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
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)
BRAIN STRUCTURE – FUNCTION
antenna
antennal lobe antennal gl. tract
mushroom body lateral
horn
Drosophila olfactory
BRAIN STRUCTURE – FUNCTION
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
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
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
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
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
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
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
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
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
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
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
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
auditory pathway: mustached bat (FM & CF)cochlea
auditory nerve
cochlear nucleus
inferior colliculus
nucleus of lateral lemniscus
medial geniculate nucleus
superior olivary nucleus
CF-CFFM-FM DSCF
auditorycortex
auditorycortex
sensory
interneuron
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
CF-CFFM-FM DSCF
auditorycortex
auditorycortex
auditorycortex
lower centers
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
auditory cortex
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
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
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)cochlea
auditory nerve
cochlear nucleus
inferior colliculus
nucleus of lateral lemniscus
medial geniculate nucleus
superior olivary nucleus
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
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
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