Subjective postural vertical in peripheral and central vestibular disorders

Area of Science:

• Neuroscience
• Vestibular System Research
• Human Perception

Background:

• The subjective postural vertical (SPV) is crucial for maintaining balance and spatial orientation.
• Vestibular disorders, including peripheral and central conditions, can disrupt SPV perception.
• Spasmodic torticollis may also impact postural verticality due to head positioning.

Purpose of the Study:

• To assess the perception of subjective postural vertical in individuals with various vestibular disorders and spasmodic torticollis.
• To determine the impact of vestibular deficits and head tilt on the accuracy of SPV perception.
• To investigate potential correlations between vestibulo-ocular function asymmetry and directional bias in SPV.

Main Methods:

• Subjects were seated in a motorized gimbal with head and torso restrained and eyes closed.
• The gimbal performed sinusoidal pitch or roll rotations at 1.5 degrees/s.
• Participants used a joystick to indicate perceived upright and tilted positions, defining a sector of perceived verticality.

Main Results:

• Normal subjects perceived upright within a 5-6 degree sector.
• Patients with absent vestibular function, torticollis, and acute unilateral peripheral lesions showed significantly larger sectors.
• Long-standing vestibular deficits and nystagmus near upright also resulted in abnormally large sectors of perceived uprightness.

Conclusions:

• Vestibular function is essential for accurate subjective postural vertical perception.
• Directional bias in SPV is not always present even with vestibular asymmetry or head tilt.
• Impaired vestibular function broadly affects the range of perceived verticality, not just directional accuracy.