Tonotopic and Default Frequency Fitting for Music Perception in Cochlear Implant Recipients: A Randomized Clinical Trial

Abstract

Importance: Cochlear implants are an effective technique for enhancing speech perception abilities in quiet environments for people with severe to profound deafness. Nevertheless, complex sound signals perception, such as music perception, remains challenging for cochlear implant users.

Objective: To assess the benefit of a tonotopic map on music perception in new cochlear implant users.

Design, setting, and participants: A prospective, randomized, double-blind, 2-period crossover study including 26 new cochlear implant users was performed over a 6-month period (June 2021 to November 2021). An anatomical tonotopic map was created using postoperative flat-panel computed tomography and a reconstruction software based on Greenwood function. New cochlear implant users older than 18 years with bilateral severe to profound sensorineural hearing loss or complete hearing loss for less than 5 years were selected in the University Hospital Centre of Rennes in France. The trial was conducted from June to November 2021 (inclusion) and to February 2022 (end of the assessment procedure at 12 weeks postactivation), and the analysis itself was completed in December 2022.

Intervention: Each participant was randomized to receive a conventional map followed by a tonotopic map or vice versa.

Main outcomes and measures: Participants performed pitch-scaling tasks (multidimensional qualitative assessment, melodic contour identification, melodic recognition test) after 6 weeks of each setting.

Results: Thirteen participants were randomized to each sequence. Two of the 26 participants recruited (1 in each sequence) had to be excluded due to the COVID-19 pandemic. The multidimensional qualitative assessment (Gabrielsson test), melodic contour identification, and melodic recognition scores were significantly higher with the tonotopic setting than the conventional one (mean effect [ME], 7.8; 95% CI, 5.0-10.5; ME, 12.1%; 95% CI, 5.7%-18.4%; ME, 14.4%, 95% CI, 8.5%-20.2%; and ME, 2.1, 95% CI, 1.7-2.5, respectively). Among the different dimensions evaluated by the Gabrielsson test, the mean scores for clarity, spaciousness, fullness, nearness, and total impression were significantly higher with tonotopic fitting. Ninety-two percent of the participants kept the tonotopy-based map after the study period.

Conclusions: In this randomized clinical trial of patients with new cochlear implants, a tonotopic-based fitting was associated with better results in perception of complex sound signals such as music listening experience.

Trial registration: ClinicalTrials.gov Identifier: NCT04922619.

Figure 1.. Flowchart According to Consort Recommendations

Figure 2.. Frequency Shift in Semitones Between the Frequency According to Organ of Corti (OC) Map and the Center Frequency With Tonotopic Fitting (TF) or Conventional Fitting (CF) For Each Electrode Contact

The triangles indicate the mean value. The top line of the box shows the third quartile. The bottom line of the box is the first quartile. The line in the box shows the median value with the whiskers showing the highest and lowest values.

Figure 3.. Boxplot for the Musical Test Score Study Arms A and B

A, Gabrielsson test total score. In study arm A, the mean (SD) total score (on 80) was 43.0 (7.2) for CF and 51.9 (3.7) for TF. In study arm B, the mean (SD) scores were 46.8 (5.8) and 53.5 (3.4), respectively. B, MCI1: in study arm A, the mean (SD) score was 45.4% (16.0%) for CF and 48.2% (16.6%) for TF. In study arm B, the mean (SD) scores were 42.1% (24.0%) and 63.4% (24.0%), respectively. C, MCI2: in study arm A, the mean (SD) score was 44.4% (17.6%) for CF and 55.6% (19.8%) for TF. In study arm B, they were 37.9% (23.8%) and 55.6% (22.0%), respectively. D, MRT: in study arm A, the mean (SD) score (on a scale of 10) was 5.8 (1.3) for CF and 8.4 (1.3) for TF. In study arm B, the mean (SD) scores were 5.8 (1.7) and 7.5 (1.4). The points indicate the maximal and minimal values (outliers). The triangles show the mean value. The top line of the box shows the third quartile with the bottom line of the box indicating the first quartile. The line in the box is the median value. The upper whisker is the highest value still within quartile 3 + 1.5 ×  the interquartile range and the bottom whisker shows the lowest value within quartile 1 – 1.5 ×  the interquartile range. CF indicates conventional fitting; MRT, melodic recognition test; TF, tonotopic fitting.