Semicircular canal dynamics:
Three canals per side (horizontal, anterior, posterior) detect rotational acceleration. The cupula is deflected by endolymph inertia during head rotation.
Transfer function: H(s) = s·τ₁/(1+s·τ₁) × 1/(1+s·τ₂)
where τ₁≈7s (long time constant), τ₂≈0.003s
The canal responds to velocity, not position. Constant-velocity rotation → sensation decays in ~20s (cupula returns to rest). Initial sensation of deceleration after stopping = post-rotatory vertigo.
VOR reflex arc (3 neurons):
1. Vestibular nerve (VIII) → vestibular nucleus
2. Vestibular nucleus → abducens nucleus (CN VI)
3. Abducens → lateral rectus muscle
Latency: ~7ms (fastest reflex arc). Compare: visual pursuit ~100ms.
VOR gain = eye velocity / head velocity. Ideal gain = 1.0 (perfect compensation). Gain < 1: retinal slip. Gain > 1: overcompensation. Gain adapts over days with prismatic goggles.