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Parker, D. E.

Publications and source records attributed to Parker, D. E..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Self-motion perception: assessment by real-time computer-generated animations

We report a new procedure for assessing complex self-motion perception. In three experiments, subjects manipulated a 6 degree-of-freedom magnetic-field tracker which controlled the motion of a virtual avatar so that its motion corresponded to the subjects' perceived self-motion. The real-time animation created by this procedure was stored using a virtual video recorder for subsequent analysis. Combined real and illusory self-motion and vestibulo-ocular reflex eye movements were evoked by cross-coupled angular accelerations produced by roll and pitch head movements during passive yaw rotation in a chair. Contrary to previous reports, illusory self-motion did not correspond to expectations based on semicircular canal stimulation. Illusory pitch head-motion directions were as predicted for only 37% of trials; whereas, slow-phase eye movements were in the predicted direction for 98% of the trials. The real-time computer-generated animations procedure permits use of naive, untrained subjects who lack a vocabulary for reporting motion perception and is applicable to basic self-motion perception studies, evaluation of motion simulators, assessment of balance disorders and so on.

Non-NASA Center↗
NASA NTRS1998

Relationship between selected orientation rest frame, circular vection and space motion sickness

Space motion sickness (SMS) and spatial orientation and motion perception disturbances occur in 70-80% of astronauts. People select "rest frames" to create the subjective sense of spatial orientation. In microgravity, the astronaut's rest frame may be based on visual scene polarity cues and on the internal head and body z axis (vertical body axis). The data reported here address the following question: Can an astronaut's orientation rest frame be related and described by other variables including circular vection response latencies and space motion sickness? The astronaut's microgravity spatial orientation rest frames were determined from inflight and postflight verbal reports. Circular vection responses were elicited by rotating a virtual room continuously at 35 degrees/s in pitch, roll and yaw with respect to the astronaut. Latency to the onset of vection was recorded from the time the crew member opened their eyes to the onset of vection. The astronauts who used visual cues exhibited significantly shorter vection latencies than those who used internal z axis cues. A negative binomial regression model was used to represent the observed total SMS symptom scores for each subject for each flight day. Orientation reference type had a significant effect, resulting in an estimated three-fold increase in the expected motion sickness score on flight day 1 for astronauts who used visual cues. The results demonstrate meaningful classification of astronauts' rest frames and their relationships to sensitivity to circular vection and SMS. Thus, it may be possible to use vection latencies to predict SMS severity and duration.

short duration↗
NASA NTRS1998

Self-motion perception: assessment by computer-generated animations

The goal of this research is more precise description of adaptation to sensory rearrangements, including microgravity, by development of improved procedures for assessing spatial orientation perception. Thirty-six subjects reported perceived self-motion following exposure to complex inertial-visual motion. Twelve subjects were assigned to each of 3 perceptual reporting procedures: (a) animation movie selection, (b) written report selection and (c) verbal report generation. The question addressed was: do reports produced by these procedures differ with respect to complexity and reliability? Following repeated (within-day and across-day) exposures to 4 different "motion profiles," subjects either (a) selected movies presented on a laptop computer, or (b) selected written descriptions from a booklet, or (c) generated self-motion verbal descriptions that corresponded most closely with their motion experience. One "complexity" and 2 reliability "scores" were calculated. Contrary to expectations, reliability and complexity scores were essentially equivalent for the animation movie selection and written report selection procedures. Verbal report generation subjects exhibited less complexity than did subjects in the other conditions and their reports were often ambiguous. The results suggest that, when selecting from carefully written descriptions and following appropriate training, people may be better able to describe their self-motion experience with words than is usually believed.

Non-NASA Center↗
NASA NTRS1998

The relative roles of the otolith organs and semicircular canals in producing space motion sickness

Inflight and post-landing "immunity" to the "coriolis sickness susceptibility test", observed during the Skylab M131 experiment, suggests that the otolith organs play a major role in space motion sickness (SMS). This view is supported by the report that ocular counter-torsion asymmetries correlate with SMS incidence and severity. Further data indicate that sensory-motor adaptation to microgravity includes a process whereby central interpretation of otolith signals is biased from "tilt" toward translation. However, unexpected responses to linear acceleration suggest the importance of graviceptors distributed throughout the body in addition to the vestibular otolith organs. Research is needed to assess distributed graviceptor effects.

Non-NASA Center↗
NASA NTRS1997

Microgravity vestibular investigations: perception of self-orientation and self-motion

Four astronauts experienced passive whole-body rotation in a number of test sessions during a 7-day orbital mission. Pitch (Y-axis) and roll (X-axis) rotation required subject orientations on the rotator in which the otolith system was at radius of 0.5 m. Thus subjects experienced a constant -0.22 Gz stimulus to the otoliths during the 60 s constant-velocity segments of "pitch" and "roll" ramp profiles. The Gz stimulus, a radius-dependent vector ranging from -0.22 Gz at the otoliths to +0.36 Gz at the feet, generated sensory information that was not interpreted as inversion in any of the 16 tests carried out in flight (12 in pitch and 4 in roll orientation). None of the subjects was rotated with head off-center during the first 33 h of the mission. In the state of orbital adaptation of these subjects, a -0.22 Gz otolith stimulus did not provide a vertical reference in the presence of a gradient of +Gz stimuli to the trunk and legs.

NASA Experiment Number 284058↗
NASA NTRS1993

Perceived self-orientation and self-motion in microgravity, after landing and during preflight adaptation training

The research described in this paper is intended to support development and evaluation of preflight adaptation training (PAT) apparatus and procedures. Successful training depends on appropriate manipulation of visual and inertial stimuli that control perception of self-motion and self-orientation. For one part of this process, astronauts are trained to report their self-motion and self-orientation experiences. Before their space mission, they are exposed to the altered sensory environments produced by the PAT trainers. During and after the mission, they report their motion and orientation experiences. Subsequently, they are again exposed to the PAT trainers and are asked to describe relationships between their experiences in microgravity and following entry and their experiences in the trainers.

Space Flight↗
NASA NTRS1988

Preadaptation to the stimulus rearrangement of weightlessness: Preliminary studies and concepts for trainer designs

An effort to develop preflight adaptation training (PAT) apparatus and procedures to adapt astronauts to the stimulus rearrangement of weightless spaceflight is being pursued. Based on the otolith tilt-translation reinterpretation model of sensory adaptation to weightlessness, two prototype preflight adaptation trainers (PAT) have been developed. These trainers couple pitch movement of the subject with translation of the visual surround. Subjects were exposed to this stimulus rearrangement for periods of 30 m. The hypothesis is that exposure to the rearrangement would attenuate vertical eye movements was supported by two experiments using the Miami University Seesaw (MUS) PAT prototype. The Dynamic Environment Simulator (DES) prototype failed to support this hypothesis; this result is attributed to a pecularity of the DES apparatus. A final experiment demonstrated that changes in vertical eye movements were not a consequence of fixation on an external target during exposure to a control condition. Together these experiments support the view that preflight adaptation training can alter eye movements in a manner consistent with adaptation to weightlessness. Following these initial studies, concepts for development of operational preflight trainers were proposed. The trainers are intended to: demonstrate the stimulus rearrangement of weightlessness; allow astronauts to train in altered sensory environment; modify sensory motor reflexes; and reduce/eliminate space motion sickness symptoms.

Parker, D. E.↗
NASA NTRS1988

Ground-based training for the stimulus rearrangement encountered during spaceflight

Approximately 65-70% of the crew members now experience motion sickness of some degree during the first 72 h of orbital flight on the Space Shuttle. Lack of congruence among signals from spatial orientation systems leads to sensory conflict, which appears to be the basic cause of space motion sickness. A project to develop training devices and procedures to preadapt astronauts to the stimulus rearrangements of microgravity is currently being pursued. The preflight adaptation trainers (PATs) are intended to: demonstrate sensory phenomena likely to be experienced in flight, allow astronauts to train preflight in an altered sensory environment, alter sensory-motor reflexes, and alleviate or shorten the duration of space motion sickness. Four part-task PATs are anticipated. The trainers are designed to evoke two adaptation processes, sensory compensation and sensory reinterpretation, which are necessary to maintain spatial orientation in a weightless environment. Recent investigations using one of the trainers indicate that self-motion perception of linear translation is enhanced when body tilt is combined with visual surround translation, and that a 270 degrees phase angle relationship between tilt and surround motion produces maximum translation perception.

Non-NASA Center↗
NASA NTRS1987

Effects of proposed preflight adaptation training on eye movements, self-motion perception, and motion sickness - A progress report

The preflight adaptation trainer (PAT) was designed to produce rearranged relationships between visual and otolith signals analogous to those experienced in space. Investigations have been undertaken with three prototype trainers. The results indicated that exposure to the PAT sensory rearrangement altered self-motion perception, induced motion sickness, and changed the amplitude and phase of the horizontal eye movements evoked by roll stimulation. However, the changes were inconsistent.

Parker, D. E.↗
NASA NTRS1987

Space motion sickness preflight adaptation training: preliminary studies with prototype trainers

Preflight training frequently has been proposed as a potential solution to the problem of space motion sickness. The paper considers successively the otolith reinterpretation, the concept for a preflight adaptation trainer and the research with the Miami University Seesaw, the Wright Patterson Air-Force Base Dynamic Environment Simulator and the Visually Coupled Airborne Systems Simulator prototype adaptation trainers.

NASA Discipline Neuroscience↗
NASA NTRS1986

Preadapting to Weightlessness

Report discusses physiological and physical concepts of proposed training system to precondition astronauts to weightless environment. System prevents motion sickness, often experienced during early part of orbital flight. Also helps prevent seasickness and other forms of terrestrial motion sickness, often experienced during early part of orbital flight. Training affects subject's perception of inner-ear signals, visual signals, and kinesthetic motion perception. Changed perception resembles that of astronauts who spent many days in space and adapted to weightlessness.

Reschke, M. F.↗
NASA NTRS1985

Space motion sickness preflight adaptation training Preliminary studies with prototype trainers

Based on the otolith tilt-translation reinterpretation hypothesis (Parker et al., 1985), preflight adaptation procedures and several preflight adaptation trainers (PATs) have been developed. Two PAT prototypes, the Miami University Seesaw (MUS) and the Dynamic Environmental Simulator (DES), include a physical room that is moved relative to the restrained subject. Results from the MUS and DES PAT experiments indicate that exposure to the produced sensory rearrangement can change eye movement reflexes. The changes persisted for a period longer than the training exposure period, indicating similarity with the eye-movement reflexes observed immediately postflight in weightlessness-adapted astronauts. It is concluded that the apparatus and procedures to preadapt astronauts to the sensory rearrangement of weightless space flight can be developed on the basis of the reported PATs and procedures. The third PAT prototype tested, which employs a computer-generated scene, failed to produce changes similar to those recorded in the MUS and DES experiments.

Parker, D. E.↗
NASA NTRS1985

Otolith tilt-translation reinterpretation following prolonged weightlessness - Implications for preflight training

Observations with three astronauts yielded two major findings. First, perceived self-motion during sinusoidal roll differed immediately postflight from preflight. Between 70 and 150 min after landing, roll was perceived primarily as linear translation. Secondly, more horizontal eye movement was elicited by roll simulation immediately postflight relative to both preflight and later postflight observations. These results support an 'otolith tilt-translation reinterpretation' hypothesis, which has clear implications for understanding astronaut reports of space motion sickness during the early period of orbital flight. A proposal for 'prophylactic adaptation training' which may provide preflight adaptation to weightlessness, derives from this reearch.

Parker, D. E.↗
NASA NTRS1985

Reinterpretation of otolith input as a primary factor in space motion sickness

It is hypothesized that exposure to prolonged free fall is a form of sensory/motor rearrangement rather than a direct change in otolith sensitivity or sensory compensation for a reduced otolith input. The rearrangement of stimuli will force a new interpretation by the CNS of otolith input. This reinterpretation is necessary for a structured and meaningful interaction with the new environment. Data from two flight experiments are presented which support an otolith reinterpretation hypothesis. The first experiment measured vestibulo-spinal reflex changes as a function of sustained free fall. Findings indicate that when a monosynaptic reflex (H-reflex), measured from the major postural muscles (soleus), is used adaptation to space flight includes a change in how the CNS interprets a fall. In a normal gravity environment a sudden unexpected fall will produce a potentiated H reflex. After seven days in flight an equivalent fall does not potentiate the reflex. During postflight a greatly increased reflex is observed in those crewmen most susceptible to space motion sickness. In the second experiment self motion perception and torsional eyemovements were modified as a function of exposure to sustained free fall. Preflight roll motion (about the X axis) was perceived as pure roll, and the eye movements recorded were countertorsional. Postflight, roll stimulation was perceived as linear translation (side to side movement) with a small angular motion component. Eye movement measurements confirmed significantly more horizontal motion.

Reschke, M. F.↗
NASA NTRS1984

Tilt from a head-inverted position produces displacement of visual subjective vertical in the opposite direction

Observers who lie supine with their heads inverted report large (up to 60 deg) tilt of a light line in an otherwise dark room when their heads and/or bodies are tilted. Most observers report that visual subjective vertical is tilted in the direction opposite to the head/body tilt. The results can be interpreted by employing a model developed by Mittelstaedt (1983), which suggests that visual subjective vertical is derived from a gravity vector transduced by vestibular and somesthetic receptors combined with 'idiotropic vectors' that represent the orientation of the observer's own head and body axes.

Parker, D. E.↗
NASA NTRS1983

Physiological and behavioral effects of tilt-induced body fluid shifts

This paper addresses the 'fluid shift theory' of space motion sickness. The primary purpose of the research was the development of procedures to assess individual differences in response to rostral body fluid shifts on earth. Experiment I examined inner ear fluid pressure changes during head-down tilt in intact human beings. Tilt produced reliable changes. Differences among subjects and between ears within the same subject were observed. Experiment II examined auditory threshold changes during tilt. Tilt elicited increased auditory thresholds, suggesting that sensory depression may result from increased inner ear fluid pressure. Additional observations on rotation magnitude estimation during head-down tilt, which indicate that rostral fluid shifts may depress semicircular canal activity, are briefly described. The results of this research suggest that the inner ear pressure and auditory threshold shift procedures could be used to assess individual differences among astronauts prior to space flight. Results from the terrestrial observations could be related to reported incidence/severity of motion sickness in space and used to evaluate the fluid shift theory of space motion sickness.

Parker, D. E.↗
NASA NTRS1983

Spatial orientation - Visual-vestibular-somatic interaction

The compensation signals from somatosensory and vestibular receptors, which act to compensate for disturbances produced by the displacement of our eyes relative to other parts of our bodies and for visual disturbances such as tilted frames or moving visual fields, are investigated. Disturbances were evoked by tilting the head and by rotating a large visual display, while compensation signals related to gravity were altered by placing the subjects horizontally on a board or seating them vertically. The first experiment studied the effects of visual disturbance on the ability of supine observers to set a line to the longitudinal body axis while the head was tilted toward one shoulder or while the head was straight. Results showed that the effects of the visual disturbance were greater when the head was tilted than when it was straight, which indicates that the effects of visual disturbance were greater for a task that required compensation. The second experiment compared the performance of supine and erect observers. No differences were found between the performance of observers on a task requiring the use of compensation signals under these two conditions, which suggests that the enrichment of compensatory signals did not reduce the effects of visual disturbancs.

Parker, D. E.↗