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Objective: To determine whether the impairment of perceptual-motor performance often observed during the initial stages of space flight is attributable to the direct effects of microgravity on sensory-motor input-output relationships or to cognitive overload arising from the variety of stressors encountered in this environment.Background: Experimental evidence is contradictory, and the present experiment investigated the role of two variables: use of ajoystick with tracking or aiming tasks and degree of arm restraint.Methods: Five well-trained astronauts performed Fitts' reciprocal aiming task on three occasions (preflight, on the International Space Station, and postflight) under the following conditions: (a) with a stylus or ajoystick, (b) with the arm restrained or unrestrained, and (c) as a single task or together with auditory reaction time (RT) as a dual task. In addition to the speed and accuracy of responses, kinematic measures were derived from the joystick.Results: In space, the slope of Fitts' function increased only in the dual task condition with the joystick. RT was also slowed in the dual condition, and there was an increase in aiming and RT errors. Percentage time to peak acceleration, velocity, and deceleration were increased when the aiming task was performed alone.Conclusion: These results support the cognitive overload rather than the microgravity hypothesis and indicate that an impairment in sensory-motor performance is not a necessary concomitant of space flight.Application: Impairments in perceptual-motor performance in space can be eliminated or mitigated by appropriate training and task design. [ABSTRACT FROM AUTHOR]

Recent single-subject experiments in space have reported impaired dual-task performance that could result from either a direct effect of microgravity on the central nervous system or from the multistressor environment. We sought to distinguish between these hypotheses using 6 astronauts in the 16-day NASA Neurolab mission, testing them at intervals with a dual task consisting of primary pursuit tracking without vision of the hand and secondary reaction time (RT). The participants were highly trained, instructed to maintain a fixed attention strategy, and restrained in the apparatus. The results showed that absolute and variable tracking error, as well as correct RT and the standard deviation of RT, were unimpaired. However, RT errors became more variable, an effect attributed to a decrease in strategic control. We conclude that the impairments observed in previous dual-task space experiments can be attributed to stressors rather than to microgravity and that performance deficits are probably not a necessary concomitant of space flight if attention is paid to task design and astronaut training. [ABSTRACT FROM AUTHOR]

Ten subjects breathed experimental mixtures of 20% and 35% nitrous oxide (N2O) balanced with oxygen and then aligned a pointer with a target using vision, kinesthesis, or combinations of these senses. In a prior session the subjects had been trained on the task with feedback while breathing N2O. The results showed that N2O did not influence variable error (VE), constant error, (CE), or absolute CE, but perceptual conditions influenced VE and absolute CE. These results suggest that the demonstration by Legge (1965) of changes in the variability and accuracy of matching on this task under N2O are indicative of changes in response bias and/or attention rather than perceptual sensitivity. It is argued that narcosis slows rather than distorts information processing. Slowing is accompanied by strategic changes that may be maladaptive. This suggests that, contrary to conventional wisdom, the safety and efficiency of divers exposed to narcosis could be improved with training. [ABSTRACT FROM AUTHOR]

A central feature of the impairment in performance produced by inert gas narcosis, which poses a threat to divers breathing compressed air, is a slowing of reaction time (RT). To investigate the locus of this slowing, the effects of 35% nitrous oxide on Crossman's confusion function were determined using line-length and weight discrimination tasks, with accuracy held constant. For both tasks narcosis slowed RT by increasing the intercept rather than the slope of Crossman's function. These results are interpreted in terms of additive factors method logic as being consistent with the predictions of the slowed processing model that has been proposed to account for the effects of narcosis on human performance. [ABSTRACT FROM AUTHOR]

Positive pressure breathing (PPB) is a survival system that delivers high-pressure oxygen and body counterpressure in the event of cockpit depressurization at high altitude, but the ability of aircrew to perform an emergency "get-me-down" maneuver with this system is unknown. To address this question, a serial choice reaction time (RT) task was administered to six participants, who were sustained with PPB after rapid decompression to 60,000 feet (18,288 m) or 72,000 feet (21,946 m) in a hypobaric chamber (Experiment 1). Hypoxia was monitored by blood oxygen saturation (SaO2). Experiment 2 assessed the effects of PPB alone on performance. In Experiment 3, performance was measured while the rate of decrease of SaO2 observed in Experiment 1 was replicated with low oxygen mixtures at ground level. During the first 60 s at 72,000 feet, RT increased by 79 ms because of a shift of the whole distribution to the right. PPB at ground level did not increase RT. Decreasing SaO2 at ground level increased RT, but only after a delay. We conclude that inattention to the task, PPB alone, or, surprisingly, hypoxia cannot explain the majority of the impairment observed in Experiment 1. Rather, PPB and low pressure at high altitude interacted to exacerbate lacrimation, thereby degrading vision. Implications for the design of get-me-down maneuvers are discussed.

The P300 component of the event-related brain potential was assessed as a measure of mental workload using 12 subjects who flew simulated visual flight rules final approaches and landings under workloads varied by manipulating turbulence and hypoxia. P300 was elicited with auditory and visual "oddball" subsidiary tasks requiring the detection of infrequent tones or flashes of an artificial horizon. The results showed that root mean square error flying performance was systematically degraded by both workload manipulations. P300 amplitude exhibited a complex pattern that was not strongly related to performance. By contrast P300 latency covaried closely with performance, increasing as a function of workload in both modalities. These results suggest that P300 latency indexes the slowing of perceptual/cognitive processing caused by workload and that this measure is sensitive to an important aspect of flying.