Auditory selective attention in cochlear implant users:: An event-related potential study

Introduction: Electrical stimulation of the cochlear nerve by a cochlear implant (Cl) may partly restore hearing function after profound bilateral hearing loss. Cl users often show a reduced speech perception ability in noisy environments, thus indicating an impaired attentive selection mechanism for relevant auditory stimuli. Method: 32-channel event-related potentials (ERPs) were recorded in 5 cochlear implant users for 1. frequent standards, 2. rare frequency deviants, 3. rare auditory novel stimuli (active and passive listening conditions). Besides data on behavioural reactions ("hit rates"), the Nd-attention effect and the P3b-component were analysed to quantify attentive auditory stimulus selection. The mismatch negativity (MMN) was measured to trace preattentive auditory stimulus detection in the passive listening condition. Results: Cl users showed good performance values for rare auditory novels, whereas no overt responses were detected for less salient frequency deviants. A stable Nd-attention effect initiated 60 ms after stimulus onset. The MMN was evident for both, deviant and novel stimuli and indicated the integrity of the preattentive change detection system for novel stimuli and for the less salient deviant stimuli that could not be actively detected. Discussion: The results indicate that even weak auditory changes are preattentively monitored in Cl users but fail to activate attentive stimulus detection. ERP recordings provide a promising tool to objectively characterize auditory perception in Cl users.