Chuck Goodyear

Prolongation of simple and choice reaction times in a double-blind comparison of twice-daily hydroxyzine versus terfenadine

Newer, nonsedating antihistamines provide a therapeutic alternative for the patient with allergy whose work is impaired by the side effects of traditional H1 antihistamines. To assess the differential effect of these antihistamines on reaction times and subjective symptoms, we compared terfenadine, 60 mg twice daily, to hydroxyzine, 25 mg twice daily, in a double-blind, placebo-controlled, crossover study of 16 healthy, asymptomatic adults. Simple reaction time and choice reaction time were measured with a computer-based, eye-hand, reaction-time testing apparatus. Reaction times and symptom scores were assessed 90 minutes after the fourth and tenth doses of each drug. Hydroxyzine, but not terfenadine, significantly prolonged both simple and choice reaction time (p less than or equal to 0.0001). However, decision time, the time to process one bit of spatial information, was not prolonged by either antihistamine. Therefore, hydroxyzine prolonged the interpretation and response to stimuli of the central nervous system without increasing single-bit processing time. Although terfenadine was not different from placebo for any symptom assessed, hydroxyzine produced significant drowsiness (p = 0.001), dry mouth (p = 0.022), and irritability (p = 0.021). During the 5 days of hydroxyzine administration, neither objective nor subjective symptoms demonstrated the development of tolerance. No correlation was found between subjective symptoms and prolongation of reaction times by hydroxyzine, suggesting that side effect symptoms of traditional antihistamines are unreliable predictors of objective performance. Terfenadine provides a promising therapeutic alternative to traditional antihistamines for individuals performing critical tasks.

Detection of vigilance performance using eye blinks.

Research has shown that sustained attention or vigilance declines over time on task. Sustained attention is necessary in many environments such as air traffic controllers, cyber operators, and imagery analysts. A lapse of attention in any one of these environments can have harmful consequences. The purpose of this study was to determine if eye blink metrics from an eye-tracker are related to changes in vigilance performance and cerebral blood flow velocities. Nineteen participants performed a vigilance task while wearing an eye-tracker on four separate days. Blink frequency and duration changed significantly over time during the task. Both blink frequency and duration increased as performance declined and right cerebral blood flow velocity declined. These results suggest that eye blink information may be an indicator of arousal levels. Using an eye-tracker to detect changes in eye blinks in an operational environment would allow preventative measures to be implemented, perhaps by providing perceptual warning signals or augmenting human cognition through non-invasive brain stimulation techniques.

A Comparison of the Effects of Transcranial Direct Current Stimulation and Caffeine on Vigilance and Cognitive Performance During Extended Wakefulness

BACKGROUND Sleep deprivation from extended duty hours is a common complaint for many occupations. Caffeine is one of the most common countermeasures used to combat fatigue. However, the benefits of caffeine decline over time and with chronic use. OBJECTIVE Our objective was to evaluate the efficacy of anodal transcranial direct current stimulation (tDCS) applied to the pre-frontal cortex at 2 mA for 30 min to remediate the effects of sleep deprivation and to compare the behavioral effects of tDCS with those of caffeine. METHODS Three groups of 10 participants each received either active tDCS with placebo gum, caffeine gum with sham tDCS, or sham tDCS with placebo gum during 30 h of extended wakefulness. RESULTS Our results show that tDCS prevented a decrement in vigilance and led to better subjective ratings for fatigue, drowsiness, energy, and composite mood compared to caffeine and control in sleep-deprived individuals. Both the tDCS and caffeine produced similar improvements in latencies on a short-term memory task and faster reaction times in a psychomotor task when compared to the placebo group. Interestingly, changes in accuracy for the tDCS group were not correlated to changes in mood; whereas, there was a relationship for the caffeine and sham groups. CONCLUSION Our data suggest that tDCS could be a useful fatigue countermeasure and may be more beneficial than caffeine since boosts in performance and mood last several hours.

Effect of directional response variables on eye-hand reaction times and decision time.

To determine if direction of response affects reaction time, we measured the time for hand response to a visual stimulus, using a sensitive, microprocessor-based testing device to determine simple reaction itme (RT), choice RT, and decision time. Mean simple RT was 207 ± 3.7 msec, (mean ± SEM); mean choice RT was 268 ± 4.2 msec.; and mean decision time was 61 msec. No differences were noted for leftward versus rightward movements, or midline versus lateral movements. Choice RT increased by 1.49 msec./yr. of age. Simple RT increased significantly with age for the nondominant hand, but not for the dominant hand. Right-handed subjects were more rapid with the dominant hand for choice RT. We conclude that dominance of hand tested and test initiation mechanism have major effects, but direction of movement in the lateral plane has little effect on reaction time.

Detection of vigilance performance with pupillometry

Sustained attention (vigilance) is required for many professions such as air traffic controllers, imagery analysts, airport security screeners, and cyber operators. A lapse in attention in any of these environments can have deadly consequences. The purpose of this study was to determine the ability of pupillometry to detect changes in vigilance performance. Each participant performed a 40-minute vigilance task while wearing an eye-tracker on each of four separate days. Pupil diameter, pupil eccentricity, and pupil velocity all changed significantly over time (p<.05) during the task. Significant correlations indicate that all metrics increased as vigilance performance declined except for pupil diameter, which decreased and the pupil became miotic. These results are consistent with other research on attention, fatigue, and arousal levels. Using an eye-tracker to detect changes in pupillometry in an operational environment would allow interventions to be implemented.

Augmenting Visual Search Performance with Transcranial Direct Current Stimulation (tDCS)

Military personnel endure rigorous and demanding man-hours designated to monitoring and locating targets in tasks such as cyber defense and Unmanned Aerial Vehicle (UAV) operators. These tasks are monotonous and repetitive, which can result in vigilance decrement. The objective of the study was to implement a form of noninvasive brain stimulation known as transcranial DC stimulation (tDCS) over the left frontal eye field (LFEF) region of the scalp to improve cognitive performance. The participants received anodal and cathodal stimulation of 2 mA for 30 min as well as placebo stimulation on 3 separate days while performing the task. The findings suggest that anodal and cathodal stimulation significantly improves detection accuracy. Also, a correlation was detected between percent of eye closure (PERCLOS) and blinking frequency in relation to stimulation condition. Our data suggest that tDCS over the LFEF would be a beneficial countermeasure to mitigate the vigilance decrement and improve visual search performance.

Eye Metrics: An Alternative Vigilance Detector for Military Cyber Operators

Military operators in various environments such as cyber, remotely piloted aircraft, and image analysis are required to use sustained attention or vigilance for long periods. During this time they encounter lapses in attention attributable to the monotonous nature of their tasks. Mistakes during these tasks can have serious consequences. The purpose of this study was to investigate the use of an eye-tracker to detect changes in vigilance performance during a simulated cyber operator task. Twenty participants performed 4 sessions of a 40-min vigilance task while wearing an eye-tracker. Blink frequency, blink duration, PERCLOS (percentage of eye closure), pupil diameter, pupil eccentricity, pupil velocity, and signal detection all had a significant change over time (p < .05) during the task. The significant change of oculometric measurements indicates oculometrics could be used to detect changes in vigilance for military operators. Future research is needed to assess real-time effects of these oculometrics on performance, especially in a real-world setting.

Transcranial Direct Current Stimulation (tDCS) Versus Caffeine to Sustain Wakefulness at Night When Dosing at Start-of-Shift

Shift work is necessary in many industries such as healthcare, trucking, defense, and aviation. It is well documented that during the night shift, workers experience the lowest levels of performance and alertness (Czeisler et al. in Science 210:1264–1267, 1980; Akerstedt and Gillberg in Sleep 4:159–169, 1981 [1, 2]). Research has shown caffeine can enhance alertness and performance during overnight work (Muehlbach and Walsh in Sleep 18(1):22–29, 1995 [4]). However, benefits of caffeine decline over time (Miller et al. in Fatigue and its Effect on Performance in Military Environments (Report No. 0704–0188), 2007 [5]). McIntire et al. (Brain Stimul. 7(4):499–507, 2014 [6]) found a promising alternative for use during sleep deprivation called transcranial direct current stimulation (tDCS). tDCS sustained performance throughout the sleep deprivation vigil and for a longer amount of time when compared to caffeine. Three groups of participants received either active tDCS and placebo gum at the start of their shift (1800), caffeine gum with sham tDCS, or sham tDCS with placebo gum. Participants completed 13 sessions of tasks and questionnaires while remaining awake for 36 h. Our results show tDCS could be a possible fatigue countermeasure.

Individual Differences in Biophysiological Toughness: Sustaining Working Memory During Physical Exhaustion

Recent evidence suggests that increased dehydroepiandrosterone sulfate (DHEAS), in combination with decreased cortisol levels have been correlated with enhanced performance outcomes in stressful military environments. This study was implemented to replicate these findings in a group of active duty Air Force members to provide information on the usefulness of these biomarkers indices in the training and operational environment. Seventeen active duty males participated in the 4 sessions of this study. Sessions 1 and 2 were training days for the cognitive testing. Session 3 was a baseline measure of physical fitness, utilizing the VO2 Maximal Treadmill test. Session 4 was centered around a modified-Astrand treadmill protocol designed to induce physical exhaustion. Blood draws for biomarker analysis, cognitive testing (NovaScan), psychomotor vigilance, and physiological measures were collected before, during, and following the treadmill protocol. Results showed that prolonged increases in cortisol negatively correlate with working memory performance. DHEAS release from baseline to poststress was negatively related to the changes in cortisol for 20 minutes following stress. These results indicate that the ratio of DHEAS to cortisol buffers, the effect of cortisol increases that are related to poor working memory performance because of physical exhaustion.

Attention anomalies as measured by time estimation under G stress

To investigate attention anomalies under G stress, performance tests involving the estimation of time duration were conducted at sustained levels of 1 G/sub z/, 3 G/sub z/, and 5 G/sub z/ stress for a duration of 60. Two types of time-estimation tasks were conducted, counting and noncounting. Analysis of these data across all subjects indicates that the estimation of the minimum-duration counting task was grossly underestimated. Data were first analyzed across all subjects, and only the shortest counting task was affected by the 5 G/sub z/ stress condition. Overall, however, for a given stress level, the counting task was much more accurate a method of estimating time than noncounting. The 5 G/sub z/ stress level was slightly below the threshold to affect performance; however, for the documented case of one subject under great mental stress, his results were significantly affected by the combination of 5 G/sub z/ stress and the psychological stress. This effort has identified the 5 G/sub z/ stressor as the level at which performance begins to degrade, subject to the level of mental stress experienced by the subject.<<ETX>>