Auditory processing disorder (APD) in children

Abstract

A proportion of children (~ 2-4%) attending audiology clinics with ‘hearing problems’ turn out on audiometry not to have a sensitivity deficit. Additional children are identified by their teachers and parents as having ‘listening problems’. These children and their carers typically report problems with audi- tory attention and hearing speech in noise. We have been studying whether these problems relate to basic abilities of spectral, temporal and binaural hearing (‘auditory processing’ - AP - tasks), as well as other aspects of audiology, cognition and speech perception. Our main approach is population-based. By studying large, quasi-random samples of 6-11 year old children, we expected to see some children who perform poorly on AP tasks. In this paper we focus on pure tone frequency discrimination. An initial experiment found that poorly performing children tend to be younger and could be either ‘genuine’ poor performers, in that their adaptive test responses were consistent, but their thresholds were elevated, or ‘poor compliers’, in that they responded inconsistently. Further study showed no relation between thresholds on an auditory tone frequency discrimination task and a visual spatial frequency discrimination task, supporting our working hypothesis that AP poor performers may have a specific auditory attention difficulty. We have compared two groups of children receiving a clinical diagnosis either of APD or specific language impairment (SLI), in an attempt to dissociate underpinning causes. However, we found, on our full battery of tests, that both these groups performed poorly across almost all tests and that, surprisingly, their profile was almost identical. This supports the idea that a clinical diagnosis of either a listening or a language problem is determined more by the type of professional making the diagnosis (audiologist or speech/language pathologist) than by the nature of the problem. Neither the performance nor the variability on auditory and visual frequency tasks was correlated in these children, suggesting once again a dissociation between general attention skills in a near identical task and poor auditory performance. Finally, we have conducted auditory phoneme discrimination training in typical children with a view to developing means for treating APD. In contrast to an age-matched, but untrained control group, the trained children improved not only on the trained task, but also on a broad-based test of phonological awareness. Our latest research con rms the training effect for auditory, but not for procedurally equivalent visual stimulation. These results show that auditory learning is a promising means for improving language- and listening-based skills underpinning good communication.