Verbal Learning and Memory After Cochlear Implantation in Postlingually Deaf Adults: Some New Findings with the CVLT-II

Objectives: Despite the importance of verbal learning and memory in speech and language processing, this domain of cognitive functioning has been virtually ignored in clinical studies of hearing loss and cochlear implants in both adults and children. In this article, we report the results of two studies that used a newly developed visually based version of the California Verbal Learning Test–Second Edition (CVLT-II), a well-known normed neuropsychological measure of verbal learning and memory. Design: The first study established the validity and feasibility of a computer-controlled visual version of the CVLT-II, which eliminates the effects of audibility of spoken stimuli, in groups of young normal-hearing and older normal-hearing (ONH) adults. A second study was then carried out using the visual CVLT-II format with a group of older postlingually deaf experienced cochlear implant (ECI) users (N = 25) and a group of ONH controls (N = 25) who were matched to ECI users for age, socioeconomic status, and nonverbal IQ. In addition to the visual CVLT-II, subjects provided data on demographics, hearing history, nonverbal IQ, reading fluency, vocabulary, and short-term memory span for visually presented digits. ECI participants were also tested for speech recognition in quiet. Results: The ECI and ONH groups did not differ on most measures of verbal learning and memory obtained with the visual CVLT-II, but deficits were identified in ECI participants that were related to recency recall, the buildup of proactive interference, and retrieval-induced forgetting. Within the ECI group, nonverbal fluid IQ, reading fluency, and resistance to the buildup of proactive interference from the CVLT-II consistently predicted better speech recognition outcomes. Conclusions: Results from this study suggest that several underlying foundational neurocognitive abilities are related to core speech perception outcomes after implantation in older adults. Implications of these findings for explaining individual differences and variability and predicting speech recognition outcomes after implantation are discussed. ACKNOWLEDGMENTS: Data collection and analysis were supported by the National Institutes of Health, National Institute on Deafness and Other Communication Disorders (NIDCD) Career Development Award 5K23DC015539-02, and the American Otological Society Clinician-Scientist Award to A.C.M. This research was also supported by NIDCD research grant DC-000111 and the IU Grant Linking University-wide Expertise award to David Pisoni and NIDCD research grant DC-015257 to David Pisoni and William Kronenberger. ResearchMatch, used to recruit some NH participants, is supported by National Center for Advancing Translational Sciences Grant UL1TR001070. The authors acknowledge Susan Nittrouer for providing some testing materials used in this study, Beth Miles-Markley for her administrative support, and Leticia DeLeon, Gabrielle Grose, and Eleanor Gulick for their assistance in data scoring for this study. We also thank Terren Green for her help in preparing the final manuscript for publication and overseeing the research project. All authors contributed to the completion of this research project. A.C.M., D.B.P., W.G.H., L.R.H., and M.S.H. conceptualized and designed the original study and research protocol. A.C.M. and D.B.P. supervised the data collection at both sites. D.B.P., A.C.M., and W.G.K. drafted, edited, and revised the final manuscript. D.B.P., A.C.M., W.G.K., K.D.M., and H.X. carried out the statistical analyses. D.B.P., A.C.M., L.R.H., and K.D.M. prepared the graphics and figures. All authors of this article were involved in discussing the major results of the study and commented on the final manuscript in various stages of preparation. The authors declare no conflicts of interest. Address for correspondence: David B. Pisoni, Speech Research Laboratory, Department of Psychological and Brain Sciences, Indiana University, 1101 East 10th Street, Bloomington, IN 47405, USA. E-mail: Pisoni@indiana.edu Received June 23, 2017; accepted October 5, 2017. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.

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