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Development of sound localization

Development of sound localization. Acoustics, primary coding, neural computation could contribute to development of the ability to locate sound sources in space. Topics in development of sound localization. When can infants first locate sounds? How accurate is localization during development?

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Development of sound localization

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  1. Development of sound localization Acoustics, primary coding, neural computation could contribute to development of the ability to locate sound sources in space

  2. Topics in development of sound localization • When can infants first locate sounds? • How accurate is localization during development? • How could the development of binaural cue processing contribute? • Other: distance perception and precedence effect

  3. Left-right discriminations

  4. Left-right discrimination: Kittens meow

  5. Left-right discrimination: Rats

  6. Left-right discrimination: Frequency effects

  7. Left-right discrimination: Human infants

  8. Accuracy of localization during development: Minimum Audible Angle Sound Sound Speakers MAA Sound

  9. MAA measured in several studies

  10. Changes in head size with age

  11. 650 µsec ITD 20 dB IID at 6 kHz Max IID at 10 kHz Acoustic consequences of a small head 400 µsec ITD

  12. IID and ITD discrimination: Infants

  13. ITD discrimination: Infants

  14. IID and ITD discrimination: Children

  15. Localization in elevation depends on spectral cues

  16. Localization in elevation: Infants shh, shh, shh… 16º shh, shh 0º

  17. MAA in elevation: Infants

  18. Sound localization involves three dimensions elevation distance azimuth

  19. Distance perception: Infants Rattle, rattle… Rattle, rattle… Rattle, rattle… Rattle, rattle… Rattle, rattle… Rattle, rattle…

  20. Distance perception: Infants

  21. Precedence effect ? click click

  22. Precedence effect: Infants

  23. Precedence effect: Children

  24. Summary • Young animals can localize at least grossly, soon after the cochlea starts to function. • Human newborns can also localize sounds, but the MAA improves from birth to 5 years of age. • Infants can localize sounds in all three spatial dimensions. • Acoustics and interaural cue processing cannot fully account for the maturation of sound localization. • Localization under simple conditions may be mature at 5 years of age, but under complex conditions, 5 year-olds are still immature sound localizers.

  25. 400 µsec ITD = 90º azimuth 500 µsec ITD = 90º azimuth 575 µsec ITD = 90º azimuth 650 µsec ITD = 90º azimuth 2 weeks 18 months 24 weeks adult Effects of experience on sound localization

  26. Pairing of visual and auditory information leads to organization of sensory space.

  27. Effects of experience on localization by barn owls

  28. Critical period for spatial recalibration

  29. The critical period for re-adjusting after unplugging is different!

  30. The more the owl uses his map, the longer it remains “plastic”

  31. Effects of experience in humans: Wilmington, Gray and Jahrsdorfer (1994) • 19 subjects with congenital unilateral atresia • Tested before and after corrective surgery • Age at surgery ranged from 6 to 33 years. • Tests included ITD and IID discrimination, speech in noise (sound field), and sound localization.

  32. Interaural time discrimination after correction of unilateral atresia

  33. Localization after correction of unilateral atresia

  34. Chicks in auditory space

  35. Chicks’ “maps” of auditory space

  36. Speech in noise identification after correction of unilateral atresia

  37. Summary of effects of experience on sound localization • Experience with sound is essential for the development of sound localization. • Experience with sound is less essential for the development of the ability to process the acoustic cues to location. • Although a critical period for the development of localization has been identified in some other species, a similar critical period has not yet been identified in humans.

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