The Relationship Between Interaural Insertion-Depth Differences, Scalar Location, and Interaural Time-Difference Processing in Adult Bilateral Cochlear-Implant Listeners.

Sensitivity to interaural time differences (ITDs) in acoustic hearing involves comparison of interaurally frequency-matched inputs. Bilateral cochlear-implant arrays are, however, only approximately aligned in angular insertion depth and scalar location across the cochleae. Interaural place-of-stimulation mismatch therefore has the potential to impact binaural perception.

Computed-Tomography Estimates of Interaural Mismatch in Insertion Depth and Scalar Location in Bilateral Cochlear-Implant Users.

Hypothesis: Bilateral cochlear-implant (BI-CI) users will have a range of interaural insertion-depth mismatch because of different array placement or characteristics. Mismatch will be larger for electrodes located near the apex or outside scala tympani, or for arrays that are a mix of precurved and straight types.

Background: Brainstem superior olivary-complex neurons are exquisitely sensitive to interaural-difference cues for sound localization.

Measuring Knee Joint Laxity in Three Degrees-of-Freedom In Vivo Using a Robotics- and Image-Based Technology.

Accurate and reliable information about three-dimensional (3D) knee joint laxity can prevent misdiagnosis and avoid incorrect treatments. Nevertheless, knee laxity assessments presented in the literature suffer from significant drawbacks such as soft tissue artifacts, restricting the knee within the measurement, and the absence of quantitative knee ligament property information. In this study, we demonstrated the applicability of a novel methodology for measuring 3D knee laxity, combining robotics- and image-based technology.

Biopsy-based optimization and calibration of a signal-intensity-ratio-based MRI method (1.5 Tesla) in a dextran-iron loaded mini-pig model, enabling estimation of very high liver iron concentrations.

Objective: Magnetic resonance imaging (MRI)-based techniques for non-invasive assessing liver iron concentration (LIC) in patients with iron overload have a limited upper measuring range around 35 mg/g dry weight, caused by signal loss from accelerated T1-, T2-, T2* shortening with increasing LIC. Expansion of this range is necessary to allow evaluation of patients with very high LIC.

Aim: To assess measuring range of a gradient-echo R2* method and a T1-weighted spin-echo (SE), signal intensity ratio (SIR)-based method (TE = 25 ms, TR = 560 ms), and to extend the upper measuring range of the SIR method by optimizing echo time (TE) and repetition time (TR) in iron-loaded minipigs.

Interaural Place-of-Stimulation Mismatch Estimates Using CT Scans and Binaural Perception, But Not Pitch, Are Consistent in Cochlear-Implant Users.

Bilateral cochlear implants (BI-CIs) or a CI for single-sided deafness (SSD-CI; one normally functioning acoustic ear) can partially restore spatial-hearing abilities, including sound localization and speech understanding in noise. For these populations, however, interaural place-of-stimulation mismatch can occur and thus diminish binaural sensitivity that relies on interaurally frequency-matched neurons. This study examined whether plasticity-reorganization of central neural pathways over time-can compensate for peripheral interaural place mismatch.

A Comparison of Place-Pitch-Based Interaural Electrode Matching Methods for Bilateral Cochlear-Implant Users.

Interaural place-of-stimulation mismatch for bilateral cochlear-implant (BI-CI) listeners is often evaluated using pitch-comparison tasks that can be susceptible to procedural biases. Bias effects were compared for three sequential interaural pitch-comparison tasks in six BI-CI listeners using single-electrode direct stimulation. The reference (right ear) was a single basal, middle, or apical electrode.

Acoustic Hearing Can Interfere With Single-Sided Deafness Cochlear-Implant Speech Perception.

Objectives: Cochlear implants (CIs) restore some spatial advantages for speech understanding in noise to individuals with single-sided deafness (SSD). In addition to a head-shadow advantage when the CI ear has a better signal-to-noise ratio, a CI can also provide a binaural advantage in certain situations, facilitating the perceptual separation of spatially separated concurrent voices. While some bilateral-CI listeners show a similar binaural advantage, bilateral-CI listeners with relatively large asymmetries in monaural speech understanding can instead experience contralateral speech interference.

Development and Evaluation of a Subject-Specific Lower Limb Model With an Eleven-Degrees-of-Freedom Natural Knee Model Using Magnetic Resonance and Biplanar X-Ray Imaging During a Quasi-Static Lunge.

Musculoskeletal (MS) models can be used to study the muscle, ligament, and joint mechanics of natural knees. However, models that both capture subject-specific geometry and contain a detailed joint model do not currently exist. This study aims to first develop magnetic resonance image (MRI)-based subject-specific models with a detailed natural knee joint capable of simultaneously estimating in vivo ligament, muscle, tibiofemoral (TF), and patellofemoral (PF) joint contact forces and secondary joint kinematics.

The fluctuating masker benefit for normal-hearing and hearing-impaired listeners with equal audibility at a fixed signal-to-noise ratio.

Normal-hearing (NH) listeners can extract and integrate speech fragments from momentary dips in the level of a fluctuating masker, yielding a fluctuating-masker benefit (FMB) for speech understanding relative to a stationary-noise masker. Hearing-impaired (HI) listeners generally show less FMB, suggesting a dip-listening deficit attributable to suprathreshold spectral or temporal distortion. However, reduced FMB might instead result from different test signal-to-noise ratios (SNRs), reduced absolute audibility of otherwise unmasked speech segments, or age differences.

Interaural Time-Difference Discrimination as a Measure of Place of Stimulation for Cochlear-Implant Users With Single-Sided Deafness.

Current clinical practice in programming a cochlear implant (CI) for individuals with single-sided deafness (SSD) is to maximize the transmission of speech information via the implant, with the implicit assumption that this will also result in improved spatial-hearing abilities. However, binaural sensitivity is reduced by interaural place-of-stimulation mismatch, a likely occurrence with a standard CI frequency-to-electrode allocation table (FAT). As a step toward reducing interaural mismatch, this study investigated whether a test of interaural-time-difference (ITD) discrimination could be used to estimate the acoustic frequency yielding the best place match for a given CI electrode.

Role of intracranial cavities in avian directional hearing.

Whereas it is clear from anatomical studies that all birds have complex interaural canals connecting their middle ears, the effect of interaural coupling on directional hearing has been disputed. A reason for conflicting results in earlier studies may have been that the function of the tympanic ear and hence of the interaural coupling is sensitive to variations in the intracranial air pressure. In awake birds, the middle ears and connected cavities are vented actively through the pharyngotympanic tube.

Lingual articulation in songbirds.

Lingual articulation in humans is one of the primary means of vocal tract resonance filtering that produces the characteristic vowel formants of speech. In songbirds, the function of the tongue in song has not been thoroughly examined, although recent research has identified the oropharyngeal-esophageal cavity as a resonance filter that is actively tuned to the frequency of the song. In northern cardinals (Cardinalis cardinalis), the volume of this cavity is inversely proportional to the frequency of the song above 2 kHz.

Light-dependent orientation responses in animals can be explained by a model of compass cue integration.

The magnetic compass sense of animals is currently thought to be based on light-dependent processes like the proposed radical pair mechanism. In accordance, many animals show orientation responses that depend on light. However, the orientation responses depend on the wavelength and irradiance of monochromatic light in rather complex ways that cannot be explained directly by the radical pair mechanism.

Measurements and predictions of hooded crow (Corvus corone cornix) call propagation over open field habitats.

In a study of hooded crow communication over open fields an excellent correspondence is found between the attenuation spectra predicted by a "turbulence-modified ground effect plus atmospheric absorption" model, and crow call attenuation data. Sound propagation predictions and background noise measurements are used to predict an optimal frequency range for communication ("sound communication window") from an average of crow call spectra predicted for every possible combination of the sender/receiver separations 300, 600, 900, and 1200 m and heights 3,6,9 m thereby creating a matrix assumed relevant to crow interterritorial communication. These predictions indicate an optimal frequency range for sound communication between 500 Hz and 2 kHz.

Songbirds use pulse tone register in two voices to generate low-frequency sound.

The principal physical mechanism of sound generation is similar in songbirds and humans, despite large differences in their vocal organs. Whereas vocal fold dynamics in the human larynx are well characterized, the vibratory behaviour of the sound-generating labia in the songbird vocal organ, the syrinx, is unknown. We present the first high-speed video records of the intact syrinx during induced phonation.

Comodulation detection differences in the hooded crow (Corvus corone cornix), with direct comparison to human subjects.

Envelope modulations have been shown important in determining the effectiveness of masking noises. For example, the threshold for detecting a signal flanked by maskers is lower if the maskers and the signal are modulated with different envelopes, rather than the same envelope (comodulation). This threshold change is called the comodulation detection difference (CDD).

Hearing sensitivity and critical ratios of hooded crows (Corvus corone cornix).

The hearing threshold and critical ratios were estimated psycho-acoustically for captive wild-caught hooded crows by a yes/no procedure and the method of constant stimuli. Human subjects were tested in the same setup for direct comparison and to check for experimental artifacts. The hooded crows were found to have excellent low-frequency hearing capabilities compared to other passerine birds.