What happens to sound localization if you experience hearing loss during development? Approximately 80% of children experience some form of hearing loss before the age of 2. This is commonly caused by ‘glue ear’, which often produces a hearing loss in one ear. Sound localization in the horizontal plane typically relies on differences between the sound heard by each ear (so-called binaural cues) and is therefore impaired by this type of hearing loss. This paper shows that the brain (primary auditory cortex) can adapt to a developmental hearing loss in one ear without compromising its ability to use normal hearing if it is restored later in life.
In particular, the brain adapts by learning to rely more on the sound heard by the ear with normal hearing. This is possible because the pinna produces subtle changes in the quality of a sound that vary with direction (known as spectral cues), and the brain can use this to locate sounds using a single ear. Surprisingly, though, if we restore normal hearing later in life, the brain rapidly reverts to relying more on the differences between the sound heard by each ear. This means that the brain can learn different strategies for sound localization and switch between them depending on the circumstances.
Action on Hearing Loss and the Wellcome Trust wrote excellent articles on this research intended for non-scientists [AHL article, WT article].
Keating P, Dahmen JC, King AJ (2013a) Context-specific reweighting of auditory spatial cues following altered experience during development. Current Biology 23:1291-1299.
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