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Unit 4 Lecture 1
Terms in this set (51)
Sound pressure wave
sound is a mechanical wave that results from back and forth vibration of the particles of the medium through which the sound wave is moving.
sound pressure waves are associated with areas of compression (increased pressure) and rarefaction (decreased pressure)
What is the relationship between frequency and pitch?
frequency is physical. pitch is perceptual. both are directly proportional. (high pitch corresponds to high frequency, low pitch corresponds to low frequency)
-the sensation of frequency is often referred to as the pitch of a sound
How are frequency and amplitude related?
Frequency will remain the same as sound travels through distance, amplitude will decrease as sound travels through distance.
What is the relationship between amplitude and loudness?
amplitude is physical. loudness is perceptual. both are directly proportional
What is a decibel?
unit to measure the intensity of a sound.
What is the audibility curve?
From the graph, it shows at what point we can begin hearing stimuli relative to frequency and decibels.
-depicts the relationship between the loudness of a pure tone, expressed in decibels, sound-pressure level (dB, SPL) and the frequency of the tone, expressed in Hz
What is the frequency range that humans are most sensitive (i.e. can best detect sound)?
What is a complex tone?
the sum of pure tones.
The anatomy of the Ear
ear is the organ of hearing and balance
outer, middle, and inner ear function together to convert sound waves into nerve impulses that travel to the brain, where they are perceived as sound
A) What is the outer ear?
B) What is it important for?
A) includes pinna (aka auricle) and auditory canal and ends at the tympanic membrane (aka eardrum)
B) the pinna is important in localizing sound from front vs. back and helps with vertical sound localization (i.e whether sound is higher or lower).
A) What is the tympanic membrane?
B) What is its function?
A) aka eardrum thin membrane that separates the external ear from the middle ear.
B) transmit sound from the air to the ossicles inside the middle ear.
A) What is the middle ear?
B) What are the ossicles?
C) What happens in the absence of the ossicles?
A) connects the tympanic membrane to the oval window. middle ear job is to really amplify the sound wave.
B) (malleus, incus, stapes) three smallest bones in the human body. Serve to transmit sounds from the air to the fluid-filled cochlea.
B) moderate-severe hearing loss.
What are the bones of the ossicles?
A) malleus (aka hammer): connects eardrum to incus
B) incus (aka anvil): connects malleus to the stapes
C) stapes (aka stirrup): attaches incus to oval window
How is the sound carried and transferred from environment to ear?
Stimulus travels through outer ear to the tympanic membrane to move air. Then it moves through the middle ear to the oval window to move water. Where it finally reaches the inner ear for fluid compression and expansion.
-the oval window is a membrane-covered opening which leads from the middle ear to vestibule of the inner ear
A) What is conductive hearing loss?
B) What is ostosclerosis?
C) What can cause it?
D) What are some treatments?
A) mechanical hearing loss (from blockage in canal, ruptured eardrum or restriction of movement of the tiny bones in middle ear)
B) hearing loss from abnormal growth of bone of the middle ear (conductive hearing loss)-loss of low frequencies at first, higher frequencies affected later
C) exact cause is unclear- genetic factors play a role, viruses like measles may be involved as well
D) hearing aids or removing of stapes bone.
What is the inner ear?
from oval window to auditory nerve; includes: oval window, round window, cochlea, auditory nerve fibers, and the semicircular canals of the vestibular systems
What is the cochlea?
the coiled and channeled main structure of the inner ear.
-consists of fluid filled canals that run along its entire length; the fluid filled canals are separated by membranes, one of which is the basilar membrane, on which thousand of hair cells (auditory receptors) are arranged and stimulated by the vibration of the stapes
How are complex tones processed in the cochlea?
The complex tones are broken down into simple frequencies in the cochlea.
What is the basilar membrane?
(it's within the cochlea) stiff structural element that separates two liquid-filled tubes that run along the coil of the cochlea, forming a base for the hair cells that sit in the basilar membrane to transduce the sound waves in the cochlea to fluid electrochemical signals in the brain.
A) What is the Organ of Corti?
B) What is transduction?
A) (in the basilar membrane) contains the hair cells (auditory sensory cells).
B) vibrating structures causes displacement of the cochlear fluid and movement of hair cells. Moving the hair cells produce electrochemical signals that activate the auditory nerve fibers synapsing on the inner hair cells.
map of tones
-each section of basilar membrane responds to preferential frequency and are organized high to low
What is the tectorial membrane?
This is the membrane that interacts with the hairs in the basilar membrane. It moves the hairs back and forth
What happens if you lost the outer hair cells?
The frequency you could hair (hear) would be reduced
A) stereocilia are projections at the top of the hair cell that are attached to one another by structures which link the tips of one cilium to another. Stretching and compressing the tip links may open an ion channel and produce the receptor potential in the hair cell.
B) The kinocilium is one larger, more stable cilium to which the stereocilium attach at the tips.
A) What is the inner hair cell?
B) What is the outer hair cell?
A) sensory receptors of auditory system located on basilar membrane in cochlea that convert sound waves to nerve signals by having the hair like stereocilia being physically moved by the sound waves in the cochlear fluid
B) hair like cells on basilar membrane that are involved in amplifying sounds and improving frequency selectivity; only found in mammals; these don't directly send neural signals to the auditory nerve fibers but they do appear to modulate the signal (aka acoustical pre-amplification, extend hearing range)
What is sensorineural hearing loss?
-hearing loss caused by damage to the sensory cells and/or nerve fibers of the vestibulocochlear nerve, the inner ear, or central processing centers of the brain.
-may be genetic or congenital or acquired due to aging-ranges from mild to total deafness
What are the treatments for sensorineural hearing loss?
A) hearing aids: amplifies sound to any remaining hair cells
B) cochlear implants: creates neural signal; connects directly to the auditory neurons and can return sound frequencies for which there are no more functional hair cells on the basilar membrane
A) When is the best time to give a cochlear implant?
A) it's best to give it very early on.
B) (as with vision) there is a critical period that helps with brain development that has to happen for normal processing. (think of Patient MM who had to consciously use cognitive tricks to process what he would see)
Auditory pathways to cortex
1) left ear
2) auditory nerve
3) cochlear nucleus
4) superior olive nucleus
5) inferior colliculus
6) medial geniculate nucleus
7) auditory cortex
What is the cochlear nucleus?
group of cell bodies in the lower section (medulla) of the brainstem that receives inputs from all the auditory nerve fibers coming from the cochlea
-tonotopic (frequency based organization is preserved)
-may play a role in localization (up/down; elevation)
What is the superior olive?
-binaural inputs (from both ears)
-left/right sound localization (timing and intensity)
Medial superior olive
interaural time difference-time difference of arrival of sounds between the ears
Lateral superior olive
interaural level difference-the difference of the intensity level of sounds between the ears
A) What is the inferior colliculus?
B) What information does it likely integrate?
C) Where does it project its information?
A) located just below the visual processing centers
B) information regarding sound localization
C) to the thalamus (MGN) and cortex
A) What is the medial geniculate nucleus?
B) What information does it relay?
C) What is it responsible for detecting?
A) section of the thalamus that the auditory pathway connects through prior to reaching primary auditory cortex (A1) (similar to how visual input connects through the lateral geniculate nucleus (LGN) of the thalamus before reaching primary visual cortex)
B) frequency, intensity and binaural information to cortex.
C) relative intensity and duration of a sound.
AKA Sylvian fissure or lateral fissure; divides the frontal and temporal lobes of the brain. this is where the primary auditory cortex (A1) is located
superior temporal gyrus
-superior gyrus in the temporal lobe
-situated just below lateral sulcus
- much of the auditory cortex is here
superior temporal sulcus
The most superior sulcus in the temporal lobe, situated just below the superior temporal gyrus
Primary auditory cortex (A1)
the main area of the cortex which first processes auditory information in the brain, situated on the inferior surface of the lateral sulcus; contains core belt and parabelt subdivisions. Each subdivision contains multiple auditory field maps (tonotopy and periodotopy)
How are the auditory field maps formed?
multiple tonotopic gradients and multiple periodotopic gradients combine.
What are the sections of the auditory field maps?
What does the core process?
(includes A1) pure tones, thalamic input, and tonotopic (sharp freq.)
-on Heschl's gyrus with many inter-hemispheric connections
What type of processing does the belt do?
processing coarser tonotopy
What type of processing does the parabelt do?
most coarse tonotopy. projects to widely parietal, temporal and frontal regions.
A) What is cortical deafness?
B) What causes it?
C) To what extent are they deaf?
A) Sensorineural hearing loss (can be thought of as combo of auditory verbal agnosia + auditory agnosia)
B) bilateral damage to primary auditory cortex such as: stroke, trauma or birth defect
C) similar to blindsight, they are completely deaf but retain some auditory reflexes
A) What is auditory agnosia?
B) What can cause it?
A) rare form of agnosia; inability to recognize or differentiate between sounds BUT they can still hear the sounds.
B) likely from damage to anterior temporal lobes ('what' pathway/perception for recognition). typically has to be bilateral damage but can be unilateral.
What is pure word deafness?
aka auditory verbal agnosia. the selective inability to comprehend the spoken word, in the absence of aphasia or defective basic hearing. perception of environmental sounds and other non-speed sounds generally normal.
What causes pure word deafness?
usually from bilateral damage to temporal lobes
A) What is non-verbal auditory agnosia?
B) What can cause it?
A) selective impairment in nonverbal auditory comprehension. in the absence of verbal comprehension deficits, other aphasias, or defective basic hearing
B) may arise from lesions in/near Wernicke's area
A) What is amusia?
B) What can cause it?
A) inability to recognize musical tones or to reproduce them (I.e. agnosia for music); often they report the music as clutter and pots + pans.
B) can be congenital or come from brain damage later in life.
What is Word-meaning deafness?
comprehension deficit specific to the auditory modality. Written comprehension is unimpaired. Unlike pure word deafness, the ability to repeat is intact.
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