Scientists have discovered that children who suffer temporary deafness can develop a “lazy ear” that affects them long-term.
The condition may be similar to having a “lazy eye”, whereby balanced visual signals are not transmitted from each eye during a crucial period of brain development.
The eye condition is known as amblyopia. With hearing, a blockage may degrade the quality of acoustic signals to the brain.
Dr Daniel Polley, who led the new research at the Massachusetts Eye and Ear Infirmary in Boston, the US, said: “An analogous problem may exist in the realm of hearing, in that children commonly experience a build-up of viscous fluid in the middle ear cavity, called otitis media with effusion, which can degrade the quality of acoustic signals reaching the brain and has been associated with long-lasting loss of auditory perceptual acuity.”
In a laboratory study, Dr Polley’s team reversibly blocked hearing in one ear of infant, juvenile and adult rats.
The scientists then looked at how parts of the brain involved with hearing were affected.
Temporary hearing loss in one ear distorted sensory connections in the brain. As a result, the “deaf” ear’s representation in the brain was weakened and the “open” ear’s representation strengthened.
The re-organisation was most pronounced in the auditory cortex region, and most evident when hearing loss occurred in infancy.
Badly programmed connections in the developing auditory cortex may underlie “amblyaudio” in the same way that a wrongly wired visual cortex contributes to “amblyopia”, said the researchers writing in the journal Neuron.