Lecture 10

Question 1

Physical properties of sound (3)

Answer 1

Frequency
Amplitude
Complexity

Question 2

Fundamental frequency - complexity

Answer 2

Rate at which the complex waveform patter repeats

Question 3

Outer ear (3)

Answer 3

Pinna/auricle
External ear canal
Eardrum

Question 4

Middle ear (3)

Answer 4

Hammer/malleus
Anvil/incus
Stirrup/stapes

Question 5

Inner ear (5)

Answer 5

Oval window
Round window
Cochlea
Organ of corti
Auditory nerve

Question 6

Outer ear functioning

Answer 6

The pinna catches sound waves and deflects them into the external ear canal.
Waves are amplified and directed to the eardrum causing it to vibrate.

Question 7

Middle ear functioning

Answer 7

Once the ear drum vibrates it causes the ossicles to vibrate. Ossicles amplify and convey vibrations to the oval window.

Question 8

Inner ear functioning

Answer 8

Vibration of the oval window sends waves of fluid through the cochlear fluid, causing the basilar and tectorial membranes to bend.
This causes cilia of outer hair cells, embedded in the tectorial membrane, to bend. This bending generates neural activity in the hair cells.

Question 9

Outer hair cells

Answer 9

Connected to the tectorial membrane
NOT receptors: only influence the stiffness of the tectorial membrane > motor function

Question 10

Inner hair cells

Answer 10

NOT connected to the tectorial membrane, only make loosely contact
Auditory receptors
Do not regenerate.

Question 11

Movement of the cilia

Answer 11

Changes the inner hair cell’s membrane polarisation and its rate of neurotransmitter release

• Movement in one direction results in depolarisation: K+ influx > Ca2+ influx > more neurotransmitter in synaptic cleft (excitation)
• Movement in the other direction results in hyperpolarisation: K+ efflux > less neurotransmitter in synaptic clef (inhibition)

Question 12

Audition - right thalamus

Answer 12

Medial geniculate nucleus to auditory complex
Auditory input

Question 13

Audition - cochlea of left ear

Answer 13

Auditory nerve

Question 14

Audition - hindbrain

Answer 14

Trapezoid body
Cochlear nucleus
Superior olivary nucleus

Question 15

Audition - midbrain

Answer 15

Inferior colliculus (receives auditory input)

Question 16

Tonotopic organisation in the cochlea

Answer 16

Hair cells in the cochlea code frequency as a function of their location on the basilar membrane

• Maintained throughout auditory pathways into A1.
• Sound below 200 Hz are not coded tonotopically but temporally

Question 17

High frequencies in the cochlea

Answer 17

At the base of the cochlea, the basiliar membrane is narrow, thick and stiff

• Here the hair cells respond primarily to high frequencies (up to 20000 Hz)

Question 18

Low frequencies in the cochlea

Answer 18

At the apex of the cochlea, basiliar membrane is wide, thin, and soft

• Here the hair cells respond primarily to low frequencies (from 20 Hz upwards)

Question 19

Temporal coding

Answer 19

Larger amplitude of the sound waves lead to

• More intense vibration of the oval window
• More intense waves in the cochlear fluid
• More intense vibration of the basiliar and tectorial membranes
• More intense cochlear fluid flow past the cilia of the inner hair cells
• More release of neurotransmitter
• Bipolar neurons fire more frequently

Question 20

Interaural time difference (ITD)

Answer 20

Arrival time

• Detection threshold in humans is around 10 us.
• Computed in medial superior olivary complex.

Question 21

Interaural intensity difference (IID)

Answer 21

Loudness

• Computed in lateral superior olivary complex and trapezoid body
• Most effective for high requencies

Question 22

Ventral for audition

Answer 22

• Auditory object recognition
• Understanding language
• Left temporal lobe > Wernicke’s area

Question 23

Doral for audition

Answer 23

• Audition for action
• Producing language
• Left frontal lobe, Broca’s area

Question 24

Music

Answer 24

The organisation of music in the brain is lateralised to the right hemisphere instead of the left hemisphere

• Music processing does not occur exclusively in the right hemisphere.