This report provides an overview of many research projects conducted by the Dallas Cochlear Implant Program, a joint enterprise between The University of Texas at Dallas, The University of Texas Southwestern Medical Center and Children’s Medical Center. The studies extend our knowledge of factors influencing communication outcomes in users of cochlear implants. Multiple designs and statistical techniques are used in the studies described including both cross sectional and longitudinal analyses. Sample sizes vary across the studies and many of the samples represent large populations of children from North America. Multiple statistical techniques are used by the team to analyze outcomes. The team has provided critical information regarding electrode placement, signal processing, and communication outcomes in users of cochlear implants.

It has been hypothesized that one cause of children's language disorders is poor temporal processing. When children are not able to follow the rapid modulations in the speech signal that cue phonemic information, development of critical language concepts might be missed. It has also been suggested that intensive auditory training on a hierarchy of temporal tasks may significantly improve language processing. Temporal processing was evaluated in children with normal language and those with language impairment who were enrolled in an intensive computerized auditory training program. The psychoacoustic tasks were aimed at evaluating the ability to (1) process signals arriving in very close succession, and (2) discriminate signals changing rapidly in frequency. Three dependent variables included thresholds for brief tones presented in three conditions: quiet, just before a masker, and simultaneously with a masker. A fourth dependent variable was the minimum detectable change in a tone sweeping up in frequency. Despite minimal changes in performance over the five-week period, there were overlaps in performance on all tasks between the groups suggesting a complex relationship between temporal processing and language development. Children with language impairment who had better performance on the masking and frequency discrimination tasks showed greater success on the auditory training program.

We administered a battery of both behavioral and electrophysiologic measures to a pair of fraternal twin girls, one of whom exhibited symptoms consistent with an auditory processing disorder. Both twins were within normal limits on standardized tests of cognitive and language skills. Basic audiometric measures, as well as behavioral tests of simultaneous masking, backward masking, gap detection, and frequency-sweep discrimination, showed little difference between the twins. Significant differences, however, were evident on event-related potentials (ERPs) in response to both within-channel and across-channel gap detection tasks. Substantial differences were also noted for ERPs to both linguistic and nonlinguistic targets in dichotic listening paradigms. The pattern of electrophysiologic results was consistent with a deficit in the efficiency of interhemispheric transfer of auditory information. A possible reason for the greater effectiveness of electrophysiologic over behavioral measures is discussed.