Different evolutionary modifications as a guide to rewire two-component systems.

Two-component systems (TCS) are short signalling pathways generally occurring in prokaryotes. They frequently regulate prokaryotic stimulus responses and thus are also of interest for engineering in biotechnology and synthetic biology. The aim of this study is to better understand and describe rewiring of TCS while investigating different evolutionary scenarios. Based on large-scale screens of TCS in different organisms, this study gives detailed data, concrete alignments, and structure analysis on three general modification scenarios, where TCS were rewired for new responses and functions: (i) exchanges in the sequence within single TCS domains, (ii) exchange of whole TCS domains; (iii) addition of new components modulating TCS function. As a result, the replacement of stimulus and promotor cassettes to rewire TCS is well defined exploiting the alignments given here. The diverged TCS examples are non-trivial and the design is challenging. Designed connector proteins may also be useful to modify TCS in selected cases.

Performance groups in adult cochlear implant users: speech perception results from 1984 until today.

INTRODUCTION: More than 3,000 patients have received a cochlear implant in Hannover. METHODS: A group of 864 patients was selected from the main group for the analysis of speech perception development. Depending on the term of introduction of new implant technology, the viewed group was divided into 5 subgroups. RESULTS: The test battery during regular clinical checkups included speech perception tests. Those tests changed during 20 years; only speech tracking and monosyllable word test remained and were the bases for forming performance classes shown in this study. Three performance classes can be specified for all 5 subgroups by mean values and standard deviations. CONCLUSION: In all subgroups, an improvement of speech perception can be observed over time. The current patient group showed significant better performing results than those of the first group.

Evaluation of the Harmony soundprocessor in combination with the speech coding strategy HiRes 120.

OBJECTIVE: The Advanced Bionics Harmony BTE processor was developed to support the new speech coding strategy HiRes 120 with a resolution of 120 channels based on "current steering." Compared with the previous Auria, the front end has been re-designed and power consumption reduced. STUDY DESIGN: HiRes 120 as well as the impact of the improved Harmony processing concerning a better speech understanding were evaluated. Subject's performance was evaluated using a test battery of the Hochmair-Schulz-Moser (HSM) sentence test and questionnaires regarding general sound quality, music perception, battery life time and processor handling. PATIENTS: In the first study group, 11 postlingually deafened adult subjects participated with a minimum of 9 months experience. The second study group consisted of 14 postlingually deafened adult subjects with a minimum of 2 years experience. INTERVENTIONS: Tested were the 2 speech coding strategies HiRes and HiRes 120 on the Harmony and the clinical system, respectively. MAIN OUTCOME MEASURES: Speech perception tests in quiet, in CCITT noise, as well as with a competing talker, questionnaires regarding sound quality and handling and perceptual channel tests. RESULTS: A total of 84% showed a clear preference for the Harmony processor compared with their previous processor with HiRes. The speech test results showed a 7.7% average increase in the HSM sentence test with 5 dB SNR competing talker. CONCLUSION: The majority of the subjects wanted to change to the new Harmony processor because of a better understanding in everyday life, handling, and improved battery-life time.

Current steering and results from novel speech coding strategies.

OBJECTIVE: Advanced Bionics' cochlear implants have independent current sources that can share stimulation current between 2 contacts (Current Steering). By stimulating 2 adjacent electrodes with different weights, different pitches can be evoked, allowing to increase the number of processing channels. STUDY DESIGN: A counterbalanced crossover design was used to compare 3 different current steering implementations to the clinical HiRes strategy. SETTING: The study was a prospective, within-subject, repeated-measure experiment. PATIENTS: The study group consisted of 8 postlingually deaf subjects with a minimum of 12-month experience in HiRes. INTERVENTION: The following programs were evaluated: 1) a Fast Fourier Transformation (FFT)-based current steering implementation with 120 stimulation sites; 2) the same current steering implementation but with 16,000 stimulation sites; and 3) a current steering implementation based on a sinusoidal decomposition of the original signal with 16,000 stimulation sites. MAIN OUTCOME MEASURES: Speech perception tests in quiet and in Comité Consultatif International Télégraphique et Téléphonique (CCITT) noise, as well as with competing talker; an adaptive test of the frequency difference limen; a Quality Assessment Questionnaire. RESULTS: Current results do not show any improvement in speech perception for a certain current steering strategy compared with HiRes. However, when selecting the optimal current steering strategy, subjects could achieve a significant benefit compared with the clinical HiRes. In addition, the frequency difference limen could be reduced significantly at 1,280 Hz. CONCLUSION: Current steering seems to have the potential to improve both understanding in adverse listening situations and frequency resolution. However, the optimal implementation needs further investigation.