Neurophysiology of auditory perception

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Hearing Auditory system Auditory cortex Auditory evoked potentials Acoustic nerve Ear Psychophysics Acoustics Audiology Audiometers Audiometry Auditory acuity Auditory discrimination Auditory localization Auditory masking Auditory stimulation Auditory thresholds Auditory perception Auditory displays Auditory feedback Auditory hallucinations Loudness perception Music perception Pitch perception Speech perception Other aspects Auditory displays Listening (interpersonal) Clinical issues Ear disorders Hearing disorders Hearing impairment Deaf Cochlear implants Hearing aids Tinnitus

Basic structure of the auditory system

There are three main components of the human ear: the outer ear, the middle ear and the inner ear.

The outer ear includes the visible part of the ear (or the pinna), the auditory canal and the eardrum. The eardrum is made of an airtight flap of skin. Sounds travel in waves, and when these waves arrive at the eardrum, they cause it to vibrate, following the waveform of the sound. The eardrum simplifies incoming air pressure waves to a single change with a certain amplitude. This allows for the differentiation of sound.

The middle ear consists of a small air filled chamber that is located behind the eardrum. Within this chamber are the three smallest bones in the body, known collectively as the ossicles. They aid in the transmission and amplification of the vibrations from the ear drum to the inner ear.

The inner ear contains the cochlea, which is a spiral shaped, fluid filled tube that is considered the organ of auditory transduction. It is divided lengthwise by the basilar membrane, a structure that vibrates when waves from the middle ear propagate through the cochlear fluid–membrane system. The basilar membrane is tonotopic, so that each frequency has a characteristic place of resonance along it. Characteristic frequencies are high at the basal entrance to the cochlea, and low at the apex. Basilar membrane motion causes the movement of the hair cells, specialized auditory receptors located within the basilar membrane. The space–time pattern of vibrations in the basilar membrane is converted to a spatial–temporal pattern of firings on the auditory nerve, which transmits information about the sound to the brainstem.

See also

• Neurologic music therapy
• Neuronal encoding of sound