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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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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 • pt 2: sensory input • ch 2: echolocation in bats • bat behavior • decoding the acoustic environment • hunting bats • neural mechanisms • moth responses to predation • summary
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...
BRAIN STRUCTURE – FUNCTION • brain functions determined by... • proximity & connectivity known inputs & outputs (eg, olfaction) • experimentation
BRAIN STRUCTURE – FUNCTION • Drosophila brain
BRAIN STRUCTURE – FUNCTION • Drosophila olfactory mushroom body lateral horn antennal gl. tract antennal lobe antenna
BRAIN STRUCTURE – FUNCTION • human brain
NEURAL MECHANISMS • human auditory
NEURAL MECHANISMS • human auditory
) ) ) ) ) ) ) NEURAL MECHANISMS • bat auditory • ear drum vibration • hair displacement • amplitude • frequency • 1° auditory neurons in spiral ganglion • CNS
excitation... • inhibition... NEURAL MECHANISMS • human auditory (b) • hair cells on basilar membrane = basilar fibers • shorter @ base, frequency • longer @ apex, frequency
NEURAL MECHANISMS • ranges of auditory perception HUMAN BAT 1 10 100 1K 10K 100K FREQUENCY (Hz)
) ) ) ) ) ) ) • 1° auditory neurons • more of them NEURAL MECHANISMS • bat auditory specializations echolocation • frequency range • CF bats... acoustic fovea on membrane • thicker • longer
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
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 ?
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
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
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
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
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
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
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
NEURAL MECHANISMS • inferior colliculus encoding FM signal-echo delay • inferior colliculus neurons fixed spike rate ~ • call • echo delay • not ~ intensity • frequency tuned • low threshold
NEURAL MECHANISMS • inferior colliculus encoding CF Doppler effect • # of frequency tuned neurons at acoustic fovea • target information • encode insect wing beats
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
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
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
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
NEURAL MECHANISMS • auditory cortex lower centers • individual parameters • parallel centers
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
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
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
NEURAL MECHANISMS • mustached bat • FM-FM area distance & size coding
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
NEURAL MECHANISMS • FM-FM area size coding • FM-FM neurons delay & amplitude tuned • disruption no influence on freq. discrimination
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
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
NEURAL MECHANISMS • mustached bat • FM-FM area distance & size coding • CF-CF area velocity coding
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
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)
NEURAL MECHANISMS • mustached bat • FM-FM area distance & size coding • CF-CF area velocity coding • DSCF area Doppler shifted CF2
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
NEURAL MECHANISMS • why harmonics ? • many bats & signals • H2 > H3 > H4 > H1 • fundamental H1 weak • only heard by sender • vs other harmonics • ~ dual password
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
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
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
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
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
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
SUMMARY • flow diagram • basilar membrane expanded AF • inferior colliculus FM echo delays • med. geniculate nuc. FM coincidence • auditory cortex tonotopic maps