Mild to moderate forms of hearing loss can have a lasting impact on the auditory cortex, according to findings by researchers at New York University's Center for Neural Science. The study, which is the first to show central effects of mild hearing loss, appears in the latest issue of the Journal of Neuroscience.
The study was authored by NYU scientists Han Xu, Vibhakar Kotak, and Dan Sanes, working in NYU's Center for Neural Science.
Previously, researchers had been unable to conclusively determine the neurological impact of mild forms of hearing loss, which occurs when the pathway by which sound reaches the cochlea is disrupted--such as is experienced with middle ear infections during childhood. The NYU study sought to address this question in an animal model by measuring the impact of conductive hearing loss without injury to the cochlea.
The researchers induced hearing loss in the subjects during early development, then measured the functionality of neural connections within the subjects' auditory cortex, which processes all acoustic cues.
The results showed that the projection to auditory cortex had changed following a brief period of hearing loss. Specifically, the researchers found that the synaptic response of the auditory neurons adapted more rapidly and to a greater extent. They also found that auditory cortex neurons became more sensitive to stimulation.
These findings indicate that auditory cortex function is susceptible to relatively modest loss of hearing loss during development and suggest that perceptual deficits may be linked to alterations in the central nervous system.