Turn an Ear to Hear: How Hearing-Impaired Listeners Can Exploit Head Orientation to Enhance Their Speech Intelligibility in Noisy Social Settings.

Turning an ear toward the talker can enhance spatial release from masking. Here, with their head free, listeners attended to speech at a gradually diminishing signal-to-noise ratio and with the noise source azimuthally separated from the speech source by 180° or 90°. Young normal-hearing adult listeners spontaneously turned an ear toward the speech source in 64% of audio-only trials, but a visible talker's face or cochlear implant (CI) use significantly reduced this head-turn behavior. All listener groups made more head movements once instructed to explore the potential benefit of head turns and followed the speech to lower signal-to-noise ratios. Unilateral CI users improved the most. In a virtual restaurant simulation with nine interfering noises or voices, hearing-impaired listeners and simulated bilateral CI users typically obtained a 1 to 3 dB head-orientation benefit from a 30° head turn away from the talker. In diffuse interference environments, the advice to U.K. CI users from many CI professionals and the communication guidance available on the Internet most often advise the CI user to face the talker head on. However, CI users would benefit from guidelines that recommend they look sidelong at the talker with their better hearing or implanted ear oriented toward the talker.

Hydrogel limits stem cell dispersal in the deaf cochlea: implications for cochlear implants.

Auditory neurons provide the critical link between a cochlear implant and the brain in deaf individuals, therefore their preservation and/or regeneration is important for optimal performance of this neural prosthesis. In cases where auditory neurons are significantly depleted, stem cells (SCs) may be used to replace the lost population of neurons, thereby re-establishing the critical link between the periphery (implant) and the brain. For such a therapy to be therapeutically viable, SCs must be differentiated into neurons, retained at their delivery site and damage caused to the residual auditory neurons minimized. Here we describe the transplantation of SC-derived neurons into the deaf cochlea, using a peptide hydrogel to limit their dispersal. The described approach illustrates that SCs can be delivered to and are retained within the basal turn of the cochlea, without a significant loss of endogenous auditory neurons. In addition, the tissue response elicited from this surgical approach was restricted to the surgical site and did not extend beyond the cochlear basal turn. Overall, this approach illustrates the feasibility of targeted cell delivery into the mammalian cochlea using hydrogel, which may be useful for future cell-based transplantation strategies, for combined treatment with a cochlear implant to restore function.

The benefit of bilateral versus unilateral cochlear implantation to speech intelligibility in noise.

OBJECTIVES: To develop a predictive model of spatial release from masking (SRM) for cochlear implantees, and validate this model against data from the literature. To establish the spatial configurations for which the model predicts a large advantage of bilateral over unilateral implantation. To collect data to support these predictions and generate predictions of more typical advantages of bilateral implantation. DESIGN: The model initially assumed that bilateral cochlear implantees had equally effective implants on each side, with which they could perform optimal better-ear listening. Predictions were compared with measurements of SRM, using one and two implants with up to three interfering noises. The effect of relaxing the assumption of equally effective implants was explored. Novel measurements of SRM for eight unilateral implantees were collected, including measurements using speech and noise at azimuths of ± 60 degrees, and compared with prediction. A spatial map of bilateral implant benefit was generated for a situation with one interfering noise in anechoic conditions, and predictions of benefit were generated from binaural room impulse responses in a variety of real rooms. RESULTS: The model accurately predicted data from a previous study for multiple interfering noises in a variety of spatial configurations, even when implants were assumed to be equally effective (r = 0.97). It predicted that the maximum benefit of bilateral implantation was 18 dB. Predictions were little affected if the implants were not assumed to be equally effective. The new measurements supported the 18 dB advantage prediction. The spatial map of predicted benefit showed that, for a listener facing the target voice, bilateral implantees could enjoy an advantage of about 10 dB over unilateral implantees in a wide range of situations. Predictions based on real-room measurements with speech and noise at 1 m showed that large benefits can occur even in reverberant spaces. CONCLUSIONS: In optimal conditions, the benefit of bilateral implantation to speech intelligibility in noise can be much larger than has previously been reported. This benefit is thus considerably larger than reported benefits of summation or squelch and is robust in reverberation when the interfering source is close.