Abstract
There is strong clinical impetus to provide bilateral hearing early in life, not only for safety in navigating the
environment, but also to maximize learning and socializing in mainstreamed settings. Although this topic is an
active area of research, we lack critically important information on how to assess and interpret the impact of age
at onset of deafness and auditory experience in children with bilateral cochlear Implants (CIs). Four groups of
bilateral CI users and normal hearing (NH) participants in the same age ranges will be recruited to test
hypotheses about the role of auditory experience and inter-implant delay in emergence of binaural hearing,
functional listening and cognition. Here we propose novel studies aimed at gaining fresh insight into the role of
auditory experience and inter-implant delay on outcomes. We will integrate perceptual and
electroencephalographical (EEG) measures of binaural integrity (Aim 1), and functional listening with binaural
cues (Aim 2). Further, cognitive measures of executive function (EF) are introduced to promote novel discovery
of the association between binaural listening measures and EF (Aim 3). By synergistically combining these
approaches, this project will be the first to provide urgently needed answers to timely and clinically critical
questions regarding pediatric cochlear implantation. An important barrier to maximizing outcomes stems from
engineering limitations whereby CIs are lacking binaural coordination. In addition, while speech envelope (ENV)
cues are preserved in speech signals, cues that are significant for binaural hearing, namely temporal fine
structure (TFS) cues, are not preserved in CI processing. We will systematically manipulate the control of ENV
and TFS cues by using either research processors that allow exquisite control of timing of stimuli reaching each
electrode or presenting stimuli to clinical processors and in free field, where stimulation is more akin to today’s
CI processing. comprehensive investigation into outcomes in children with bilateral CIs, using perceptual, eye
tracking and EEG measures at multiple levels of auditory processing. The stepwise assessment along the neural
axis, from brainstem to auditory cortex, to cortical connectivity and whole brain coherence analyses, will enable
us to understand which perceptual deficits are associated with abnormal neural processing. Cognitive measures
are introduced to promote novel discovery of how abnormal neural development is related to EF, and if these
effects show pervasive effects beyond auditory-based EF tasks. This information is important for understanding
how the timing of bilateral CIs is related to a set of cognitive processes– regulating attention, memory, and
controlling cognitive behaviors – necessary for success across academic, social, and daily living domains. We
will harness the tests used in our studies to develop a clinical assessment toolbox that can be used by clinicians
to assess binaural hearing abilities, and our findings will further identify which cognitive EF measures should be
use along with auditory measures to clinically assess outcomes in children. Results will inform selection of design
features in engineering CIs, with an emphasis on binaural processors, thus aiming to reduce the gap in
performance relative to NH listeners.