Transcript PowerPoint Presentation - Hearing and echolocation

Hearing and echolocation
• Human hearing
• Adaptations for hearing in bats
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Outer ear
Middle ear
Inner ear
Auditory pathways
The human ear
Next slide
Human cochlea
Hair cell damage
Frequency
detection
in the
cochlea
Hearing is tuned to echolocation: How?
CF bats
are tuned
to dominant
frequency
FM bats
show broad
frequency
sensitivity
Ear pinna
amplifies
selected
frequencies
- Pinna acts as a horn
- Larger pinna transmit lower
frequencies better
- Wavelength of the resonant
frequency equals 4 x length
of the ear canal
Middle ear adaptations
Tympanum:oval window area = 53:1 in Tadarida, 35:1 in a cat
Malleus:incus = 3-5:1 in bats, 1.5:1 in a cat
Ear tympanum speed
Faster at high
frequencies
because it is
much thinner
Inner ear
(cochlea)
adaptations
Basilar membrane is
longer and thicker at
base
A basilar membrane
that is thicker at the
base increases
sensitivity to high
frequencies
Rhinolophus ferrumequinum
The auditory pathway
Tonotopic map in the auditory system
Auditory cortex
Gray areas correspond to call
frequencies
Auditory cortex is expanded at
frequencies associated with
echolocation
Open space
Tonotopic
representation
varies by
species Blood feeder
Inferior colliculus
frequency maps
Ground gleaner
Neuronal tuning in horseshoe bats
Q10 = best freq/ bandwidth at -10 dB
Pteronotus parnellii
Information decoded from echos
Range
pulse-echo time delay
Velocity
pulse-echo frequency change
Target size
frequency of echo
Location
ear amplitude difference
Combination-sensitive neurons encode
range and velocity in CF bats
Cortical maps vary by species