Gravity affects the preferred vertical and horizontal in visual perception of orientation

Area of Science:

• Neuroscience
• Human Factors
• Space Biology

Background:

• Visual orientation is crucial for spatial awareness and navigation.
• The human sensory system integrates multiple inputs, including visual, proprioceptive, and vestibular information.
• The role of gravity in the representation and storage of visual orientation remains incompletely understood.

Purpose of the Study:

• To investigate the influence of gravity on the perception and memory of visual orientation.
• To determine how body orientation relative to the gravitational vector affects visual stimulus processing.
• To explore the reference frames used for storing visual orientation information under different gravitational conditions.

Main Methods:

• Participants performed a visual orientation alignment task on Earth and in microgravity.
• Response times and variability were measured for horizontally and vertically oriented stimuli.
• Experiments involved conditions with aligned and tilted body axes relative to gravity.

Main Results:

• On Earth, a significant preference for horizontal and vertical stimuli was observed when the body axis aligned with gravity.
• This orientation preference diminished when the body was tilted relative to gravity on Earth.
• The preference for horizontal and vertical stimuli was maintained in microgravity, irrespective of body orientation.

Conclusions:

• Visual orientation information is stored in a multi-modal reference frame.
• This reference frame integrates proprioceptive and gravitational cues when both are available.
• The findings suggest that gravity plays a key role in calibrating our sense of visual orientation.