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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 BRAIN STRUCTURE – FUNCTION 2 polar views of brain structure-function relationships... ball of wool... anatomical homogeneity cell function diversity network & structure... anatomical diversity cell function homogeneity both... 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 lateral horn antennal gl. tract mushroom body 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 NEURAL MECHANISMS human auditory (b) hair cells on basilar membrane = basilar fibers shorter @ base, frequency longer @ apex, frequency excitation... inhibition... NEURAL MECHANISMS ranges of auditory perception HUMAN BAT 1 10 100 1K 10K FREQUENCY (Hz) 100K NEURAL MECHANISMS bat auditory specializations echolocation frequency range CF bats... acoustic fovea on membrane thicker ) ) ) ) ))) longer 1° auditory neurons more of them 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 ? NEURAL MECHANISMS auditory pathway: mustached bat (FM & CF) cochlea sensory auditory auditory nerve interneuron cortex cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus auditory cortex sensory interneuron auditory cortex NEURAL MECHANISMS auditory pathway: mustached bat (FM & CF) cochlea sensory auditory auditory nerve interneuron cortex cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus auditory cortex sensory interneuron auditory cortex NEURAL MECHANISMS auditory pathway: mustached bat (FM & CF) cochlea sensory auditory auditory nerve interneuron cortex cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus auditory cortex sensory interneuron auditory cortex NEURAL MECHANISMS auditory pathway: mustached bat (FM & CF) cochlea sensory auditory auditory nerve interneuron cortex cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus auditory cortex sensory interneuron auditory cortex NEURAL MECHANISMS auditory pathway: mustached bat (FM & CF) cochlea sensory auditory auditory nerve interneuron cortex cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus auditory cortex sensory interneuron 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 NEURAL MECHANISMS auditory pathway: mustached bat (FM & CF) cochlea sensory auditory auditory nerve interneuron cortex cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus auditory cortex sensory interneuron 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 NEURAL MECHANISMS auditory pathway: mustached bat (FM & CF) cochlea sensory auditory auditory nerve interneuron cortex cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus auditory cortex sensory interneuron auditory cortex NEURAL MECHANISMS auditory pathway: mustached bat (FM & CF) cochlea sensory auditory auditory nerve interneuron cortex cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus auditory cortex sensory interneuron auditory cortex NEURAL MECHANISMS auditory pathway: mustached bat (FM & CF) sensory auditory cochlea auditory nerve interneuron cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus FM-FM CF-CF DSCF cortex auditory cortex 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 FM-FM CF-CF DSCF lower centers auditory cortex NEURAL MECHANISMS auditory cortex lower centers individual parameters parallel centers NEURAL MECHANISMS auditory pathway: mustached bat (FM & CF) cochlea auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus auditory cortex NEURAL MECHANISMS auditory pathway: mustached bat (FM & CF) cochlea auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus 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 cochlea auditory nerve cochlear nucleus superior olivary nucleus nucleus of lateral lemniscus inferior colliculus medial geniculate nucleus FM-FM CF-CF DSCF auditory cortex NEURAL MECHANISMS FM-FM area distance auditory & size coding medial geniculate nuc. delays call signal FM-FM call + delay coincidence FM-FM 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 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 SUMMARY flow diagram basilar membrane expanded AF inferior colliculus FM echo delays med. geniculate nuc. FM coincidence auditory cortex SUMMARY auditory specializations echolocation auditory cortex tonotopic maps FM-FM area distance information map onto freq. & delay-sensitive columns of neurons CF-CF area velocity information maps onto Doppler shift-sensitive columns of neurons DCSF area velocity information maps onto AF range of Doppler shift-sensitive neurons SUMMARY bat-moth co-evolution ... maintains balance moths respond to bat signals signal rate (approach), moths fly away from signal signal rate (terminal), moths either dive or fly irratically some emit pulses to jam bat radar
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