Three challenges for future research on cochlear implants

Cochlear implants (CIs) often work very well for many children and adults with profound sensorineural (SNHL) hearing loss.Unfortunately,while many CI patients display substantial benefits in recognizing speech and understanding spoken language forlowing cochlear implantation,a large number of patients achieve poor outcomes.Understanding and explaining the reasons for poor outcomes forlowing implantation is a very challenging research problem that has received little attention despite the pressing clinical significance.In this paper,we discuss three challenges for future research on CIs.First,we consider the issue of individual differences and variability in outcomes following implantation.At the present time,we still do not have a complete and satisfactory account of the causal underlying factors that are responsible for the enormous individual differences and variability in outcomes.Second,we discuss issues related to the lack of preimplant predictors of outcomes.Very little prospective research has been carried out on the development of preimplant predictors that can be used to reliably identify CI candidates who may be at high risk for a poor outcome forlowing implantation.Other than conventional demographics and hearing history,there are no prognostic tools available to predict speech recognition outcomes after implantation.Finally,we discuss the third challenge-what to do with a CI-user who has a poor outcome.We suggest that new research efforts need to be devoted to studying this neglected clinical population in greater depth to find out why they are doing poorly with their Cl and what novel interventions and treatments can be developed to improve their speech recognition outcomes.Using these three challenges as objectives for future research on Cls,we suggest that the field needs to adopt a new narrative grounded in theory and methods from Cognitive Hearing Science and information processing theory.Without knowing which specific biological and neurocognitive factors are responsible for individual differences or understanding the underlying sensory and neurocognitive basis for variability in performance,it is impossible to select a specific approach to habilitation after a deaf adult or child receives a CI.Deaf adults and children who are performing poorly with their CIs are not a homogeneous group and may differ in many different ways from each other,reflecting the dysfunction of multiple brain systems associated with both congenital and acquired deafness.Hearing loss is not only an ear issue,it is also a brain issue too reflecting close links between perception and action and brain,body and world working together as a functionally integrated information processing system to support robust speech recognition and spoken language processing after implantation.

Visual working memory span in adults with cochlear implants： Some preliminary findings

Objective:Neurocognitive functions,specifically verbal working memory (WM),contribute to speech recognition in postlingual adults with cochlear implants (CIs) and normal-hearing (NH) listener shearing degraded speech.Three hypotheses were tested:(1) WM accuracy as assessed using three visual span measures-digits,objects,and symbols-would correlate with recognition scores for spectrally degraded speech (through a CI or when noise-vocoded);(2) WM accuracy would be best for digit span,intermediate for object span,and lowest for symbol span,due to the increasing cognitive demands across these tasks.Likewise,response times,relating to processing demands,would be shortest for digit span,intermediate for object span,and longest for symbol span;(3) CI users would demonstrate poorer and slower performance than NH peers on WM tasks,as a result of less efficient verbally mediated encoding strategies associated with a period of prolonged auditory deprivation.Methods:Cross-sectional study of 30 postlingually deaf adults with CIs and 34 NH controls.Participants were tested for sentence recognition in quiet (CI users) or after noise-vocoding (NH peers),along with WM using visual measures of digit span,object span,and symbol span.Results:Of the three measures of WM,digit span scores alone correlated with sentence recognition for CI users;no correlations were found using these three measures for NH peers.As predicted,WM accuracy (and response times) were best (and fastest) for digit span,intermediate for object span,and worst (and slowest) for symbol span.Cl users and NH peers demonstrated equivalent WM accuracy and response time for digit span and object span,and similar response times for symbol span,but contrary to our original predictions,Cl users demonstrated better accuracy on symbol span than NH peers.Conclusions:Verbal WM assessed using visual tasks relates weakly to sentence recognition for degraded speech.CI users performed equivalently to NH peers on most visual tasks of WM,but they outperformed NH peers on symbol span accuracy.This finding deserves further exploration but may suggest that CI users develop alternative or compensatory strategies associated with rapid verbal coding,as a result of their prolonged experience of auditory deprivation.