Spatial orientation: Visual-vestibular-somatic interaction

The role of gravity in spatial coordinate assignment and the mental representation of space were studied in three experiments, varying different perceptual cues systematically: the retinal, the visual background, the vestibular, and proprioceptive information. Verbal descriptions of visually presented arrays were required under different head positions (straight/tilt) and under different gravitational conditions (gravity present/gravity absent). The results of two experiments conducted with 2 subjects who participated in a space flight revealed that subjects are able to adequately assign positions in space in the absence of gravitational information, and that they do this by using their head-retinal coordinates as primary references. This indicates that they cognitively adapted to the perceptually new situation. The findings from a third experiment conducted with a larger group of subjects under a condition in which the gravitational information was present but irrelevant to the task being solved (subjects were in a horizontal supine position) show that subjects, in general, are flexible in using cues other than gravitational ones as references when the latter cannot serve as a referential system. These findings, together with the observation that consistent spatial assignment is possible even immediately after first exposure to the perceptually totally novel situation of weightlessness, seem to suggest that the mental representation of space, onto which given perceptual information is mapped, is independent of a particular percept.Perception of, orientation in, and communication about space are some of the most fundamental abilities in human beings. These abilities, which involve the storage and retrieval of spatial information in and from memory, necessarily require the existence of some mental representation or model of space. On the basis of such a mental model, one's perception of, behavior in, and, moreover, communication about space are organized. Unambiguous localization in space necessarily requires a frame of reference with respect to which spatial positions are defined.

Section: Discussionmentioning

confidence: 99%

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confidence: 98%

Spatial reference in weightlessness: Perceptual factors and mental representations

Friederici

Levelt

1990

“…However, when the tilt is restricted to the head, results vary from one experiment to another. They are E effects (Day & Wade, 1969;Wade, 1968Wade, , 1969Witkin & Asch, 1948a), A effects (Dichgans, Diener, & Brandt, 1974;Parker, Poston, & Gulledge, 1983), or occasionally no general effect (DiLorenzo & Rock, 1982;Merker & Held, 1981).…”

Section: Aubert and Miiller Effectsmentioning

confidence: 99%

The role of head-centric spatial reference with a static and kinetic visual disturbance

Guerraz

Poquin

Ohlmann

1998

A static or kinetic visual disturbance affects subjects' ability to estimate the direction of the gravitational vertical. This kind of error is increased by a head roll inclination. In two experiments, we combined head orientation with a static (Experiment 1: tilted frame) versus kinetic (Experiment 2: rotating disk) visual disturbance. The results showed that with a static visual disturbance, the increase of errors in the inclined head condition was mainly the consequence of a postural head effect like an Aubert effect. On the contrary, with a kinetic visual disturbance, it appears that the disk effect increases with head inclination. However, individual errors observed with the head inclined in front of a stationary disk were systematically correlated with the errors triggered by the same head inclination in front of a rotating disk. These observations confirm that the head axis spatial reference plays an important role in orientation perception, whatever the head position and the kind of visual display.The subjective visual (SV) oftilted observers with tilted head in front of a static-or kinetic visual disturbance has been shown to deviate from the gravitational vertical more than that ofobservers with head upright. This increase is generally believed to be due to the increase ofthe weighting of the visual influence, despite the fact that head inclination should produce its own effects. The main aim of the paper was to break down and mutually compare the relative effects of head tilt and visual disturbance on the sv. Aubert and Miiller EffectsIn darkness, tilts of the head and body are well known to induce constant errors in SV that are displaced either in the direction of postural inclination (the Aubert, or A effect) or in the opposite direction (the Miiller, or E effect). Many authors (for a review, see Howard, 1986) have suggested that the E effect is characteristic of small degrees of body inclination (up to 60°), whereas the A effect is observed for greater angles (>60°) oftilt. Consequently, tilting the head alone would be expected to proThis work was supported by grants from the University Pierre Mendes France ofGrenoble (CNRS) and by the Ministere de la Defense (DRET, Contract 92/150). We are grateful to Elwyn Leek for his help with the translation and to the anonymous reviewers for their helpful comments. Correspondence should be addressed to T. Ohlmann,

“…The dissimilarities observed between A-effects and E-effects are usually explained by a difference in the perceived body tilt. It is often argued that small angles of body tilt are associated with an overestimation of one's own body position (E-effect) and large angles of body tilt are associated with an underestimation (A-effect; Day & Wade, 1969;Howard & Templeton, 1966;Parker, Poston, & Gulledge, 1983). Thereby, it is assumed that the SVV and the perception of body position are based on the same reference for the physical vertical (Van Beuzekom & Van Gisbergen, 2000).…”

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confidence: 99%

Contribution of somesthetic cues to the perception of body orientation and subjective visual vertical

Trousselard

Cian

Nougier

et al. 2003

Without relevant visual cues, the subjective visual vertical (SVV) is biased in roll-tilted subjects toward the body axis (Aubert or A-effect). This study focused on the role of the somatosensory system with respect to the SVV and on whether somesthetic cues act through the estimated body tilt. The body cast technology was used to obtain a diffuse tactile stimulation. An increased A-effect was expected because of a greater underestimation of the body position in the body cast. Sixteen subjects placed in a tilt chair were rolled sideways from 0º to 105º. They were asked to verbally indicate their subjective body position and then to adjust a luminous line to the vertical under strapped and body cast conditions. Results showed a greater A-effect ( p < .001) but an overestimation of the body orientation ( p < .01) in the body cast condition for the higher tilt values (beyond 60º). Since the otolith organs produced the same gravity response in both conditions, errors were due to a change in somesthetic cues. Visual and postural errors were not directly related (no correlation). However, the angular distance between the apparent body position and the SVV remained stable, suggesting that the change in somatosensory pattern inputs has a similar impact on the cognitive processes involved in assessing the perception of external space and the sense of self-position.