What is auditory deprivation? Why does auditory deprivation occur after unilateral deafness?
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What does hearing deprivation mean?
Hearing deprivation refers to the gradual decline of auditory function due to the reduction of acoustic information stimulation. It is common in patients with bilateral symmetrical hearing loss who gain hearing in one ear for a long time. If the hearing loss is compensated, the speech recognition rate of the ear that does not receive hearing compensation will progressively decline over time. The occurrence of this phenomenon is related to the fact that both ears receive asymmetric sound stimulation for a long time and unequal information input. When a patient receives a hearing aid in one ear, the hearing loss is relatively weak. Therefore, the signal from the hearing aid ear is suppressed. Over time, the brain seems to give up processing the information from the non-hearing ear, resulting in auditory deprivation.
Early understanding of the effects of auditory deprivation focused on patients with sensorineural deafness (such as noise-induced, senile, ototoxic deafness, etc.), subject training, hearing aids, and believed that the effects of auditory deprivation Only occurs in middle-aged and elderly patients. Later, it was discovered that the effects of auditory deprivation can also occur in children. However, due to the development of children's auditory system and language system, the side effects of auditory deprivation in non-hearing ears may be suppressed, and their speech recognition rate may not show a decrease, but will increase with time. It gradually increases over time, but the degree of increase should be lower than that of hearing aid ears.
As early as 1984, foreign audiologists discovered that if a patient with symmetrical hearing loss only wears one hearing aid, after a period of time, the speech recognition ability of the non-hearing ear will suffer further damage that is not related to the hearing loss. In audiology, this phenomenon is called delayed auditory deprivation effect. According to statistics, the incidence rate of this phenomenon is as high as 33% between 7 months and 4 years. Therefore, the main reason why patients feel that the listening effect of non-wearable ears is reduced is that the speech resolution of non-wearable ears is reduced, not because of hearing loss.
Therefore, clinically, for patients with bilateral ear damage, if there are no other influencing factors, in order to avoid further decline in speech ability in the ear without a hearing aid, it is recommended to wear hearing aids in both ears.
The relationship between the occurrence of auditory deprivation effect and the degree of hearing loss
Current research suggests a link between the degree of hearing loss and the onset of auditory deprivation effects. The greater the hearing loss, the more likely it is that the auditory deprivation effect will occur. It is generally believed that it is less likely to occur when the average hearing threshold is less than 35 dB. Different researchers have reported different incidence rates of auditory deprivation effects, ranging from 25% to 39%.
The time when the auditory deprivation effect occurs
Because the interval between pre- and post-tests may be months or even years, the exact time when the auditory deprivation effect occurs The time is unclear.
Recovery and prevention of auditory deprivation effects
Some patients with bilateral symmetrical deafness who only wear a hearing aid in one ear also have hearing aids in the other ear. After receiving hearing aids, the speech recognition rate that originally dropped gradually increases and can even return to the original level. This phenomenon attracted the attention of audiologists, and through research it was found that some of the effects of auditory deprivation can indeed be restored. Eriksholm's working group calls this auditory acclimation, which mainly refers to the improvement of auditory function caused by the increase in acoustic information. Not all auditory deprivation effects can be recovered after they occur, and the best measure is to prevent them from happening.
Binaural operation of the auditory system and common intervention methods
1) The auditory system mainly achieves bilateral listening through the following three mechanisms Advantages:
①Binaural integration effect;
②Head shadow effect;
③Squelch effect. The auditory center of the normal auditory system distinguishes and locates sound sources by comparing, processing, and merging the subtle intensity difference (ILD) and time difference (ITD) of sounds between the two ears. Through the binaural integration effect, the two ears are more sensitive to noise. Good discrimination ability improves hearing in quiet and noisy environments through head shadow effect and squelch effect, ultimately achieving binaural listening.
2) Binaural intervention model and intervention advantages:
When intervening in patients with bilateral hearing loss, the principle of bilateral intervention must be adhered to. The current bilateral intervention methods include:
① Bilateral fitting of hearing aids;
② Bilateral cochlear implantation;
③ Bimodal stimulation mode of implanting a cochlear implant on one side and fitting a hearing aid on the contralateral side.
Advantages:
① Delayed auditory deprivation can be avoided;
② Give full play to the advantages of bilateral listening. During binaural intervention, the advantages of bilateral listening are partially retained, so that both ears can Intervention has more advantages than unilateral intervention (unilateral wearing of hearing aids or unilateral cochlear implantation);
③Better speech recognition, especially speech recognition in noise;
④ Better sound source localization ability;
⑤ Better tone recognition and music perception;
⑥ Better auditory memory.