The Journal of Neuroscience, May 1, 2000, 20(9):3469-3486
A Site of Auditory Experience-Dependent Plasticity in the Neural
Representation of Auditory Space in the Barn Owl's Inferior
Colliculus
Joshua I.
Gold and
Eric I.
Knudsen
Department of Neurobiology, Stanford University, Stanford,
California 94305-5125
The barn owl's optic tectum contains a map of auditory space that
is based, in part, on a map of interaural time difference (ITD).
Previous studies have shown that this ITD map is shaped by auditory
experience. In this study, we investigated whether the plasticity
responsible for experience-induced changes in ITD tuning in the tectum
occurs within the tectum itself or at an earlier stage in the auditory pathway.
We altered auditory experience in young owls by implanting an acoustic
filtering device in one ear that caused frequency-dependent changes in
sound timing and level. We analyzed the representation of ITD in normal
and device-reared owls in two nuclei in the ascending pathway: the
external nucleus of the inferior colliculus (ICX), the primary source
of ascending auditory input to the tectum, and the lateral shell of the
central nucleus of the inferior colliculus (ICCls), the primary source
of input to the ICX. In the ICX, device rearing caused adaptive,
frequency-dependent changes in ITD tuning, as well as changes in
frequency tuning. These changes in tuning were similar to changes that
occurred in the optic tectum in the same owls. In contrast, in the
ICCls, tuning for ITD and frequency was unaffected by device rearing.
The data indicate that plasticity at the level of the ICX is largely
responsible for the adaptive adjustments in ITD tuning and frequency
tuning that are observed in the optic tecta of owls raised with
abnormal auditory experience.
Key words:
Tyto alba; sound localization; hearing
impairment; development; sensory experience; superior colliculus; inferior colliculus
Copyright © 2000 Society for Neuroscience 0270-6474/00/2093469-18$05.00/0