bird song & hearing 746 - lecture 1 aim noutline the physiology of hearing and vocalisations u...
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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
intensity/time
sonogram
time
freq
uenc
y
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
controls song
only in song birds
auditory inputto area L
Brainstem (bilateral coordination)
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
intensity
sonogram
total count of spikes
spike replicates
HVc neuron-synthetic song
intensity
sonogram
total count of spikes
spike replicates
Another synthetic song
intensity
sonogram
total count of spikes
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
elevation
azimuth
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
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