Lecture 9 Sound localisation and sensory interactions

Question 1

Explain the map of the auditory space

Answer 1

Perception of auditory space - forms a map of sound frequency, not of the auditory space. Not intrinsically represented by R cells like the visual system

Question 2

What is also associated with monoaural cues

Answer 2

HRTFs = head related transfer functions

Question 3

HRTFs depend on

Answer 3

sound frequency and elevation

Question 4

What occurs if put insert into the ear

Answer 4

Alters DTF = directed transfer function so can no longer recognise sound in the vertical plane

Question 5

Describe the auditory pathway

Answer 5

Hairs in cochlea
Spiral ganglion - type 1 afferents
Cochlear nucleus = all fibres from cochlea = in all brain stem
2 main pathways - ventral (sound localisation), dorsal (sound recognition)
SOC
IC/SC - integration of non-auditory inputs
MGN - learning/memory
Auditory cortex

Question 6

What occurs as go further up brain

Answer 6

Increased integration

Question 7

Name of the model of ITDs in bird

Answer 7

Jeffress

Question 8

Summary of birds ITDs - as sounds go round the head

Answer 8

different neurones activated depending on delay

Question 9

ITD between 2 ears so sound position is encoded by

Answer 9

activation of specific neurones in brainstem

Question 10

• The two MSOs act as

Answer 10

act as broad hemispheric channels tuned to sounds from the opposite hemisphere.

Question 11

The overall position of a sound is encoded

Answer 11

by the balance between the average population response of the two MSO channels.

Question 12

ITDs mainly for

Answer 12

Mainly for low frequency hearing (<3KHz) –

Question 13

ITD evolution

Answer 13

evolved later in mammals and is less conserved.

Question 14

In mammals, ILDs and ITDs represented by

Answer 14

ILDs are represented in the LSO and ITDs in the MSO.

Question 15

ITD and ILD encoded by

Answer 15

ILDs – encoded by the coincidence of excitatory and inhibitory inputs
- ITDs – encoded by the coincidence of two excitatory inputs.

Question 16

In mammals both ITDs and ILDs are represented by two

Answer 16

broadly tuned channels with the balance of output accurately encoding a sounds position.

Question 17

Prisms affect

Answer 17

the functional alignment of visual and auditory maps in the midbrain.

Question 18

Before prisms:

Answer 18

the normal pathway

Question 19

• ITDs are mapped to

Answer 19

frequency specific layers in the ICC

Question 20

• These frequency layers converge

Answer 20

to form a space map in the ICX

Question 21

• The auditory map in the ICX is aligned with the

Answer 21

visual map in the OT with instruction from the OT.

Question 22

• After prisms:

Answer 22

instruction from the OT realigns the ICX to match.