Apparent body tilt and postural aftereffect

Abstract

Apparent orientation of the body tilted laterally in the frontal plane was studied with the methods of absolute judgments in four experiments. In Experiment 1, 17 subjects, who maintained the normal adaptation of body to gravity,estimated their body tilts under the condition of seeing the gravitational vertical and under the condition of eliminating it. The results showed that (1) there was not a significant difference between the two conditions and (2) the small tilts of less than 45°were exactly estimated, whereas the large tilts of 45°-108°were overestimated. In Experiment 2, 10subjects estimated their body tilts under three velocities of a rotating chair on which each subject was placed. Although both body tilt and chair velocity were found to influence tilt estimation, the effect of body tilt was overwhelmingly greater than that of chair velocity. In Experiment 3, 11 subjects adapted their bodies to a 72°left tilt for 10 min and then estimated various body tilts around the adapting tilt. The estimations obtained under the 72°adaptation were lower than those obtained under the 0°adaptation, and this reduction was greater for the test tilt that was farther away from the adapting tilt. In Experiment 4, 11 subjects adjusted their own body tilts to designated angles. The results confirmed the outcomes of absolute estimation in Experiments 1-3. From these findings and past literature, the judgments of body tilt were considered to be subserved by a single sensory process that was based on the cutaneous and muscular proprioceptors, rather than the vestibular and joint proprioceptors. 331We investigated apparent orientation of the body by tilting it laterally in the frontal plane.' The first concern was to establish psychophysical scale for body tilt under normal adaptation of the body to gravity. The second concern was to explore the processes and proprioceptors that make the perception ofbody tilt possible. For the latter concern, we made use of postural aftereffects or postural persistence: the sense of position of a limb, the head, or the eyes that may be temporarily affected when an asymmetrical posture is maintained for some time (F. 1. Clark & Horch, 1986;Howard, 1982). In this study, after being placed at a certain fixed tilt for some time, the subjects judged their various body tilts around the fixed tilt. On the basis of extent and magnitude of postural aftereffects, we assessed how many processes (single or double) exert in the perception of body tilt. Moreover, we considered how the processes are related to the nonvisual proprioceptors, such as the cutaneous, vestibular, joint, and muscular proprioceptors.?One conventional method of measuring apparent body tilt is to have the subject indicate his or her apparent bodyThe authors are grateful to Y.Ohta, who helped collect the data of Experiments 2 and 3, and to K. Shimono, who critically read the earlier manuscript. Correspondence should be addressed to K. Koga, Research Institute of Environmental Medicine, Nagoya University, Furo-cho Nagoya 464-0 I, Japan...

Gender differences in spatial perception of body tilt

“…These results indicate that when judgments of body orientation are made, adding visual information may actually reduce the extent of the overestimations of body tilt. Similar findings by Higashiyama and Koga (1998) support the view that the distribution of atmospheric pressure on skin provides another cue to body tilt perception. Both studies showed no significant difference in estimated body tilt between participants whose eyes were open and those whose eyes were closed, although the average overall tilt overestimation was somewhat lower with eyes open.…”

“…Models such as those of Perrone (1982) or Proffitt (Proffitt et al, 2001;Stefanucci et al, 2005) help explain the occurrence of slant overestimation as a visual illusion; yet other work supports the view that additional, nonvisual factors can also contribute to the perceived slant distortion, particularly when judgments involve multisensory information such as occurs with body tilt (Aksamit & Husak, 1983;Higashiyama & Koga, 1998;Ito & Gresty, 1997).…”

“…The findings support the view that the perception of body tilt is multisensory and is consistent with women's more strongly utilizing auditory information in their multisensory spatial judgments, relative to men. uting variables in judgments of spatial position and orientation (Aksamit & Husak, 1983;Higashiyama & Koga, 1998;Isableu & Vuillerme, 2006).…”

“…Jeka, Easton, Bentzen, and Lackner (1996) suggested that multisensory systems contribute to how we perceive spatial orientation, including a combination of kinesthetic and cutaneous cues. Higashiyama and Koga (1998) also proposed that human beings use cutaneous and muscular proprioceptors in estimating body tilt. These and other findings support the view that spatial orientation perception is determined through multisensory processes (Bringoux et al, 2003;Bronstein, 1999;Mittelstaedt, ence the largest tilt bias in the absence of both visual and auditory information and that the bias will be diminished when information from either sensory modality is present.…”

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

“…Regarding the estimation of body tilt, results are quite inconsistent. Higashiyama and Koga (1998) recorded some fairly accurate estimates up to a 45º roll tilt. At higher roll tilts, the values were overestimated.…”