studying barn owls in the laboratory sound intensity cues sound timing cues

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#08: PREY LOCATION IN BARN OWLS II

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#08: PREY LOCATION IN BARN OWLS II

owls are auditory & visual animals

systems integrated locate source of stimulus

recall experimental set up...

VISUAL CALIBRATION OF THE AUDITORY WORLD

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

monaural occlusion experiments location error elevation azimuth (minor)

2 critical observations...

p.67 fig.3.4

1. correction after weeks ? young owls yes old owls less

2. remove occlusion error persists, but... corrected / time

BEHAVIORAL ANALYSIS

monaural occlusion experiments location error elevation azimuth (minor)

p.67 fig.3.4

other cues... vision ? prisms correct ~ visual offset

BEHAVIORAL ANALYSIS

hypothesis: vision guides evaluation of auditory cues raised young (sensitive) owls with prisms do owls adjust auditory targeting ~ visual input ?

results: normal visual shift only ...auditory shift

p.83 fig.3.15

shift remains

VISUAL vs AUDITORY STIMULI

developmental regulation of shift 7 mo, shift ~ 20° adults, shift only a few °

results: normal visual shift only ...auditory shift

p.83 fig.3.15

shift remains

VISUAL vs AUDITORY STIMULI

convergence: azimuthal (ITD) & horizontal (ILD) info in ICX auditory & visual information in optic tectum

receptive fields of optic tectum aligned in columns

p.84 fig.3.16

NEURAL CORRELATES OF PLASTICITY

receptive fields of optic tectum aligned in columns

p.85 fig.3.17

(A) multimodal space map in optic tectum

(B) prisms shift visual receptive field

(C) + 8 wks... auditory receptive field shifts

NEURAL CORRELATES OF PLASTICITY

azimuthal plane... expect horizontal shift in auditory perceptive fields induced by abnormal visual cues accompanied by ~ shift in ITDs of tectal neurons

p.85 fig.3.17

what causes this shift in alignment ?

NEURAL CORRELATES OF PLASTICITY

adaptation of ITD map ~ visual experience

p.86 fig.3.18

(A) optic tectum neurons normal visual tuning @ 0 s (center of field) 8 wks of prism visual tuning @ ~ 50 s

(B) optic tectum neuron arrays shifts follow pattern of visual experience

NEURAL CORRELATES OF PLASTICITY

ITD tuning curves in ICX neurons of prism-reared owls

shaded = normal & learned

2 stages of ITD adjustment

p.87 fig.3.19

(A) initial: az.= 0°, ITD = 0 s(B) transition: az., ITD (C) shift: az.= 23°, ITD = 40 s

NEURAL CORRELATES OF PLASTICITY

visual experience modification of auditory localization

young < juvenile > adult 60 days 200

monaural occlusion displacement prisms

optic tectum ITD tuning

(A) juveniles: sensitive to prisms

(B) adults: naïve – insensitive to prisms () experienced – sensitive ()

p.88 fig.3.20

SENSITIVE PERIOD FOR CALIBRATION

visual horizontal displacement auditory space maps optic tectum ITD map

auditory space maps: ICC ICX op.tectum

p.90 fig.3.21

SITES OF ADAPTIVE PLASTICITY

auditory space maps: ICC ICX op.tectum

prism reared owls: ICC map normal ICX map shifted ~ optic tectum shift anatomy

normal ICC-ICX input additional ICC-ICX input to shifted ITD region accounts for recovery during lifetime normal accounts for rapid readjustment prisms again

p.90 fig.3.21

SITES OF ADAPTIVE PLASTICITY

cellular mechanisms ?

involves: glutamate - excitatory neurotransmitter glutamate receptor - NMDA receptor

p.90 fig.3.21

SITES OF ADAPTIVE PLASTICITY

experiments identified 2 critical auditory cues... time info, ITD NM azimuthal information intensity info, ILD NA elevation information parallel processed, cochlear nuclei ICX

ITD & ILD information ICX space-specific neurons each neuron receptive field in auditory space emergent / unique property (not signal addition)

coordinated auditory & visual world visual tuning of auditory space young / juvenile > adult

SUMMARY

multimodal maps of sensory world in optic tectum auditory maps can shift register with visual young < juvenile > adult realignment by new ICC ICX connections connections persistent

SUMMARY