The potential use of auditory brainstem response (ABR) with sensory gating function to identify auditory processing disorder (APD) in children

Abstract

Auditory Processing Disorder (APD) is characterized by a difficulty to perceive sound due to inability to accurately process the auditory information. Several issues have been debated about APD including; (i) the conceptualization on the origin of APD, especially on the involvement of top-down processing of cognitive function in APD, (ii) the absence of gold standard assessment for APD, and (iii) the limitations in the existing APD assessments to assess younger children. To address the above-mentioned issues, this study aimed; (i) to examine the influence of attention on auditory processing performance in children with and without APD, including those with co-existing attention deficit, and (ii) to explore the potential use of Auditory Brainstem Response (ABR) test with Stroop Task to objectively identify APD. The ABR test with Stroop task in this study integrates the role of top-down processing through sensory gating pathway that possibly related to auditory processing. This thesis was divided into three main studies. In Study 1, 94 children (8 to 11 years old) with normal hearing, intelligent quotient and working memory were recruited. These children were divided into two main groups, normal and APD group, based on their performance on five APD assessments; (i) Dichotic Digit Test, (ii) Gap-in-noise Test, (iii) Pitch Pattern Sequence Test, (iv) Masking Level Difference Test and (v) Digit Triplet Test. The children in each group were further categorized into three sub-groups based on their attention status - normal attention, suspected with Attention Deficit Disorder (ADD), and suspected with Attention Deficit Hyperactivity Disorder (ADHD), by using the Swanson, Nolan and Pelham, Fourth Edition (SNAP-IV) questionnaire. In Study 2 and 3, a counting Stroop Task with three Stroop conditions (congruent, incongruent and neutral) was used. ABRs were recorded in two general conditions - with and without cognitive task. For ABRs with cognitive task, the ABR test was conducted whilst the participant performing Stroop Task in three conditions - congruent, incongruent, and neutral. The Stroop Task was conducted to generate cognitive interference, which would then activate sensory gating process. The ABR waveforms hypothetically would be affected from the effect of neural suppression as a result of sensory gating. In Study 1, the results indicate that, patient with attention problems (suspected with ADD or ADHD) may also has problem with their auditory processing skills that include significantly poor performance in binaural integration, temporal resolution and temporal ordering skill. In Study 2, two patterns of ABR with Stroop Task results were observed. Among children without APD and no attention problem, a reduction in wave V amplitude during ABR recording with cognitive interference in comparison with those without cognitive interference (a negative downward pattern) was observed. This is consistent with neural suppression as a result of normal sensory gating abilities. For children without APD but with attention deficit (ADD or ADHD), minimal reduction in wave V amplitude was observed suggesting a decline in sensory gating abilities. On the contrary, no reduction in the ABR wave V amplitude (positive upward pattern) was observed among children with APD especially those with attention problem (ADD or ADHD) suggesting absence of neural suppression that could be due to poor sensory gating abilities. In Study 3, a significant relationship were found between sensory gating and majority of auditory processing skills including; (i) binaural integration, (ii) binaural interaction, (iii) temporal resolution, and (iv) temporal sequencing. In summary, attention deficit may influence the auditory processing abilities and the ABR conducted with Stroop task has the potential to be used as a tool to identify children with APD.