While parallel stimulation provides a lot of flexibility, it’s not simple because channels that are stimulated simultaneously interfere with each other. This is why, in practice, parallel stimulation would not result in the desired benefits in hearing outcomes without another technology: Intelligent Parallel Stimulation. Only MED-EL cochlear implants have patented Intelligent Parallel Stimulation (IPS) technology—a sophisticated algorithm in our audio processors that compensates for detrimental crosstalk, or interference, between channels.

IPS technology has opened up opportunities for innovation in sound coding strategies. This is crucial because coding strategies define the pattern with which the hearing nerve is stimulated. Thus, sound coding strategies have a great influence on hearing performance and sound quality perception.

In MED-EL’s approach to providing closest to natural hearing with cochlear implant stimulation, two aspects are important:

1) Stimulating along as much of the cochlea as possible. A prerequisite is a cochlear implant electrode array long enough to cover the cochlea so it can stimulate a full natural range of sound frequencies. You can’t accurately stimulate a specific frequency if the electrode array doesn’t physically reach that part of the cochlea. When this is attempted with shorter electrode arrays, the end result is place-pitch mismatch.

2) Mimicking natural rate coding (phase-locking) in the apical region of the cochlea. It is not only important to stimulate the entire cochlea but to stimulate it like nature does. In natural hearing, nerve activity in the low frequencies is synchronized with the phase of the incoming sound signal. This is called phase-locking. This paradigm is replicated in MED-EL’s FineHearing coding strategies: While all other channels stimulate in a regular time pattern, the four apical channels (“fine structure channels”) stimulate in time with the incoming sound. And this is where IPS may be beneficial.

The results of the questionnaire shown above indicate that MED-EL cochlear implant recipients with single-sided deafness rate the sound of FS4-p as 26% clearer than the sound with FS4. In addition, when asked how much they like the sound on the scale from one to ten, FS4-p scored 36% higher than FS4. Tavora-Vieira and Rajan concluded that “the subjective benefit of FS4-p was significantly greater than the subjective benefit of FS4 on all five questions of the questionnaire.”

The authors of the study noted that patients with bilateral hearing loss may tend to rate quality “based solely on their auditory memory and/or an input from acoustic amplification on the contra-lateral ear” whereas unilaterally deafened cochlear implant users “are in the unique position of being able to assess and compare the quality of speech coding strategies directly with the correlating sound percepts of their normal hearing ear.” Thus, while research has shown that cochlear implant users with FS4 and FS4-p maps have similar speech perception scores, users with unilateral hearing loss may show a preference for sound with the FS4-p map over the FS4 map.

MED-EL Cochlear Implants: Closest to Natural Hearing Now and in the Future

Cochlear implants from MED-EL are equipped with independent current sources to provide Intelligent Parallel Stimulation and an electrode array long enough to stimulate the entire length of the cochlea. This provides your recipients with the closest to natural hearing at present, along with the option to choose between FSP, FS4, and FS4-p based on their personal preferences. Thanks to Intelligent Parallel Stimulation, MED-EL’s cochlear implants are also capable of providing more sophisticated stimulation if there are future sound coding advancements that require many areas of the cochlea to be stimulated at the same time.

More on FineHearing, Sound Coding, and Pitch Perception

MED-EL ExpertsONLINE: Natural Pitch with Cochlear Implants

How Does FineHearing Work and What are the Benefits for MED-EL Cochlear Implant Patients?

Why You Need Both Tonotopic and Temporal Fine Structure Coding

MED-EL Sound Coding in Depth

References

1. Schatzer, R., Koroleva, I. A., Griessner, A., Levin, S. V., Kuzovkov, V. E., Yanov, Y., & Zierhofer, C. (2015). Speech perception with interaction-compensated simultaneous stimulation and long pulse durations in cochlear implant users. Hearing Research, 322, 99–106. https://doi.org/10.1016/j.heares.2014.11.002
2. Riss, D., Hamzavi, J., Blineder, M., Honeder, C., Ehrenreich, I., Kaider, A., Baumgartner, W., Gstoettner, W., & Arnoldner, C. (2014). FS4, FS4-p, and FSP: A 4-Month Crossover Study of 3 Fine Structure Sound-Coding Strategies. Ear And Hearing, 35(6), e272–e281. https://doi.org/10.1097/aud.0000000000000063
3. Távora-Vieira, D., & Rajan, G. P. (2014). Assessment of Fine Structure Processing Strategies in Unilaterally Deafened Cochlear Implant Users. International Journal of Otolaryngology and Head & Neck Surgery, 03(06), 347–353. https://doi.org/10.4236/ijohns.2014.36062