Auditory Processing Review Questions

1.1 Sound and the Spectrogram

  1. What physical properties of pure tones (sin waves) correlate with pitch and loudness?
  2. What is the spectrum of a sound and what does Fourier analysis do?
  3. What is the spectrogram and what is its relationship to how the ear works?

1.2 Outer and Middle Ear

  1. What is the function of the pinna?
  2. Draw a labelled diagram of the middle ear.
  3. How does the middle ear increase the sensitivity of the inner ear to sound? Why is this necessary?
  4. Does the middle ear amplify all frequencies the same at all times? If not, why not?

1.3 Inner Ear

  1. Draw a labelled cross-section of the cochlea.
  2. How does endolymph differ from perilymph and why is this important for the function of hair cells?
  3. How does frequency selectivity vary along the basilar membrane and how is this achieved?
  4. Draw a labelled diagram of a hair cell and show its relative position to the basilar membrane and tectorial membrane.
  5. What happens to the membrane potential of a hair cell when the basilar membrane moves? Outline the key steps involved (e.g. channels, ions etc.).
  6. Outer hair cells amplify movements of the basilar membrane. How is this achieved?
  7. Outer hair cells make it easier to discriminate between different frequencies (i.e. they increase frequency selectivity of the basilar membrane). How do they do this?

2.1 Auditory Nerve Fibres

  1. Inner and outer hair cells are innervated by different auditory nerve fibres in different ways. Explain these differences.
  2. What determines the frequencies that an auditory nerve fibre responds to?
  3. Auditory nerve fibres vary in their spontaneous rate, threshold, saturation point and coding range. Explain each of these terms using a diagram.
  4. What is the volley theory of phase-locking? How is phase-locking achieved by auditory nerve fibres, and why does phase-locking decline at higher frequencies? How does phase-locking help an auditory nerve fibre keep track of frequency?
  5. What is a frequency tuning curve? Draw an example and indicate the threshold and characteristic frequency.

2.2 Cochlear Nucleus and Superior Olive

  1. What is tonotopic organization?
  2. The cochlear nucleus is not completely homogeneous in its function. Explain.
  3. Why are two ears important for sound localization? Are sound localization cues the same at low and high frequencies?
  4. How do neurons in the lateral and medial superior olive differ in their sensitivity to sound localization cues? Explain how neurons in the superior olive become sensitive to Interaural Level Differences using a simple diagram.

2.3 Inferior Colliculus and Above

  1. Draw a simple diagram showing the major structures and pathways that transmit sound from the cochlea to the cortex.
  2. The inferior colliculus has a map of frequency but the superior colliculus has a map of space. Explain.
  3. Different areas of the cortex are specialized for different functions. Give examples.
  4. Auditory processing requires different cortical areas to work together, but descending connections from the cortex are also important. Explain.
  5. The superior olive is able to modulate activity in the cochlea through descending connections. Use simple diagrams to show these connections and explain how they can adjust the sensitivity of auditory nerve fibres. 

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