Suppression of eye movements improves balance

Area of Science:

• Neuroscience
• Vestibular System Research
• Human Motor Control

Background:

• Vestibulo-ocular reflex (VOR) and vestibulo-spinal reflex (VSR) are crucial for balance.
• Vestibular neuritis disrupts these reflexes, leading to postural instability.
• The interplay between VOR suppression and VSR modulation in patients is not fully understood.

Purpose of the Study:

• To investigate the interaction between vestibulo-ocular and vestibulo-spinal functions.
• To determine if suppressing spontaneous nystagmus affects postural sway in vestibular neuritis patients.
• To elucidate the role of ocular motor signals versus visual cues in postural control.

Main Methods:

• Simultaneous recording of eye movements and body sway in 10 vestibular neuritis patients and 11 healthy controls.
• Subjects fixated a head-fixed target to suppress spontaneous nystagmus.
• Postural sway was measured while standing on foam rubber.

Main Results:

• Fixating the target significantly reduced spontaneous nystagmus slow-phase velocity in patients (13.5 to 4.3 deg/s).
• This nystagmus suppression also significantly reduced postural sway in patients (25.2 to 16.2 mm).
• Healthy subjects showed no significant difference in sway between eyes open and target fixation.

Conclusions:

• Suppression of nystagmus in vestibular neuritis patients leads to reduced postural sway.
• Ocular motor efference copy signals, rather than visual cues, likely contribute to postural instability.
• This suggests ocular motor signals play a role in visual control of postural sway in this paradigm.