Visual perception of axes of head rotation

Area of Science:

• Neuroscience
• Perception
• Human spatial orientation

Background:

• Accurate self-motion perception is crucial for navigation.
• The brain integrates vestibular (head motion) and visual (optical flow) information for self-motion registration.
• The role of eye-in-head movements in combining these signals for self-rotation perception remains unclear.

Purpose of the Study:

• To investigate how eye-in-head movements contribute to the perception of self-rotation.
• To determine if visual self-rotation signals are organized according to the semi-circular canal (SCC) axes in the human cortex.
• To examine if human cortical sensitivity to head rotation direction aligns with SCC axes.

Main Methods:

• Simulated optic flow with varying eye-in-head rotations was presented to participants with stationary heads.
• Blood oxygenated level-dependent (BOLD) signals were analyzed for responses to simulated head rotation along different axes.
• Subject sensitivity to head rotation axis direction was measured.

Main Results:

• Perceived self-rotation matched simulated head rotation, not gaze rotation, indicating eye-in-head signals transform visual flow into head-relative rotation.
• BOLD responses in visual cortex (MST and V6+) to simulated head rotation were uniform across SCC axes.
• Sensitivity to head rotation direction was uniformly distributed, not specific to SCC axes.

Conclusions:

• Eye-in-head movements are essential for translating scene-relative visual motion into head-relative self-rotation perception.
• Human cortical processing of visual self-rotation signals does not appear to be organized based on the semi-circular canal axes.
• Visuo-vestibular integration in the human cortex is not arranged in the semi-circular canal frame.