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Updated: Mar 11, 2026
Laser-guided Neuronal Tracing In Brain Explants
Published on: November 25, 2015
Midbrain Frequency Representation following Moderately Intense Neonatal Sound Exposure in a Precocious Animal Model
Lisa M D'Alessandro1, Robert V Harrison2
1Department of Physiology, University of Toronto, Toronto, Canada M5S 1A8; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada M5S 3G9; The Auditory Science Laboratory, Program in Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Canada M5G 1X8.
Abstract:
Auditory brain areas undergo reorganization resulting from abnormal sensory input during early postnatal development. This is evident from studies at the cortical level but it remains unclear whether there is reorganization in the auditory midbrain in a species similar to the human, that is, with early hearing onset. We have explored midbrain plasticity in the chinchilla, a precocious species that matches the human in terms of hearing development. Neonatal chinchillas were chronically exposed to a 2 kHz narrowband sound at 70 dB SPL for 4 weeks. Tonotopic maps in inferior colliculus (central nucleus) were defined based on single neuron characteristic frequency. We hypothesized an overrepresentation of the 2 kHz region of the maps. However, we observed a significant decrease in the proportion of neurons dedicated to the 2 kHz octave band and also away from the exposure frequency at 8 kHz. In addition, we report a significant increase in low frequency representation (<1 kHz), again a change to tonotopic mapping distant to the 2 kHz region. Thus in a precocious species, tonotopic maps in auditory midbrain are altered following abnormal stimulation during development. However, these changes are more complex than the overrepresentation of exposure related frequency regions that are often reported.
