Lecture 19- Auditory System Flashcards
How does sound waves travel from the inner ear to the brain?
Inner Ear → Brain: The vibrations cause waves in the fluid
within the cochlea. These waves move the hair cells, which
convert the mechanical signal into an electrical signal. The
electrical signal from hair cells is transmitted to spiral
ganglion cells, whose axons exit the cochlea, join the
vestibulocochlear nerve, and the synapse onto cells in the
brain stem.
Summaries the auditory system and the role that each part of the ear has by labelling and writing about the diagram…
Answers on slides
What is the vestibulocochlear nerve where does it take information to and from?
The vestibulocochlear nerve carries the signal from the signal from the cochlea into the brain stem, where the spiral ganglion cells synapse on neurons in the cochlear nuclei cochlear nuclei,
which are located at the level of the lower pons-upper medulla.
Summarize the auditory pathways…
-From the cochlear nuclei, auditory information ascends bilaterally to the inferior colliculi, which are part of the midbrain.
-Neurons in the inferior colliculus synapse on neurons in the medial
geniculate nucleus of the thalamus.
-Neurons in the medial geniculate nucleus synapse on neurons in primary auditory cortex.
What is the key takeaway from the auditory pathways?
From each ear information ascends bilaterally
Which structure the MGN or the LGN is associated with auditory system?
MGN= medial geniculate nucleus is important. This is part of the thalamus and receives input from the inferior colliculus and sends information to primary auditory cortex.
What is primary auditory cortex?
-The first region of the cortex is process sound
-Located in the superior temporal superior temporal lobe and buried
within the lateral sulcus (pull apart the lateral sulcus/ digging in exposes more)
-Also called Heschl’s gyri or A1
In primary auditory cortex what map is created?
-In primary auditory cortex, the frequency tuning properties
of the neurons define a tonotopic map.
-The tonotopic organization of the cells within the cochlea
is maintained through to primary auditory cortex is maintained through to primary auditory cortex.
What is interaural time? What does it allow for?
-The difference in the arrival time of a sound at each ear is called the interaural time.
-Sounds can be localized based on slight asymmetries in the arrival time at the two ears (e g sound sources on your left arrival time at the two ears (e.g., sound sources on your left arrive at your left ear first).
In what cases might it be hard to localize sound?
-If it directly infront of behind you (along vertical plane), then will be equal distance from both ears and their will be no disparity.
-To determine the elevation of sound sources, humans depend
on the bumps and ridges of the outer ear, called pinna, as these produce reflections of the entering sound. Our ability to determine the determine the elevation of a sound source is seriously impaired if the pinnae are covered.
What are cochlear implants?
-In the case of severely reduced cochlear function (resulting in severe hearing loss), a cochlear implant device may be surgically installed device may be surgically installed.
-Unlike hearing aids, the cochlear implant does not amplify sound, but works by directly stimulating any works by directly stimulating any functioning spiral ganglion cells inside the cochlea with electrical impulses.
-Even modern cochlear implants have only about 24 electrodes to replace the 16,000 hair cells that are used for normal hearing. Therefore, doesn’t fully solve problem but does result in improvement.
Do you think the outcome is better if you damage a sensory system for which information is transmitted unilaterally or bilaterally? What is the audition system in regards to this?
-Not all auditory information crosses the midline.
-Consequent, in the context of monaural auditory input (i.e., input via one ear), damage to contralateral primary auditory cortex
does not result in cortical deafness. Indeed the deficit that results
from unilateral damage to primary auditory cortex is minor.
