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A
Control
23º prisms
ear
squeak
squeak
Interaural time
difference: 60
μ
s
°
Interaural time difference: 0
Visual location: 0
Apparent visual location: 0
°
μ
s
B
Inject tracer into auditory
region responding to 20 s
R
+20
°
0
°
Inferior colliculus
-20
°
Caudal
Rostral
ICX
C
Optic tectum
Optic tectum
C
Projection from Auditory Map Adjusts to Match Visual Map
Control
23º prisms
FIGURE 9.19 Remapping in the owl auditory pathway. A. Barn owls were reared with prismatic goggles
that shifted the visual field by 23°. In control animals, a squeaking mouse in front of the owl would appear
at 0°, and the sound would reach both ears simultaneously (0 msec interaural time difference). With prisms
in place, a squeaking mouse at 23° to the left would appear at 0°, and the squeak would reach the left ear first
(60 msec interaural time difference). B. A tracer was injected into the auditory nucleus (ICC, central nucleus
of the inferior colliculus) that encodes the ITD of the sound stimulus (left). The IC relays this information to
the ICX where the map of auditory space is assembled. ICX then projects to the optic tectum where visual
and auditory information is first integrated (right). C. In control animals, the projection from a region in ICC
that responds to a 20 ms interaural time difference projects to a narrow region in the ICX (and ICX then pro-
jects to an optic tectal location that responds to visual cues about 8 degrees from the midline). In prism-reared
animals, ICC projects to a more rostral region of ICX. Thus, a new projection is formed within the auditory
space map which compensates during prism rearing such that sound and sight can once again be integrated.
(Adapted from DeBello et al., 2001)
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