Active and Passive Processing of Novel Sounds in Cochlear-Implanted Subjects: Event-Related Potentials of Bottom-Up and Top-Down Processes - OMAI 2018- The 10th International Symposium on Objective Measures in Auditory Implants

Irina Schierholz ^1,2 Constanze Schönermark ¹ Bruno Kopp ³ Esther Ruigendijk ^2,4 Andrej Kral ^1,2,5 Andreas Buechner ^1,2

¹Department of Otorhinolaryngology, Hannover Medical School, Hannover, Germany
²Cluster of Excellence, "Hearing4all", Germany
³Department of Neurology, Hannover Medical School, Hannover, Germany
⁴Department for Dutch Studies, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
⁵Institute for AudioNeuroTechnology (VIANNA), Hannover Medical School, Germany

Background: To effectively process novel acoustic stimuli from the environment, a balance between bottom-up and top-down processes is required. This not only allows to appropriately respond to changes in the environment, but also serves as a control mechanism for learning.

Objectives: The study aims at evaluating the interaction between bottom-up and top-down processes in cochlear-implant (CI) patients, and its influence on CI performance.

Methods: 27 post-lingually deafened CI patients and 27 normal-hearing (NH) listeners performed a three-stimulus oddball paradigm, including standard (p=70%), target/deviant (p=15%), and novel and unique environmental (p=15%) sounds. Participants performed the paradigm actively (attention to tones) and passively (no attention to tones). During the task, behavioral responses were recorded together with high-density electroencephalography (EEG) activity.

Results: Initial data point to an attenuated sensory processing (reduced N1 amplitudes) in CI patients compared to NH controls, whereas the higher-order target processing (Target-P3) was comparable between groups. Both, CI patients and NH controls show a bottom-up-related early Novelty-P3 and a top-down-related late Novelty-P3. As expected, in both groups the late Novelty-P3 was reduced in the passive condition. Group differences show up for the amplitudes of the early, but not the late Novelty-P3.

Conclusion: The current study enables the objective comparison of active and passive processing of novel acoustic stimuli in CI patients. The observed reduction in N1 and early Novelty-P3 amplitudes suggests an impairment in bottom-up processes in CI subjects compared to NH controls. The comparable late Novelty-P3, however, suggests preserved top-down processing mechanims.