and use of feedback. These deficits were the most severe in the responders. Anamnestic data, IQ scores, and neurological variables did not discriminate between groups. MPH selectively alleviates attention deficits. MPH did not affect divided attention, except for an increased accuracy of response organization. The drug, however, greatly improved focused and sustained attention, vigilance, impulsivity, and the behavioral adaptivity to feedback.

Impulsivity and Time of Day: Is Rate of Change in Arousal a Function of Impulsivity?

Abstract: Impulsivity has been interpreted as a stable mediator of rate of change in arousal states. To test this hypothesis, 129 Ss differing in impulsivity were given placebo or caffeine at 9:00 a.m. or 7:30 p.m. Recognition memory was tested for the last 20 items from 2 lists of 24 items and 2 lists of 80 items. Scores from this paradigm reflect sustained attention and are thus sensitive to changes in arousal. A 4-way interaction among impulsivity, time of day, drug, and prior stimuli (p < .05) indicated that for those given placebo, recognition memory for long and late lists was poorer the higher the impulsivity in the morning; this pattern reversed in the evening. Caffeine reduced recognition errors. These results indicate that impulsivity is not a stable predictor of rate of change in arousal states. Instead, susceptibility to attentional lapses is mediated by impulsivity-r elated phase differences in diurnal arousal rhythms.

Enhancing caffeine reinforcement by behavioral requirements following drug ingestion.

Abstract: Each morning eight adults with caffeine versus placebo discrimination histories ingested letter-coded capsules containing 100 mg caffeine or placebo and then engaged in a relaxation or vigilance activity. Subjects were first exposed to caffeine and placebo once each with each activity. Then each day for 10 days subjects made two choices; they chose which compound they would prefer if vigilance were scheduled and which they would prefer if relaxation were scheduled, with the restriction that they could not choose the same compound with both activities; only one choice (randomly selected) was reinforced. Eight of eight subjects always chose caffeine with vigilance. The next choice condition was identical, except that subjects were free to take either compound with both activities. Six of six subjects reliably chose caffeine with vigilance. Four reliably chose placebo with relaxation. In the final condition, each day for 10 days subjects chose between each drug and each of 52 monetary values; those choices were made separately for vigilance and relaxation; only one choice (randomly selected) was reinforced. For six of seven subjects, the maximum dollar value at which subjects chose drug over money was higher for caffeine in vigilance than for placebo in either activity. For five subjects, the maximum value at which subjects chose caffeine over money was higher in vigilance than in relaxation. Overall, this study demonstrates enhanced caffeine reinforcement when a vigilance activity followed drug ingestion.

Monitor Surveillance and Vigilance of Anesthesia Residents

Abstract: Background: Anesthesia residents take longer to detect changes in electronically monitored data during the induction phase of anesthesia than 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

Cognitive effects of milacemide and methylphenidate in healthy young adults

Abstract: Cognitive effects of the novel glycine prodrug milacemide (400 mg), the catecholaminergic agonist methylphenidate (20 mg), and placebo were evaluated in 48 healthy young adults. Throughout a 6-h drug treatment day, subjects repeatedly performed tests of target-detection vigilance, immediate and delayed verbal free recall, and Buschke Selective Reminding; total free recall and forced-choice recognition tests were administered at the end of the day. Significant improvement in both vigilance reaction time and Selective Reminding Sum Recall was observed in the methylphenidate group. Contrary to expectations, the milacemide group evidenced significantdeclines in both vigilance perceptual sensitivity and free-recall difference scores (delayed-immediate). Vigilance reaction times significantly decreased over repeat testing in all groups, but only the methylphenidate group differed from placebo. The reaction-time functions for milacemide and placebo were similar, suggesting arousal was not diminished under milacemide and could not account for the cognitive decrements. No significant drug effects obtained for total free recall or recognition performance. Although the glycine prodrug milacemide was ineffective as a cognitive enhancer, the involvement of the NMDA receptor in memory function reported in the literature supports continued exploration of other approaches for manipulating NMDA receptor activity.

Modulation of drug reinforcement by behavioral requirements following drug ingestion.

Abstract: Eight volunteers with histories of drug abuse participated in two experiments examining the modulation of drug choice by behavioral requirements following drug ingestion. Each morning subjects ingested color-coded capsules containing triazolam (0.25 mg), d-amphetamine (15 mg), or placebo and then engaged in a relaxation or a computer vigilance activity. Experiment 1 involved two phases (i.e. a triazolam and a d-amphetamine phase), presented in counterbalanced order. Within each phase, subjects were first exposed to each of two compounds (placebo and either triazolam or d-amphetamine) once with each activity. Then every other day for 20 days subjects chose which compound they ingested with the vigilance and relaxation activities, with the restriction that they could not choose the same compound with both activities. Seven of eight subjects reliably chose d-amphetamine with the vigilance activity; all subjects always chose triazolam with the relaxation activity. In experiment 2 (5 days' duration), after re-exposure to the color-coded compounds used in experiment 1, subjects chose which compound (placebo, d-amphetamine or triazolam) they ingested with the vigilance activity, and on another occasion (in counterbalanced order), which they ingested with relaxation activity. Seven of eight subjects chose d-amphetamine with the vigilance activity; all subjects chose triazolam with the relaxation activity. The relaxation and vigilance activities modulated triazolam and d-amphetamine reinforcement, thereby demonstrating a new class of environmental variable that can influence drug self-administration.

Attention and vigilance functions in normal aging.

Abstract: Clinical observation and considerable research have documented that a slowing of cognitive processing occurs in many healthy older persons. The neuropsychological characterization of this slowing, however, remains unclear, as does its neuroanatomic basis. In a preliminary attempt to help clarify this issue, we conducted two studies with healthy older individuals to evaluate whether declines in immediate and/or sustained attention appear with advancing age. In Study I, 166 subjects aged 50-69 and 70-90 were given several standard tests of immediate attention. No major differences in simple attentional function emerged. In Study II, 38 subjects in the same age ranges were administered tests of sustained attention. Significant differences between groups were seen on a digit cancellation task, despite similar performances on other measures requiring visual scanning and psychomotor speeded responses. The results of the two studies suggest that whereas simple attention tends to remain stable with aging, sustained attention appears to decline after the age of 70. This factor likely contributes to the general slowing of cognition often reported in the elderly, and may be associated with specific age-related neuroanatomic changes.

Effects of target probability and memory demands on the vigilance of adults with and without mental retardation

Abstract: The vigilance of young adults with mild mental retardation and without mental retardation was compared in two experiments in which observers performed two memory demanding, cognitively based, 60-minute tests. In Experiment 1, target probability was 5% or 30% with a 1.5-second event rate. Detection by observers with mental retardation declined more rapidly than did that of observers without mental retardation in both target probability conditions; further, their response criterion became increasingly more conservative. In Experiment 2, target probability was 10% or 30% with an 8-second event rate. Observers with mental retardation detected fewer targets under both target probability conditions. Subjects' response criterion differed as a function of level of intelligence from the onset of the vigil and did not change with time on task. Intelligence-related differences in vigilance were explained in terms of subjects' information-processing abilities.

Sleep apnea and vigilance performance in a community-dwelling older sample

Abstract: Impaired vigilance performance has been reported in older subjects with sleep apnea syndrome (SAS). The current study is an attempt to extend these findings and to investigate additional factors that might have implications for vigilance in the older adult. Fifty-nine older adults [age: 62 +/- 5 (mean +/- SD), range 54-75 years; respiratory disturbance index (RDI): 8.8 +/- 14.4 (mean +/- SD), range 0-67.5] were categorized as SAS or NotSAS, based on various classification criteria [i.e. apnea index (AI) > or = 5, and 10, RDI > or = 5, 10 and 15], and were compared on their vigilance performance as assessed by the computer program "Steer Clear". Vigilance performance did not discriminate the groups, independent of how they were formed. Groups were then formed based on vigilance performance (HiVig vs. LowVig) and compared on assorted sleep variables, periodic leg movements, and self-reported hypersomnolence and depression. Only age discriminated vigilance performance (an inverse relationship), accounting for 31% of the observed variance. Our findings suggest that subject selection may unintentionally bias findings regarding the neuropsychological functioning of individuals with SAS, that vigilance may be impaired only in relatively more "severe" SAS, and that severity of SAS in older adults may not be well characterized by current classification standards. Age clearly impacted vigilance performance, despite the constricted age range sampled, and should be taken into account in future research.

A laboratory study of patients with chronic allergic rhinitis: Antihistamine effects on skilled performance

Abstract: Twenty-four patients with chronic allergic rhinitis participated in a study of antihistamine effects on skilled performance They were tested while experiencing symptoms and when they were free of symptoms Within each symptom condition, they attended two sessions; each patient received a placebo capsule at one session and a 50 mg diphenhydramine capsule at the other Subjects performed a battery of skilled performance tests, which included the Divided-Attention, Visual Backward Masking, Stimulus Response Conflict, and Vigilance tests They rated the treatments and their performance Affective states were assessed with the Profile of Mood States Symptoms did not affect performance Diphenhydramine impaired vigilance performance and measures of Divided Attention and Stimulus Response Conflict Visual Backward Masking performance was not affected The largest performance changes occurred when diphenhydramine was administered to subjects when they were free of symptoms

Countering loss of vigilance in sonar watchstanding using signal injection and performance feedback

Abstract: Sonar operators are confronted with a watchstanding task that demands high levels of vigilance for the appearance of weak or transitory signals. Maintaining vigilance is difficult because of very low target signal rates and an open loop system with (usually) no performance feedback. Four experiments were conducted to see whether operator vigilance, as reflected by target detection latency, could be enhanced through signal injection and performance feedback. In each of these experiments, target detection performance was markedly enhanced. The effects were operationally and statistically significant and generally increased with time on watch. The beneficial effects were shown not to be simply a function of increased signal rate due to signal injection. Analysis using a signal detection theory model showed that the target reporting threshold dropped under the experimental treatment and detection efficiency increased. In addition, it was shown that the subjects spent significantly more time observing the sear...

Auditory information processing in sleep : late cortical potentials in an oddball paradigm

Abstract: Information processing of auditory stimuli in sleeping healthy volunteers is studied by means of an oddball paradigm. Latencies of the early (N1P2) complex are affected by NREM sleep depth and show a progressive slowing. The amplitude of the early N1 component depends on stimulus type and probability and is increased following deviant stimuli. In strict comparison with waking, late responses (N2-P3) complex only follows deviant stimuli. Both latencies and amplitude increase more in NREM than in REM sleep. Thus the early response is mainly affected by vigilance, the late response mainly depends on stimulus type. Results are discussed in terms of comparison processing, context updating and orienting response patterning hypotheses put forward in cognitive psychophysiology.

Maintaining vigilance on a simulated atc monitoring task across repeated sessions

Abstract: This study assesses changes in vigilance/attention of air traffic controllers across 3 separate days as subjects performed an air traffic control (ATC) simulation task. Twenty subjects on 3 days monitored a simulated ATC task for 44 critical events over a 2-hour session. The complex monitoring task included the detection of: altitude malfunctions; aircraft conflict/ no conflicts where 2 aircraft were at the same altitude on an airway simultaneously; and triangular targets representing visual flight rules (VFR) aircraft that appeared either centrally or peripherally on the screen during the course of each session. Changes in performance on the complex monitoring task associated with either time on task or repeated sessions were dependent on nature of the task. Performance on the component involving detection and decision making (conflict/no conflict detection) evidenced a decrement associated with time on task on each of the 3 days. Improvement was evident from the first to the third day. Performance on the identification of the altitude malfunctions remained relatively immune to the effects of time on task or repeated sessions. Detection of the VFR aircraft intruders presented a mixed picture, with improvement noted in some aspects of performance but not in others, and some evidence of time on task effects. Outcomes were generally consistent with previous findings with this task and consistent with other literature with respect to the presence of performance decrements associated with time on task. The results were consistent with a view that the decrements are associated with lapses in attention, rather than a generalized fatigue effect or a general modification in overall scanning behavior. Furthermore, results suggest that there were aspects of monitoring performance that remain relatively immune to time on task effects.

High false alarm rates on a vigilance task may indicate recreational drug use.

Abstract: Neuropsychologists need more sensitive methods to detect and measure recreational drug use in both research and clinical settings. In a study comparing the sensitivity of information processing tasks and neuropsychological instruments to detect early HIV-related cognitive decrements, 18 of 129 subjects tested positive for recreational drugs. Sixteen of these 18 subjects had elevated false alarm rates on one of the information processing tasks, the vigilance task. Another 45 subjects who tested negative for recreational drugs also had elevated false alarm rates. Neuropsychological measures of premorbid functioning, attention, speed of information processing, and manual dexterity were lower in the high false alarm subjects than in the remaining 66 drug-negative, low false alarm subjects. These results suggest that a high false alarm rate may reflect long-standing cognitive disturbances and the effects of drug use. The vigilance task may be a sensitive and efficient screening tool for recreational drug use.

Effect of hashish on vigilance performance.

Abstract: A group of 11 hashish users were compared with 11 controls on a visual sustained attention (vigilance) task. Analysis indicated that hashish use affected subjects' sensitivity. Subjects who used hashish responded in an indiscriminate manner, making more false alarms (8.7) than controls (2.6). The importance of vigilance in the assessment of adverse effects of hashish is discussed.

Blinks, saccades, and fixation pauses during vigilance task performance: i. time on task

Abstract: Operators of complex equipment increasingly are spending more time monitoring computer controlled devices rather than having hands-on control. The operator intervenes in system operation under unusual conditions or when there is a computer malfunction. The operator's task thus becomes a "vigilance" task, one requiring attention to monitoring equipment with little need for action. An individual's ability to maintain vigilance is easily compromised, with time-on-task (TOT) a major detractor of performance. This research asks if gaze control measures can be used to reflect and predict periods of impaired vigilance. The results of this study clearly demonstrate that a number of aspects of eye movements and eye blinks show significant TOT effects. These effects are more likely to be associated with short periods of attentional lapses or "microsleep" than with more tonic changes in alertness level. The literature dealing with indicants of fatigue and time-on-task effects is reviewed. The study evaluated aspects of blinking and eye movements in subjects performing an air traffic control simulation task. Subjects performed the task for a 2-hour period on 3 separate occasions. Significant increases in blink frequency, blink closing duration, blink flurries, eye closures and fixation pause were obtained as well as similar effects for derivative measures. Though the current data was collected through electrodes attached to the participant, much of the information can be acquired with remote monitoring technologies. This makes possible the application of such measures in a field setting where subjects are required to work on a display terminal.