The Journal of Neuroscience, February 1, 2003, 23(3):1059
Adaptive Plasticity in the Auditory Thalamus of Juvenile Barn
Owls
Greg L.
Miller and
Eric I.
Knudsen
Department of Neurobiology, Stanford University School of Medicine,
Stanford, California 94305-5125
Little is known about the capacity of the thalamus for
experience-dependent plasticity. Here, we demonstrate adaptive changes in the tuning of auditory thalamic neurons to a major category of sound
localization cue, interaural time differences (ITDs), in juvenile barn
owls that experience chronic abnormal hearing. Abnormal hearing was
caused by a passive acoustic filtering device implanted in one ear that
altered the timing and level of sound differently at different
frequencies. Experience with this device resulted in adaptive,
frequency-dependent shifts in the tuning of thalamic neurons to ITD
that mimicked the acoustic effects of the device. Abnormal hearing did
not alter ITD tuning in the central nucleus of the inferior colliculus,
the primary source of input to the auditory thalamus. Therefore, the
thalamus is the earliest stage in the forebrain pathway in which this
plasticity is expressed. A visual manipulation, chronic prismatic
displacement of the visual field, which causes adaptive changes in ITD
tuning at higher levels in the forebrain, had no effect on thalamic ITD tuning. The results demonstrate that, during the juvenile period, auditory experience shapes neuronal response properties in the thalamus
in a frequency-specific manner and suggest that this thalamic
plasticity is driven by self-organizational forces and not by visual instruction.
Key words:
medial geniculate nucleus; auditory experience; Hebbian learning; self-organization; auditory cortex; inferior
colliculus
Copyright © 2003 Society for Neuroscience 0270-6474/03/2331059-07$05.00/0