The broad objective of the proposed research is to evaluate auditory temporal processing in children with dyslexia, or specific reading disability (RD), a condition that affects 5 to 17 percent of the school-age population, depending on how it is defined. While it is well established that deficits in phonological processing are strongly associated with RD, the underlying source of these deficits is unclear. The primary hypothesis to be tested in the proposal is that children with RD have an associated auditory temporal processing deficit that: 1) extends to non-speech stimuli; 2) is independent of the presence of attention deficit/hyperactivity disorders (ADHD), a behavioral disorder which exhibits substantial comorbidity with RD; and 3) relates directly to performance on phonological processing tasks. This proposal is based on a 2 (RD, no-RD) by 2 (ADHD, no-ADHD) experimental design. In order to test this hypothesis, the investigators propose the following Specific Aims: 1) Replication of seminal temporal order judgment and speech perception studies in a group of children who have been classified using definitions of RD and ADHD that are widely accepted, psychometrically rigorous, and validated in previous studies; 2) Evaluation of the effects of RD and ADHD on auditory temporal, intensity, and frequency processing of non-speech stimuli. The auditory temporal deficit hypothesis predicts that children with RD will be deficient in processing temporal cues, but perform normally when processing intensity and frequency cues in non-speech stimuli. Children with ADHD should not exhibit the dissociation; and 3) Evaluation of the relationship between auditory temporal processing and phonological processing and rate of language processing measures. The auditory temporal deficit hypothesis predicts a strong relationship between language measures and auditory temporal, but not intensity and frequency processing. A second hypothesis concerning the etiology of RD, the speech specific hypothesis, makes different predictions regarding the relationship of phonological processing and rate of processing measures with auditory temporal, intensity, and frequency processing, as well as speech perception. This allows for a comparison of the two hypotheses.
