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Biomedical subjects

A W Gaillard

Publications and source records attributed to A W Gaillard.

At least 19 recordsLinked to original sources
PubMed1998

Social loafing under fatigue.

In 2 experiments, 64 male students worked almost continuously for 20 hr without sleep under varying social conditions. In Experiment 1, participants worked either individually or as a group. As hypothesized, performance deteriorated over time, especially in the group condition, which allowed participants to loaf. In Experiment 2, all participants worked in groups. They were instructed that public feedback would be provided either on the group result only or on the individual results of all group members. As expected, when individual results were made public, performance deteriorated less. Overall, the data suggest that fatigue increases social loafing. However, both individualizing the task and providing public individual feedback seem to counteract these effects.

Adult↗
PubMed1998

Physiological workload reactions to increasing levels of task difficulty.

The sensitivity of physiological measures to mental workload was investigated in a flight simulator. Twelve pilots had to fly through a tunnel with varying levels of difficulty. Additionally, they had to perform a memory task with four levels of difficulty. The easiest memory task was combined with the easiest tunnel task and the most difficult memory task with the most difficult tunnel task. Between the tunnel tasks, subjects had to fly a pursuit task in which a target jet had to be followed. Rest periods before and after the experiment were used as a baseline for the physiological measures. Mental workload was measured with heart period, continuous blood pressure, respiration and eye blinks. Several respiratory parameters, heart rate variability, blood pressure variability and the gain between systolic blood pressure and heart period (modulus) were scored. All measures showed differences between rest and flight, and between the pursuit and the tunnel task. Only heart period was sensitive to difficulty levels in the tunnel task. Heart rate variability increased when respiratory activity around 0.10 Hz increased, which occurred often. The modulus was hardly influenced by respiration and therefore appears to be a better measure than heart rate variability. Among the respiratory parameters, the duration of a respiratory cycle was the most sensitive to changes in workload. The time in between two successive eye blinks (blink interval) increased and the blink duration decreased as more visual information had to be processed. Increasing the difficulty of the memory task led to a decrement in blink interval, probably caused by subvocal activity during rehearsal of target letters. The data show that physiological measures are sensitive to mental effort, whereas rating scales are sensitive to both mental effort and task difficulty.

Adult↗
PubMed1998

Influence of drive and timing mechanisms on breathing pattern and ventilation during mental task performance.

Assessment of multiple respiratory measures may provide insight into how behavioral demands affect the breathing pattern. This is illustrated by data from a study among 44 subjects, in which tidal volume, respiration rate, minute ventilation and indices of central drive and timing mechanisms were assessed via inductive plethysmography, in addition to end-tidal PCO2. After a baseline, three conditions of a memory comparison task were presented. The first two conditions differed only with regard to the presence or absence of feedback of performance (NFB and FB). In the third 'all-or-nothing' (AON) condition, subjects only received a monetary bonus, if their performance exceeded that of the previous two conditions. Minute ventilation increased from baseline to all task conditions, and from NFB and FB to AON. Respiration rate increased in all task conditions, but there were no differences between task conditions. Tidal volume decreased during NFB, but was equal to baseline during FB and AON. Of the respiratory control indices, inspiratory flow rate covaried much more closely with minute ventilation than duty cycle. The task performance induced a minor degree of hyperventilation. The discussion focusses on how behavioral demands affect respiratory control processes to produce alterations in breathing pattern and ventilation.

Adult↗
PubMed1997

Evoked heart rate and blood pressure in an S1-S2 paradigm.

Phasic changes in heart rate (HR) and blood pressure (BP) in an S1-S2 paradigm were studied in three experiments. In each experiment, a memory search task was performed at S1. The outcome of this task indicated whether a fast or a delayed response had to be given after S2. Besides this response instruction, there were two other task manipulations: in one experiment the memory load at S1 was varied, whereas in each experiment a different kind of performance feedback was given. Both HR and BP showed a triphasic pattern, consisting of an initial decrease, followed by an increase and another decrease. The BP patterns were quite consistent, and delayed a few seconds relative to the HR pattern. The memory load manipulation at S1 showed that the changes early in the S1-S2 interval (initial decrease and subsequent increase) reflect the processing of S1. The effects of response instruction showed that the second HR deceleration, and the subsequent BP decrease, reflect the preparation of the motor response. In Experiment 2 the level of the evoked HR and BP pattern was shifted as a function of the type of reward (a bonus or noise).

Acoustic Stimulation↗
PubMed1996

Physiological indices of workload in a simulated flight task.

The sensitivity of physiological measures to evaluate workload was investigated in a simulated flight task. Heart rate, blood pressure (from beat to beat), respiration and eye blinks were recorded in 14 subjects while they performed a complex task in a flight simulator. Workload was manipulated by introducing an additional task and by varying the task difficulty of segments of the flight scenarios. Heart rate and blood pressure were both affected by the different levels of task difficulty. Heart-rate variability was found to be confounded by respiration. Slow respiratory activity contributed considerably to heart rate variability, especially after periods of high workload (for example, after landing). The gain between blood-pressure and heart-rate variability (modulus) was sensitive to mental effort and was not influences by respiration. Eye blinks, in particular the duration, were specifically affected by the visual demands of the task and not by the workload in general. When subjects had to process visual information, the number and duration of blinks decreased.

Adult↗
PubMed1996

Cardiovascular and respiratory responses during a complex decision-making task under prolonged isolation.

Self-administered psychophysiological assessment during a mission is not only feasible, but yields reliable data that can be related to mission demands in a meaningful way. The unique methodology that has been employed during the EXEMSI campaign, may be of great promise for the development of techniques that provide daily monitoring of physiological cost of mission demands. This approach can thus be used for obtaining a better understanding of problems that can arise with regard to the functioning of individual crew members. The response profiles of the individual crew members showed remarkable quantitative and qualitative differences during isolation. Due to the limitations of this study, these differences could by no means all be explained in terms of mission demands, operator workload or other relevant parameters. However, the findings do seem to permit some tentative conclusions. In subjects B and D the cardiovascular response profiles suggested that cumulative stress effects emerged, in particular during the second part of the mission. It is important to note that both subjects carried specific responsibilities for the success of the mission, and that there was evidence for a conflict between them. Concerning the question which physiological measures are most appropriate for in-mission psychophysiological assessment, these results can appear to imply that cardiovascular measures yield more valid information about the effects of mission demands that respiratory measures. However, it should be noted that important aspects of respiratory activity, namely, respiratory volume measures and ventilation, could not be reliably determined in this study. Therefore, definitive conclusions concerning the choice of measures wait until the validity of the measures has been more extensively evaluated. Although the methodology that was developed for this study appears to be promising, it is obvious that its value can only be properly assessed when the physiological findings are correlated with behavioral, performance and subjective data. An extensive analysis of the covariation of the daily variations in physiological response, performance measures, and subjective assessments of workload and mood, is currently in progress in collaboration with Hockey and Sauer. Finally, if the usefulness and validity of this type of in-mission self-administered psychophysiological assessment are confirmed in ongoing and future studies (e.g., the 1994 HUBES mission), protocols will have to be worked out for practical implementation during actual spaceflights. In this regard, it has been advocated that psychophysiological monitoring techniques should include feedback and support policies, make crew members aware of potential risks for breakdown, and enable them to take appropriate measures when necessary. Initially, this can perhaps best be realized by procedures which include a data-link between the spacecraft and ground mission control. On the basis of ground-based analysis and evaluation of the data, psychologists at mission control may decide to provide information to the crew concerning potential individual or intragroup overload or stress problems, and to implement specific supportive measures. The effectiveness of the supportive activities should be closely monitored by mission control. Future work should also be aimed at developing expert-systems, which will enable the crew to maintain an appropriate degree of inflight biobehavioral self-regulation by providing a range of support techniques, like biofeedback, coping techniques against individual and group stressors, work/rest and sleep/wake schedules, and emergency procedures.

Adult↗
PubMed1995

Pharmacokinetics and pharmacodynamics of Ro 41-3696, a novel nonbenzodiazepine hypnotic.

This report describes the first evaluation in humans of Ro 41-3696. Based on its preclinical profile, Ro 41-3696, a nonbenzodiazepine partial agonist at the benzodiazepine receptor, offers promising perspectives as an innovative hypnotic drug in that it does not exhibit most of the disadvantages associated with full agonists. Single oral doses of 0.1, 0.3, 1.0, 3.0, 10, and 30 mg were administered sequentially to six groups of six healthy male volunteers in a placebo-controlled, double-blind design. Tolerability was assessed and pharmacokinetic and pharmacodynamic measurements were conducted during a period of 28 hours after drug intake. Ro 41-3696 was well tolerated at all doses, causing no clinically relevant changes in vital signs or laboratory parameters. At doses of 10 and 30 mg there were signs of unsteady gait, indicating a central nervous system depressant effect. Pharmacokinetic analyses revealed that Ro 41-3696 was absorbed and eliminated rapidly (tmax = approximately 1 hour; t1/2 = approximately 4 hours). At all times plasma levels of Ro 41-3290, the desethylated derivative of Ro 41-3696, were higher than those of the parent drug (tmax and t1/2 values = approximately 2 and 8 hours, respectively). Area under the curve (AUC) data indicated dose-proportional pharmacokinetics for both Ro 41-3696 and Ro 41-3290. Performance in both a tracking and a memory search test was significantly affected by doses of 10 and 30 mg, and long-term memory, as assessed by a word learning and recall test, was slightly impaired at these doses. The results of this study support the initiation of therapeutic efficacy studies with Ro 41-3696 in doses up to approximately 5 mg and further exploration of the characteristics of Ro 41-3290.

Administration, Oral↗
PubMed1995

The relation between event-related brain potential, heart rate, and blood pressure responses in an S1-S2 paradigm.

Event-related brain potential (ERP), heart rate (HR), and blood pressure (BP) responses were examined during the 6 s foreperiod of a choice-reaction task. Low and high trait-anxious males were required to make same/different judgements based on the similarity of two successively presented visual patterns. The pitch of a warning tone, presented at the beginning of the foreperiod, indicated whether speed or accuracy was to be emphasized on that trial. In different conditions, subjects received either a monetary reward or aversive noise, depending on their performance. Two clusters of parallel variations were observed in the foreperiod: (1) speed/accuracy instructions affected the amplitude of the CNV and, in interaction with anxiety group, the initial decreases in HR and diastolic BP; (2) type of reward, in interaction with speed/accuracy instructions, affected the amplitude of the P300 and PSW, the mid-interval HR acceleration, and subsequent increases in diastolic and systolic BP. A correlational analysis showed a close relationship between changes in HR and BP, whereas no relationship was evident between changes in ERPs and changes in HR and BP.

Adult↗
PubMed1994

The effects of sleep loss in a combined tracking and time estimation task.

The present study examines whether monitoring and control behaviour are affected by sleep loss and fatigue. The effects of one night of sleep loss are investigated in a dual-task consisting of a monotonous tracking task that requires continuous control behaviour and a time estimation task that requires monitoring with an 'open-loop' character. In the tracking task subjects had to keep a square cursor in the centre of a U-shaped target. In the time estimation task subjects had to estimate consecutive time intervals and to respond when an interval had ended. There were three experimental conditions. In the first condition a clock was presented continuously on the screen; thus, subjects had a clear notion of the time course. In the second condition subjects could obtain time information by pressing a key. In the third condition subjects could not obtain time information, but the status of the time interval could be obtained by pressing a key; that is, information was given whether a time interval had ended or not. The present study confirms earlier findings that tracking performance is sensitive to sleep loss particularly towards the end of the half hour working session. In contrast, time estimation performance was not impaired, although subjects tended to make more observations when deprived of sleep. This result would not have been expected on the basis of a decreased level of activation due to sleep loss. It appears, however, that checking the time course with a motor response requires less effort than continuously updating an internal clock, which puts heavy demands on working memory. The observed difference between the tasks with respect to the vulnerability to sleep loss is explained in terms of their motivating properties.

Adult↗
PubMed1993

The effects of sleep deprivation and incentives on human performance.

This study explores whether KR (knowledge of results) and reward compensate for the negative joint effects of sleep deprivation and signal degradation in a choice-reaction task. The negative effect of signal degradation on performance was aggravated by sleep loss and time-on-task, whereas KR improved performance, especially when signals were degraded. Reward changed the effects of time-on-task owing to lack of sleep. Performance was also improved by a brief task interruption after 30 minutes' work, with 5 more minutes to go. These results can be interpreted in terms of the performance model of Sanders (1983), which links energetic mechanisms to stages of information processing. A lack of energetic supply from the arousal mechanism to perceptual processing, induced by signal degradation, sleep deprivation, and time-on-task, was effectively counteracted by KR:KR enables the mobilization of effort to compensate for this lack of arousal. The relation between reward and KR is not yet clear. The interruption effect suggests that the influence of time-on-task is not due to loss of arousal, but causes a reallocation of resources by effort.

Adult↗
PubMed1993

Comparing the concepts of mental load and stress.

This paper delineates mental load and stress as two related concepts that originate from different theoretical frameworks. A proper distinction between the two concepts is important, not only for theory building, but because it may lead also to different interpretations of experimental results, and, consequently, to different recommendations in applied situations. High workload is regarded as an important but not a critical factor in the development of stress symptoms. It is quite possible to work hard in difficult and complex tasks, even under unfavourable conditions, without cognitive strain, psychosomatic complaints, or adverse physiological effects. High task demands can be met by mobilizing extra energy through mental effort. This 'trying harder' reaction is a normal and healthy coping strategy to adapt to situational demands. In contrast, stress is regarded as a state in which the equilibrium between cognitive and energetical processes is disturbed by ineffective energy mobilization and negative emotions. Stress typically is characterized by inefficient behaviour, overreactivity, and the incapacity to recover from work. Stress is regarded as a state in which the physiological system is disorganized, which results in decreased well-being, sleeping problems, psychosomatic complaints, and increased health risks.

Arousal↗
PubMed1993

Indices of mental workload in a complex task environment.

The aim of the present experiment is to evaluate heart rate variability (HRV) and cortisol as indices of mental workload in a complex environment. Heart rate was continuously recorded during flight scenarios that differed in difficulty. The HRV nicely reflected the changes in difficulty. The results support the idea that HRV is a sensitive index for mental workload when tasks are highly demanding and subjects are motivated to exert additional effort whenever the task becomes more demanding. Cortisol was only slightly increased on the experimental day compared to the training day. On the experimental day, post-task levels did not differ from pre-task levels. The level of cortisol in saliva was, however, related to overall task performance. Subjects who had a high level of cortisol had a low level of performance.

Adult↗
PubMed1988

The influence of antihistamines on human performance.

We have studied the effects of three antihistamines on task performance in two separate experiments. Healthy subjects were tested at weekly intervals in a double-blind, Latin square design. In Experiment I the subjects were treated orally with loratadine 10 mg, clemastine 1 mg, terfenadine 60 mg, or placebo. In Experiment II 5 mg diazepam was given orally with each of the four treatments used in Experiment I. In both experiments subjects' performance was evaluated in reaction time and tracking tasks after treatment. In both experiments, the tracking task initially was performed alone and then simultaneously with a continuous memory task; the subject also graded their mental status on visual analogue rating scales. In both experiments task performance was not generally impaired after treatment with loratadine or terfenadine. The concomitant administration of diazepam in Experiment II appeared not to affect subjects' performance. However, clemastine caused a decay in subjects' performance in both Experiments I and II, but only on the tracking task. At the conclusion of both experiments, sleepiness was reported by more subjects when treated with clemastine than when treated with loratadine, terfenadine, or placebo.

Administration, Oral↗
PubMed1988

Problems and paradigms in ERP research.

The ERP technique may provide noninvasive measures that are associated with the processing of psychological information during the performance of a task. Some investigators even regard ERPs as direct manifestations of the psychological processes induced by the demands of the task. Before such a strong claim can be made several methodological problems must be resolved. The present paper discusses the definition and identification of the endogenous components in the ERP, the separation of endogenous components from exogenous components, and the different ways in which inferences can be made about psychological processes on the basis of ERP measures.

Cognition↗
PubMed1988

Thiamin, riboflavin, and vitamins B-6 and C: impact of combined restricted intake on functional performance in man.

A double-blind study of combined restriction of thiamin, riboflavin, and vitamins B-6 and C was carried out with 23 healthy males. During 8 wk of low vitamin intake, 12 deficient subjects consumed daily a diet of normal food products, providing maximally 32.5% of the Dutch Recommended Dietary Allowances (RDA) for thiamin, riboflavin, vitamins B-6 and C. Other vitamins were supplemented at twice the RDA. Eleven control subjects consumed the same diet but with a supplementation of twice the RDA of all vitamins. In deficient subjects blood vitamin levels, urinary vitamin excretion, and erythrocytic enzyme activities decreased; in vitro enzyme stimulation increased. Vitamin depletion had no ill effects on health, physical activity, and mental performance. A significant decrease was observed in aerobic power (VO2max) and onset of blood lactate accumulation (p less than 0.001) of 9.8 and 19.6%, respectively. A combined restricted intake of thiamin, riboflavin, and vitamins B-6 and C causes a decrease in physical performance within a few weeks.

Adult↗
PubMed1986

Event-related potentials (ERPs) in a learning and memory test.

The present study outlines a new paradigm to investigate the effects of learning and memory on event-related potentials (ERPs). In the learning phase, subjects had to learn a sequence of 12 auditory consonant-vowel syllables. In the test phase, subjects had to detect and report a change in the learned sequence. Auditory ERPs were recorded from the frontal, vertex, and parietal midline positions. In the learning phase, an early negative effect (EN) and a P3 with a slow wave (SW) occurred for the learned syllables, whereas a pre-stimulus negativity (PSN) occurred prior to the syllables not yet learned. In the test phase, the PSN preceded both the replaced syllables and those presented in their old positions. The EN and an N2-P3 complex were elicited by the replaced syllables, the EN by the syllables presented in their old positions. It was concluded that the ERPs can display specific effects related to cognitive processes underlying learning and memory. The PSN was suggested to reflect the expectation of the stimuli, the EN the activation of a template and the rehearsal of the stimuli. The SW was suggested to be related to a template match process with the learned syllables. The N2, elicited by the replaced stimuli, could imply a cognitive template mismatch and the P3 with the SW the updating of working memory.

Adult↗
PubMed1986

Task and driving performance of patients with a severe concussion of the brain.

Patients who had sustained a severe concussion of the brain more than 2 years earlier were tested in choice reaction time tasks in the laboratory in order to investigate their impaired reactive capacity. The focus of investigation was whether specific stages in the chain of the information process are affected by the injury. In addition, driving skills were measured in an instrumented car to determine if reaction time performance is predictive of car driving. In general, patients were much slower than control subjects, both in the reaction time and in the driving tasks. The results obtained in the reaction time tasks provide no conclusive evidence, however, that severe concussion of the brain affects particular stages in information processing. Reaction time tasks appear to have predictive value for the ability to drive a car.

Accidents, Traffic↗