Development of a monosyllabic adaptive speech test for the identification of central auditory processing disorder.

Abstract

Auditory processing is the ability of the brain to manipulate and utilise the neural output of the ear based on the frequency, intensity, and temporal features of the incoming acoustic signal. An auditory processing disorder (APD) is a deficiency in this ability. One category of tests that examine auditory processing ability are the various versions of the "filtered words test" (FWT), whereby a monaural, low-redundancy speech sample is distorted by using filtering to modify its frequency content. Due to the richness of the neural pathways in the auditory system and the redundancy of acoustic information in spoken language, a normal listener is able to recognize speech even when parts of the signal are missing, whereas this ability is often impaired in listeners with APD. One limitation of the various versions of the FWT is that they are carried out using a constant level of low-pass filtering (e.g. a corner frequency of 1000 Hz), which is prone to ceiling and floor effects. The purpose of this study was to counter these effects by modifying the FWT to use a computer-based adaptive procedure, to improve the sensitivity of the test over its constant-level counterparts. The University of Canterbury Monosyllabic Adaptive Speech Test (UC MAST) was performed on 23 normal adults, and 32 normal children (7 to 11 years of age). The child participants also underwent the SCAN-C test for APD in Children (Revised). Findings indicated a significant maturational effect on the UC MAST. Adult participants performed significantly better on the UC MAST in comparison to the child participants. In addition, adult participants performed the UC MAST more reliably than their younger counterparts. No correlation was found between performance on the UC MAST and SCAN-C test. The development of the UC MAST is discussed and the clinical implications of the findings are explored.