The Mind's Machine: Chapter 6

decibel (dB)

a measure of sound intensity perceived as loudness

hertz (Hz)

cycles per second, as of an auditory stimulus. Hertz is a measure of frequency

transduction

the conversion of one form of energy to anotther

pinna

the external part of the ear

ear canal

also called auditory canal. the tube leading from the pinna to the tympanic membrane

inner ear

the cochlea and vestibular apparatus

middle ear

the cavity between the tympanic membrane and the cochlea

tympanic membrane

also called eardrum. the partition between the external ear and the middle ear.

ossicles

three small bones (incus, malleus, and stapes) that transmit vibration across the middle ear, from the tympanic membrane to the oval window.

oval window

the opening from the middle ear to the inner ear

malleus

latin for hammer. a middle ear bone that is connected to the tympanic membrane

incus

latin for anvil. a middle ear bone situated between the malleus and the stapes

stapes

latin for stirrup. a middle ear bone that is connected to the oval window

cochlea

a snail-shaped structure in the inned ear that contains the primary receptor cells for hearing.

vestibular canal

also called scala vestibuli. one of three principal canals running along the length of the cochlea.

middle canal

also called scala media. the central of the three spiraling canals insdie the cochlea, situated between the vestibular canal and the tympanic canal.

tympanic canal

also called scala tympani. one of three principal canals running along tthe length of the cochlea.

round window

a membrane separating the tympanic canal from the middle ear.

organ of corti

a structure in the inner ear that lies on the basilar membrance of the cochlea and contains the hair cells and terminations of the auditory nerve.

hair cell

one of the receptor cells for hearing in the cochlea.

basilar membrane

a membrane in the cochlea that contains the principal structures involeved in auditory transduction

stereocilium

a relatively stiff hair that protrudes from a hair cell in the audicory or vestibular system

inner hair cell (IHC)

one of the two types of receptor cells for hearing in the cochlea. compared to outer hair cells, IHC's are possitioned closer to the central azis of the coiled cochlea.

outer hair cell (OHC)

one of the two types of receptor cells for hearing in the cochlea. compared to inner hair cells, OHCs are positioned farther from the central axis of the coiled cochlea.

vestibulocochlear nerve

cranial nerve VIII, which runs from the cochlea to the brainstem auditory nuclei.

tuning curve

a graph of the responses of a single auditory nerve fiber or neuron to sounds that vary in frequency and intensity.

cochlear nucleus

either of two brainstem nuclei-left and right-that receive input from auditory hair cells and send output to the superior olivary nuclei.

superior olivary nucleus

either of two brainstem nuclei-left and right-in the thalamus that receive input from the inferior colliculi and send output to the auditory cortex.

tonotopic organization

a major organizational feature in auditory systems, in which neurons are arranged as an orderly map of stimulus frequency, with cells responsive to high frequencies located at a distance from those responsive to low frequencies.

place coding

frquency discrimination in which the pitch of a sound is determined by the location of activated hair cells along the length of the basilar membrane.

temporal coding

frequency discrimination in which the pitch of a sound is determinned by the rate of firing of auditory neurons.

ultrasound

high-frequency sound, above the threshold for human hearing, at about 20,000 Hz

infrasound

very low frequency sound; in general, below the threshold for human hearing, at about 20 Hz.

intensity difference

a perceived difference in loudness between the two ears, which the nervous system can use to localize a sound source.

latency difference

a difference between the two ears in the time of arrival of a sound, which the nervous system can use to localize a sound source.

spectral filtering

the process by which the hills and valleys of the external ear alter the amplitude of some, but not all, frequencies in a sound.

amusia

a disorder characterized by the inability to discern tunes accurately or to sing.

conduction deafness

a hearing impairment in which the sound vibrations in air fail to be converted into waves of fluid in the cochlea. it is associated with defects of the external ear or middle ear.

sensorineural deafness

a hearing impairment most often caused by the permanent damage or destruction of hair cells, or by interruption of the vestibulocochlear nerve that carries auditory information to the brain.

tinnitus

a sensation of noises or ringing in the ears not caused by external sound

central deafness

a hearing impairment in which the auditory areas of the brain fail to process and interpret action potentials from sound stimuli in meaningful ways. it is related to damage in auditory brain areas, such as by strokes, tumors, or traumatic injuries.

word deafness

a form of central deafness that is characterized by the specific inability to hear words, although other sounds can be detected.

cortical deafness

a form of central deafness, caused by damage to both sides of the auditory cortex, that is characterized by difficulty in recognizing all complex sounds, whether verbal or nonverbal.

cochlear implan

an electromechanical device that detects sounds and selectively stimulates nerves in different regions of the cochlea via surgically implanted electrodes

vestibular system

the sensory system that detects balance. it consists of several small inner-ear structures that adjoin the cochlea

semicircular canal

any one of three fluid-filled tubes in the inner ear that are part of the vestibular system. each of the tubes, which are at right angles to each other, detects angular acceleration in a particular direction.

ampulla

an enlarged region of each semicircular canal that contains the receptor cells (hair cells) of the vestibular system

vestibular nucleus

a brainstem nucleus that receives information from the vestibular organs through cranial nerve VIII (the vestibulocochlear nerve)

motion sickness

the experience of nausea brought on by unnatural passive movement, as in a car or boat

sensory conflict theory

a theory of motion sickness suggesting that discrepancies between vestibular information and visual information simulate food poisoning and therefore trigger nausea.

taste

any of the five basic sensations detected by the tongue: sweet, salty, sour, bitter, and umami.

flavor

the sense of taste combined with the sense of smell

papilla

a small bump that projects from the surface of the tongue. papillae contain most of the taste receptor cells.

taste bud

a cluster of 50-150 cells that detects tastes. taste buds are found in papillae.

T1R

a family of taste receptor proteins that, when particular members bind together, form taste receptors for sweet flavors and umami flavors.

T2R

a family of bitter taste receptors

umami

one of the five basic tastes--the meaty, savory flavor. (the other four tastes are salty, sour, sweet, and bitter)

gustatory system

the sensory system that detects taste

odor

the sensation of smell

olfaction

the sensory system that detects smell; the act of smelling.

anosmia

the inability to detect odors

olfactory epithelium

a sheet of cells, including olfactory receptors, that lines the dorsal portion of the nasal cavities and adjacent regions, including the septum that separates the left and right nasal cavities

olfactory bulb

an anterior projection of the brain that terminates in the upper nasal passages and, through small openings in the skull, provides receptors for smell.

glomerulus

a complex arbor of dendrites from a group of olfactory cells

pheromone

a chemical signal that is released outside the body of an animal and affects other members of the same species.

vomeronasal system

a specialized sensory system that detects pheromones and transmits information to the brain

vomeronasal organ (VNO)

a collection of specialized receptor cells near to but seperate from the olfactory epithelium, that detect pheromones and send electical signals to the accessory olfacory bulb in the brain.

trace amine-associated receptor (TAAR)

any one of a family of probable pheromone receptors produced by neurons in the main olfactory epithelium