Deficits in Visual Processing During Hypoxia as Evidenced by Visual Mismatch Negativity.

INTRODUCTION: Hypoxia is an ever-present threat in tactical aviation and gained recent attention due to its putative role in physiological episodes. Previous work has demonstrated that hypoxia negatively impacts a variety of sensory, cognitive, and motor systems. In particular, the visual system is one of the earliest systems affected by hypoxia. While the majority of previous studies have relied on self-report and behavioral testing, the use of event-related potentials as a novel tool to monitor responses to low oxygen in humans has recently been investigated. Specifically, ERP components that are evoked passively in response to unattended changes in background sensory stimulation have been explored.METHOD: Subjects (N 28) completed a continuous visuomotor tracking task while EEG was recorded. During the tracking task, a series of standard color checkerboard patterns were presented in the periphery while occasionally a deviant color checkerboard was presented. The visual mismatch negativity (MMN) component was assessed in response to the deviant compared to the standard stimuli. Subjects completed two sessions in counterbalanced order that only differed by the oxygen concentration breathed (10.6% vs. 20.4%).RESULTS: Results demonstrated a significant reduction in the amplitude of the visual MMN under hypoxic compared to normoxic conditions, showing a 50% reduction in amplitude during hypoxia. Our results suggest that during low-oxygen exposure the ability to detect environmental changes and process sensory information is impaired.DISCUSSION: The visual MMN may represent an early and reliable predictor of sensory and cognitive deficits during hypoxia exposure, which may be of great use to the aviation community.Blacker KJ, Seech TR, Funke ME, Kinney MJ. Deficits in visual processing during hypoxia as evidenced by visual mismatch negativity. Aerosp Med Hum Perform. 2021; 92(5):326332.

Impaired Sensory Processing During Low-Oxygen Exposure: A Noninvasive Approach to Detecting Changes in Cognitive States.

The ability to detect novelty in our environment is a critical sensory function. A reliable set of event-related potentials (ERP), known as the auditory deviance response (ADR), are elicited in the absence of directed attention and indexes functionally relevant networks. The ADR consists of three peaks: mismatch negativity (MMN), P3a, and reorienting negativity (RON) that are sequentially evoked in response to unattended changes in repetitive background stimulation. While previous studies have established the ADR's sensitivity to a range of pharmacologic and nonpharmacologic interventions and are leading candidate biomarkers of perturbations of the central nervous system (CNS), here we sought to determine if ADR peaks are sensitive to decreases in breathable oxygen. Participants performed a visuomotor tracking task while EEG was recorded during two 27-min sessions. The two sessions differed in the amount of environmental oxygen available: 10.6% O2 (hypoxia) versus 20.4% O2 (normoxia). ERPs were measured while a series of identical, or "standard," tones combined with occasional "oddball," tones, were presented. MMN, P3a, and RON were assessed in response to the oddball compared to the standard stimuli. Behavioral impairment during hypoxia was demonstrated by a deficit in tracking performance compared to the normoxia condition. Whereas no changes were detected in the MMN or RON, the amplitude of the P3a component was significantly reduced during hypoxia compared to normoxia, within the first 9 min of exposure. To our knowledge, this is the first study to demonstrate the effect of low oxygen exposure on passively elicited neural measures of early sensory processing. This study demonstrates that passively elicited EEG measures, reflecting preattentive auditory processing, are disrupted by acute hypoxia. Results have implications for the development of biomarkers for the noninvasive assessment of CNS perturbations.

Evaluation of Aircrew Low-Intensity Threat Laser Eye Protection.

Prototype low-intensity threat laser eye protection (LIT-LEP) spectacles were evaluated for US Coast Guard (USCG) cockpits and night vision goggle compatibility. The impetus for interest in aviation LIT-LEP is driven in part by the fact that easily accessible 0.5-2.0 W high-power laser pointers exceed safety standards for direct on-axis viewing. A repeated-measures experimental design was used to assess LIT-LEP performance relative to a no-LEP control for the following tasks: Near- and far contrast acuity, night vision goggle far-contrast acuity, emissive and non-emissive light source color-vision screening, and USCG multifunctional display color symbol discrimination reaction time and accuracy. Near- and far-contrast acuity results demonstrated good LIT-LEP performance for typical in- and out-of-cockpit lighting conditions. Night vision goggle performance suffered marginally at only one contrast level (85%; 20/30 acuity line). Color vision test results showed good color balance in that S-, M-, and L-cone performance did not demonstrate a clinical diagnostic color defect for emissive or non-emissive light sources when wearing LIT-LEP. Color symbol discrimination reaction-time-task results based on inverse efficiency scores revealed that some non-primary flight display colors exhibited a combination of slower speed and decreased accuracy. The findings will contribute to an acquisition decision as well as guide future LEP designs.

Vigilance Tasks: Unpleasant, Mentally Demanding, and Stressful Even When Time Flies.

OBJECTIVE: To determine whether perceived time progression (PTP) moderates participants' negative reactions to vigilance tasks. BACKGROUND: Vigilance tasks are rated by participants to be unenjoyable and as having high levels of workload and stress. Based on the adage, "You are having fun when time flies," we tested the possibility that accelerating PTP might reduce these negative experiences. METHOD: Two studies were performed, involving a long 30-min and a short 12-min vigil. We manipulated participants' PTP by creating a mismatch between their expectations about how long they would perform the task and the actual time that they were engaged. RESULTS: PTP was significantly faster for participants who were led to expect that the vigilance task would last longer than it did relative to those led to expect that task duration would be shorter than it actually was and for controls for whom task duration was equal to the expected duration. However, accelerating PTP had no effect in either experiment on undesirable reactions to the vigilance tasks. Participants uniformly rated both tasks as unenjoyable, as having a high level of workload, and as stressful. Apparently, vigilance isn't fun even when time flies. CONCLUSION: Our findings greatly underscore the depth to which negative subjective reactions are embedded in the nature of vigilance tasks and therefore that these tasks can have potentially serious costs to participants in terms of health, safety, and productivity. APPLICATION: These costs must be considered at the operational level.

The Neuroergonomics of Vigilance.

OBJECTIVE: The aim of this study was to examine the effects of uncertainty about where in the field of view critical signals for detection appear during a vigilance task (spatial uncertainty) on cerebral blood flow velocity (CBFV) and oculomotor fatigue. BACKGROUND: Neuroergonomics is a dimension of human factors founded by Raja Parasuraman that studies brain functions underlying performance at work. Neuroergonomic studies have shown that observers in vigilance tasks lose information-processing resources over time and experience oculomotor fatigue as indexed by a temporal decline in CBFV and elevation in eye closure as reflected in the PERCLOS metric. Because spatial uncertainty increases an observer's need for visual scanning relative to a spatial certainty condition, it was anticipated that spatial uncertainty would result in a greater temporal decline in CBFV and increased eye closure in a vigilance session. METHOD: Observers performed a simulated unmanned aerial vehicle (UAV) control task wherein collision flight paths were the events to be detected. UAV images could appear at random in any one of five locations on the controller's display (spatial uncertainty) or only in a fixed location (spatial certainty). RESULTS: Signal detection was poorer in the spatial-uncertain relative to the certain condition, and predictions regarding CBFV and eye closure were confirmed. CONCLUSION: Vigilance tasks involving spatial uncertainty are more neurophysiologically taxing than those in which spatial uncertainty is not a factor. APPLICATION: The neuroergonomic approach helps in understanding the effects of psychophysical factors in vigilance and to signify when performance aiding is needed.

The Independence and Interdependence of Coacting Observers in Regard to Performance Efficiency, Workload, and Stress in a Vigilance Task.

OBJECTIVE: We investigated performance, workload, and stress in groups of paired observers who performed a vigilance task in a coactive (independent) manner. BACKGROUND: Previous studies have demonstrated that groups of coactive observers detect more signals in a vigilance task than observers working alone. Therefore, the use of such groups might be effective in enhancing signal detection in operational situations. However, concern over appearing less competent than one's cohort might induce elevated levels of workload and stress in coactive group members and thereby undermine group performance benefits. Accordingly, we performed the initial experiment comparing workload and stress in observers who performed a vigilance task coactively with those of observers who performed the vigilance task alone. METHOD: Observers monitored a video display for collision flight paths in a simulated unmanned aerial vehicle control task. Self-reports of workload and stress were secured via the NASA-Task Load Index and the Dundee Stress State Questionnaire, respectively. RESULTS: Groups of coactive observers detected significantly more signals than did single observers. Coacting observers did not differ significantly from those operating by themselves in terms of workload but did in regard to stress; posttask distress was significantly lower for coacting than for single observers. CONCLUSION: Performing a visual vigilance task in a coactive manner with another observer does not elevate workload above that of observers working alone and serves to attenuate the stress associated with vigilance task performance. APPLICATION: The use of coacting observers could be an effective vehicle for enhancing performance efficiency in operational vigilance.

Cognitive and perceptual deficits of normobaric hypoxia and the time course to performance recovery.

BACKGROUND: Many in-flight hypoxia-like incidents involve exposure to normobaric hypoxia following an oxygen delivery equipment failure. Studies have documented the effect of hypoxia on specific aspects of human performance. The goal of the present study was to establish the effects of acute hypoxia on cognitive, psychomotor, and perceptual abilities and to chronicle the time required for these capabilities to fully recover to pre-exposure levels. METHODS: Subjects were presented with a battery of tests designed to assess visual acuity, contrast sensitivity, color vision, executive control, and reaction time (simple reaction time, SRT, and choice reaction time, CRT) before, during, immediately following, 60 min, 120 min, and 24 h after hypoxic exposure. Oxygen saturation was continuously measured throughout the duration of the study using near-infrared spectroscopy measured on the forehead and finger pulse oximetry. RESULTS: During the course of six assessment periods, contrast sensitivity, color vision, and subjective workload were affected to varying degrees during hypoxic exposure, but returned to baseline levels soon after a return to normoxia. Conversely, reaction time values and regional cerebral oxygen saturation (MrSO2), while also affected during hypoxic exposure (MSRT = 362.17 ms, MCRT = 389.55 ms, MrSO2 = 79.36%), did not return to baseline levels (MSRT = 337.35 ms, MCRT = 372.75 ms, MrSO2 = 99.75%) until the assessment period 24 h following exposure (MSRT = 324.35 ms, MCRT = 366.22 ms, MrSO2 = 99.10%). DISCUSSION: Evidence from this study suggests an impairment of specific performance characteristics following hypoxic exposure - some for a considerable period of time. Mitigation efforts should focus more on the prevention of hypoxia exposure rather than relying exclusively on training operators to recognize and react earlier to hypoxic symptomology.

Effects of Stereoscopic Depth on Vigilance Performance and Cerebral Hemodynamics.

OBJECTIVE: We tested the possibility that monitoring a display wherein critical signals for detection were defined by a stereoscopic three-dimensional (3-D) image might be more resistant to the vigilance decrement, and to temporal declines in cerebral blood flow velocity (CBFV), than monitoring a display featuring a customary two-dimensional (2-D) image. BACKGROUND: Hancock has asserted that vigilance studies typically employ stimuli for detection that do not exemplify those that occur in the natural world. As a result, human performance is suboptimal. From this perspective, tasks that better approximate perception in natural environments should enhance performance efficiency. To test that possibility, we made use of stereopsis, an important means by which observers interact with their everyday surroundings. METHOD: Observers monitored a circular display in which a vertical line was embedded. Critical signals for detection in a 2-D condition were instances in which the line was rotated clockwise from vertical. In a 3-D condition, critical signals were cases in which the line appeared to move outward toward the observer. RESULTS: The overall level of signal detection and the stability of detection over time were greater when observers monitored for 3-D changes in target depth compared to 2-D changes in target orientation. However, the 3-D display did not retard the temporal decline in CBFV. CONCLUSION: These results provide the initial demonstration that 3-D displays can enhance performance in vigilance tasks. APPLICATION: The use of 3-D displays may be productive in augmenting system reliability when operator vigilance is vital.

The sustained attention to response task (SART) does not promote mindlessness during vigilance performance.

OBJECTIVE: In this study, we evaluated the validity of the Sustained Attention to Response Task (SART) as a means for promoting mindlessness in vigilance performance. BACKGROUND: Vigilance tasks typically require observers to respond to critical signals and to withhold responding to neutral events. The SART features the opposite response requirements, which supposedly leads it to promote a mindless, non-thoughtful approach to the vigilance task To test that notion, we compared the SART to the traditional vigilance format (TVF) in terms of diagnostic accuracy assessed through decision theory measures of positive and negative predictive power (PPP and NPP), perceived mental workload indexed by the Multiple Resource Questionnaire, and oculomotor activity reflected in the Nearest Neighbor Index and fixation dwell times. METHOD: Observers in TVF and SART conditions monitored a video display for collision flight paths in a simulated air traffic control task. RESULTS: Diagnostic accuracy in terms of NPP was high in both format conditions. While PPP was poorer in the SART than in the TVF, that result could be accounted for by a loss of motor control rather than a lack of mindfulness. Identical high levels of workload were generated by the TVF and SART tasks, and observers in both conditions showed similar dynamic scanning of the visual scene. CONCLUSION: The data indicate that the SART is not an engine of mindlessness. APPLICATION: The results challenge the widespread use of the SART to support a model in which mindlessness is considered to be the principal root of detection failures in vigilance.

Event-related cerebral hemodynamics reveal target-specific resource allocation for both "go" and "no-go" response-based vigilance tasks.

Transcranial Doppler sonography was used to measure cerebral blood flow velocity (CBFV) in the right and left cerebral hemispheres during the performance of a 50-min visual vigilance session. Observers monitored a simulated flight of unmanned aerial vehicles for cases in which one of the vehicles was flying in an inappropriate direction relative to its cohorts. Two types of vigilance tasks were employed: a traditional task in which observers made button press ("go") responses to critical signals, and a modification of the traditional task called the Sustained Attention to Response Task (SART) in which "go" responses acknowledged nonsignal events and response withholding ("no-go") signified signal detection. Signal detections and global CBFV scores declined over time. In addition, fine-grained event-related analyses revealed that the detection of signals was accompanied by an elevation of CBFV that was not present with missed signals. As was the case with the global scores, the magnitude of the transient CBFV increments associated with signal detection also declined over time, and these findings were independent of task type. The results support the view of CBFV as an index of the cognitive evaluation of stimulus significance, and a resource model of vigilance in which the need for continuous attention produces a depletion of information-processing assets that are not replenished as the task progresses. Further, temporal declines in the magnitude of event-related CBFV in response to critical signals only is evidence that the decrement function in vigilance is due to attentional processing and not specific task elements such as the required response format.