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pt 2: sensory input ch 2: echolocation in bats bat behavior decoding the acoustic environment

PART 2: SENSORY WORLDS #06: ECHOLOCATION IN BATS II. pt 2: sensory input ch 2: echolocation in bats bat behavior decoding the acoustic environment hunting bats neural mechanisms moth responses to predation summary. PART 2: SENSORY WORLDS #06: ECHOLOCATION IN BATS II.

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pt 2: sensory input ch 2: echolocation in bats bat behavior decoding the acoustic environment

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  1. PART 2: SENSORY WORLDS #06: ECHOLOCATION IN BATS II • pt 2: sensory input • ch 2: echolocation in bats • bat behavior • decoding the acoustic environment • hunting bats • neural mechanisms • moth responses to predation • summary

  2. PART 2: SENSORY WORLDS #06: ECHOLOCATION IN BATS II • pt 2: sensory input • ch 2: echolocation in bats • bat behavior • decoding the acoustic environment • hunting bats • neural mechanisms • moth responses to predation • summary

  3. ball of wool... • anatomical homogeneity • cell function diversity • network & structure... • anatomical diversity • cell function homogeneity • both... BRAIN STRUCTURE – FUNCTION • 2 polar views of brain structure-function relationships...

  4. BRAIN STRUCTURE – FUNCTION • brain functions determined by... • proximity & connectivity  known inputs & outputs (eg, olfaction) • experimentation

  5. BRAIN STRUCTURE – FUNCTION • Drosophila brain

  6. BRAIN STRUCTURE – FUNCTION • Drosophila olfactory mushroom  body   lateral horn antennal gl. tract   antennal lobe   antenna 

  7. BRAIN STRUCTURE – FUNCTION • human brain

  8. NEURAL MECHANISMS • human auditory

  9. NEURAL MECHANISMS • human auditory

  10. ) ) ) ) ) )  ) NEURAL MECHANISMS • bat auditory • ear drum vibration •  hair displacement • amplitude • frequency • 1° auditory neurons in spiral ganglion •  CNS

  11. excitation...  • inhibition...    NEURAL MECHANISMS • human auditory (b) • hair cells on basilar membrane = basilar fibers • shorter @ base,  frequency • longer @ apex,  frequency

  12. NEURAL MECHANISMS • ranges of auditory perception HUMAN BAT 1 10 100 1K 10K 100K FREQUENCY (Hz)

  13. ) ) ) ) ) )  ) • 1° auditory neurons • more of them NEURAL MECHANISMS • bat auditory specializations  echolocation • frequency range • CF bats... acoustic fovea on membrane • thicker • longer

  14. NEURAL MECHANISMS • bat auditory specializations  echolocation • frequency range • CF bats... acoustic fovea on membrane • thicker • longer • 1° auditory neurons • more of them • tuned to acoustic fovea

  15. NEURAL MECHANISMS • bat auditory specializations  echolocation • frequency range • CF bats... acoustic fovea on membrane • thicker • longer • 1° auditory neurons • more of them • tuned to acoustic fovea ?

  16. cochlea sensory interneuron auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus NEURAL MECHANISMS • auditory pathway: mustached bat (FM & CF) auditory cortex auditory cortex sensory interneuron auditory cortex

  17. sensory interneuron NEURAL MECHANISMS • auditory pathway: mustached bat (FM & CF) auditory cortex auditory cortex cochlea auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus sensory interneuron medial geniculate nucleus auditory cortex

  18. sensory interneuron NEURAL MECHANISMS • auditory pathway: mustached bat (FM & CF) auditory cortex auditory cortex cochlea auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus sensory interneuron medial geniculate nucleus auditory cortex

  19. sensory interneuron NEURAL MECHANISMS • auditory pathway: mustached bat (FM & CF) auditory cortex auditory cortex cochlea auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus sensory interneuron medial geniculate nucleus auditory cortex

  20. sensory interneuron NEURAL MECHANISMS • auditory pathway: mustached bat (FM & CF) auditory cortex auditory cortex cochlea auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus sensory interneuron medial geniculate nucleus auditory cortex

  21. NEURAL MECHANISMS • bat auditory specializations  echolocation • FM bats... sensitivity to emitted call during call • contract middle ear muscles • attenuation in nucleus of lateral lemniscus* • CF bats... remain sensitive to signal during call • ~ deaf to narrow band of call,  membrane sensitivity

  22. sensory interneuron NEURAL MECHANISMS • auditory pathway: mustached bat (FM & CF) auditory cortex auditory cortex cochlea auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus sensory interneuron medial geniculate nucleus auditory cortex

  23. NEURAL MECHANISMS • inferior colliculus  encoding FM signal-echo delay • inferior colliculus neurons  fixed spike rate ~ • call • echo delay • not ~ intensity • frequency tuned • low threshold

  24. NEURAL MECHANISMS • inferior colliculus  encoding CF Doppler effect •  # of frequency tuned neurons at acoustic fovea • target information • encode insect wing beats

  25. sensory interneuron NEURAL MECHANISMS • auditory pathway: mustached bat (FM & CF) auditory cortex auditory cortex cochlea auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus sensory interneuron medial geniculate nucleus auditory cortex

  26. sensory interneuron NEURAL MECHANISMS • auditory pathway: mustached bat (FM & CF) auditory cortex auditory cortex cochlea auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus sensory interneuron medial geniculate nucleus auditory cortex

  27. cochlea sensory interneuron auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus NEURAL MECHANISMS • auditory pathway: mustached bat (FM & CF) auditory cortex auditory cortex FM-FM CF-CF DSCF

  28. NEURAL MECHANISMS • auditory pathway: mustached bat (FM & CF) auditory cortex auditory cortex auditory cortex cochlea lower centers auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus FM-FM CF-CF DSCF

  29. NEURAL MECHANISMS • auditory cortex  lower centers • individual parameters • parallel centers

  30. cochlea auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus NEURAL MECHANISMS • auditory pathway: mustached bat (FM & CF) auditory cortex

  31. cochlea auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus NEURAL MECHANISMS • auditory pathway: mustached bat (FM & CF) FM-FM CF-CF DSCF

  32. NEURAL MECHANISMS • mustached bat • CF & FM components • pulse & echo • 4 harmonic frequencies • H1 = fundamental • 4 amplitudes (volumes) • H2 > H3 > H4 > H1 • map onto different cortical areas

  33. NEURAL MECHANISMS • mustached bat • FM-FM area  distance & size coding

  34. NEURAL MECHANISMS • FM-FM area  distance coding • respond best to FM call + delayed FM echo • FM-FM neurons delay tuned, in columns • FM1-FM2, FM1-FM3 & FM1-FM4 zones

  35. NEURAL MECHANISMS • FM-FM area  size coding • FM-FM neurons delay & amplitude tuned • disruption  no influence on freq. discrimination

  36. NEURAL MECHANISMS • auditory pathway: mustached bat (FM & CF) auditory cortex auditory cortex cochlea auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus FM-FM CF-CF DSCF

  37. NEURAL MECHANISMS • FM-FM area  distance & size coding • medial geniculate nuc. delays call signal  FM-FM •  call + delay coincidence  FM-FM auditory cortex auditory cortex

  38. NEURAL MECHANISMS • mustached bat • FM-FM area  distance & size coding • CF-CF area  velocity coding

  39. NEURAL MECHANISMS • CF-CF area  velocity coding (Doppler shift) • CF-CF neurons Doppler shift tuned, in columns • CF1- CF2 compares 30 vs 61 kHz tones • CF1- CF3  compares 30 vs 92 kHz tones

  40. NEURAL MECHANISMS • CF-CF area  velocity coding (Doppler shift) • columns map relative velocity coordinates • -2  +9 m/s • most 0  +4 m/s (biologically relevant)

  41. NEURAL MECHANISMS • mustached bat • FM-FM area  distance & size coding • CF-CF area  velocity coding • DSCF area  Doppler shifted CF2

  42. NEURAL MECHANISMS • DSCF area  Doppler shifted CF2 signals • 60.6  62.2 kHz • signal @ 61 kHz • neurons tuned for freq. & amplitude of echo • cortical acoustic fovea • disruption  no influence on delay discrimination

  43. NEURAL MECHANISMS • why harmonics ? • many bats & signals • H2 > H3 > H4 > H1 • fundamental H1 weak • only heard by sender • vs other harmonics • ~ dual password

  44. MOTH RESPONSES TO PREDATION • why are there any moths left ? • moths hear rate signals • early stages (...6) • moth hears pulse before bat hears echo • fly in opposite direction

  45. MOTH RESPONSES TO PREDATION • why are there any moths left ? • moths hear  rate signals • late stages (9...) • moth hears pulse after detection • moths dive  ground & shelter • erratic flight  confusing echo

  46. SUMMARY • bats echolocate to • navigate • locate, identify, track & capture prey (flying insects) • 2 kinds of signals • FM, broad band, short duration (< 5 ms) • CF, narrow band, long duration (5 – 100 ms) • complex analyses of emitted calls & returning echos

  47. SUMMARY • complex analyses of emitted calls & returning echos • FM call-echo delay  distance • echo amplitude (volume)  angular size • distance + amplitude  absolute size • spatial location... • binaural comparisons  azimuth • amplitude @ different ear positions  horizontal • CF Doppler shift  relative velocity of target

  48. SUMMARY • acoustic fovea • narrow CF range  Doppler shift analyses • overrepresented throughout auditory system • Doppler shift compensation of call  echo in acoustic fovea • 3 stages of hunting ~ # pulses / s (resolution of target) • search @ ~ 10 Hz • approach @ ~ 50 Hz • terminal @ ~ 100-200 Hz

  49. SUMMARY • auditory specializations  echolocation • acoustic fovea  Doppler shifted CF echoes • basilar membrane (cochlea)  expanded AF range • nuc. of lateral lemniscus  attenuate FM calls • inferior colliculus  responds to FM echo delays • medial geniculate nuc.  call-echo coincidence detection & relay to auditory cortex • auditory cortex tonotopic maps

  50. SUMMARY • flow diagram • basilar membrane  expanded AF • inferior colliculus  FM echo delays • med. geniculate nuc.  FM coincidence • auditory cortex tonotopic maps

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