Human ocular torsion and perceived roll responses to linear acceleration

Area of Science:

• Vestibular Neuroscience
• Human Physiology
• Sensory Perception

Background:

• The human vestibular system processes head motion and orientation.
• Ocular torsion (OT) and perceived roll (PR) are key vestibular outputs.
• Previous research explored OT at limited frequencies; this study expands the frequency range and includes PR.

Purpose of the Study:

• To investigate whether human ocular torsion (OT) and perceived roll (PR) are elicited by dynamic interaural linear acceleration or dynamic roll tilt of the gravito-inertial force (GIF).
• To compare OT and PR responses across different experimental conditions and frequencies.
• To elucidate the distinct neural mechanisms governing OT and PR.

Main Methods:

• Simultaneous measurement of OT (via video-oculography) and PR (via somatosensory bar).
• Testing across four frequencies (0.01, 0.02, 0.05, and 1 Hz).
• Three experimental conditions: Y-Upright (interaural acceleration, upright), Y-Supine (interaural acceleration, supine), and Z-RED (rostro-caudal acceleration, right-ear-down).

Main Results:

• OT and PR exhibited qualitatively different responses.
• Large OT responses were observed in Y-Upright and Y-Supine conditions.
• Large PR responses were observed in Y-Upright and Z-RED conditions, with absent PR in Y-Supine and small OT in Z-RED.

Conclusions:

• OT and PR are governed by distinct neural mechanisms.
• OT appears influenced by central low-pass filtering of interaural graviceptor cues.
• PR appears primarily influenced by the roll tilt of the gravito-inertial force (GIF).