Hearing And Brain Flashcards
Which nerve fibres connect to inner hair cells
Auditory nerve fibres type 1
How many type 1 nerve fibres connect to a single inner hair cell
10+
Which auditory nerve fibres connect to more than 1 outer hair cell
Type 2
Why is it important to have more then one type 1 nerve fibres connected to inner hair cell
Each fibre has a specific frequency they are most sensitive to , this way they cover all frequencies to send to brain
What would happen to auditory nerve fibres at inner hair cells if outer hair cells were damaged
Not as sensitive to frequencies and sound becomes blurred
Name the 2 ways frequency is detected by the brain
Place code
Time code
What does place code mean
The auditory nerve fibres near the base of cochlea are at high frequency hz if there’s maximal displacement of basilar at the base
Nerve fibres at apex stimulated show low frequency as maximal displacement at apex
Where do the nerve fibres synapse in place code to detect frequency
Cochlea nucleus
Base high freq nerves go to anterior nucleus
Apex low frequency go to posterior
What is place code called when frequency is detected by placement at the cochlea nucleus
Tonotopic organisation
How does time code work to detect frequency
Ap firing to the cochlea nucleus by nerve fibres synchronised with the peak of the wave
Space between AP firing is t
Frequency is 1/t
Which frequency does time code not work
High frequency, the t is too small for ap firing consistency
What is time code actually called
Phase locking
Why is having 10+ fibres attached to inner hair cell allowing time code/phase locking of frequency
Because they can fire ap at a faster rate to keep up with high frequency peak
Where does info cross over after going to the cochlea nucleus
Superior olive (right ear goes to left auditory cortex)
Which neurone does info travel from superior olive to midbrain
Lateral Lemniscus
Where is the next synapse after midbrain lateral lemniscus
Thalamus
Where does info travel to from thalamus
Left or right auditory cortex
Where is the auditory cortex
Superior temporal lobe
Where does sound localisation for horizontal plane occur
Interaural (in between ears)
Why are timing and intensity of sounds computed
Because it can’t be detected via the basilar membrane displacement where sound comes from
What are the 2 interaural sound cues
For short or long sounds : difference in sound time onset between ears
For long low frequency sounds: difference in phase
What is detected interaural phases of sound mean
Depending on location of sound, one ear will have peak phase and the other ear will have the trough phase at low frequency waves
When does phase detection interaurally for sound not work
If it is at a high frequency where not enough diff between peak and trough
Both ears would be in the same phase and brain can’t distinguish location of sound
How is high frequency sound detected via INTENSITY/LOUDNESS interaural if not via phase differences
Through head casting a shadow of sound
If sound was to the left there would be a shadow caused by brain so right ear would have lower sound intensity
Why would low frequency sound not have a sound shadow and therefore intensity not detected interaurally
Long wavelengths which are larger than diameter of brain
Where does info get integrated for both ears to localise sound
Superior Olivary complex
How is localisation of sound detected vertically
Through the pinna
Some sounds go directly into ear canal, some refract from the pinna causing inference in waves
What is used for severe hearing loss and how does it work
Cochlea implant
Electrode is stimulated electrically to stimulate cochlea nerve fibres
Stimulation is arranged in frequency as always (time and place code)
