Exam 2 - Audition Flashcards
3 stimulus properties of sound waves
pitch, loudness, timbre
Pitch
determined by frequency (Hertz, Hz), cycles per second
Loudness
Determined by amplitude (intensity). Greater amplitude means louder sound
timbre
determined by complexity and tonal quality. Like knowing the difference between instruments
Outer ear
captures, focuses, and filters sound. Has pinna and auditory canal
Pinna
Flesh, cartilage ear. sticks out from the side of the head. Captures, funnels, & amplifies sound. Helps w/ localizing sound. Amplifies sound into the Tympanic membrane
Auditory canal
channel for sound to travel through
Middle Ear
Hollow region behind the tympanic membrane that transfers vibrations. Converts air vibrations into mechanical movement. Important bc inner ear is filled with fluid & more force is needed to move fluid than air. Link between outer & inner ear. Has tympanic membrane, ossicles, oval window, and round window
tympanic membrane
aka the eardrum. transmits sound energy to middle ear. Damage to this structure impairs hearing, esp. low
frequency sounds
ossicles
“small bones.” convert air vibrations into mechanical movement. Has malleus (hammer) - attached to tympanic membrane, incus (anvil), stapes (stirrup) - bottom presses against membrane behind oval window, info from here to cochlea
oval window
opening in the bone surrounding the cochlea. receives vibrations from ossicles (specifically the stapes)
round window
membrane separating cochlear duct from middle-ear. Allows fluid in cochlea to move back and forth
Inner ear
includes cochlea which has the organ of corti
cochlea
Snail-shaped; filled with fluid; surrounded by bone. It important for auditory transduction (where energy transforms from soundwaves to action potentials), contains organ of corti. The cochlea has 3 sections
-Scala vestibuli (entrance stairway)
-Scala media (middle stairway)
-Scala tympani (tympanic stairway)
Organ of Corti
receptive organ in scala media. where auditory transduction takes place. The vibratory energy on the oval window causes basilar membrane to bend. Different regions respond to different frequencies of vibrations in the fluid. Consists of 2 parallel membranes and hair cells in between. 1. basilar membrane. 2. Tectorial membrane.
auditory transduction
Transforms energy from sound waves into APs (in the cochlea). Analyzes frequency of sound waves. Ex. pitch
Hair cells
located in between basilar membrane and tectorial membrane. Hair cells are anchored to the basilar membrane. Cilia are at the top of the hair cell. Synapse on bipolar neurons whose axons make up the auditory/cochlear nerve
tectorial membrane
“top shelf” against which the cilia move
Auditory transduction
- Sound waves cause vibrations/movement of basilar and tectorial membrane in cochlea.
- Cilia of the hair cells bend/are displaced.
- Receptor Potentials –> increased tension aka cilia movement can depolarize membrane, opening (calcium and potassium) ion channels in the cilia (bc of movement to tallest one). (does not necessarily mean AP is reached).
- Hair cells form synapses with axons of the cochlear (auditory) nerve bc of depolarization and moving over enough. Auditory nerve can trigger AP
- Action Potentials sent to the CNS/brain via the auditory nerve
Hair cells role in transduction
hair cells are the auditory receptors (similar to dendritic spine of a neuron). They have cilia on them
2 types of hair cells
inner - necessary for normal hearing. convert vibrations into electrical signals
outer - influences the effects of sound on the inner hair cells
Both are located on basilar membrane
Cilia role in transduction
they are on top of hair cells and arranged according to height (shortest to tallest). Adjacent cilia are linked to each other by elastic filaments links (Tip links). Points of attachment are called Insertional Plaques (point where receptor potentials form!).
If the cilia move towards the tallest one, stretching them, and depolarization happens, opening ion channels.
If the cilia move towards the shortest one, they relax, and hyperpolarization happens, closing ion channels.
The cilia movement stimulates the cells of the auditory nerve
Role of auditory nerve in transduction
auditory aka cochlear nerve is a bundle of axons of bipolar neurons that sent auditory info to brain. When hair cells release NT, triggers EPSPs, triggering APs to excite the auditory nerve. Auditory nerve (starts at organ of corti) forms synapses with the medulla (connect with brain)
Auditory Pathway Chart
cochlea
auditory nerve
medulla
inferior colliculi (in midbrain)
medial geniculate nucleus (in thalamus)
primary auditory cortex
auditory association cortex
Primary auditory cortex
Most info comes from the contralateral ear (but receives info from both ears. Located in the superior temporal cortex. Responds best to tones of a certain frequency.
tonotopic representation
Different areas of cells respond best to different frequencies of sound. Same for basilar membrane in cochlea. Tones arranged spatially.
Basilar membrane (in cochlea) –> HIGH freq towards BASE. LOW freq towards APEX.
Primary auditory cortex –> HIGH freq most represented MEDIALLY (middle), corresponds to BASE. LOW freq represented most LATERALLY (away from middle), corresponds to APEX
Auditory association cortex
located under primary auditory cortex. Synthesizes info. There are 2 streams, anterior and posterior.
Other names for primary auditory cortex and auditory association cortex
primary auditory cortex = core region.
auditory association cortex = belt and parabelt region (transmits signals to other parts of brain)
anterior stream and posterior stream
in the association auditory cortex
anterior stream - “what” stream. analyzes complex info
posterior stream - “where” stream. sound localization
Perception of pitch ((freq of sound)
cochlea codes frequencies through place coding and rate coding
Place coding
for moderate to high freq. firing of hair cells in diff locations on the basilar membrane code diff frequencies. more concerned with action potentials
Rate coding
low frequencies. hair cells at the apex of basilar membrane fire in synchrony with the freq of the sound wave. more about detecting sound wave, are hairs moving
perception of loudness
Cochlea codes loudness by action potentials.
Moderate to high frequencies –>
Louder sounds produce more intense vibrations of the eardrum and ossicles, which produce intense force on the cilia –> makes them release more NTs –> greater firing rate by the cochlear nerve axons. Determined by the RATE of APs from hair cells
Low frequencies –>
Determined by NUMBER of hair cell axons firing
perception of timbre
decipher between pitches (fundamental frequency) and overtones. Diff between sounds like identifying diff instruments
fundamental frequency
corresponds to perceived pitch of the note
overtone
Frequency of complex tunes that occurs at multiples of the fundamental frequency. Different parts of the basilar membrane respond to each of the overtones. Produces a unique anatomically coded pattern in the cochlear nerve which gets processed by the auditory association cortex
hearing loss
decreased sensitivity to sound. most common sensory disability. 1 in 4 older adults; 15% of US population. Causes: damage/loss of auditory system functioning or genetic factors.
deafness
loss of hearing where speech perception is lost
3 types of hearing loss
conduction deafness, sensorineural deafness, central deafness
Conductive deafness (outer/middle ear deafness)
Outer or Middle ear is prevented from transmitting sound waves to the cochlea. Sometimes temporary, can be improved by surgery or hearing aids.
Causes: Disease, infection, tumor, issues during development.
Otosclerosis
type of cause for hearing loss. Ossicles fuse w/ surrounding bone (small bones fuse together).
Sensorineural deafness
aka Nerve deafness (inner ear deafness).
Impairs hearing certain frequencies. Damage to cochlea, hair cells, or auditory nerve. Loud noise may damage synapses & neurons in the auditory system. Usually permanent, because damage to organ of Corti, especially hair cells, are irreversible. Treatment may involve cochlear implant.
Causes: genetic, infections, disease, exposure to loud noises
Listening to sounds over 85-90 decibels for extended periods of time can cause hearing loss.
Listening to sounds 110 dB and higher for as little as 30 min can be harmful.
Potential treatment involving stem cells to restore hair cell growth.
Cochlear implant
Stimulates the auditory nerve. Provides a limited range of frequencies & loudness. Contain microphone, transmitter, wires, electrodes implanted in the basilar membrane. Useful for those who became deaf in adulthood & very young children.
Central deafness
Hearing loss caused by brain lesions (ex. stroke, tumor). Complex changes in auditory perception after cortical damage. Can be word deafness or cortical deafness
word deafness
People show normal speech & hearing for SIMPLE sounds but cannot recognize spoken words. May be due to abnormally slow auditory inputs
cortical deafness
Difficulty recognizing both verbal and nonverbal auditory stimuli. Bilateral damage to the auditory cortex
Tinnitus
Frequent or constant ringing in the ears. Damage to the cochlea or other structures in the auditory pathway. Many potential causes: loud noises, medication, various health problems (allergies, tumors, infection)
Amusia
Type of auditory agnosia. Tone deafness; inability to produce or comprehend musical sounds. Cannot recognize or differentiate between melodic or rhythmic aspects of music. About 4% of people have congenital amusia. Result from damage to the auditory cortex or prefrontal cortex. Abnormality with the neural networks for music. Poorly understood, people tend to underreport; training makes no difference
