week 9 - audition: hearing and the brain Flashcards
In an overview, what is the order of the auditory cortex?
- vestibulocochlear nerve
- cochlear nerve
- inferior colliculus
- medial geniculate nucleus
- A1
primary auditory cortex (A1)
- on an area called the superior temporal cortex
- receives input fromt the medial geniculate complex; thus, it contains a precise tonotopic map
What did researchers find in monkeys’ primary cortices?
- figured out what neurons respond best to by measuring frequencies
- developed the tonotopic map
tonotopic map
low frequencies towards anterior and high frequencies towards posterior
What do pitch neurons respond to?
- preferred frequency/tone
- complex sounds
- harmonics
- unusual sounds
- changes in sounds
complex sounds
dominant tone of a sound is associated with the neuron which activates firing
harmonics
relation to dominant tone
What is the A1 responsible for?
perceiving pitch and simple sounds
What is the core area responsible for?
locating sound
What is the belt area responsible for?
locating sound
What are the surrounding areas of the A1?
- core area
- belt area
- parabelt area
In what ways are sounds perceived and grouped?
- location
- proximity in time
- good continuation
- similarity
Jeffress Model: narrowly tuned ITD neurons
receive signals from both ears
neural coincidence detectors
activated when they receive signal from both ears at the same time
partial neural coincidence detectors
detect difference in hearing based on how fast/slow the signal is received from each ear
barn owls and ITD
- evidence in support of Jeffress Model
- good at locating sound because their ITD neuron activation is very narrow which leaves less room for time difference
- specificity coding
gerbils and ITD
- more bass heavy/broad in comparison to owls
- indicates that we are likely to be using distributed coding to measure time difference
distributed coding
all neurons in an area respond to a sound
How do hemispheric differences play a role in audition?
- we have neurons that respond to the contralateral side of the body
- right hemisphere responds to sound from the left and vice versa
What does lesioining in the A1 cause?
decrease in ability to localize sound but not eliminated
What happens when you cool the A1?
poor localization
How did the A1 compare/differ from belt neurons
belt neurons provided more a more precise location
What are the auditory pathways?
- ventral stream
- dorsal stream
ventral stream
- determines what the sound is
- starts from the front portion of A1 and ends toward prefrontal cortex
dorsal stream
- determines where the sound is located
- starts from the back portion of A1 and goes toward parietal and prefrontal cortices
What does damage to the temporal lobe cause?
inability to recognize what the sound it
What does damage to the frontal lobe cause?
inability to localize the sound
conductive deafness
- middle ear deafness
- damage to any part of the middle ear can cause inability to conduct sound information to inner ear
tympanic membrane
moves at the same vibration of sound and must be able to move fluid in the inner ear
What is the treatment for conductive deafness?
hearing aids that raise volume in order to increase vibrations of middle ear
nerve deafness
- inner ear deafness
- damage to cochlea/cochlear nerve
What happens when the cochlea is damaged?
action potentials on the cochlear nerve cannot travel up to the brain
How can nerve deafness be treated if the cochlea is damaged but not the cochlear nerve?
cochlear implants can bypass the cochlea by having an external portion pick up external frequencies and an internal portion send electrical stimuli straight to the cochlear nerve
What does damage to the A1 cause in regards to hearing loss?
results in the inability to tell differences in frequencies (amusia)
