Effect of stimulation rate on cochlear implant users' phoneme, word and sentence recognition in quiet and in noise.

High stimulation rates in cochlear implants (CI) offer better temporal sampling, can induce stochastic-like firing of auditory neurons and can increase the electric dynamic range, all of which could improve CI speech performance. While commercial CI have employed increasingly high stimulation rates, no clear or consistent advantage has been shown for high rates. In this study, speech recognition was acutely measured with experimental processors in 7 CI subjects (Clarion CII users). The stimulation rate varied between (approx.) 600 and 4800 pulses per second per electrode (ppse) and the number of active electrodes varied between 4 and 16. Vowel, consonant, consonant-nucleus-consonant word and IEEE sentence recognition was acutely measured in quiet and in steady noise (+10 dB signal-to-noise ratio). Subjective quality ratings were obtained for each of the experimental processors in quiet and in noise. Except for a small difference for vowel recognition in quiet, there were no significant differences in performance among the experimental stimulation rates for any of the speech measures. There was also a small but significant increase in subjective quality rating as stimulation rates increased from 1200 to 2400 ppse in noise. Consistent with previous studies, performance significantly improved as the number of electrodes was increased from 4 to 8, but no significant difference showed between 8, 12 and 16 electrodes. Altogether, there was little-to-no advantage of high stimulation rates in quiet or in noise, at least for the present speech tests and conditions.

Hyaluronidase-Facilitated High-Dose Subcutaneous IgG Effectively Controls Parvovirus B19 Infection in a Pediatric Cardiac Transplant Patient With Severe T-Cell Lymphopenia.

We treated three pediatric cardiac transplant patients with chronic parvovirus viremia with high-dose intravenous immunoglobulin (HD-IVIG). One patient with severe T-cell lymphopenia suffered recurrent viremia and aseptic meningitis, which resolved remarkably when he was switched to high-dose hyaluronidase-facilitated subcutaneous immunoglobulin (HD-SCIG-Hy). We discuss the advantages of HD-SCIG-Hy vs HD-IVIG treatment for similar cases.

Adaptive beam shaping by controlled thermal lensing in optical elements.

We describe an adaptive optical system for use as a tunable focusing element. The system provides adaptive beam shaping via controlled thermal lensing in the optical elements. The system is agile, remotely controllable, touch free, and vacuum compatible; it offers a wide dynamic range, aberration-free focal length tuning, and can provide both positive and negative lensing effects. Focusing is obtained through dynamic heating of an optical element by an external pump beam. The system is especially suitable for use in interferometric gravitational wave interferometers employing high laser power, allowing for in situ control of the laser modal properties and compensation for thermal lensing of the primary laser. Using CO(2) laser heating of fused-silica substrates, we demonstrate a focal length variable from infinity to 4.0 m, with a slope of 0.082 diopter/W of absorbed heat. For on-axis operation, no higher-order modes are introduced by the adaptive optical element. Theoretical modeling of the induced optical path change and predicted thermal lens agrees well with measurement.

Effects of stimulation rate on speech recognition with cochlear implants.

Phoneme and speech recognition were measured as a function of stimulation pulse rate in 12 listeners with three types of cochlear implants. Identification of consonants and vowels and recognition of words and sentences were measured in 5 Clarion C1 subjects fit with continuous interleaved sampling (CIS) processors having 4 or 8 electrodes, 4 Nucleus 24 subjects fit with CIS processors having 4, 8, 12 or 16 electrodes and 3 Clarion C2 subjects fit with CIS processors with 4, 8, 12 and 16 electrodes. Stimulation rates ranged from 200 to more than 5000 Hz per electrode, depending on the device, number of electrodes used and stimulation strategy. Listeners were also tested on the same materials with their original processor prior to receiving the experimental processors. All testing was done in quiet listening conditions with essentially no practice with the experimental processor prior to data collection. Listeners scored the highest with their original processor. Little difference in speech understanding was observed for listener scores with processors using different stimulation rates. Speech recognition was significantly poorer only at the lowest stimulation rate and at high rates that used noninterleaved pulses. Speech recognition was similar for processors using 8, 12 or 16 electrodes. Only 4-electrode processors produced a significantly poorer performance. These results suggest that patients with present commercial implants are not able to make full use of the number of channels of spectral information delivered by the present speech processors. In addition, the results show no significant change in performance as a function of stimulation rate, suggesting that high stimulation rates do not result in improved access to temporal cues in speech, at least under quiet listening conditions.