Publications from 2001-2002

Titles:

Effects of Gravitational and Optical Stimulation on the Perception of Target Elevation

Readaptation of Rat Locomotor Activity and Deep Body Temperature Circadian Rhythms Following Exposure to Chronic Hypergravity

Chronic Centrifugation (Hypergravity) Influences the Circadian System of the Rat

Visual and Vestibular Determinants of Perceived Eye-level

Effects of Gravitational and Optical Stimulation on the Perception of Target Elevation

Malcolm M. Cohen, Robert B. Welch, and Charles W. DeRoshia, Arnold E. Stoper (CSU Hayward)

We examined the combined effects of gravitational and optical stimulation on perceived target elevation by independently altering gravitational-inertial force and both the orientation and structure of a background visual array. Eighteen observers set a target to the apparent horizon while experiencing 1.0, 1.5, or 2.0 Gz in the human centrifuge at NASA-Ames Research Center. The target was viewed against the far wall of a box that was pitched at various angles; the box was brightly illuminated, had only its interior edges dimly illuminated, or was kept dark. Target settings were lowered as Gz increased; this effect was reduced when the box was illuminated. Also, target settings were displaced in the direction the box was pitched when it was visible. Results are attributed to the combined influence of otolith-oculomotor mechanisms that underlie the elevator illusion and visual-oculomotor mechanisms (optostatic responses) that underlie the perceptual effects of viewing pitched visual arrays.

Perception and Psychophysics, 2001, 63(1): 29-35

Readaptation of Rat Locomotor Activity and Deep Body Temperature Circadian Rhythms Following Exposure to Chronic Hypergravity

Objectives: This study was conducted to evaluate the adaptation response of rat deep body temperature (DBT) and locomotor activity (LMA) circadian rhythms to acute hypergravity onset and chronic hypergravity exposure. Our study differs from previous reports (1,2) in that we provide a comprehensive mathematical analysis to quantitate the physiological adaptation of the circadian timing system to three chronic hypergravity intensities (1.25, 1.5, and 2 G.) and also provide a statistically quantitative evaluation of rhythmic readaptation and stabilization durations for several circadian rhythm metrics.

Paper presented at The Future of Chronic Acceleration Meeting, Davis, CA, January 30, 2001

Chronic Centrifugation (Hypergravity) Influences the Circadian System of the Rat

Objectives: This study was conducted to quantitate the effect of chronic centrifugation on animal energy expenditure, and to evaluate the response of the DBT and LMA circadian oscillators (biological clocks) to acute hypergravity onset and adaptation to chronic hypergravity exposure. We report herein the analysis of the gross animal locomotor activity (LMA) data (which was measured as an indirect indicator of animal energy expenditure), and the deep body temperature (DBT) data. Our study differs from previous reports on this topic (2,3,6), in that we provide a comprehensive mathematical analysis to quantitate the physiological adaptation of the circadian timing system to three chronic hypergravity “doses” (1.25, 1.5 , and 2 G).

Paper presented at the Future of Chronic Acceleration Meeting in Davis, CA, Jan 31, 2001

Visual and Vestibular Determinants of Perceived Eye-level

Malcolm M. Cohen

Both gravitational and optical sources of stimulation combine to determine the perceived elevations of visual targets. The ways in which these sources of stimulation combine with one another in operational aeronautical environments are critical for pilots to make accurate judgments of the relative altitudes of other aircraft and of their own altitude relative to the terrain. In a recent study (Cohen, Stoper, Welch, & DeRoshia, 2001), my colleagues and I required eighteen observers to set visual targets at their apparent horizon while they experienced various levels of Gz in the human centrifuge at NASA-Ames Research Center. The targets were viewed in darkness and also against specific background optical arrays that were oriented at various angles with respect to the vertical; target settings were lowered as Gz was increased; this effect was reduced when the background optical array was visible. Also, target settings were displaced in the direction that the background optical array was pitched. Our results were attributed to the combined influences of otolith-oculomotor mechanisms that underlie the elevator illusion and visual-oculomotor mechanisms (optostatic responses) that underlie the perceptual effects of viewing pitched optical arrays that comprise the background. This paper presents a mathematical model that describes both the independent and combined effects of Gz intensity and the orientation and structure of background optical arrays; the model predicts quantitative deviations from normal accurate perceptions of target localization under a variety of conditions. Our earlier experimental results and the mathematical model are described in detail, and the effects of viewing specific optical arrays under various gravitational-inertial conditions encountered in aeronautical environments are discussed.

Abstract of Poster presented to the NATO-RTO Conference on Spatial Disorientation in Military Vehicles, La Coruña, Spain 15-17 April 2002