Neuroanatomy Draw It To Know It

14. Vestibular and Auditory Systems 233

Auditory Physiology ( Advanced )

■ Preservation of tone localization throughout the
central auditory system is called tonotopy.
■ Th e base of the cochlea encodes high-frequency
sounds and the apex encodes low-frequency sounds.
■ Low-frequency sounds lie anterior within the ventral
and dorsal cochlear nuclei.
■ High-frequency sounds lie posterior within the
ventral and dorsal cochlear nuclei.

■ Within the transverse temporal g yri (Heschl’s g yri),

low-frequency sounds localize laterally whereas

high-frequency sounds localize medially.

■ When there is a unilateral lesion to the central

auditory pathway, hearing is preserved from the

duplication of auditory information in the

contralateral cerebral hemisphere.

Integument

Facial

musculature

Squama of

temporal bone

Meninges

Brain

Auricle

Cartilages

of external ear

Mastoid air cells

Mastoid

process

Styloid process

Tympanic membrane and cavity

Vestibule

Secondary tympanic membrane

Levator veli palatini

Auditory tube

Mucous membrane

Scala vestibuli

Cochlear duct

Scala tympani

Perilymphatic duct

(in cochlear canaliculus)

Endolymphatic sac

(in dura mater)

Endolymphatic duct

(in vestibular aqueduct)

Externalacoustic meatus

Semicircular ducts

(in canals)

Auditory ossicles

Epitympanic recess

FIGURE 14-1 Outer, middle, and inner ear. Used with permission from Baloh, Robert W., and Vicente Honrubia. Clinical Neurophysiology of the
Vestibular System, 3rd ed. Contemporary Neurology Series 63. Oxford; New York: Oxford University Press, 2001.