3Ear & Hearing

Question 1

What does the ear canal do?

Answer 1

Carries sound waves to the ear drum

Question 2

What bone surrounds the middle ear?

Answer 2

Mastoid bone

Question 3

What role does the ear drum play?

Answer 3

Sound wave vibrations set the middle ear bones in motion

Question 4

Name the 3 ossicles, which transmit sound waves to the inner ear;
What does their lever action do?

Answer 4

Malleus (hammer), Incus (anvil) & Stapes (stirrup);

Amplify the vibrations

Question 5

What role do the semicircular canals play?

Answer 5

Helps maintain balance

Question 6

What does the eustachian tube help control?

Answer 6

Air pressure in the middle ear

Question 7

What does the facial nerve control?;

What about the vestibular nerve?

Answer 7

Muscles in the face;

Carries balance signals to the brain

Question 8

What mechanism picks up sound waves & produces nerve signals?;
Where does it send these nerve signals?

Answer 8

Cochlea;

To the auditory nerve which carries them to the brain

Question 9

What are the hair cells (stereo cilia) in the cochlea sensitive to?

Answer 9

Changes of pressure in the fluid

Question 10

How are vibrations converted into neural impulses?;

When deflection occurs, what happens?

Answer 10

Hair cells lie between the tectorial & basilar membrane (joined at one end) & the shear force of both membranes activate the hair cells causing a neural impulse;
The cells depolarise & cause an action potential, releasing glutamate & forcing an electrical signal to the brain

Question 11

Describe Tonotopic organisation

Answer 11

Spatial layout of frequencies - organisation of the cochlea is preserved all the way up the auditory pathway (resulting from projections from specific locations along basilar membrane); action potentials help to encode frequencies, intensity & duration

Question 12

What is the base of the basilar membrane tuned for?; What is the apex tuned for?

Answer 12

High frequencies (point of maximum deflection); 
Low frequencies (travels further)

Question 13

A sound signal travels up the brain stem via what?

Answer 13

The 8th cranial nerve

Question 14

Where is the auditory receiving area?;

In order, what other auditory pathways are involved?

Answer 14

Temporal lobe (in Heschl's gyrus - part of superior temporal gyrus); 
Cochlea, Auditory Nerve, Cochlea Nuclei, Superior Olivary Nuclei, Lateral Lemniscus, Inferior Colliculus (tectum), Medial Geniculate Nucleus (thalamus), Primary Auditory Cortex

Question 15

Which part of the brain stem receives input bilaterally from the Cochlea Nuclei, enabling them to play a role in sound localisation?;
Axons then ascend via which side of the brain?

Answer 15

Superior Olivary Nuclei;

Some ipsilaterally & some contralaterally

Question 16

Axons activated by certain frequencies in the basilar membrane have the same tonotopic mapping as which regions?

Answer 16

Inferior Colliculi of the tectum & Primary Auditory Cortex in Heschl’s gyrus

Question 17

How are temporal & spectral resolution lateralised in the auditory cortex?

Answer 17

Higher temporal resolution in left & higher spectral resolution in right

Question 18

Where is most of the output of primary auditory cortex conducted to?

Answer 18

Secondary Auditory Cortex (belt area)

Question 19

Describe Auditory Scene Analysis

Answer 19

Processing of information from a complex sonic environment via the auditory system into information about individual sounds making up the mix

Question 20

In the process of auditory scene analysis, what components are analysed?;
What underpins signal recognition?

Answer 20

Frequency & which components belong together (i.e. are they emanating from the same person or place; amplitude, duration, location);
Putting together the right frequency components over time (stream segregation &/or integration; auditory system infers physical event from sound waves

Question 21

What are Interaural Time Differences (ITD)?;
What do Interaural Level Differences (ILD) relate to?;
What’s another way to optimise sound localisation?

Answer 21

Measurable & detectable time for sound to travel across the width of the head;
Difference in sound intensity between ear directed towards sound source & away from sound source;
Azimuth (turn of head) or elevation of head

Question 22

What is the Rhombencephalon (where the Superior Olive lies) responsible for?

Answer 22

Segregation into different pathways; temporal & spectral analysis of acoustic cues

Question 23

What can be measured in Electroencephalography (EEG)?;
How is the temporal resolution in these recordings?;
Why is spatial resolution poor?

Answer 23

Timing & amplitude of neural firings/electrical activity in the brain;
Excellent - less than a millisecond;
Many neurons needed to measure signal; sulci, gyri, skin, etc attenuate sound so only a tiny amount of microvolts come through

Question 24

Why are the brain wave graphs on an EEG recording cut up & layered?

Answer 24

To filter out noise components & accentuate only frequencies of interest; can be more specific

Question 25

What do Auditory Evoked Potentials allow us to do?;

Describe an example of how this is carried out?

Answer 25

Attribute response of neurons along auditory pathway for a particular sonic event ;
Play a stimulus such as clicking sound to baby via headphones, then analyse the auditory brainstem response (e.g first peak relates to cochlea, 2nd - auditory nerve, 3rd - cochlea nuclei, etc)

Question 26

We can measure how time is locked to an event (e.g. sound) using what method?;
Provide an example of how this could be carried out in an auditory event?

Answer 26

Event-Related Potentials (ERP);

Play a stimulus (e.g. musical interval); amplify the sound; record many presentations & average the signals

Question 27

When would N1 in an ERP be enhanced?;
What about P2?;
N2?;
P3?

Answer 27

When a change is made (mismatch negativity);
Comparison of sensory inputs with stored memory;
Sensory discrimination matched with memory;
Cognitive decision making/categorising

Question 28

What’s the difference between Bottom-up & Top-down processing?

Answer 28

Bottom-up - stems from auditory system; should all have a similar response (psychoacoustic & primarily perceptual); Top-down - dependent on familiarity & cognitive processing (e.g. training, experience, culture, etc)

Question 29

Theoretically, frequency difference, psychoacoustically driven propositions juxtapose what?;
Explain the concept of critical bandwidth

Answer 29

Pythagorean frequency ratios which relate to Western music theory;
The further apart two frequencies are from each other, the more pleasant/consonant the tone; if too close or similar, it’s harder for auditory system to process (resulting in beating/dissonance)

Question 30

How does the theory of frequency ratios differ from the critical bandwidth theory?

Answer 30

Deals with frequency ratios vs. frequency difference; closer interval ratios = pleasant/consonant sound (e.g. unison 1:1, octave 2:1; perfect 5th 3:2 vs. dissonant tritone 41:29)

Question 31

Where is the perception of consonance/dissonance distinguished in the brain?

Answer 31

Primitive brain regions (i.e brain stem) before higher levels of cortex

Question 32

What evidence for sensory consonance did Itoh et al. (2010) find which supports the critical bandwidth theory?;
What did Kung et al. (2014) find?

Answer 32

Intervals up to 3 semitones are the most rough & there was no difference between trained & untrained musicians (bottom-up);
Differences according to musical training (top-down)

Question 33

What is an Electroencephalophone?;

What are the therapeutic implications of this?

Answer 33

The use of brainwaves to generate/change sound via EEG (using biofeedback to create music);
Can give disabled people the ability to create music via brainwaves