Effects of Binaural Hearing on Listening Effort and Cognitive Development in Mandarin-speaking Children With Cochlear Implants

Listening effort is measured synchronously during listening tasks using a multimodal approach, including pupillometry metrics (peak pupil dilation and mean pupil dilation, expressed as percentage of dynamic range) and fNIRS cortical hemodynamic metrics (HbDiff activation levels in bilateral inferior frontal gyrus and superior temporal gyrus regions). For participants with bilateral listening devices (bilateral CIs or bimodal stimulation), listening effort is measured under both better-ear-only and binaural listening conditions. Assessed at baseline, 1-year follow-up, and 3-year follow-up.

Cognitive function is assessed using the Wechsler Intelligence Scale for Children, Fourth Edition (WISC-IV), including four index scores - Verbal Comprehension, Perceptual Reasoning, Working Memory, and Processing Speed - as well as the Full-Scale Intelligence Quotient (FSIQ). Assessed at baseline, 1-year follow-up, and 3-year follow-up.

Speech recognition is assessed using Mandarin BKB sentences (6-8 characters per sentence) selected from a daily spoken language corpus of Beijing children aged 4-5 years, covering common sentence patterns relevant to Chinese children's daily communication. Participants repeat keywords from each sentence. Testing is conducted under both quiet and noise conditions. In quiet conditions, BKB scores are calculated as the percentage of correct keywords. In noise conditions, BKB-SIN testing presents 10 sentences at signal-to-noise ratios ranging from +21 to -6 dB (4-talker babble), with SNR-50 determined by the formula: SNR-50 = 23.5 - total correct keywords. All participants complete at least 1 practice list before 2 formal test lists, with scores averaged. Normal-hearing controls and unilateral CI participants complete testing under binaural conditions only, while bilateral CI and bimodal participants complete testing under binaural, left-ear-only, and right-ear-only conditions.

Listening-related fatigue is measured using the Vanderbilt Fatigue Scale, including both the Child version (VFS-C) and the Parent version (VFS-P). The VFS-C is a 10-item 5-point Likert scale completed by the child, and the VFS-P is completed by the parent or guardian. Both versions assess the child's fatigue experienced during daily listening situations.

Social adaptability is assessed using the Chinese version of the Adaptive Behavior Assessment System, Second Edition (ABAS-II), administered via parent interview concurrent with cognitive testing. The scale covers three domains: conceptual skills, including communication, functional academics, and self-direction; social skills, including leisure and social interaction; and practical skills, including community use, home/school living, health and safety, and self-care.

Spectral resolution is measured using the Spectral-Temporally Modulated Ripple Test (SMRT), an adaptive three-interval, two-alternative forced-choice paradigm. The ripple discrimination threshold is determined by averaging the last 6 of 10 reversals, with higher scores indicating better spectral resolution. Temporal resolution is measured using the Temporal Modulation Transfer Function (TMTF) test, a two-alternative forced-choice method with a 2-down-1-up adaptive procedure at 100 Hz modulation frequency. The modulation depth detection threshold (MDT) is expressed as 20log₁₀(mᵢ), averaged across 2 tests. For both tests, normal-hearing controls and unilateral CI participants complete testing under binaural conditions only, while bilateral CI and bimodal participants complete testing under binaural, left-ear-only, and right-ear-only conditions.

Resting-state functional connectivity (rsFC) is measured using functional near-infrared spectroscopy (fNIRS) while participants watch a 5-minute "Inscapes" video (abstract geometric animations designed for children). Cortical hemodynamic signals are recorded and rsFC is calculated across channel pairs of interest, serving as a neurophysiological marker of executive function development.

Speech development is assessed using two structured parent/guardian interview scales. The Meaningful Auditory Integration Scale (MAIS) evaluates vocalization, sound awareness, and sound comprehension in daily life. The Meaningful Use of Speech Scale (MUSS) evaluates speech production including vocal communication, speech communication ability, and speech communication skills, scored 0-4 per item (total 40 points), reported as percentage scores.