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Binaural Hearing: Lessons from Evolution . Conference on Neural Dynamics and Computation in honor of John Rinzel NYU Courant Institute June 2009. Tetrapod auditory systems evolved in parallel. Sphenodontidae. Mammalia. Gymno-phiona. Aves. Testudines. Anura. Squamata. Crocodilia.

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binaural hearing lessons from evolution

Binaural Hearing: Lessons from Evolution

Conference on Neural Dynamics and Computation

in honor of John Rinzel

NYU Courant Institute June 2009

tetrapod auditory systems evolved in parallel
Tetrapod auditory systems evolved in parallel

Sphenodontidae

Mammalia

Gymno-phiona

Aves

Testudines

Anura

Squamata

Crocodilia

Urodela

Quaternary

1.8

Cenozoic

Tertiary

Plesiosauria

Ptero-sauria

Ichthyo-sauria

Dinosauria

65

Cretaceous

146

Mesozoic

Jurassic

208

Triassic

250

Thecodontia

Permian

Therapsida

“Stem reptiles”

290

Pelycosauria

Carboniferous

Paleozoic

Early amphibians

360

Modified from Grothe, Nat. Rev. Neurosci, 2003

Devonian

Rhipidistia

410

Sensitive, high-frequency hearing of airborne sound may be a recent event in vertebrate evolution

hearing of airborne sound evolved multiple times in parallel
Hearing of airborne sound evolved multiple times - in parallel
  • Each groups should be regarded as an independent experiment in hearing
  • Current theories suggest that there are major differences between directional hearing in bird and mammal brainstem
  • Compare with circuits for directional hearing in lizards
  • Identify computational principles underlying sound localization
a circuit for detection of interaural time differences itd
A circuit for detection of interaural time differences (ITD)
  • Delay line inputs synapse on coincidence detector neurons
  • These neurons compute the new variable, ITD, and transform the time code into a place code

Jeffress model

slide5

ITD detection circuits in the barn owl conform to the Jeffress model

IPSI

NM neurons project bilaterally to NL to form maps of ITD

CONTRA

nl act as coincidence detectors
NL act as coincidence detectors

Sound signals from left & right ears converge through the two prominent dendrites

From Macleod, 2007

From Ashida, 2007

similar not identical circuits in mammals
Similar (not identical) circuits in mammals
  • Neurons in MSO act as coincidence detectors
  • But do the inputs form a map of ITD?
  • Currently debated
does itd coding require a map
Does ITD coding require a map?
  • Harper and McAlpine (2004) proposed optimal coding strategy for ITD depends on head size.
  • Test their predictions in the chicken
good enough solutions
Good enough solutions ?
  • Gerbils may have a population rate code rather than a map.
  • birds a ‘labeled line’ population code

Diagrams from Grothe and Köppl

can evolutionary history explain the differences
Can evolutionary history explain the differences?

Aves

Crocodilia

  • How did ITD circuits evolve?
  • Compare with other birds and alligators
  • Do ITD computations constrain map formation?

Ptero-sauria

Dinosauria

computational principles in the auditory system
computational principles in the auditory system
  • Computing source location is evolutionarily important
  • Birds, crocodilians and mammals use parallel coding strategies
  • Lizards have another solution
  • sound location circuits highlight evolutionary constraints in circuit design and coding
binaural hearing lessons from evolution12
Binaural Hearing: Lessons from Evolution
  • And at the same time tomorrow…
  • Stay tuned for Leo van Hemmen’s talk
  • Theory of internally coupled ears – the ICE model: How lizards and birds provide us with a novel category of hearing