Modification of the cervico-ocular reflex by canal plugging

Area of Science:

• Neuroscience
• Vestibular System
• Oculomotor Reflexes

Background:

• The cervico-ocular reflex (COR) normally exhibits low gain in animals.
• The angular vestibulo-ocular reflex (aVOR) is compromised in a specific low/midband frequency range due to semicircular canal plugging.

Purpose of the Study:

• To investigate if increases in COR gain are specific to the frequency range where aVOR is impaired.
• To compare COR and aVOR gain and phase in normal and canal-plugged animals.

Main Methods:

• Monkeys with intact or plugged semicircular canals were subjected to body oscillations (0.05-6 Hz).
• The gain and phase of yaw and pitch COR and aVOR were measured.
• Animals were restrained with their head fixed in space while the body oscillated.

Main Results:

• Normal animals showed low COR gains (0.1-0.2) below 1 Hz, decreasing to zero above 1 Hz.
• Canal-plugged animals exhibited significantly increased COR gains, approaching 1.0 at low frequencies.
• COR gains in plugged animals decreased to 0.6 at 0.5 Hz and 0.2 above 3 Hz, with phase shifts observed.

Conclusions:

• COR gain adaptation is frequency-tuned to the range where aVOR is compromised.
• This frequency specificity suggests a mechanism for adapting compensatory eye movements when vestibular input is reduced.