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Psyc 202 > lecture 2 - hearing > Flashcards

lecture 2 - hearing Flashcards

1
Q

What is sound?

A

a sequence of pressure waves which propagate through this elastic net.

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2
Q

What is amplitude

A

Loudness

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3
Q

What is frequency?

A

Pitch

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4
Q

What is complexity?

A

Timbre

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5
Q

How is a complex sound wave produced?

A

By adding together sinusodial sound waves (pure tones)

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6
Q

What do the amplitudes and frequencies determine?

A

The spectrum of the sound

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7
Q

How does sound enter the ear?

A

It is transformed free- field sound (without head present) to the sound at the ear drum.

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8
Q

What is the transformation of sound to the ear called?

A

Head-Related Transfer function . (HRTF)

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9
Q

What does the middle ear contain?

A

A set of intricate interconnected bones: stapes, incus, and malleus.

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10
Q

What do the bones in the middle ear do?

A

They amplify the motion of the ear drum into pressure waves transmitted via the . oval window into the fluid filled cochlea (in the inner ear)

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11
Q

Where is the basilar membrane?

A

Inside the Cochlea- in the inner ear.

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12
Q

What makes the basilar membrane vibrate?

A

The frequency structure of sound

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13
Q

What does the basilar membrane do with the vibrations?

A

Hair cells attached to the BM transduce this mechanical signal into action potentials in auditory nerve.

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14
Q

What does the BM create through its vibrations.

A

A map of sound frequency- the tonotopic map.

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15
Q

What is the structure of the BM?

A

It is wide and stiff at the base, narrow and loose at the apex.

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16
Q

Where are different frequencies on the BM?

A

Higher frequencies make the base and apex portions vibrate respectively.

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17
Q

How is the frequency in a complex sound represented and how does this relate to the auditory nerve?

A

Each frrequency in a complex sound is represented by a specific portion of the BM vibrating - this excited specific cells in the auditory nerve. So the frequency structure of sound is represented by a specific set of auditory nerves firing.

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18
Q

What is synchronized?

A

The cells of the auditory nerve synchronise their firing to the vibrations of the basilar membrane.

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19
Q

How are the frequency components of sound are represented in two ways in the auditory nerve.

A
  1. Place of activity- tonotopic mapping or place coding
  2. Timing of activity- temporal coding in which sounds with higher frequencies produce higher rated or synchronized firing.
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20
Q

What does the Medial geniculate nucleus of the thalamus do?

A

Attentional control

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21
Q

What does the Inferior Colliculus do?

A

Major integrative centre; pitch may be extracted here

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22
Q

What does the Superior olivary nucleus do?

A

Sound source location processing.

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23
Q

What does the cochlear nucleus do?

A

Inputs from the two ears combined & sound location coded.

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24
Q

What is the order of the auditory pathway?

A
  1. Auditory nerve
  2. Cochlear Nuclei
  3. Superior olivary nucleus
  4. inferior Colliculus
  5. Medial geniculate nucleus of the thalamus
  6. primary auditory cortex
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25
Q

What is the main task of subcortical processing ?

A

Sound source localization utilizing cross-ear differences in:
sound wave amplitude
sound wave arrival time

26
Q

How many photoreceptors are in the retina?

A

260 million laid out in two dimensions

27
Q

What do cones respond to?

A

Colour

  • Red
  • Green
  • Blue
28
Q

What do rods respond to?

A

Low levels of light

29
Q

How many hair cells are there in the cochlea?

A

24,000 laid out in one dimension

30
Q

How does the cochlea deal with information?

A

All information from different sound sourced is mixed into a single signal, the . signal in the auditory represents a mess of overlapping sounds

31
Q

How many dimensions does the BM provide info on?

A

One .

32
Q

What does the auditory nerve do?

A

Frequency content of the incoming sound wave

This sound wave is the sum of all signals from around

Task for auditory objects is huge

Subcortical pathway performs (at least) source localisation as part of the solution.

33
Q

What does the visual nerve do?

A

Provides colour and shape information

Task for visual system to separate out visual objects relatively easy

34
Q

How many dimensions is the retina?

A

2

35
Q

What are the primary Cortex structures in the brain?

A

Motor
Somatosensory
Auditory
Visual

36
Q

What are the secondary areas of the cortex?

A

Motor association area
Somatosensory association area
Visual association area
Auditory association area

37
Q

What areas are in the secondary auditory cortex?

A

HS- Heschl’s sulcus

STG- Superior temporal gyrus

38
Q

What is in the primary auditory cortex?

A

HG- Heschl’s gyrus

39
Q

How are the deep neural networks organized? (Levels)

A

Core: Primary fields (HG) receiving input from thalamus

Belt: secondary fields surrounding core

Parabelt: secondary fields next to belt (STG)

40
Q

How are deep neural networks organized? (Organisation)

A

Hierarchical organisation- activity progresses from C to B to PB

Parallel organisation: activity propagates along multiple C- B- PB

41
Q

What do retinotopic maps show?

A

Each areas that represent the visual field

42
Q

What are characteristics of visual processing?

A

They are distributed and specialised: each area represents specific type of information.
There is an element of hierarchical processing.

43
Q

What are Jennifer Aniston Cells?

A

Cells in the Medial Temporal Lobe respond to images of Jennifer Aniston (Quiroga et al., 2005)
Are these grandmother cells? Unlikely

44
Q

What is meant by grandmother cells?

A

Hierarchical- more complex as you go up, so specialised cells

45
Q

What are auditory cortical fields doing?

A

Core fields respond to pure tones and complex sounds
No tonotopic organisation in parabelt
There is little evidence of the kind of specialization seen in visual cortex.

46
Q

What is the auditory cortex partitioned into?

A

Fields, so each field contains one low-high frequency (tonotopic) map, but these maps are melded together.

47
Q

What are the features in multiple overlaid maps in each fields for which cells in auditory cortex show selectivity?

A
  1. Intensity
  2. Bandwidth
  3. Sound source location
    - however there are no separate intensity, bandwidth or localization areas or fields in auditory cortex.
48
Q

What do cells already in the core show?

A

A wide variety of tuning to frequency and time. That is:
> Sharp & wide tuning to frequency
> Tuning to sounds with complicated spectral structure
> Tuning to sounds whose spectral structure changes in time

49
Q

How is the auditory cortex involved in cognitive processing?

A

It is modulated by top-down effects which can be seen in discrimination tasks

50
Q

What does attention modulate?

A

Spectro-temporal receptive field (STRF)

Fritz et al, 2003

51
Q

What does working memory show up as in the auditory cortex?

A

Sustained activity in the auditory cortex. (Huang et al 2016)

52
Q

What is mapped in the auditory cortex?

A

Perceptual learning changes

53
Q

What happens with perceptual learning in auditory cortex?

A

Rats trained to discriminate stimuli either according to pitch or loudness

Pitch discrimination training leads to expansion of frequency representation

Loudness discrimination training leads to expanded loudness representations

Thus representations are modulated by top-down effects of learning

54
Q

What happens with surface recordings from cortex?

A
  • Mesagarani & Chang (2012) presented sentences to human epileptic patients
  • Surface recordings from auditory cortex
  • Method: stimulus spectrogram reconstruction from neural population responses + using machine learning classifier to decode stimulus from neural response
55
Q

What happens with speech processing in the brain?

A
  • Basic auditory processing of complex sound
  • Distinguishing speech from non-speech
  • Identifying speech sounds (e.g. vowels)
  • Semantics at word, sentence and discourse level
  • Recognising prosodic aspects of speech
  • Recognising individual voices, accents & style of speech
  • Recognising emotions
  • Merging auditory and visual information
56
Q

What is the traditional model of speech processing?

A

Speech production: Broca’s are in inferior frontal gyrus (IFG)

Speech comprehension: Wernicke’s area in posterior superior temporal gyrus (pSrG)

57
Q

What contrasting evidence is there for Broca’s and Wernicke’s area?

A

Speech Intelligibility
Scott et al (2000), PET study:
- contrasted responses to intelligible vs, non-intelligible speech stimuli
- Larger responses to intelligible speech in left anterior STG (NOT WERNICKE”S AREA)

58
Q

What evidence supports speech production?

A

Obleser et al 2007

  • An fMRI study looking at processing of degraded speech
  • A semantic predictability enhances intelligibility
  • This enhancement in intelligibility is associated with left-lateralized widely distributed system becoming active
  • This system is associated with semantic processing
59
Q

What is the problem of studying comprehension?

A
  • Contrasts are needed to study the processing of intelligible speech
  • Unintelligible stimuli tend to differ from intelligible stimuli in terms of acoustic complexity or structure
  • We can’t be sure that differences in brain activation reflect intelligibility only .
60
Q

What did Hakonen et al 2017 find?

A
  • Intelligibility leads to increased activity in Anterior Cingulate Cortex (ACC), Frontal Pole (FP) and right frontal operculum
  • These areas associated with retrieval mode of episodic memory
  • Episodic memory needed in comprehension of speech in noise
  • Intelligible speech leads to decreased activation in auditory cortex: this might be due to predictive coding: top down signals dampen predictable bottum-up signals in sensory cortex.

Psyc 202 (7 decks)

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