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The human visual system is sensitive to second-order modulations of the local contrast (CM) or amplitude (AM) of a carrier signal. Second-order cues are detected independently of first-order luminance signals; however, it is not clear why vision should benefit from second-order sensitivity. Analysis of the first- and second-order contents of natural images(More)
We applied a novel MR imaging technique to investigate the effect of acute mountain sickness on cerebral tissue water. Nine volunteers were exposed to hypobaric hypoxia corresponding to 4572 m altitude for 32 h. Such an exposure may cause acute mountain sickness. We imaged the brains of the volunteers before and at 32 h of hypobaric exposure with two(More)
D. N. Lee (1976) described a braking strategy based on optical expansion in which the driver brakes so that the target's time-to-contact declines around a constant slope in the range -0.5 < or = tau < 0. The present results from a series of braking simulations confirm and extend earlier reports (E. H. Yilmaz & W. H. Warren, 1995) that performance is broadly(More)
A controlled experiment used instrumented vehicles in a real-world driving task to compare D. N. Lee's (1976) tau-dot hypothesis of braking control with an alternative based on the direct estimation and control of ideal deceleration (T. Yates, M. Harris, & P. Rock, 2004). Drivers braked to stop as closely as possible to a visual target from different(More)
BACKGROUND Acute mountain sickness occurs in some unacclimatized persons who travel to terrestrial altitudes at which barometric pressures are the same as those in commercial aircraft during flight. Whether the effects are similar in air travelers is unknown. METHODS We conducted a prospective, single-blind, controlled hypobaric-chamber study of adult(More)
This study examined the effects of dexamethasone and exposure to high terrestrial altitude on cognitive performance, affect, and personality. Cognitive performance was evaluated by five cognitive tasks, affect was evaluated by the Clyde Mood Scale and the Multiple Affect Adjective Check List, and personality was examined using the Minnesota Multiphasic(More)
PURPOSE This study tested the hypothesis that antioxidant supplementation would attenuate plasma cytokine (IL-6, tumor necrosis factor (TNF)-alpha), and C-reactive protein (CRP) concentrations at rest and in response to exercise at 4300-m elevation. METHODS A total of 17 recreationally trained men were matched and assigned to an antioxidant (N = 9) or(More)
People perceive smooth luminance variations as being due to the shading produced by surface undulations: shape-from-shading. To do this the visual system must simultaneously estimate the nature of the illumination and the shape of the surface. Shape-from-shading operates even when both these properties are unknown and neither can be estimated directly from(More)
  • M Uhm Jm, S Ignal Tl, R Ock Pb, J Ones Sp, W Eaver O 'k Eeffe Km, Z Mr +14 others
  • 2009
Introduction: Crewmembers on ultra long-range commercial fl ights have the opportunity for rest and sleep in onboard areas in which the barometric pressure is 75.3 kPa (565 mmHg) or higher, equivalent to a terrestrial altitude of 2438 m (8000 ft) or lower. Sleep at higher altitudes is known to be disturbed, resulting in postsleep neurobehavioral performance(More)
The purpose of this study was to examine the resting and exercise response patterns of plasma Peptide F immunoreactivity (ir) to altitude exposure (4300 m) and caffeine ingestion (4 mg.kg b.w.-1). Nine healthy male subjects performed exercise tests to exhaustion (80-85% VO2max) at sea level (50 m), during an acute altitude exposure (1 hr, hypobaric chamber,(More)
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