Auditory Processing Pathway Flashcards
3 parts of the ear?
- Outer (visible)
- Middle (filled with air)
- Inner (filled with fluid)
Function of the tympanic membrane?
soundwaves apply force, sets off vibration of malleolus
What does the malleolus do?
connects to tympanic membrane
3 bones in the ear?
malleolus, incus, stapes
2 boundaries within the middle ear?
oval window and tympanic membrane
What occurs at the oval window?
Vibration transfers mechanical wave into water waves in Inner EAR
What is the sensory receptor of the cochlea?
Organ of Corti (rows outer hair cells, 1 row inner hair cells)
What do the hair cells do after bent by the sound waves?
convert mechanical energy to electrical energy
Describe the semi-circular canals
fluid filled
* Three-dimensional perception of position
* Sound waves do not travel in semicircular canals
* Crystal located in three semicircular canals
What do the crystals do when head/body moves?
Movement of head/body causes crystals to move and provided feedback regarding position (CN 8)
What are bipolar cells?
Spiral ganglion (type I) cells located in cochlea
2 sets of fibers in the bipolar cells?
- primary auditory fibers – longer & central fibers
- peripheral process
2 branches of the vestibulocochlear nerve?
- Vestibular branch
- Cochlear branch
What does the inferior colliculus do?
essential to sound localization,
second location binaural processing
Auditory Cortex Location?
Temporal Lobe
most of auditory cortex hidden view in lateral sulcus, on collection gyri known as Heschl’s gyri.
Some visible area auditory cortex extends into superior temporal gyrus
Primary Auditory Cortex/Core region (A1)
superior temporal plane
Heschl’s Gyrus
Regions of the Auditory Association Cortex (A2)
belt and parabelt parietal & temporal borders
Belt region – region adjacent to core region
Parabelt region – neighboring areas around to belt
Which area is imprecise?
Demarcation area
Function of auditory cortex?
to perceive sound
perception of pitch
where originated from (direction of the sound)
source of the sound
discernment of speech sounds
What is a tonotopic map?
Core region organized tonotopically
Arranged by frequency; humans have 6 tonotopic maps (regions)
Neurons tuned to ONLY respond to specific frequencies
Neurons that respond to info from one ear; inhibit same info to the ____ ear
Other neurons activated by info from ____ears
opposite; both
What components are not as well known as the visual cortex?
Mechanism and component auditory cortex
What is the left sylvian fissure important for?
speech production & speech recognition
How is the left sylvian fissure described?
2 lane, 2 way highway
What happens if damage occurs above/below the sylvian fissure?
above: parietal & frontal lobes speech production deficits
below: temporal lobe– caused speech recognition deficits
5 part Sequence from hearing to lang. comp. and memory
- COchlea
- central auditory pathway
- primary and secondary
-Auditory aka core, belt, and parabelt
cortex - Sylvian Fissure parietal-temporal
- Pre-Frontal Cortex
Primary Auditory Pathway
-cochlear nuclei (dorsal & ventral)
cross through trapezoid body
-superior olivary complex (pons) – SOC – info from two ears, now have two fields
-lateral lemniscus tract
cross at nucleus
-inf colliculus (midbrain)
communicate with each other
-medial geniculate (thalamus)
-geniculocortical fibers (internal capsule)
Acoustic reflex?
Involuntary muscle contraction of stapes in middle ear in response to loud sound
Muscle contraction pulls stapes from oval window & stiffens osculation chain
Does the coordination of head and eye movement to maintain equilibrium involve other cranial nerves?
YES!
inferior colliculi to superior colliculi (CN III)
SOC to medial longitudinal (CN IV, VI)
auditory and vestibular branches of CN VIII with cerebellum
What is involved in sound localization?
superior olivary complex – neurons sensitive to time & intensity differences
inferior colliculi – receive binaural input
in cortex, too - maybe
How small is the timing difference for arrival of sound between the ears?
Can detect timing difference as small as 10 microseconds
What are auditory evoked potentials??
Test completed to identify Central hearing disorders/tumors
Measure with electrodes on skull
Interpretation of results:
Amplitude/Latency/Interpeak latency/Interaural Latency
What are dichotic listening tasks used for?
Used to determine hemispheric lateralization of language
What is the right ear advantage?
for perception of words = left hemisphere lateralization of language
Causes of conductive hearing loss?
Ear Infection, fluid, loss Eustachian tube function, benign tumors
Causes of sensorineural hearing loss?
Ototoxic drugs, aging, illness, noise exposure, tumors
What is an acoustic neuroma?
benign tumor grows on CN VIII; can impact hearing & balance, diagnosed MRI
What is labrynthitis?
inflammation of inner ear
What is Meniere’s disease?
inner ear disorder causes vertigo. Onset 1 ear but can progress to both
Otosclerosis?
hearing loss due to inability of oscillating bones to freely vibrate, hereditary
What is tinnitus?
ringing or buzzing in ears, unilateral or bilateral, varies in severity and consistency
What is central hearing loss?
result of tumor or injury to auditory pathway or auditory cortex
What is usher syndrome?
rare genetic disorder impacts hearing & vision, sometimes balance. Abnormal development hair cells.
What is pendred syndrome?
genetic disorder causes early hearing loss children due to lack protein called pendrin needed to keep salt levels balanced
Where is the planum temporale?
Posterior to auditory cortex within Sylvian fissure, forms the heart of Wernicke’s Area
Cortical area in the brain, in the right and the left.
Right ear advantage?
words are sent to both hemispheres
but language processed in (L)
thus word processed initially by right ear,
must then proceed to (L) via Corpus Collosum
Signs of APD?
difficulty understanding speech in degraded situations (non-optimal environment/loud environment)
delayed, inconsistent, or inappropriate responses
misunderstanding
many requests for repetition
problems with auditory attention and localization
poor musical skills
associated reading, spelling, and learning problems
What do we know about APD?
-Aud processing improves with age
-It’s cortical and complicated
-Probably not a sensory problem
-Probably more related to executive function, attention, and cognition
