Measuring Spectrotemporal Sensitivity in Cochlear Implant Users With a Reaction-Time Paradigm: A Comparison of Two Implementations.

This study evaluated two implementations of a reaction-time paradigm to assess spectrotemporal modulation sensitivity in cochlear implant (CI) users, aiming to support both clinical and research applications. Reaction times directly reflect task difficulty, enabling rapid testing with stimuli presented well above modulation detection thresholds. Twenty unilateral CI users completed a task involving the unpredictable onset of broadband and narrowband spectrotemporal modulations embedded in noise. Testing was conducted using two implementations: an app on a smartphone with direct wireless streaming to the CI processor and touchscreen responses ("App"), and a free-field setup with laptop and spacebar responses ("Laptop"), administered 2 to 3 months apart. Speech-in-noise perception was assessed with a matrix test. Reaction times showed strong within-participant consistency across implementations, demonstrating robustness over time and across different delivery and response setups. Individual differences in sensitivity to spectral and temporal modulations were evident and showed strong correspondence between the two implementations. Reaction-time-based modulation transfer functions matched those reported in previous psychophysical studies. Notably, reaction times correlated most strongly (r = 0.6-0.7) with speech-in-noise scores for spectrotemporal modulations relevant to speech, particularly spectral densities of 0.25-0.5 cycles/octave combined with temporal rates up to 16 Hz. These findings support the use of reaction times to measure spectrotemporal sensitivity in CI users.