unit 4a

Question 1

Sound pressure wave

Answer 1

sound= mechanical wave that results f/ back & forth vibration of particles of the medium thru which the sound wave is moving
- if a sound wave is moving f/ left → right thru air, then particles of air will be displaced both right/left~ward as the energy of sound wave passes thru it. Motion of particles is parallel (& antiparallel) to the direction of energy transport
- a sine wave can be used to encode info abt the compression & rarefaction (expansion) of sound pressure waves

– Increases of the physical properties of FREQUENCY f/ low → high are assoc w/ incr. in the perceptual exp. of PITCH
–Increases of the physical property of AMPLITUDE f/ sml to log (blue arrow) are assoc. w/ incr. in the perceptual exp. of LOUDNESS
–Wavelength stays constant over distance, but AMPLITUDEof sound pressure wave DECREASEs
→ The energy contained in sound pressure wave is lost as the sound pressure propagates thru the atmosphere. As a result the amt of compression & rarefaction (amp. of wave) decr. over distance, but the timing of the compression & rarefaction (freq.) does not

Question 2

Audibility curve

Answer 2

a graph that depicts the relat. b/t the loudness of a pure tone, expressed in decibels, sound-pressure lvl (dB SPL), & the freq. of the tone

Question 3

Outer ear

Answer 3

incl. the pinna (AKA auricle) + auditory canal & ends at the tympanic membrane

Pinna: consists of cartilage covered by skin & shaped to capture sound waves + funnel them thru ear canal → tympanic membrane
-important in localizing sounds f/ front v. back & helps w/ vertical sound localization (ex: sound is higher/lower)

Ear Canal: directs the sound pressure wave onto tympanic membrane & amplifies sounds that are b/t 3-12 kHz.

Question 4

Tympanic membrane

Answer 4

(AKA eardrum)

thin membrane that separates the external ear f/ the middle ear

Function: transmit sound f/ air to the ossicles inside middle ear

Question 5

Middle ear

Answer 5

f/ tympanic membrane → oval window: incl. the ossicles & frames out thru the eustachian use to the back of the throat

Question 6

Ossicles

Answer 6

AKA auditory ossicles

3 smallest bones in body. Contained w/in the middle ear space & serve to transmit & amplify sounds f/ air → fluid-filled cochlea. Absence of auditory ossicles would constitute a moderate-severe hearing loss

Bones: Malleus, Incus, Stapes

Question 7

Malleus

Answer 7

the malleus/ hammer is a hammer-shaped small bone/ossicle of the middle ear
- connects w/ the incus & is attached to the inner surface of the eardrum

Question 8

Incus

Answer 8

the incus/anvil is an anvil-shaped small bone/ossicle in middle ear
- Connects the malleus to the stapes

Question 9

Stapes

Answer 9

Stapes/stirrup is stirrup-shaped small bone/ossicle in the middle ear which is attached to the incus & oval window
- the bottom of the stapes on the oval window is called the FOOTPLATE

Question 10

Oval window

Answer 10

A membrane-covered opening which leads f/ the middle ear to the vestibule of the inner ear

Question 11

Conductive hearing loss

Answer 11

mechanical hearing loss, resulting f/ blockage in the ear canal, ruptured eardrum, restric. of mvmt of the ossicles, which prevents sound vibrations being transferred to the cochlea
- seen in otosclerosis

Question 12

Otosclerosis

Answer 12

a form of conductive hearing loss

a condition in which there is abnormal growth of bone in middle ear which can result in hearing loss

-seen in 0.5%-10% of pop., usually starts in middle age
-exact cause is unclear
→ genetic factors play a role, viruses like measles may be involved
-treated w/ hearing aids &/or surgery to remove stapes

Question 13

Inner ear

Answer 13

f/ oval window to auditory nerve

-incl. oval window, round window, cochlea, auditory nerve fibers, & the semicircular canals of the vestibular system

Question 14

Cochlea

Answer 14

the coiled & channeled Amin structure of the inner ear

incl. 3 fluid-filled canals that run along its entire convoluted length
- the fluid filled canals are separated by membranes, one of which is the basilar membrane - which 1000s of hair cells (auditory receptors) are arranged & stimulated by vibration of the stapes

Question 15

Basilar membrane

Answer 15

w/in the cochlea

a stiff structural element that separates 2-liquid filled tubes (the Scala) that run along the coil of the cochlea, - forming a base for hair cells to transduce the sound waves in the cochlear fluid to electrochemical signals in the brain

Question 16

Tonotopic organization

Answer 16

map of tones:

Each section of basilar membrane responds to preferential freq. & the sections are org. f/ high to low.
- Tonotopic org. is also seen in cortex as tonotopic gradients (org. cortical repr. of tones)

Question 17

Inner hair cells

Answer 17

the sensory receptors of the auditory system
- located on basilar membrane in the cochlea
-convert sound waves to nerve signals by having their hair-like stereocilia being physically moved by sound waves in the cochlear fluid

Hair cells are columnar ells, each w. a bundles of 100-200 specially stereo cilia at the top. these cilia are mechanosensors for hearing. Lightly resting atop of longest cilia is the TECTORIAL MEMBRANE, which moves back/forth w/ each cycle of sound, tilting cilia & allowing electric current into hair cells

→ Hair cells show graded response, instead of spikes typical of other neutrons

Loud noise can damage/destroy hair cells, (do not regrow). Continued exposure to loud noise causes progressive damage, eventually resulting in hearing loss & sometimes ringing in ears (tinnitus)

Question 18

Stereocilia & Kinocilium

Answer 18

Stereocilia: projections @ top of the hair cells that are attached to one another by structures which link the tips of 1 cilium to another
- stretching & compressing the tip links may open an ion channel & produce the receptor potential in the hair cell

Kinocilium: one larger, more stable cilium to which stereo cilium attach at the tips

Question 19

Outer hair cells

Answer 19

hair-like cells on basilar membrane
-involved in amplifying sounds & improving frequency selectivity:
only found in mammels

Although there are nearly 3x more outer hair cells than inner hair cells, outer hair cells dont directly transduce sound pressure waves to neural signals

Question 20

Organ of Corti

Answer 20

the organ in inner ear of mammals that contain the hair cells ( auditory sensory cells)

Transduction occurs thru vibrations of structures in the inner ear causing displacement of cochlear fluid & mvmt of hair cells @ the organ of Corti → to produce electrochemical signals that activate auditory never fibers synapsing on the inner hair cells.

Question 21

Sensorineural hearing loss

Answer 21

hearing loss caused by damage to sensory cells and/or nerve fibers of the vestibulocochlear nerve (auditory nerve/ cranial nerve VIII), inner ear, or central processing centers of the brain
- seen in many forms of congenital & acquired deafness

Question 22

Cochlear implant

Answer 22

a surgically implanted electronic device that provides a sense of sound to a person who is profoundly deaf or severe hard of hearing.

Most commonly, used when hair cells of patient are damaged/developed w/ a genetic abnormality affecting action potentials

In order for implant to work, auditory nerve fibers (along the basilar membrane) must still be intact, as the electrodes of implant serve to activate these auditory nerve fivers

Question 23

Cochlear nucleus

Answer 23

a grp of cell bodies in lower section (medulla) of brainstem
- receive the inputs f/ all auditory nerve fibers coming f/ cochlea

Question 24

Superior olive

Answer 24

a small group of cell bodies (nucleus) in middle sections (pons) of the brainstem involved in localization of sound by determ. diff. in the timing (MEDIAL superior olive) & intensity/lvl (LATERAL superior olive) of neural responses f/ each ear for a particular sound

Question 25

Medial superior olive

Answer 25

interaural TIME diff- the time diff. of arrival of sounds b/t ears

Question 26

Lateral superior olive

Answer 26

Intramural LEVEL diff.- the diff. of the intensity lvl of sounds b/t ears

Question 27

Inferior colliculus (IC)

Answer 27

Located below visual processing centers known as superior colliculus

Contains neurons that are tonotopically org. & likely integrates info regarding sound localization

IC projects to thalamus (MGN) & cortex

Question 28

Medial geniculate nucleus (MGN)

Answer 28

section of THALAMUS that auditory pathway connects thru prior to reaching primary auditory cortex

Question 29

Lateral sulcus

Answer 29

AKA Sylvian fissure / lateral fissure
- fissure = large sulcus
- divides the frontal & temporal lobes of the brain
-primary auditory cortex (A1) is located w/in the lateral sulcus`

Question 30

Superior temporal gyrus

Answer 30

the most superior gyrus in the temporal lobe
- situated below lateral sulcus, on which is much of auditory cortex

Question 31

Superior temporal sulcus

Answer 31

most superior sulcus in temporal lobe
-situated below superior temporal gyrus

Question 32

Primary auditory cortex (A1)

Answer 32

Main area of cortex which 1st processes auditory info in the brain, situated on the interior surface of the lateral sulcus: contains core, belt, and parable subdivisions.
- each subdivision contains multiple AUDITORY FIELD MAPS
→ tonotopy= cortical map of sound frequency (single tones)
→ periodotopy: cortical map of sound time duration (periodicity)

Question 33

Cortical deafness

Answer 33

rare form of sensorineural hearing loss
- caused by BILATERAL cortical lesions in P1 located in temporal lobes of brain
(although its likely damage to primary &/or neighboring regions of P1)

Auditory disorder where patient is unable to hear sounds but has no apparent damage to anatomy of ear
(can be thought of combo of auditory verbal agnosia +auditory agnosia)
- patients can’t hear any sounds [not aware of sounds incl. non-speech, voices & speech sound]
- can appear & feel completely deaf, they can still exhibit some reflex response such as turning head toward loud sound

Question 34

Auditory agnosia

Answer 34

rare form of agnosia

Manifests itself primarily in the inability to recognize or differentiate b/t sounds.
- not a defect of ear or “hearing “ but rather neurological inability of the brain to pocess sound meaning
- Caused by bilateral damage to anterior superior temporal gyrus (part of the auditory pathway resp. for sound recog., the auditory “what pathway”)

Persons w/ auditory agnosia can physically hear sounds & describe them using unrelated terms but unable to recog. them
- Dont tend to report ‘feeling deaf’

Question 35

Pure word deafness (auditory verbal agnosia)

Answer 35

selective inability to comprehend the spoken word, in absence of aphasia or defective basic hearing

Perception of environ. sounds & other complex, non-speech sounds is generally normal

Patients cannot recognize spoken words, making the speech sound unintelligible.

Usually caused by bilateral damage to temporal lobes (often incl. white matter connecting temporal & frontal lobes)
- patients can still read & write)

Question 36

Non-verbal auditory agnosia

Answer 36

selective impairment in nonverbal(ex: environs. sounds) auditory comprehension
- in absence of verbal comprehension deficits, other aphasias, or defective basic hearing

-may arise f/ lesions in/near Wernicke’s area

Question 37

Amusia

Answer 37

selective inability to recog. musical ones or to reproduce them (agnosia for music)

Involves loss of ability to recog. musical notes, rhythms & intervals & inability to experience music as musical

Patients often describe music as being indistinguishable f/sound of pots baking together

Can be congenital or be acquire later in life f/ brain damage

Question 38

Word meaning deafness

Answer 38

inability to understand spoken words despite normal hearing and speech abilities

• Patients can recognize and repeat spoken words but cannot understand their meanings.