Abstract
Accurate perception of the orientations of the body axis and gravity is essential for actions. The ability to perceive these orientations during head and body tilt varies across individuals, and its underlying neural basis is unknown. To address this, we investigated the association between inter-individual differences in local gray matter (GM) volume and inter-individual differences in the ability to estimate the directions of body longitudinal axis or gravity during whole-body tilt using voxel-based morphometry (VBM) analysis in 50 healthy adults (20–46 years, 25 men and 25 women). Although no anatomical regions were identified relating to performance requiring estimates of gravitational direction, we found a significant correlation between the GM volume in the right middle occipital gyrus and the ability to estimate the body axis orientation. This finding provides the first evidence on neuroanatomical substrates of the perception of body axis orientation during body tilt.
Highlights
Accurate perception of the orientations of the body axis and gravity is essential for actions
Errors in the subjective visual body axis (SVBA) and subjective visual vertical (SVV) tasks were biased toward the direction of body tilt, the magnitude of the bias was larger for the SVBA (LSD, − 13.05° ± 1.75°; RSD, 13.34° ± 1.77°) than for the SVV (LSD, − 2.07° ± 0.47°; RSD, 1.50° ± 0.56°)
The OKSeffect of clockwise OKS (CW-OKS) was − 3.74° ± 0.66° for the SVBA task and − 1.78° ± 0.33° for the SVV task, and that of counterclockwise OKS (CCW-OKS) was 4.13° ± 0.59° for the SVBA task and 1.80° ± 0.29° for the SVV task, which indicates that perceived directions of body axis and gravity were biased rightward by CW-OKS and leftward by CCW-OKS
Summary
Accurate perception of the orientations of the body axis and gravity is essential for actions. Electroencephalograph (EEG) and transcranial magnetic stimulation (TMS) studies have shown the involvement of bilateral occipito-temporal and left parieto-occipital regions[13] and the right temporoparietal junction (rTPJ) in judgments of the orientation of a visual line relative to gravity (i.e., gravity-centered judgment)[14, 15]. These studies suggest common and distinct neural substrates for the perception of the orientations of body axis and gravity, methodological concerns may affect their validity. This enables assessment of perceived orientation of body axis and gravity independently
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