Heading Direction Is Significantly Biased by Preceding Whole-Body Roll-Orientation While Lying

Area of Science:

• Neuroscience
• Human Physiology
• Biomechanics

Background:

• Prolonged whole-body roll-tilt causes a bias in internal gravity direction estimates.
• This bias affects the subjective visual vertical, indicating a disruption in spatial orientation.

Purpose of the Study:

• To investigate if post-tilt bias in gravity perception extends to spatial orientation and navigation.
• To determine if perceived straight-ahead is biased after prolonged roll-tilt.

Main Methods:

• Twenty-five healthy participants underwent a 5-minute adaptation period in supine, right-ear-down, or left-ear-down positions.
• Participants then walked blindfolded for 2 minutes while heading direction was recorded using inertial measurement units and shoe insoles.

Main Results:

• A significant bias in heading direction towards the previous roll-tilt position was observed.
• This bias was consistent across both measurement systems and gradually decreased during the 2-minute walk.

Conclusions:

• Prior knowledge significantly influences spatial orientation and navigation, as evidenced by the post-tilt heading bias.
• The findings highlight the broad impact of shifting gravity estimates on spatial perception and suggest increased fall risk upon waking due to temporary disorientation.