Phonemic Regression: Why it takes time to relearn forgotten sounds


Phonemic Regression

Max Stanley Chartrand Ph.D.,

As a geriatrician I've noticed that some of my hearing impaired patients can still hear reasonably well for about a half-hour after removing their hearing aids. How is this possible? --- Dr. K.O.

This question relates nicely to plasticity of the human brain and its role in rehabilitation. When one's hearing deteriorates, for a period of time they will compensate through subconscious speechreading, context, and phoneme substitution. Over time, though, compensation adds stress to one's life, deep-seated emotional and psychosocial responses set in to the point that most observers might think of the hearing impaired individual as ''aloof,'' ''not all there,'' or ''not paying attention.''

By the time progressive hearing loss has deteriorated to the point of affecting personal relationships, speech discrimination ability plummets and social isolation sets in. In this case, a slight decline in thresholds can make one appear to go from ''hearing'' to ''not hearing'' almost overnight!

Conversely, when everyone finally decides the hearing impaired person is really a good guy with a bad hearing loss, the first obstacle they bump into is Phonemic Regression. This central auditory condition is often exposed when wearing hearing aids for the first time. Even with appropriate amplification, the patient may still have tremendous difficulty understanding speech for quite a while.

The rehabilitative timeline to overcome this delay varies tremendously, but may last from 90 to 120 days of continuous hearing aid use before the neurological system of the brain ''relearns'' forgotten sounds of speech. This requires patience and understanding on everyone's part.

Once the patient acclimates to hearing aids, a more normal communicative lifestyle can occur. The portion of the brain dedicated to hearing and communication often becomes able to process sound closer to the ''normal'' format after the brain is accustomed to the sound, thanks to neural plasticity.

However, when the patient takes their hearing aids off for a short period of time, they may enjoy the ability to again compensate somewhat for the loss of hearing. That's because the ''memory'' of sound and utilization of acoustic clues is still fresh. But should our hypothetical patient only wear their hearing aids on Sundays, for instance, they will surely continue to suffer from Phonemic Regression, preventing their neurological system from ever adapting to the world of sound.

Using myself as an example to the extreme, I am bilaterally and profoundly deaf. But with my cochlear implant of 10 years, people tend to think of me as relatively ''normal'' in speech and social interaction. However, if I remove my implant speech processor for, say, two weeks' time, my speech would soon deteriorate into ''deaf speech'' and everyday social situations will become unbearable.

Time and the deprived ear can create havoc on one's happiness and social well-being in ways few can imagine. Likewise, time and appropriate hearing correction can restore life and enjoyment in ways one would least expect until they get it all back again.

About the author:

Max Stanley Chartrand Ph.D., Health & Human Servics/Research in Communicative Disorders, serves as Director of Research for DigiCare Hearing Research & Rehabilitation, Rye, CO. He is author of many books and articles on hearing health topics, and is an internationally recognized professional educator. Correspondence: