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

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

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...

experimentation

proximity & connectivity known inputs & outputs (eg, olfaction)


Drosophila brain


antenna

antennal lobe antennal gl. tract

mushroom body lateral

horn

Drosophila olfactory


human brain


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

1 10 100 1K 10K 100K

FREQUENCY (Hz)

HUMAN

BAT

NEURAL MECHANISMS

bat auditory specializations echolocation

) ) ) ))))

frequency range

CF bats... acoustic fovea on membrane

thicker longer

1° auditory neurons more of them

NEURAL MECHANISMS


frequency range


thicker longer

1° auditory neurons more of them tuned to acoustic fovea

NEURAL MECHANISMS


frequency range


thicker longer

1° auditory neurons more of them tuned to acoustic fovea

?

NEURAL MECHANISMS

auditory pathway: mustached bat (FM & CF)cochlea

auditory nerve

cochlear nucleus

inferior colliculus

nucleus of lateral lemniscus

medial geniculate nucleus

superior olivary nucleus

auditorycortex

auditorycortex

sensory

interneuron

sensory interneuron

auditory cortex

NEURAL MECHANISMS


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 nerve

cochlear nucleus

inferior colliculus




auditorycortex

auditorycortex

sensory

interneuron

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 nerve

cochlear nucleus

inferior colliculus




auditorycortex

auditorycortex

sensory

interneuron

sensory interneuron

auditory cortex

NEURAL MECHANISMS


auditory nerve

cochlear nucleus

inferior colliculus




CF-CFFM-FM DSCF

auditorycortex

auditorycortex

sensory

interneuron

NEURAL MECHANISMS


auditory nerve

cochlear nucleus

inferior colliculus




CF-CFFM-FM DSCF

auditorycortex

auditorycortex

auditorycortex

lower centers

NEURAL MECHANISMS

auditory cortex lower centers

individual parameters parallel centers

NEURAL MECHANISMS


auditory nerve

cochlear nucleus

inferior colliculus




auditory cortex

NEURAL MECHANISMS


auditory nerve

cochlear nucleus

inferior colliculus




CF-CFFM-FM 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 nerve

cochlear nucleus

inferior colliculus




CF-CFFM-FM DSCF

auditorycortex

auditorycortex

NEURAL MECHANISMS

FM-FM area distance& size coding

medial geniculate nuc. delays call signal FM-FM

call + delay coincidence FM-FM

auditorycortex

auditorycortex

NEURAL MECHANISMS

mustached bat


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


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

NEURAL MECHANISMS

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

MOTH RESPONSES TO PREDATION

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

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

SUMMARY

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

Documents

auditory neurons

frequencyneural mechanisms

bats bat behavior

basilar membrane

sensory worlds

sensory input ch

predation summary

basilar fibers shorter