Angular vestibuloocular reflex responses in Otop1 mice. I. Otolith sensor input is essential for gravity...

Area of Science:

• Neuroscience
• Vestibular System Physiology
• Otolith Function

Background:

• Determining the otoliths' role in mammalian angular vestibuloocular reflex (VOR) is challenging due to surgical limitations.
• The Otopetrin1 (Otop1) mouse model offers a unique opportunity to study otolith function without damaging semicircular canals.

Purpose of the Study:

• To investigate the role of otoliths in the baseline function and adaptation of the angular VOR in mammals.
• To utilize the Otop1 mouse model to assess otolith contribution to VOR gain and context-specific adaptation.

Main Methods:

• Measured ocular countertilt and sinusoidal VOR gain (horizontal and vertical) in Otop1 mice and control littermates.
• Assessed VOR adaptation through gain-increase and gain-decrease training protocols.
• Compared VOR responses across different head-centric axes and testing contexts (e.g., left ear down, right ear down).

Main Results:

• Otop1 mice exhibited significantly reduced countertilt responses.
• Baseline horizontal and vertical VOR gains, as well as horizontal VOR adaptation, were similar between Otop1 and control mice.
• Vertical VOR adaptation in control mice was context-dependent, while Otop1 mice showed adaptation regardless of context.

Conclusions:

• Otoliths do not contribute to baseline angular VOR in mice, likely due to the compensatory nature of the VOR.
• Otoliths do not alter the magnitude of normal angular VOR adaptation.
• Otoliths are critical for gravity context-specific adaptation of the angular VOR.