Divided-attention and directed-attention listening modes in children with dichotic deficits: an event-related potential study.

Dichotic listening (DL) procedures are commonly employed in the evaluation of auditory processing in children. Review of the various clinical tests reveals considerable diversity in both the signals employed and their mode of administration. The extent to which other non auditory-specific factors influence the test outcome is often difficult to determine. Individual differences in memory, attention, facility with test stimuli, and report strategy are always of potential concern in the interpretation of results. In the present study, we examined behavioral and electrophysiological (ERP) responses for 20 children during two DL tasks. Two groups of children were evaluated. One group was comprised of children who showed substantial ear differences on clinical measures of DL; the other group showed no such deficits and served as age-matched controls. In one of the DL tasks, participants monitored dichotic stimuli using the divided-attention (unfocused) mode. In the other DL task, a directed-attention (focused) mode was employed. Both tasks involved simple "same-different" judgments for real words presented in a basic reference-probe paradigm. We purposefully sought an easy DL task in order to minimize the number of extra-auditory factors influencing their performance. For control purposes, a diotic procedure involving the same stimuli was also included. Results showed that the amplitude of the elicited late-positive component (LPC) was smaller and prolonged in latency for the group of poor listeners as compared to the control group. This finding occurred only when dichotic stimuli were presented in the divided-attention mode. When participants directed their attention to a single side, or when listening in a diotic mode, the LPC for both groups was more similar. Group differences in the N400 component were apparent for both listening tasks. Results are discussed in relation to an inability of some children to inhibit processing of unattended auditory information. Implications for the clinical administration of dichotic listening tests are also discussed.