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Bird Song &
hearing
746 - Lecture 1
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
Birdsong
 What is a sonogram?
 time
on x axis; frequency on y axis
 intensity shown by colour / black
frequency 
intensity/
time
sonogram
time 
Birdsong
 Each species has its own song
Dialects
 White-crowned sparrow
Isolated from sound
 juveniles hear no sound will sing in spring
Play song to juveniles (I)
 Played another species song only
 Record next spring song
Play song to juveniles (II)
Summary so far
 Dialects in many passerines
 Juveniles learn father’s song
 Prefer
own species song
 develop their own
 Next: how is this achieved in brain?
Song brain map
only in song birds
auditory input
to area L
Brainstem
(bilateral
coordination)
controls song
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
During learning
 forebrain essential
LMAN
X

 LMAN carries “jitter”
needed in learning
process
HVc neuron - own song
spike replicates
total count of spikes
sonogram
intensity
HVc neuron-synthetic song
spike replicates
total count of spikes
sonogram
intensity
Another synthetic song
total count of spikes
sonogram
intensity
Summary of HVc expt
 HVc is sensitive
to own song
 selective
During singing
 network via UVA &
NIF acts a delay
 produces efference
copy
 comparison with
acoustic input
 Check that birds is
singing “correctly”
Seasonality
 Canaries add/replace syllables annually
 HVc grows/shrinks annually
 new
neurons!
 testosterone causes
 more
growth in males
 singing in females and
castrati
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
Major impacts:
 Neurons
added to brain
 Focused nuclei affected during learning
 Male and female radically different
Owl hearing
 Problem
 locate
mouse
 1) how far away
 2) which direction
 implies ability to locate mouse in x,y
coordinates
Going ...
 Total darkness
 Infra-red picture
Behaviour Method
 azimuth 
elevation
mount high frequency coil on head in magnetic field
Results
 Error less than 5o
for most angles
Owl ears
 are hidden behind facial ruff
Owl ears are asymmetric
 Left up
 Right down
Sound at the 2 ears has:
 Time difference
 gets
to further away
ear later
 ITD
 Intensity difference
 quieter
in auditory
shadow
 IID
How so accurate?
 both ears contribute to L/R and U/D
Neurons respond...
 only to one point in space
count of spikes to sound
2-d tonotopic map
Map generated from ?
 IID
 intensity
coded by spikes;
 summate at synapse
 ITD
 Jeffress hypothesis:
 axon
conduction delay
 leads to coincidence
Jeffress hypothesis
N. laminaris
Time delay
 coincidence detection
Pathways
IID pathway: orange
ITD pathway: blue
Local anaesthetic used to
show separate pathways
Summary
 Asymmetry of ears allows
 ITD
 IID
 Separation of intensity and time delay in
CNS allows
 tonotopic
map
 align to visual cortex
 Catch mouse