Final answer:
Turning the head to the left decreases activity in the left vestibular nerve and increases activity in the right vestibular nerve. Irrigating the left ear with water can cause a similar response by stimulating the hair cells in the vestibular labyrinth, creating an illusion of head movement.
Step-by-step explanation:
When a person's head turns horizontally to the left, the activity levels in their vestibular nerves change. The left vestibular nerve's activity decreases, while the right vestibular nerve's activity increases.
This pattern occurs due to the vestibulo-ocular reflex (VOR), which helps maintain visual stability by coordinating eye movements with head movements.
This reflex induces a compensatory movement of the eyes in the opposite direction of the head turn to keep the visual field stable.
If you were to irrigate the left ear with cool or warm water, a similar pattern of activity would be obtained in the vestibular nerves.
This technique, known as caloric stimulation, induces a temperature gradient across the horizontal semicircular canal, causing the fluid inside the canal to either rise or fall due to convection.
As a result, the hair cells in the canal are stimulated, and an illusion of head movement is created, even though the head remains still. This stimulation can mimic natural vestibular responses such as the ones elicited by actual head movements.
However, the specific results of ear irrigation can vary depending on the temperature of the water used and individual variations in the anatomy and physiology of the inner ear.
The left ear irrigation with warm water would increase firing rates in the left vestibular nerve, resembling the effect of a leftward head turn.
Conversely, cool water would decrease the firing rate, akin to the effect of a rightward head turn. The response of the hair cells in the vestibular labyrinth dictates the pattern of activity change.