studying barn owls in the laboratory sound intensity cues sound timing cues
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PART 2: SENSORY WORLDS #07: PREY LOCATION IN BARN OWLS I. studying barn owls in the laboratory sound intensity cues sound timing cues neural pathways for sound location auditory space interaural time differences delay lines & coincidence detectors - PowerPoint PPT PresentationTRANSCRIPT
studying barn owls in the laboratory sound intensity cues sound timing cues
neural pathways for sound location auditory space interaural time differences delay lines & coincidence detectors
visual calibration of the auditory world summary
PART 2: SENSORY WORLDS#07: PREY LOCATION IN BARN OWLS I
studying barn owls in the laboratory sound intensity cues sound timing cues
neural pathways for sound location auditory space interaural time differences delay lines & coincidence detectors
visual calibration of the auditory world summary
PART 2: SENSORY WORLDS#07: PREY LOCATION IN BARN OWLS I
Intensity differences
Timing differences
high frequency ...
short wavelength
low frequency ...
long wavelength
AUDITORY CUES
Tyto alba, hunt using auditory cues height: 1-1.5 ft wing span: 3 ft velocity: 4-8 m/s forms pair bonds hunting nocturnal
& crepuscular small rodents > other
small animals prey of great horned
owls restricts barn owl hunting to deep night
BARN OWL BIOLOGY
Tyto alba, hunt using auditory cues locates prey in space
horizontal vertical relative to self
prey capture... FIG 1
how to determine the cues? not visual (test in dark) heat, olfactory, auditory ? early mouse/paper expt.
p.63 fig.3.1
BARN OWL BIOLOGY
1st important behavioral observation...
owls turn their heads rapidly toward sound
bring source to center
tested experimentally...
p.63 fig.3.1
BARN OWLS IN THE LABORATORY
monitor head orientation behavior
used “search coil” weak electric field
signal magnitude + sign head position
~ sounds
no echoes
total darkness
sound & head positions correlated by computer
p.64 fig.3.2
BARN OWLS IN THE LABORATORY
features of barn owl auditory system
face covered with rows of stiff feathers... facial ruff
sound-collecting surface auditory canals
ears asymmetrical right ear & opening directed , sensitivity head left ear & opening directed , sensitivity head
BARN OWLS IN THE LABORATORY
2D mapping of sound dimensions
azimuth horizontal
elevation vertical
can target soundwithin 1°-2°
3x human accuracyin vertical dimension
p.65 fig.3.3
BARN OWLS IN THE LABORATORY
2D mapping of sound dimensions
most sensitive tosound in front
frequency range100 Hz - 12 kHz
azimuth: accurate within 1 - 9 kHz
elevation: accuratewithin 3 - 10 kHz p.65 fig.3.3
BARN OWLS IN THE LABORATORY
experiments identified 2 critical auditory cues...
sound intensity cues elevation dimension
sound timing cues azimuth dimension
BARN OWLS IN THE LABORATORY
attenuated sound, blocking ears with 2 types of plugs soft modest hard severe
sound location... recall that the ears are asymmetrical...
right ear & opening directed , sensitivity head left ear & opening directed , sensitivity head
interaural intensity differences to target elevation, also called interaural level differences (ILD)
SOUND INTENSITY CUES
attenuated sound, blocking ears with 2 types of plugs soft modest hard severe
sound location error... elevation some azimuth
not sufficient to explain accuracy
p.67 fig.3.4
SOUND INTENSITY CUES
removed facial ruff
sound location error... mostly elevation (head oriented @ horizontal plane) azimuth OK ruff amplifies directional asymmetry of ears
SOUND INTENSITY CUES
sounds arrive @ different times to each ear difference in time = temporal disparity
barn owls can distinguish 10 ms temporal disparity interaural time difference (ITD) use ITD for azimuthal sound source determinations
p.68 fig.3.5a
SOUND TIMING CUES
sounds arrive @ different times to each ear 2 types of temporal disparity
transient (onset / offset) ongoing
can use both which is used ?
p.68 fig.3.5b
SOUND TIMING CUES
implanted miniature speakers decouple disparities
measured orientation ~ ongoing temporal disparity range of 10 - 80 s head movement to target represented by disparity
orientation not ~ transientdisparity
p.69 fig.3.6
SOUND TIMING CUES
anatomical structures
basilar mem. / inner ear frequency coding phase locking intensity coding
cranial nerve VIII
cochlear nuclei NA NM p.71 fig.3.7
NEURAL PATHWAYS FOR SOUND LOCALIZATION
anatomical structures
cochlear nuclei NA NM
NL
LL
higher auditory centers ICC (~ mam. IC) ICX p.71 fig.3.7
NEURAL PATHWAYS FOR SOUND LOCALIZATION
p.72 fig.3.8a
external nucleus (ICX) neuron response
frontal sound
ICX space-specificneurons
AUDITORY SPACE
p.72 fig.3.8b
external nucleus (ICX) neuron response
frontal sound
ICX space-specificneurons
map
AUDITORY SPACE
p.73 fig.3.9
external nucleus (ICX) neuron response
frontal sound
ICX space-specific neurons
map
2nd roving speaker
excitatory (peaks) & inhibitory (trough) regions
AUDITORY SPACE
p.74 fig.3.10
2D field
space-specific neurons are binaural
driven by bilateral stimuli
eg, neuron peak response...
response ILD & ITD specific
ILD ~ 11 dB
ITD ~ 32 s
AUDITORY SPACE
cochlear nuclei ICX
NM time info ITD azimuth phase sensitive intensity sensitive
NA intensity info ILD elevation intensity sensitive
p.71 fig.3.7
AUDITORY SPACE
cochlear nuclei ICX... parallel pathways ?
inject reversible local anesthetics, record from space-specific ICX neuron, sound target stimuli
NM disruption selectivity for time disparity no effect on level disparity
NA disruption selectivity for level disparity no effect on time disparity
AUDITORY SPACE
Jeffress’s neuronal circuit model for encoding time
coincidence detector C fires best with L & R coincident signals
delay line L (eg) codes R delay
p.77 fig.3.11
INTERAURAL TIME DIFFERENCES
Konishi model built on Jeffress for encoding ITD
coincidence detector neuron arrays variable delays
features encodes ITD neurons encode different ITDs but... = output ITD place code p.78 fig.3.12
INTERAURAL TIME DIFFERENCES
does the owl use this mechanism ? ... evidence
anatomy... NM NL (putative neural substrate for model) ipsilateral & contralateral innervation of NL innervation parallel
p.79 fig.3.13
DELAY LINES & COINCIDENCE DETECTORS
does the owl use this mechanism ? ... evidence
physiology... NL neurons phase-lock to binaural stimuli delay asymmetry delay ~ temp. disparity NL neurons = coincidence detectors p.79 fig.3.13
DELAY LINES & COINCIDENCE DETECTORS
does the owl use this mechanism ? ... evidence
anatomy + physiology... each ITD encoded by different delays space-specific neurons NL position info ICX
p.80 fig.3.14
DELAY LINES & COINCIDENCE DETECTORS
does the owl use this mechanism ? ... evidence
anatomy + physiology... each ITD encoded by different delays space-specific neurons NL position info ICX
p.71 fig.3.7
DELAY LINES & COINCIDENCE DETECTORS
ILD (intensity) processing ? ...
poorly understood
v. nuc. lat. lemniscus
spatial organization ~ ICX
bicoordinate signatures not yet elucidated
p.71 fig.3.7
DELAY LINES & COINCIDENCE DETECTORS
integration with other sensory input
ICX optic tectum sensory space maps
optic tectum brain stem
p.84 fig.3.16
sens
orymoto
r
sensory motor
br stem tegmentum 3D map of head position distinct circuits
AUDITORY SPACE