title: Balancing current levels in children with bilateral cochlear implants using electrophysiological and behavioral measures.
abstract: Children have benefited from bilateral cochlear implants (CIs) over unilateral CIs despite often missing important periods in bilateral auditory development. This suggests a remarkable perceptual ability by children to "work around" abnormal changes in the auditory pathways. Nonetheless, these children rely primarily on interaural level differences as interaural timing cues are more difficult to access or detect. Mismatched levels provided to the two implants could distort interaural level cues thus compromising the benefits of bilateral CI use. We asked whether "balanced" or "centered" perception of bilateral input can be predicted by physiological or behavioral measures. Twenty-four children who had used unilateral CIs for 9.21 ± 2.66 years prior to bilateral implantation participated. "Balanced bilateral levels" were identified by responses occurring with a probability of 50% on the right side of the head and 50% on the left in a two choice lateralization task. Loudness judgments of current presented unilaterally by each implant were measured on a continuous visual scale. Maximum wave eV amplitudes were evoked unilaterally by each implant and matched amplitudes were identified. Balanced bilateral levels were predicted within 10 Clinical Units (CU) in 9 of 13 (69%) children using matched wave eV amplitudes. Bilaterally balanced levels were reasonably predicted by similar loudness judgments (<10% difference between CIs) in only 6 of 13 (46%) children. Results indicate that matching amplitudes of physiological responses can produce a balanced perception of bilateral input despite unilateral strengthening of the auditory pathways and can potentially be used clinically to provide a first approximation of balance/centered levels.
authors.affiliation: Archie's Cochlear Implant Laboratory, The Hospital for Sick Children, 555 University Avenue, Room 6D08, Toronto, Ontario, M5G 1X8, Canada; Department of Otolaryngology-Head and Neck Surgery, University of Toronto, St. George Campus, 190 Elizabeth St, Rm 3S438, RFE Building, Toronto, Ontario, M5G 2N2, Canada. Electronic address: karen.gordon@utoronto.ca.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Gordon
authors.affiliation: Archie's Cochlear Implant Laboratory, The Hospital for Sick Children, 555 University Avenue, Room 6D08, Toronto, Ontario, M5G 1X8, Canada. Electronic address: pabbasal@uwo.ca.
authors.forename: Parvaneh
authors.initials: P
authors.lastname: Abbasalipour
authors.affiliation: Archie's Cochlear Implant Laboratory, The Hospital for Sick Children, 555 University Avenue, Room 6D08, Toronto, Ontario, M5G 1X8, Canada; Department of Otolaryngology-Head and Neck Surgery, University of Toronto, St. George Campus, 190 Elizabeth St, Rm 3S438, RFE Building, Toronto, Ontario, M5G 2N2, Canada. Electronic address: blake.papsin@utoronto.ca.
authors.forename: Blake C
authors.initials: BC
authors.lastname: Papsin
mesh_terms: D001306:Auditory Pathways / Q000502:physiology; D001307:Auditory Perception / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D019929:Cochlear Implantation / Q000379:methods*; D003054:Cochlear Implants; D003463:Cues; D003638:Deafness / Q000628:therapy*; D055724:Electrophysiological Phenomena; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D006801:Humans; D007223:Infant; D011446:Prospective Studies; D013016:Sound; D013017:Sound Localization / Q000502:physiology*
keywords: Auditory; Bilateral center/balance/symmetry; Deafness; Electrically evoked auditory brainstem response; Interaural level difference; Lateralization; Loudness