Short-term deafness in childhood linked to 'lazy ear'

Researchers says that the phenomenon of ‘lazy ear’ is similar to amblyopia, also known as ‘lazy eye’–a condition which occurs when visual signals are not transmitted from each eye to the brain during the critical cortex development phase; in the similar manner, the development of the auditory cortex can be affected if it does not receive enough stimulation during the critical periods of child development.

Hearing scientist, Dr. Daniel Polley from the Massachusetts Eye and Ear Infirmary, United States, the senior study author, said, “An analogous problem may exist in the realm of hearing, in that children commonly experience a buildup 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."

Details of study
For the study, Dr Polley and his colleagues from Vanderbilt University, United States, reversibly blocked hearing in one ear of baby rats (two-week-old), juvenile (ear canals tied off at age 4 weeks) and adult rats. The researchers then analyzed how parts of the brain involved with hearing were affected.

They found that sensory connections in the brain were distorted when there was hearing loss for short term in one ear, due to which the deaf ear's representation in the brain was weakened and the open ear's representation strengthened.

The reorganisation was most pronounced in the auditory cortex region, and most evident when hearing loss occurred in infancy than in later life.

Researchers’ conclusions
Dr. Polley concluded, "The good news about amblyaudio is that it is unlikely to be a permanent problem for most people."

"Even if the acoustic signal isn’t improved within the critical period, the mature auditory cortex still expresses a remarkable degree of plasticity. We know that properly designed visual training can improve visual acuity in adult amblyopia patients.

“We are gearing up now to study whether auditory perceptual training may also be a promising approach to accelerate recovery in individuals with unresolved auditory processing deficits stemming from childhood hearing loss," he added further.

While there’s been little to no work done on how common lazy ear is in humans, the researchers think the new study could have important implications in medicine, especially for choosing how aggressively to treat childhood ear infections.

The findings were published by Cell Press in the March 11 issue of the journal Neuron.