Hearing And Brain

Question 1

Which nerve fibres connect to inner hair cells

Answer 1

Auditory nerve fibres type 1

Question 2

How many type 1 nerve fibres connect to a single inner hair cell

Answer 2

10+

Question 3

Which auditory nerve fibres connect to more than 1 outer hair cell

Answer 3

Type 2

Question 4

Why is it important to have more then one type 1 nerve fibres connected to inner hair cell

Answer 4

Each fibre has a specific frequency they are most sensitive to , this way they cover all frequencies to send to brain

Question 5

What would happen to auditory nerve fibres at inner hair cells if outer hair cells were damaged

Answer 5

Not as sensitive to frequencies and sound becomes blurred

Question 6

Name the 2 ways frequency is detected by the brain

Answer 6

Place code

Time code

Question 7

What does place code mean

Answer 7

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

Question 8

Where do the nerve fibres synapse in place code to detect frequency

Answer 8

Cochlea nucleus

Base high freq nerves go to anterior nucleus

Apex low frequency go to posterior

Question 9

What is place code called when frequency is detected by placement at the cochlea nucleus

Answer 9

Tonotopic organisation

Question 10

How does time code work to detect frequency

Answer 10

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

Question 11

Which frequency does time code not work

Answer 11

High frequency, the t is too small for ap firing consistency

Question 12

What is time code actually called

Answer 12

Phase locking

Question 13

Why is having 10+ fibres attached to inner hair cell allowing time code/phase locking of frequency

Answer 13

Because they can fire ap at a faster rate to keep up with high frequency peak

Question 14

Where does info cross over after going to the cochlea nucleus

Answer 14

Superior olive (right ear goes to left auditory cortex)

Question 15

Which neurone does info travel from superior olive to midbrain

Answer 15

Lateral Lemniscus

Question 16

Where is the next synapse after midbrain lateral lemniscus

Answer 16

Thalamus

Question 17

Where does info travel to from thalamus

Answer 17

Left or right auditory cortex

Question 18

Where is the auditory cortex

Answer 18

Superior temporal lobe

Question 19

Where does sound localisation for horizontal plane occur

Answer 19

Interaural (in between ears)

Question 20

Why are timing and intensity of sounds computed

Answer 20

Because it can’t be detected via the basilar membrane displacement where sound comes from

Question 21

What are the 2 interaural sound cues

Answer 21

For short or long sounds : difference in sound time onset between ears

For long low frequency sounds: difference in phase

Question 22

What is detected interaural phases of sound mean

Answer 22

Depending on location of sound, one ear will have peak phase and the other ear will have the trough phase at low frequency waves

Question 23

When does phase detection interaurally for sound not work

Answer 23

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

Question 24

How is high frequency sound detected via INTENSITY/LOUDNESS interaural if not via phase differences

Answer 24

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

Question 25

Why would low frequency sound not have a sound shadow and therefore intensity not detected interaurally

Answer 25

Long wavelengths which are larger than diameter of brain

Question 26

Where does info get integrated for both ears to localise sound

Answer 26

Superior Olivary complex

Question 27

How is localisation of sound detected vertically

Answer 27

Through the pinna

Some sounds go directly into ear canal, some refract from the pinna causing inference in waves

Question 28

What is used for severe hearing loss and how does it work

Answer 28

Cochlea implant

Electrode is stimulated electrically to stimulate cochlea nerve fibres

Stimulation is arranged in frequency as always (time and place code)