Bird Song

1
Bird Song hearing

• 746 - Lecture 1

2
Aim

• Outline the physiology of hearing and
  vocalisations
• seasonal variation
• developmental processes
• the way this leads to dialects
• hearing in owls
• role in prey capture

3
Birdsong

• What is a sonogram?
• time on x axis frequency on y axis
• intensity shown by colour / black

intensity/ time
frequency
sonogram
time
4
Birdsong

• Each species has its own song

5
Dialects

• White-crowned sparrow

6
Isolated from sound

• juveniles hear no sound will sing in spring

7
Play song to juveniles (I)

• Played another species song only
• Record next spring song

8
Play song to juveniles (II)
9
Summary so far

• Dialects in many passerines
• Juveniles learn fathers song
• Prefer own species song
• develop their own
• Next how is this achieved in brain?

10
Song brain map
only in song birds
auditory inputto area L
Brainstem (bilateral coordination)
controls song
11
During singing

• need
• HVc
• RA
• HVc activity precedes song by 50ms
• Stimulate HVc and disrupt singing
• Stimulate RA and disrupt singing
• HVc can generate pattern on own

12
During learning

• forebrain essential
• LMAN
• X
• LMAN carries jitter needed in learning process

13
HVc neuron - own song
spike replicates
total count of spikes
sonogram
intensity
14
HVc neuron-synthetic song
spike replicates
total count of spikes
sonogram
intensity
15
Another synthetic song
total count of spikes
sonogram
intensity
16
Summary of HVc expt

• HVc is sensitive to own song
• selective

17
During singing

• network via UVA NIF acts a delay
• produces efference copy
• comparison with acoustic input
• Check that birds is singing correctly

18
Seasonality

• Canaries add/replace syllables annually
• HVc grows/shrinks annually
• new neurons!
• testosterone causes
• more growth in males
• singing in females and castrati

19
Summary so far

• Bird song is complex behaviour
• Many songs learnt
• initial learning as juvenile
• used as adult
• HVc
• controls motor output
• responds to song pattern
• possible site of song learning

20
Major impacts

• Neurons added to brain
• Focused nuclei affected during learning
• Male and female radically different

21
Owl hearing

• Problem
• locate mouse
• 1) how far away
• 2) which direction
• implies ability to locate mouse in x,y coordinates

22
Going ...

• Total darkness
• Infra-red picture

23
Behaviour Method
? azimuth ?
??elevation
mount high frequency coil on head in magnetic
field
24
Results

• Error less than 5o for most angles

25
Owl ears

• are hidden behind facial ruff

26
Owl ears are asymmetric

• Left up
• Right down

27
Sound at the 2 ears has

• Time difference
• gets to further awayear later
• ITD
• Intensity difference
• quieter in auditory shadow
• IID

28
How so accurate?

• both ears contribute to L/R and U/D

29
Neurons respond...

• only to one point in space

count of spikes to sound
30
2-d tonotopic map
31
Map generated from ?

• IID
• intensity coded by spikes
• summate at synapse
• ITD
• Jeffress hypothesis
• axon conduction delay
• leads to coincidence

32
Jeffress hypothesis
33
N. laminaris
34
Time delay

• coincidence detection

35
Pathways
IID pathway orange
ITD pathway blue
Local anaesthetic used to show separate pathways
36
Summary

• Asymmetry of ears allows
• ITD
• IID
• Separation of intensity and time delay in CNS
  allows
• tonotopic map
• align to visual cortex
• Catch mouse