How do mice hear? - briefly
Mice detect sound with large, mobile ear pinnae that funnel vibrations into a short ear canal, leading to a cochlea densely populated with hair cells tuned to high‑frequency tones. The auditory nerve relays these signals to the brain, allowing perception of ultrasonic frequencies up to about 100 kHz.
How do mice hear? - in detail
Mice detect sound through a specialized auditory system that converts air‑borne vibrations into neural signals. Sound waves enter the external ear canal and strike the tympanic membrane, causing it to vibrate. These vibrations are transmitted via three tiny ossicles—the malleus, incus, and stapes—to the oval window of the cochlea.
Inside the cochlea, the stapes movement creates pressure waves in the fluid-filled scala vestibuli. The waves travel through the basilar membrane, whose stiffness varies along its length; high‑frequency sounds peak near the base, while low‑frequency sounds peak near the apex. Hair cells situated on the basilar membrane possess stereocilia that bend in response to the fluid motion. Deflection of the stereocilia opens mechanically gated ion channels, allowing potassium‑rich endolymph to flow into the cells, generating receptor potentials that trigger action potentials in the auditory nerve fibers.
Mice possess an expanded high‑frequency range compared with humans, hearing up to 100 kHz. This capability is supported by a relatively short, high‑frequency‑tuned cochlear base and a large population of outer hair cells that amplify basilar‑membrane motion through electromotility. The auditory nerve projects to the cochlear nucleus, then to higher auditory centers in the brainstem and midbrain, where temporal and spectral information is processed for behavior such as predator avoidance and communication.
Key components of the mouse auditory pathway:
- External ear: pinna and canal funnel sound to the tympanic membrane.
- Middle ear: malleus, incus, stapes transmit vibrations to the cochlea.
- Cochlea: fluid‑filled spiral organ with tonotopic organization; inner hair cells transduce mechanical energy, outer hair cells provide active amplification.
- Auditory nerve: carries encoded spikes to central nuclei.
- Central auditory system: cochlear nucleus → superior olivary complex → inferior colliculus → auditory cortex, integrating frequency, intensity, and timing cues.
Genetic tools in laboratory mice allow precise manipulation of each element, revealing that disruptions in hair‑cell function, ion‑channel expression, or synaptic transmission produce measurable deficits in acoustic startle reflexes and ultrasonic vocalization detection. Consequently, the mouse auditory apparatus serves as a model for studying peripheral and central hearing mechanisms.