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Neural Circuits > L10 - Sound Localisation and Sensory System Interction > Flashcards

L10 - Sound Localisation and Sensory System Interction Flashcards

1
Q

What 3 things are sound localisation important for?

A

Important mechanism for survival
Important for communication
Enables perception of auditory space

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2
Q

What is the importance of sound localisation as a mechanism for survival?

A

For prey and predator

Owl and bat - nocturnal hunting

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3
Q

What is the importance of sound localisation for communication?

A

Identify where and who people are

Concentrate on one person in a noisy environment – cocktail party effect

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4
Q

How does sound localisation enable perception of auditory space?

A

All information is taken from features of sound arriving at the two ears
Map is formed that is not intrinsically represented on receptor cells like it is in visual system

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5
Q

What are the two benefits of sound localisation?

A

Know exactly where a sound is

Improve speech understanding

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6
Q

How does sound localisation help you identify where a sound is?

A

Know what direction it is moving
Predict where it will move next
Feel part of the 3D world even with your eyes closed

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7
Q

How does sound localisation help improve speech understanding?

A

Know where people are – you can turn and listen or run away

Help to hear individuals in a noisy environment

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8
Q

What are monaural cues for sound localisation?

A

Requires input from one ear
Sound elevation in the vertical plane - elevation
Characteristic notches that differ depending on the elevation of the sound
Head related transfer functions

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9
Q

What are binaural cues for sound localisation?

A 
Requires input from both ears 
Sound position in the horizontal plane - azimuth
Either 
- Interaural timing differences - ITDs
- Interaural level differences - ILDs
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10
Q

Interaural timing differences - ITDs

A

Difference in the arrival time of sound at the two ears (Δt)
As small as 10μs
Mainly low frequency sounds

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11
Q

Interaural level differences - ILDs

A

Difference in the intensity of sound at the two ears (ΔI)
As small as 1-2dB
Mainly high frequency sounds

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12
Q

Do people use single or both binaural strategies?

A

Most species use both binaural strategies

  • One can dominate based on animals hearing range and head size
  • Also depends on evolutionary history
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13
Q

Where are sound localisation centres found?

A

Found in the Superior Olivary Complex in the Brainstem

Hair cells –> aVCN –> LSO –> MSO –> MNTB

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14
Q

What is involved in interaural level differences?

A

LSO – MNTB binaural excitatory-inhibitory pathway

Lateral superior olive (LSO) and medial nucleus of the trapezoid body (MNTB) involved

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15
Q

Interaural level differences method

A

Encoded by cells in the LSO that compare the coincidence of excitatory ipsilateral and inhibitory contralateral inputs
The two LSOs act as broad hemispheric channels tuned to sounds in each hemisphere
Overall position of a sound is encoded by the balance in average output rate of LSO channels

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16
Q

Interaural level differences evolution

A

Evolved over 200 million years ago – mainly high frequency (4-18KHz)
Very conserved among all mammals

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17
Q

Interaural level differences - sound coming from left method

A
  1. Input from left ear goes to the aVCN
  2. Excitatory input to cells in the LSO
  3. Input from right ear goes via MNTB and changes to inhibitory input
  4. Cells in the LSO detect balance between excitatory and inhibitory inputs
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18
Q

Interaural timing differences pathway birds

A

MSO binaural excitatory-excitatory pathway

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19
Q

Interaural timing differences method birds

A

Encoded by cells that compare the timing in arrival of excitatory ipsilateral and contralateral inputs
The cells are tuned to a particular timing difference for sounds originating from contralateral side
- Created by neuronal delay lines
Overall position of a sound is encoded by the particular channel activated

20
Q

Interaural timing differences evolution birds

A

Mainly low frequency hearing (100Hz–3KHz)

Very conserved among birds

21
Q

Interaural timing differences - how it works birds

A

As sound moves round the head the time it takes to get to the MSO is lower so it progressively activates cells as we go down to the shortest time difference
In the centre cells from both side MSOs are activated
The closer the sound is to the ear, the longer the pathway needs to be for activity to be coincidence in the cell

22
Q

Interaural timing differences method mammals

A

Encoded by cells in MSO that compare the coincidence of excitatory ipsilateral and contralateral input
The two MSOs act as broad hemispheric channels tuned to sounds from the opposite hemisphere
Overall position of a sound is encoded by the balance between the average population response of the two MSO channels

23
Q

Interaural timing differences evolution mammals

A

Mainly for low frequency hearing (<3KHz)

Evolved later in mammals and is not very conserved

24
Q

Sound localisation in mammals summary

A

ILDs are represented in the LSO
ITDs are represented in the MSO
Both ITDs and ILDs are represented by two hemispherically tuned channels

25
Q

Sound localisation in birds summary

A

ITDs are encoded by individual cells that are tuned to a narrow range of ITDs
This produced a hardwired topographic map of ITDs
That of mammals is more dynamic and adaptable

26
Q

How was visual dominance of space perception during development shown?

A

Demonstrated by Knudsen and Knudsen on juvenile barn owls
Showed the plasticity of auditory orienting behaviour
Owls looked 20o to the right when wearing the prism glasses

27
Q

How do prisms affect information flow in the midbrain auditory localisation pathway? - before prisms

A

ITDs are mapped to frequency specific layers in the ICC
These frequency layers converge to forma space map in the inferior colliculus
Auditory map in the inferior colliculus is aligned with the visual map in the optic tectum with instruction from the optic tectum

28
Q

How do prisms affect information flow in the midbrain auditory localisation pathway? - after prisms

A

Instruction from the optic tectum realigns the inferior colliculus to match
Shows dominance of visual input over the auditory receptor field

29
Q

What is sensory interaction?

A

Combination of different sensory modalities from a common source

30
Q

Our ability to perceive objects requires?

A

Multisensory integration

31
Q

What does sensory interaction improve?

A 
Precision
Discrimination 
Speed of perception
Improving reaction
Selective attention
Motor output
32
Q

What is the McGurk effect an example of?

A

Visual and auditory interaction

33
Q

What is the McGurk effect?

A

Our perception is context dependent – use the most statistically reliable cue to inform decisions
- Visual cues for spatial decisions
- Auditory cues for timing decisions
- Either can dominate
Sensory interaction is highly reliant on temporal synchrony or small delays that allow prediction

34
Q

What is the cocktail party effect an example of?

A

Selective attention

35
Q

What is the cocktail party effect?

A

Our ability to selectively attend to a single object is an important survival mechanism
- Improves task performance and motor output
Works by resetting rhythmic brain oscillations and is important for associating multisensory information during selective attention

36
Q

What are the 4 key processes of the cocktail party effect?

A

Active exploration of the scene active sensing
Selective attention to speaker
Stimulus driven entertainment
Cross modal predictive cues are involved in phase resetting

37
Q

What is active exploration of the scene active sensing?

A

Involves motor and visual systems to scan the scene

Fixations enable the phase resetting (PR) of brain oscillations

38
Q

What is selective attention to speaker?

A

Phase resetting synchronises the oscillatory activity in the appropriate sensory areas to the temporal pattern of the speech stream

39
Q

What is stimulus driven entertainment?

A

Visual cues and the auditory waveform fine tune the entrainment to the speech stream in the auditory cortex
Cross modal phase resetting occurs

40
Q

How are cross modal predictive cues involved in phase resetting?

A

Facial articulation and head movement precede speech
Auditory system can anticipate what is coming
Enhanced tracking of auditory stream from visual predictions

41
Q

What is the most statistically reliable input for topographic information?

A

Visual

42
Q

What is the most statistically reliable input for temporal cues?

A

Auditory

43
Q

Why does perception require multisensory integration?

A

Relies on predictive alignment of oscillatory brain waves in different sensory areas

44
Q

Alignment of sensory streams allows?

A

Allows us to perceive individual sensory objects and devote our attention selectively to one when we are confronted with may

45
Q

2.5% of the population are?

A

Supertaskers

46
Q

What are supertaskers?

A

Brain activity in supertaskers is lower than normal
Show enhanced neural efficiency that leads to better performance with a decrease in brain activity and volume
The reduced burden on these brain areas gives an improved ability to focus on more than one demanding task at a time

47
Q

What is ventriloquism?

A

Our strong visual association with mouth movement and speech is known as ventriloquism

Neural Circuits (15 decks)

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