Age Related Changes in Central Auditory Processing
Otolaryngology - Open Journal
Auditory processing is the processing of information perceived through the auditory sense. Auditory discrimination, lateralization and localization of sound, auditory pattern recognition, temporal aspects including integration, resolution, ordering and masking, auditory performance decrements with competing or/and degraded acoustic signal are the six behavioral processes involved in auditory processing as given by American Speech and Hearing Association (ASHA). 1 Auditory processing disorder
... D) leads to poor input and integration of the information presented verbally. APD has been estimated to occur in 2-3% of children 2 and in 10-20% of adults 3 CENTRAL AUDITORY PROCESSING IN CHILDREN The APD has been increasingly reported in children. The impairment in the auditory perception might be the cause for problems like learning disability. 4 Still the disorder has not been recognized as an entity affecting the school aged children (DSM-IV-TR, American Psychiatric Association, 2000). According to Carter and Musher, 5 auditory-specific perceptual deficit would be the base for learning and reading disabilities. According to Mishra, 6 children with APD have more difficulties in listening situation that are more complex like in the presence of noise. One of the possible reasons for this has been reported to the insufficient inhibition of the medial olivo-cohlear (MOC). Oto-acoustic emissions (OAE) has been used to study this. But, OAE was reported not to be stronger tool to study this effect. Hence, the efferent pathway in these children are poorly studied. In children, APD is not due to a neurogenic disorder largely, but due to an idiopathic central auditory nervous system dysfunction. 7 However, it has been stated that the central auditory nervous system might be diseased, disorganized or maturationally delayed. 8 The etiology for APD might also be Bilirubin toxicity. 9 Hence, the etiology still remains under controversy. Children with APD have normal intelligence, with or without hearing impairment. 10 These children exhibit behaviors similar to that of children having attention deficit and hyperactive disorder (ADHD), 11 learning disability (LD). 12 Keith 13 has listed out the typical profile of children with APD. This includes mostly male children, having pure tone thresholds at normal range, poor and inconsistent response to the auditory stimuli, decreased attention span, fatigue for auditory information, more distractible, poor localization skills, and difficulty in following complex verbal commands, poor auditory memory and increased reaction time for auditory information. Screening tests are available which initially helps in screening out children with APD from other children. Those children who fail in the screening test undergo the diagnostic evaluation for each processing skills as listed by ASHA. 1 The management includes auditory training specific to the impairment and environmental modifications. CENTRAL AUDITORY PROCESSING IN ADULTS Intact peripheral, central and cognitive processes are prerequisites for good auditory processing abilities. Hence, in older adults as there is a definite decline in peripheral, central and cognitive SUMMARY Auditory processing is crucial to perceive and process verbal information in our day to day life. APD are common among children. As age increases, there is a general decline in the auditory processing abilities which is reflected as APD in older adults. In older adults, APD could be the result of one or the combination of the following: peripheral changes in the auditory system, cognitive decline and the changes in the central auditory processing. Knowledge about APD is necessary among professionals like audiologist, otolaryngologist, speech language pathologist, neurologist, special educator and school teachers to screen, diagnose and to rehabilitate them appropriately.