Journal of Neuroscience, Vol 9, 3306-3313, Copyright © 1989 by Society for Neuroscience
Vision calibrates sound localization in developing barn owls
EI Knudsen and PF Knudsen
Department of Neurobiology, Stanford University School of Medicine, California 94305.
This study demonstrates that continuous exposure of baby barn owls to a
displaced visual field causes a shift in sound localization in the
direction of the visual displacement. This implies an innate dominance of
vision over audition in the development and maintenance of sound
localization. Twelve owls were raised from the first day of eye opening
wearing binocular prisms that displaced the visual field to the right by 11
degrees, 23 degrees, or 34 degrees. The prisms were worn for periods of up
to 7 months. Consistent with previous results (Knudsen and Knudsen, 1989a),
owls reared with displacing prisms did not adjust head orientation to
visual stimuli. While wearing prisms, owls consistently oriented the head
to the right of visual targets, and, as soon as the prisms were removed,
they oriented the head directly at visual targets, as do normal owls. In
contrast, prism-reared owls did change head orientation to sound sources
even though auditory cues were not altered significantly. Birds reared
wearing 11 degrees or 23 degrees prisms oriented the head to the right of
acoustic targets by an amount approximately equal to the optical
displacement induced by the prisms. Birds raised wearing 34 degrees prisms
adjusted sound localization by only about 50% of the optical displacement.
Thus, visually guided adjustment of sound localization appears to be
limited to about 20 degrees in azimuth. The data indicate that when
confronted with consistently discordant localization information from the
auditory and visual systems, developing owls use vision to calibrate
associations of auditory localization cues with locations in space in an
attempt to bring into alignment the perceived locations of auditory and
visual stimuli emanating from a common source. Vision exerts this
instructive influence on sound localization whether or not visual
information is accurate.
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