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Hyperactivity in the auditory midbrain after acoustic trauma: dependence on cochlear activity.
1The Auditory Laboratory, Discipline of Physiology, School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia. hmulders@cyllene.uwa.edu.au
Neuroscience
|August 25, 2009
Summary
Acoustic trauma causes hearing loss and hyperactivity in the brain
Area of Science:
- Neuroscience
- Auditory System Research
- Brain Plasticity
Background:
- Adult mammalian brain plasticity occurs after peripheral nerve damage and in the auditory system.
- Acoustic trauma can lead to hyperactivity in central auditory nuclei like the inferior colliculus.
- This hyperactivity is thought to be centrally generated due to altered neural input.
Purpose of the Study:
- To investigate the acute and chronic effects of acoustic trauma on cochlear sensitivity.
- To examine the development of hyperactivity in the inferior colliculus following acoustic trauma.
- To determine if established hyperactivity in the inferior colliculus relies on cochlear neural activity.
Main Methods:
- Guinea pigs were exposed to acoustic trauma (10 kHz tone at 124 dB SPL for 1 hour).
- Cochlear sensitivity and inferior colliculus activity were measured at various recovery times.
- Cochlear ablation and treatments blocking primary afferent activity were used to assess dependency.
Main Results:
- Acoustic trauma caused a small, permanent, frequency-restricted cochlear threshold loss.
- This hearing loss was accompanied by hyperactivity in corresponding frequency areas of the inferior colliculus.
- Hyperactivity in the inferior colliculus disappeared after cochlear ablation or blocking of primary afferent firing.
Conclusions:
- Central hyperactivity in the inferior colliculus following acoustic trauma depends on ongoing neural activity from the cochlea.
- This dependency suggests central hyperexcitability in the CNS, leading to increased neuronal firing in response to normal peripheral spontaneous activity.
- The findings highlight the link between peripheral sensory input and central auditory processing plasticity.
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