Fine Structure Processing Strategy Research Articles

Processing of interaural time differences in normal-hearing subjects and cochlear implant users with FSP and HDCIS coding strategy

Sound localization is necessary for social interaction and remains challenging for bilateral cochlear implant (CI) users. This study investigated the influence of fine structure processing (FSP) coding strategies on temporal accuracy and source localization. The ability to discriminate between different interaural time differences (ITD) was measured objectively and compared. Fifteen normal-hearing subjects and five CI users participated in this study. Electrophysiological recording of mismatch negativity (MMN) and psychoacoustic tests with headphones and loudspeakers were conducted to measure and compare the discrimination of ITDs. In normal-hearing subjects the discrimination threshold for ITD was 83-117 µs. Localization ability in a free sound field was below the limit of resolution. Asignificant MMN was measured. CI users showed amean angle detection error of more than 30° and adiscrimination threshold between 1100 and 2100 µs. Due to artifacts, no clear MMN component could be recorded. This study shows that MMN can be used as an objective measure of ITD discrimination in normal-hearing participants. An indication that improvements in directional hearing can be achieved with the transfer of fine structure could not be provided by this study.

Examination of Prosody and Timbre Perception in Adults With Cochlear Implants Comparing Different Fine Structure Coding Strategies.

This study aimed to investigate whether adults with cochlear implants benefit from a change of fine structure (FS) coding strategies regarding the discrimination of prosodic speech cues, timbre cues, and the identification of natural instruments. The FS processing (FSP) coding strategy was compared to 2 settings of the FS4 strategy. A longitudinal crossover, double-blinded study was conducted. This study consisted of 2 parts, with 14 participants in the first part and 12 participants in the second part. Each part lasted 3 months, in which participants were alternately fitted with either the established FSP strategy or 1 of the 2 newly developed FS4 settings. Participants had to complete an intonation identification test; a timbre discrimination test in which 1 of 2 isolated cues changed, either the spectral centroid or the spectral irregularity; and an instrument identification test. A significant effect was seen in the discrimination of spectral irregularity with 1 of the 2 FS4 settings. The improvement was seen in the FS4 setting in which the upper envelope channels had a low stimulation rate. This improvement was not seen with the FS4 setting that had a higher stimulation rate on the envelope channels. In general, the FSP strategy and the 2 settings of the FS4 strategy provided similar levels in the perception of prosody and timbre cues, as well as in the identification of instruments.

Musical Sound Quality in Cochlear Implant Users: A Comparison in Bass Frequency Perception Between Fine Structure Processing and High-Definition Continuous Interleaved Sampling Strategies.

Med-El cochlear implant (CI) patients are typically programmed with either the fine structure processing (FSP) or high-definition continuous interleaved sampling (HDCIS) strategy. FSP is the newer-generation strategy and aims to provide more direct encoding of fine structure information compared with HDCIS. Since fine structure information is extremely important in music listening, FSP may offer improvements in musical sound quality for CI users. Despite widespread clinical use of both strategies, few studies have assessed the possible benefits in music perception for the FSP strategy. The objective of this study is to measure the differences in musical sound quality discrimination between the FSP and HDCIS strategies. Musical sound quality discrimination was measured using a previously designed evaluation, called Cochlear Implant-MUltiple Stimulus with Hidden Reference and Anchor (CI-MUSHRA). In this evaluation, participants were required to detect sound quality differences between an unaltered real-world musical stimulus and versions of the stimulus in which various amount of bass (low) frequency information was removed via a high-pass filer. Eight CI users, currently using the FSP strategy, were enrolled in this study. In the first session, participants completed the CI-MUSHRA evaluation with their FSP strategy. Patients were then programmed with the clinical-default HDCIS strategy, which they used for 2 months to allow for acclimatization. After acclimatization, each participant returned for the second session, during which they were retested with HDCIS, and then switched back to their original FSP strategy and tested acutely. Sixteen normal-hearing (NH) controls completed a CI-MUSHRA evaluation for comparison, in which NH controls listened to music samples under normal acoustic conditions, without CI stimulation. Sensitivity to high-pass filtering more closely resembled that of NH controls when CI users were programmed with the clinical-default FSP strategy compared with performance when programmed with HDCIS (mixed-design analysis of variance, p < 0.05). The clinical-default FSP strategy offers improvements in musical sound quality discrimination for CI users with respect to bass frequency perception. This improved bass frequency discrimination may in turn support enhanced musical sound quality. This is the first study that has demonstrated objective improvements in musical sound quality discrimination with the newer-generation FSP strategy. These positive results may help guide the selection of processing strategies for Med-El CI patients. In addition, CI-MUSHRA may also provide a novel method for assessing the benefits of newer processing strategies in the future.

Clinical Trial Results with the MED-EL Fine Structure Processing Coding Strategy in Experienced Cochlear Implant Users

Objectives: To assess the subjective and objective performance of the new fine structure processing strategy (FSP) compared to the previous generation coding strategies CIS+ and HDCIS. Methods: Forty-six adults with a minimum of 6 months of cochlear implant experience were included. CIS+, HDCIS and FSP were compared in speech perception tests in noise, pitch scaling and questionnaires. The randomized tests were performed acutely (interval 1) and again after 3 months of FSP experience (interval 3). The subjective evaluation included questionnaire 1 at intervals 1 and 3, and questionnaire 2 at interval 2, 1 month after interval 1. Results: Comparison between FSP and CIS+ showed that FSP performed at least as well as CIS+ in all speech perception tests, and outperformed CIS+ in vowel and monosyllabic word discrimination. Comparison between FSP and HDCIS showed that both performed equally well in all speech perception tests. Pitch scaling showed that FSP performed at least as well as HDCIS. With FSP, sound quality was at least as good and often better than with HDCIS. Conclusions: Results indicate that FSP performs better than CIS+ in vowel and monosyllabic word understanding. Subjective evaluation demonstrates strong user preferences for FSP when listening to speech and music.

From TEMPO+ to OPUS 2: What can music tests tell us about processor upgrades?

Tests for quantifying the music perception abilities of cochlear implant users are currently being developed and trialled at the South of England Cochlear Implant Centre. In addition to measures of speech perception, tests of rhythm, and pitch have been administered to MED-EL C40+ implant users before and after upgrading from the TEMPO+ processor with continuous interleaved sampling strategy to the OPUS 2 processor with fine structure processing strategy, with the aims of comparing device performance and evaluating the potential of music perception tests for informing processor upgrades and tuning. Eight experienced adult C40+ implant recipients performed tests of rhythm and pitch discrimination using the TEMPO+ processor and, after a minimum of 6 weeks acclimatization, using the OPUS 2 processor. Stimuli included piano and sine tones in two note ranges for the pitch tasks, and drum beats for the rhythm task. Rhythm, pitch, and speech perception scores were comparable for both processors. An effect of note range was observed (z = −2.52, p = 0.008 (two-tailed), r = −0.63), which indicated that the higher range of notes used for the pitch tasks was easier for participants than the lower range. Measures of pitch discrimination in different frequency ranges further informed changes made to one participant's map, resulting in improved pitch discrimination and speech perception scores. The outcomes of this study demonstrate that music perception tests can provide important additional measures for tuning cochlear implant parameters and assessing the impact of changes to device type and processing strategy.

The effects of fine structure stimulation on pitch perception with cochlear implants

Introduction One of the major expectations concerning stimulation strategies that incorporate temporal fine structure is an improved perception of pitch (Smith et al., 2002). The first such coding strategy that is commercially available is the fine structure processing strategy implemented in the OPUS sound processor family (MED-EL, Austria). This strategy is based on the concept of channel-specific sampling sequences (CSSS) (Arnoldner et al., 2007). In CSSS, the zero crossings within several apical band-pass channels trigger a sequence of stimulation pulses. Thus, each fine structure channel explicitly encodes the instantaneous withinchannel frequency. A different approach is used in the concept of coherent fine structure (CFS). With CFS, the temporal fine structure information is derived from a dedicated broad-band channel and presented simultaneously on multiple apical electrodes (Zierhofer 2009; Zierhofer et al., 2009). Subjectively, cochlear implant users usually report an overall downshift of pitch when they switch from envelope-based strategies like continuous interleaved sampling (CIS) to fine-structure-based strategies. Since the very first perception with a CIS processor at hook-up is mostly that of a high-pitched machinelike voice, this shift can be regarded as a step in the right direction. In the current study, this pitch shift was explored in two distinct fine structure strategies, one based on CSSS and the other on CFS.

Comparison of the fine structure processing (FSP) strategy and the CIS strategy used in the MED-EL cochlear implant system: Speech intelligibility and music sound quality

Objective: The aim of the present study was to evaluate MED-EL's Fine Structure Processing (FSP) strategy in comparison with their variations of the standard Continuous Interleaved Sampling (CIS) strategy denoted CIS+ and High Definition CIS (HDCIS). Study Sample: Twenty experienced adult CI users participated in the study in connection with upgrading to a new speech processor and at a two-year follow-up. Design: Blinded paired-comparisons between FSP and HDCIS were performed for speech intelligibility and music sound quality. Standard speech recognition tests in quiet and in noise were also accomplished to monitor the participants’ actual performance and to evaluate long-term outcomes. Results: Overall, the paired-comparison results showed no significant differences between the strategies, however, the total numbers of significant individual preferences were: 11 FSP vs. 12 HDCIS for speech, and 4 FSP vs. 15 HDCIS for music. The average speech recognition score decreased significantly after one month with FSP, but after two years there were no significant difference compared to the initial results with CIS+. Conclusions: Owing to the large individual differences in subjective preference, and the fact that the FSP strategy was not superior to the CIS variations, the recipients should be given the opportunity of choosing between the strategiesSumarioObjetivo: El objetivo de este estudio fue evaluar la estrategia de procesamiento de la estructura fina (FSP) de MED-EL en comparación con las variaciones de la estrategia estándar de muestreo intercalado continuo (CIS) denominado CIS+ y el CIS de alta definición (HDCIS). Muestra: Veinte adultos usuarios experimentados de CI participaron en este estudio en conexión con el ascenso a un nuevo procesador y el seguimiento durante dos años. Diseño: Se efectuó una comparación ciega pareada entre FSP y HDCIS para la inteligibilidad del lenguaje y la calidad del sonido musical. Se efectuaron también pruebas estándar de reconocimiento del lenguaje en silencio y en ruido para monitorear el desempeño de los participantes y para evaluar los resultados a largo plazo. Resultados: En general el resultado de la comparación pareada no mostró diferencias significativas entre las estrategias, sin embargo, los números totales de preferencias por sujeto fueron: 11 FSP vs 12 HDCIS para lenguaje y 4 FSP vs 15 HDCIS para la música. La puntuación promedio del reconocimiento del lenguaje disminuyó significativamente después de un mes con FSP, pero después de dos años no hubo diferencias significativas al comparar con los resultados iniciales del CIS+. Conclusiones: Debido a las amplias diferencias individuales en las preferencias de los sujetos y al hecho de que la estrategia FSP no fue superior a las variaciones de CIS, los receptores del CI deben tener la oportunidad de escoger entre las estrategias.

A New Fine Structure Speech Coding Strategy

One of the most commonly used speech coding strategies for cochlear implants is continuous interleaved sampling (CIS), which codes the envelope information of an acoustic signal. Based on this strategy, MED-EL has recently developed the new fine structure processing (FSP) speech coding strategy, which also transmits subtle pitch and temporal cues. The aim of this study was to investigate the number of active channels necessary for good speech perception with FSP and whether there is an advantage for FSP compared with CIS at a reduced number of channels. Ten postlingually deafened patients using MED-EL Pulsar cochlear implants participated in this study. Patients were tested with all 12, 8, 5, 3, and 2 channels with CIS and FSP strategy, resulting in a total of 10 conditions. Performance was tested with numbers, monosyllables, and sentence tests. Our results showed an improvement in speech perception, with up to 5 channels for numbers and for monosyllables and sentence tests. Statistically significant increases in performance were noted from 3 to 8 channels for numbers, from 3 to 5 channels for monosyllables, and from 5 to 8 channels for sentence tests. No statistical significance was observed whether FSP or CIS was used. Based on these findings, the number of channels necessary for speech perception with FSP is similar to published results using CIS. There seems to be no advantage for FSP compared with CIS in the conditions of the present experiment.

Speech and music perception with the new fine structure speech coding strategy: preliminary results

Conclusions. Taking into account the excellent results with significant improvements in the speech tests and the very high satisfaction of the patients using the new strategy, this first implementation of a fine structure strategy could offer a new quality of hearing with cochlear implants (CIs). Objective. This study consisted of an intra-individual comparison of speech recognition, music perception and patient preference when subjects used two different speech coding strategies with a MedEl Pulsar CI: continuous interleaved sampling (CIS) and the new fine structure processing (FSP) strategy. In contrast to envelope-based strategies, the FSP strategy also delivers subtle pitch and timing differences of sound to the user and is thereby supposed to enhance speech perception in noise and increase the quality of music perception. Patients and methods. This was a prospective study assessing performance with two different speech coding strategies. The setting was a CI programme at an academic tertiary referral centre. Fourteen post-lingually deaf patients using a MedEl Pulsar CI with a mean CI experience of 0.98 years were supplied with the new FSP speech coding strategy. Subjects consecutively used the two different speech coding strategies. Speech and music tests were performed with the previously fitted CIS strategy, immediately after fitting with the new FSP strategy and 4, 8 and 12 weeks later. The main outcome measures were individual performance and subjective assessment of two different speech processors. Results. Speech and music test scores improved statistically significantly after conversion from CIS to FSP strategy. Twelve of 14 patients preferred the new FSP speech processing strategy over the CIS strategy.