Visual Analog of Temporal Envelope Benefits Speech Processing in Cochlear Implant Users: A Pilot Functional Near-Infrared Spectroscopy Study on the Associations Between Audiovisual Benefit, Listening Environment, and Peripheral Neural Health.

Objectives: This study compared the benefit of visual analog of temporal envelope for speech processing across listening environments in postlingually deafened adult cochlear implant users. Associations between cortical activities and peripheral neural health were explored.

Design: Speech perception was measured using Harvard/IEEE sentences in quiet and noise with a visually presented sphere whose size was synchronized with the temporal envelope of the sentences. Cortical activities were recorded concurrently using functional near-infrared spectroscopy. Audiovisual benefit was evaluated using sentence scores, activation additivity, and functional connectivity. Peripheral neural health was measured using electrically evoked compound action potentials.

Results: Behavioral results showed the largest audiovisual benefit at a signal-to-noise ratio of +10 dB. The nonsignificant trends of activation additivity agreed with the behavioral results. Correlations between functional near-infrared spectroscopy and electrically evoked compound action potential results are inconclusive and warrant further research.

Conclusion: Visual temporal envelope benefits speech perception in moderately noisy environment in cochlear implant users.