Journal of Neuroscience, Vol 6, 1918-1924, Copyright © 1986 by Society for Neuroscience
The sensitive period for auditory localization in barn owls is limited by age, not by experience
EI Knudsen and PF Knudsen
Early in life, the barn owl passes through a sensitive period during which
it can interpret and make use of abnormal auditory cues for accurate sound
localization. This capacity is lost at about 8 weeks of age, just after the
head and ears reach adult size (knudsen et al. 1984a). The end of the
sensitive period could be triggered either by an age-dependent process or
by the exposure of the auditory system to stable or adult-like cues. To
distinguish between these alternatives, we subjected baby owls to constant
abnormal cues (chronic monaural occlusion) or to frequently changing
abnormal cues (alternating monaural occlusion) throughout the sensitive
period. In the first group of animals (n = 2), one ear was plugged
continuously until 73 or 79 d of age, respectively, and then the earplug
was switched to the opposite ear. Although these animals adjusted sound
localization accuracy during the initial chronic monaural occlusion, they
could not localize sounds at all after the earplug was switched to the
opposite ear, and they remained unable to localize sounds as long as the
opposite ear remained occluded (7 and 27 weeks, respectively). When the
second monaural occlusion was finally removed, both birds localized sounds
with errors that were similar to the errors they exhibited immediately
after removal of the first monaural occlusion. One bird that was 127-d-old
at the time the second earplug was removed corrected its localization
error; the other bird, 250-d-old when the second earplug was removed, did
not.(ABSTRACT TRUNCATED AT 250 WORDS)