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Neuroscience - Quizzes 1 - 3 > 2: Audition > Flashcards

2: Audition Flashcards

1
Q

Define sound. Describe the characteristics of sound.

A

Sound: pressure waves generated by vibrating air molecules

Amplitude -> loudness
Frequency -> pitch
—Human range = 20 Hz - 20 kHz
Complexity -> timbre

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2
Q

Explain the mechanical advantages of the outer and middle ear.

A

Outer:

  • Auricle helps collect sound
  • External acoustic meatus boosts sound pressure 30-100 fold at frequencies near 3 kHz, where human speech is concentrated

Middle: boosts sound pressure 200x

  • Vibration energy of larger tympanic membrane focused on smaller oval window
  • Mechanical advantage of the ossicles
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3
Q

Describe the components of the attenuation reflex and how it occurs.

A 
Tensor tympani (CN V) and stapedius (CN VII) muscles stiffen ossicles in response to loud sounds
--Reduce the amount of sound pressure transmitted to cochlea
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4
Q

Describe the structural features of the cochlea.

A

Three compartments:

  1. Scala vestibuli - perilymph (low K)
    - –Oval window, displaced by ossicles -> pressure wave -> scala vestibuli
  2. Scala media - endolymph (HIGH K)
  3. Scala tympani - perilymph (low K)

Organ of Corti - in scala media

  1. Basilar membrane
  2. Outer hair cells - 3 rows
  3. Inner hair cells - 1 row
    - -Both have stereocilia with tip links (couple shaft of one stereocilia to mechanosensitive K channel on tip of another stereocilia)
  4. Tectorial membrane - gelatinous membrane on top of basilar membrane in which the stereocilia are stuck
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5
Q

Describe what is meant by tonotopy.

A

“Systematic representation of sound frequency”

Tones close to each other in terms of frequency are represented in topologically neighboring regions in the brain

Projections stay in an orderly manner to cortex

DETAILS:

  • -Different regions of the basilar membrane in the organ of Corti vibrate at different frequencies due to variations in thickness and width along the length of the membrane (tonotopic encoding)
  • -Tonotopy then projects -> vestibulocochlear nerve/midbrain -> primary auditory cortex, where organization is linear with relation to placement on the organ of Corti
  • —Arranged in accordance to the best frequency response (frequency at which neuron is most sensitive) of each neuron
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6
Q

Explain how auditory transduction occurs in the Organ of Corti.

A

Displacement of stereocilia in response to vibration of basilar membrane -> direction specific changes in membrane potential of hair cells
—Tops of hair cells connected to stable tectorial membrane, bottoms to vibrating basilar membrane

  • Basal = a little bit of K flowing in (because of high K in endolymph)
  • —K channel opens -> K flows IN -> DEpolarization -> opening of voltage gated Ca channels -> NT release
  • —K channels close -> opposite happens (HYPERpolarization)
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7
Q

Explain how hair cells function: two types of hair cells, function of each.

A

Inner hair cells - send afferent sensory information

  • -At base, -> high frequencies
  • -At apex, -> low frequencies

Outer hair cells - efferents from superior olive
–Act as cochlear amplifier

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8
Q

Describe the properties of the basilar membrane that help distinguish between sounds.

A

Narrower, stiffer at base (HIGH frequencies)

Wider, flexible at apex (LOW frequencies)

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9
Q

Explain what electromotility is, where it occurs, and the role it plays in the cochlear amplifier. What motor protein is involved?

A

Outer hair cells are ELECTROMOTILE - change length when stimulated -> modify response to sound by reducing/increasing how much basilar membrane can flop up and down

  • -Shorter when depolarized -> more basilar membrane movement/inner hair cell displacement
  • -Longer when hyperpolarized -> the opposite (protects cochlea from damage from loud sound)

Acts as cochlear amplifier: can change range of basilar membrane movement to amplify some sounds and dampen background noise simultaneously
—-Prestin = molecular motor protein

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10
Q

List the neural mechanisms that are used to localize sounds and where they are processed. (3)

A

SUPERIOR OLIVE!

  1. Time delay by which sound reaches two ears -> medial superior olive neurons
  2. Intensity difference (for HIGH intensity) - lateral superior olive
  3. Phase difference (for LOW intensity) (location not stated)
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11
Q

List 6 cortical structures involved in sound perception and where they are located/what areas they contain.

A
  1. Medial geniculate nucleus (thalamus)
  2. Primary auditory cortex (Heschi’s gyrus)
  3. Secondary (belt) areas (superior temporal gyrus)
  4. Wernicke’s area
  5. Ventral stream (primary auditory cortex/inferior frontal gyrus)
  6. Dorsal stream (superior parietal cortex/superior frontal gyrus)
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12
Q

Explain how elements of sound are involved in speech and language: what are phonemes and lexemes?

A

Language

  1. Phonemes (sounds) - consonants and vowels
  2. Lexemes (words; sound groups)

Human speech = series of time-varying signals and frequency combinations, with different phonetic sequences detected as syllables

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13
Q

Name the general classes of auditory disorders and describe a test that can be used to distinguish between them.

A

Conductive versus sensorineural deafness - use the Rinne test

  • Normal: air conduction is 2x as long as bone conduction
  • Conductive loss: bone conduction sound heard longer than or equal to air conduction
  • Sensorineural hearing loss: air conduction heard longer than bone conduction, but less than 2:1 ratio
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14
Q

What is the McGurk effect?

A

When presented with one sounds, but given a visual image of a face producing another closely related but distinct sound, the disconnect will result in perceiving a third, unrelated sound

Shows strong connection between visual and auditory inputs in comprehending speech

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15
Q

List where the following features of music processing and perception are detected: changes in pitch; timbre; rhythm, pitch, and familiarity; whether one is “on key.”

A
  1. Detecting changes in pitch - temporal regions of right hemisphere
  2. Timbre - right hemisphere
  3. Rhythm, pitch, familiarity - left hemisphere
  4. Broca’s area - activated when determining if “on key”

Musical training -> changes in cortex

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16
Q

List a few experimental approaches to hair cell regeneration. (3)

A
  1. Differentiation of non-sensory cells
  2. Growth factor-mediated differentiation
  3. Stem cell mediated replacement
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17
Q

What are cochlear implants used for? What are their limitations? (2)

A

Electrical stimulation of auditory nerve fibers

  • Musical stimuli sound tinny, miss prosody in voice because of limited number of electrodes
  • Better results if implanted at earlier ages
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18
Q

State what happens with a lesion of Broca’s area, Wernicke’s area, or the arcuate fasciculus.

A

Broca’s aphasia: have ability to comprehend speech, but not produce it

Wernicke’s aphasia: can produce speech, but do not comprehend it
–Produce inappropriate, incomprehensible speech

Conduction aphasia: similar to Broca’s; lesion of arcuate fasciculus

19
Q

What is presbyacusis?

A

Loss of hearing with old age

Typically age-dependent loss of high frequency hearing

20
Q

What is hyperacusis?

A

Extra sensitivity to moderate or even low intensity sounds

–Damage to tensor tympani or stapedius

21
Q

What is auditory agnosia?

A

Inability to identify meaning of a non-verbal sound

–Can hear it, but don’t know what it means (doorbell =/= door)

22
Q

What is congenital amusia?

A

Inability to detect and mimic changes in pitch (“tone deafness”)

23
Q

What is conduction deafness?

A

Disturbance in conduction of sound from outer ear to cochlea

  • -Wax in ear
  • -Rupture of tympanic membrane
  • -Pathology of ossicles
24
Q

What is nerve deafness?

A

Loss of hair cells or neurons in auditory nerve

25
Q

What can cause acquired hearing loss?

A
  • -Acoustical trauma
  • -Infection of inner ear
  • -Ototoxic drugs (kanamycin, gentamicin)
  • -Old age
26
Q

What is tinnitus?

A

Auditory perception in the absence of an external stimulus

  • -Most common cause = noise-induced hearing loss
  • -Also wax build up, high doses of antibiotics, ear infections
27
Q

What is an acoustic neuroma?

A

Benign tumor of Schwann cells on vestibular nerve -> cochlear symptoms (hearing loss and/or tinnitus)

Treat with surgical removal

28
Q

What is Ménière’s disease?

A

Progressive hearing loss with episodes of vertigo and tinnitus

Due to excess fluid in inner ear -> swelling of endolymphatic sac

29
Q

Describe how sound intensity is measured.

A

Decibels: log scale of sound pressure level

  • Measured to reference normal hearing threshold (0 dB)
  • –10x louder is 20 dB
  • –100x louder is 40 dB
  • Range = 1,000,000x (120dB)
30
Q

List the general pathway for nerve fibers from the cochlea. (7)

A

Spiral ganglion -> CN VIII -> dorsal/ventral cochlear nuclei -> superior olivary nuclei -> inferior colliculus -> medial geniculate of thalamus -> superior temporal gyrus

31
Q

Briefly state the general functions of each of the two cochlear nuclei.

A

Dorsal cochlear nuclei - analysis of frequency

Ventral cochlear nuclei - intensity (loudness) information

32
Q

Explain the process of sound localization by time delay in the two ears.

A

Neurons in medial superior olive

  • —Have an array of 5 nuclei, highest activation at nucleus where signals from both ears arrive at same time
  • —If sound arrives at same time in both ears, activate middle nucleus
  • —If signal arrives at left ear first, will activate RIGHT-most nucleus
33
Q

Explain the process of sound localization by comparing the intensity differences in the two ears.

A

(for HIGH intensity) - neurons in lateral superior olive

  • —If sound arrives on right, left ear is in a sound shadow, will get weaker intensity signal
  • —Have inhibitory neurons from one side to the other that synapse in medial nucleus of the trapezoid body
  • —–Greater intensity input -> stronger input ipsilaterally AND stronger inhibition contralaterally
34
Q

Explain the process of sound localization by comparing the phase differences in the two ears.

A

(for LOW intensity) - (location not stated)

–Sound arrives at two ears at different phases of the sound wave

35
Q

What is the role of the inferior colliculus in the auditory pathway?

A

Integration of auditory information with inputs carrying somatosensory information from parts of body

Involved in auditory startle reflex and vestibuloocular reflex

Filter out sounds from self (breathing, chewing, vocalizing)

36
Q

What is the role of the medial geniculate nucleus of the thalamus in audition?

A

Selects for combinations of frequencies and specific time differences between the two frequencies

37
Q

What is the role of the secondary (belt) areas in audition? Where are they located?

A

Specific for combination of sounds used in vocalizations

Located in superior temporal gyrus

Select for…

  • -Combinations of frequencies
  • -Sounds of specific durations
  • -Specific patterns of sounds (syllables; phonemes)
38
Q

What is the role of Wernicke’s area in audition?

A

Important for comprehending speech, semantic processing

Receives auditory and visual inputs

39
Q

What is the role of the ventral stream in audition? What areas are included?

A

Includes primary auditory cortex and inferior frontal gyrus

Important for PITCH

40
Q

What is the role of the dorsal stream in audition? What areas are included?

A

Includes superior parietal cortex and superior frontal gyrus

Important for LOCALIZATION

41
Q

What is the Doppler effect? What does it tell you? (3)

A

Frequency shift as an object is moving

Tells you:

  • How far away is the object?
  • Is it moving closer or farther away?
  • How fast is it moving?
42
Q

List the functions of Broca’s area, the arcuate fasciculus, the supramarginal gyrus, and the angular gyrus.

A

Broca’s area: motor control for speech production

Arcuate fasciculus: connects Wernicke’s and Broca’s areas

Supramarginal gyrus: important in matching incoming sounds to meaningful phonemes
–Has neurons specific for different phonemes

Angular gyrus: important for matching graphemes to phonemes

43
Q

What can cause genetic hearing loss?

A

> 50 genes, especially channels responsible for maintaining high K in endolymph

Neuroscience - Quizzes 1 - 3 (30 decks)

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