seciton 7.2

Question 1

sounds

Answer 1

vibrations of air molecules that stimulate the auditory system; humans only molecular vibrations between about 20 and 20,000 hertz (cycles per second).

Question 2

amplitude

Answer 2

loudness

Question 3

frequency

Answer 3

pitch

Question 4

complexity

Answer 4

timbre

Question 5

Pure tones (sine wave vibrations)

Answer 5

exist only in laboratories and sound recording studios; in real life, sound is always associated with complex patterns of vibrations.

Question 6

fourier analysis

Answer 6

the mathematical procedure for breaking down complex waves into their component sine waves.

Question 7

One theory of audition is that

Answer 7

the auditory system performs a Fourier-like analysis of complex sounds in terms of their component sine waves.

Question 8

For any pure tone, there is a close relationship between

Answer 8

the frequency of the tone and its perceived pitch.

Question 9

The pitch of natural sounds is related to their

Answer 9

È fundamental frequency (the highest frequency of which the various component frequencies of a sound are multiples). A sounds with a mixture of 100, 200, and 300 frequencies normally has a pitch related to 100 Hz because 100 Hz is the highest frequency of which the three components are multiples.

Question 10

An important characteristic of pitch perception is the fact that the

Answer 10

pitch of a complex sound may not be directly related to the frequency of any of the sound’s components. A mixture of pure tones with frequencies of 200, 300, and 400 Hz would be perceived as having the same pitch as a pure tone of 100 Hz – because 100 Hz is the fundamental frequency of 200, 300, and 400 Hz. This important aspect of pitch perception is referred to as the missing fundamental.

Question 11

Sound waves travel from the

Answer 11

È outer ear down the auditory canal and cause the tympanic membrane (the eardrum) to vibrate. These vibrations are then transferred to the three ossicles – the small bones of the middle ear: the malleus (the hammer), the incus (the anvil) and the stapes (the stirrup). The vibrations of the stapes trigger vibrations of the membrane called the oval window, which in turn transfers the vibrations to the fluid of the cochlea.

Question 12

cochlea

Answer 12

long, coiled tube with an internal membrane (organ of Corti) running almost to its tip.

Question 13

organ of corti

Answer 13

the internal membrane of the cochlea; auditory receptor organ. Each pressure change at the oval window travels along the organ of Corti as a wave. Composed of two membranes: the basilar membrane and the tectorial membrane.

Question 14

hair cells

Answer 14

the auditory receptors; mounted in the basilar membrane.

Question 15

tectorial membrane

Answer 15

rests on the hair cells

Question 16

A deflecton of the organ of Corti at any point along its length

Answer 16

produces a shearing force on the hair cells at the same point. This force stimulates the hair cells, which in turn increase firing in axons of the auditory nerve.

Question 17

auditory nerve

Answer 17

a branch of cranial nerve VIII (the auditory-vestibular nerve).

Question 18

The vibrations of the cochlear fluid are

Answer 18

ultimately dissipated by the round window, an elastic membrane in the cochlea wall.

Question 19

The cochlea is sensitive

Answer 19

humans can hear differences in pure tones that differ in frequency by only 0.2%.

Question 20

The major principle of cochlear coding is that

Answer 20

different frequencies produce maximal stimulation of hair cells at different points along the basilar membrane – with higher frequencies producing greater activation closer to the windows and lower frequencies producing greater activation at the tip of the basilar membrane.

Question 21

The many component frequencies that compose each complex sound activate

Answer 21

hair cells at many different points along the basilar membrane, and the many signals created by a single complex sound are carried out of the ear by many different auditory neurons.

Question 22

tonotopic

Answer 22

structures are arrayed according to frequency.

Question 23

semicircular canals

Answer 23

the receptive organs of the vestibular system.

Question 24

vestibular system

Answer 24

carries information about the direction and intensity of head movements, which helps maintain our balance.

Question 25

The axons of each auditory nerve synapse in the

Answer 25

ipsilateral cochlear nuclei, from which many projections lead to the superior olives on both sides of the brain stem at the same level.

Question 26

The axons of the olivary neurons project via

Answer 26

the lateral lemniscus to the inferior colliculi, where they synapse on neurons that project to the medial geniculate nuclei of the thalamus, which in turn project to the primary auditory cortex.

Question 27

Signals from each ear are combined

Answer 27

at a very low level (in the superior olives) and are transmitted to both ipsilateral and contralateral auditory cortex.

Question 28

Localization of sounds in space is mediated by

Answer 28

the lateral and medial superior olives.

Question 29

medial superior olives

Answer 29

some neurons respond to slight differences in the time of arrival of signals from the two ears.

Question 30

lateral superior olives

Answer 30

some neurons respond to slight differences in the amplitude of sounds from the two ears.

Question 31

medial and lateral superior olives

Answer 31

project to the superior colliculus, as well as to the inferior colliculus.

Question 32

In contrast to the general tonotopic organization of the auditory system, the deep layers of the superior colliculi

Answer 32

which receive auditory input, are laid out according to a map of auditory space. The superficial layers receive visual input and are organized retinotopically. Appears that the general function is locating sources of sensory input in space.

Question 33

Primary auditory cortex in primates

Answer 33

receives the majority of its input from the medial geniculate nucleus; located in the temporal lobe, hidden from view within the lateral fissure. Comprises three adjacent areas, which together are referred to as the core region.

Question 34

belt

Answer 34

surrounding the core region; a band of secondary cortex.

Question 35

parabelt areas

Answer 35

areas of secondary auditory cortex outside of the belt.

Question 36

There seems to be about __ separate areas of auditory cortex in primates.

Answer 36

20

Question 37

The primary auditory cortex is organized in functional columns:

Answer 37

all of the neurons encountered during a vertical microelectrode penetration of the primary auditory cortex (at right angles to the cortical layers) tend to respond optimally to sounds in the same frequency range.

Question 38

The auditory cortex, like the cochlea, is organized tonotopically:

Answer 38

each area of primary and secondary auditory cortex appears to be organized on the basis of frequency.

Question 39

Many neurons in the auditory cortex respond only weakly to

Answer 39

simple stimuli, such as pure tones.

Question 40

Auditory signals are ultimately conducted to two large areas of associated cortex:

Answer 40

prefrontal cortex and posterior parietal cortex.

Question 41

It has been hypothesized that the anterior auditory pathway is more involved in

Answer 41

identifying sounds (what), whereas the posterior auditory pathway is more involved in located sounds (where).

Question 42

Suggested that the primary function of the auditory dorsal pathway is

Answer 42

in the preparation for action.

Question 43

association cortex

Answer 43

usually defined as areas of cortex where interactions, or associations, take place. Confirmed by functional brain imaging studies, but they have also found evidence of sensory interactions at the lowest level of the sensory cortex hierarchy, in areas of primary sensory cortex.

Question 44

Most auditory neurons respond to changes in

Answer 44

frequency rather than pitch.

Question 45

Bendor and Wang

Answer 45

discovered one small area, in monkeys, just anterior to primary auditory cortex that contained many neurons that responded to pitch rather than frequency, regardless of the quality of sound. This area also contained neurons that responded frequency. They suggested that this area was likely the place where frequencies of sound were converted to the perception of pitch. Similar location in human brain with fMRI studies.

Question 46

bilateral lesions

Answer 46

often a complete loss of hearing, which presumably results from the shock of the lesion because hearing recovers in the ensuing weeks. The major permanent effects are loss of the ability to localize sounds and impairment of the ability to discriminate frequencies.

Question 47

unilateral lesions

Answer 47

suggest that the system is partially contralateral. Disrupts the ability to localize sounds in space contralateral, but not ipsilateral, to the lesion. Other auditory deficits produced by unilateral auditory cortex lesions tend to be only slightly greater for contralateral sounds.

Question 48

Total deafness is rare

Answer 48

only occurring in 1% of hearing impaired individuals.

Question 49

Severe hearing problems typically result from damage to the

Answer 49

inner ear or the middle ear or to the nerves leading from them, rather than from more central damage.

Question 50

conductive deafness

Answer 50

hearing impairments associated with damage to the ossicles.

Question 51

nerve deafness

Answer 51

hearing impairments associated with damage to the cochlea or auditory nerve. Major causes is a loss of hair cell receptors. If only part of the cochlea is damage, individual may have nerve deafness for some frequencies, but not others.

Question 52

age-related hearing loss

Answer 52

features a specific deficit in hearing high frequencies.

Question 53

tinnitus

Answer 53

ringing of the ears; hearing loss is sometimes associated with this. When only one ear is damaged, the ringing is perceived as coming from that ear; however, cutting the nerve from the ringing ear has no effect on the ringing. This suggests that changes to the central auditory system that were caused by the deafness are the cause of tinnitus.

Question 54

cochlear implants

Answer 54

helps some people with nerve deafness; bypass damage to the auditory hair cells by converting sounds picked up by a microphone on the patient’s ear to electrical signals, which are then carried into the cochlea by a bundle of electrodes. These signals excite the auditory nerve. They provide benefits, but cannot restore normal hearing. Disuse leads to degeneration of the auditory neural pathways.