Will diminishing cochlear delay affect speech perception in noise?

OBJECTIVE: Normal auditory systems appear well habituated to time/phase delays inherent to sound encoding along the hearing organ, sending frequency information non-simultaneously to the central auditory system. Eliminating, or simply perturbing, the cochlear delay might be expected to decrease speech recognition ability, especially under demanding listening conditions. Resources of a larger-scale investigation permitted a preliminary examination of this issue, particularly on a relevant timescale of empirically demonstrated cochlear delays. DESIGN: In a randomized controlled trial study, word recognition was tested for mono-syllabic tokens treated digitally to exacerbate, if not diminish/nullify, such delays. Speech-weighted noise was used to interfere with listening to time-frequency reversed (nominally no delay) versus non-reversed (natural timing) transforms under three treatments of speech tokens: (1) original-digitally recorded; digitally processed to emphasize (2) transient versus (3) quasi-steady-state components. STUDY SAMPLE: Ten normal-hearing young-adult females. RESULTS: The findings failed to demonstrate statistically significant differences between delay conditions for any of the three speech-token treatments. CONCLUSIONS: An algorithm putatively diminishing frequency-dependent cochlear delays failed to systematically deteriorate performance in all subjects for the fixed time-frequency transform, stimulus parameters, and test materials employed. Yet, trends were evident such that some effect of perturbing cochlear delays could not be ruled out completely.

Steady-state analysis of auditory evoked potentials over a wide range of stimulus repetition rates in awake vs. natural sleep.

OBJECTIVE: Auditory steady-state responses (ASSR) evoked by recurrent tones were assessed over a wide range of stimulus repetition rates embracing well the traditionally measured transient AEPs. Repetition rates of ≤ 10 Hz have received little attention in the context of the ASSR stimulus-response analysis approach which is speculated to provide technical advantages, if not additional/supplemental information, over more traditional transient stimulus-response paradigms. DESIGN: Magnitudes were measured at repetition rates from 0.75 to 80 Hz, using trains of recurrent tone-burst stimuli. STUDY SAMPLE: Twenty-five normal-hearing adults during sleep and awake. RESULTS: Results show that response magnitudes for adults tested during sleep were significantly larger than those for adults while awake at repetition rates <5 Hz. Magnitudes were largest at the two lowest repetition rates, as expected from corresponding results obtained using conventional methods. CONCLUSIONS: The analysis methods used in this paper may give information that will have applications for clinical testing. Results confirm and extend knowledge of the effects of repetition rate on AEPs over a range embracing the gamut of responses as traditionally classified, specifically at the beginning stages of natural sleep.

Steady-state analysis of auditory evoked potentials over a wide range of stimulus repetition rates: profile in children vs. adults.

OBJECTIVE: Auditory steady-state responses (ASSR) evoked by recurrent brief tones were assessed over a wide range of stimulus repetition rates apropos the traditionally measured obligatory, transient, auditory evoked potentials. Repetition rates of ≤ 10 Hz have received little attention in the context of the ASSR stimulus-response analysis approach, speculated to provide technical advantages/additional information over more traditional transient stimulus-response paradigms. DESIGN: Magnitudes were measured at repetition rates from 0.75 to 80 Hz, using trains of repeated tone-burst stimuli. STUDY SAMPLE: Twelve normal-hearing children and a reference sample of 25 young adults. RESULTS: Results show that response magnitudes were significantly larger in children than adults at repetition rates of ≤ 5 Hz. Magnitudes were largest at the two lowest repetition rates, following the trends expected from the transient auditory evoked potential (AEP) literature. The harmonic sum is proposed as a more appropriate measure of response magnitude than amplitude of the fundamental alone. CONCLUSIONS: The analysis methods used in this paper may give information that will have applications for clinical testing. Of pragmatic importance is that the stimulus rate profile could be determined without subjective wave identification and/or interpretation, and thus by a method that is inherently more objective than conventional AEP analysis.

Steady-state analysis of auditory evoked potentials over a wide range of stimulus repetition rates: profile in adults.

OBJECTIVE: Quasi-steady-state responses were assessed over a wide range of stimulus repetition rates embracing well the traditionally measured transient AEPs (obligatory auditory evoked potentials of all latencies). Repetition rates of ≤10 Hz have received little attention in the context of the ASSR stimulus-response analysis approach which is speculated to provide technical advantages, if not additional information, over more traditional transient stimulus-response paradigms. DESIGN: A measure introduced and defined as the sum of the response at the stimulus frequency and its harmonics. The magnitude of steady-state responses were measured at repetition rates from 0.75 to 80 Hz, using trains of repeated tone-burst stimuli. STUDY SAMPLE: Twenty-five normal-hearing adults. RESULTS: Results show that the magnitudes of the response across repetition rates are largest at the two lowest rates, following trends expected from the transient AEP literature. Good reliability overall was observed for the harmonic sum. CONCLUSIONS: The analysis methods used in this paper may give information that will have application for clinical testing. Of pragmatic importance is that the rate profile could be determined without subjective wave identification and/or interpretation, and thus by a method that is inherently more objective than conventional AEP tests.

Classifying subgroups of chronic low back pain patients based on lifting patterns.

OBJECTIVE: To compare self-reported measures of chronic lower back pain (CLBP) patients who were assigned to 2 subgroups based on their lifting patterns performed during a repetitive lifting task. DESIGN: Cross-sectional study. SETTING: Research laboratory PARTICIPANTS: CLBP subjects (n=81) and pain-free controls (n=53). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Measures of lifting patterns and self-reported disability, pain, and psychosocial aspects. RESULTS: Two CLBP subgroups were found: 1 group that lifts similarly to control subjects (n=35) and 1 group that lifts very differently from controls (n=46). The CLBP group that lifted differently than controls reported higher pain intensity (P=.005), higher pain severity (P=.025), and lower self-efficacy (P=.013) than the CLBP group that lifted similarly to controls. CONCLUSIONS: A classification system based on lifting patterns identified 2 CLBP subgroups that were significantly different on lifting and self-reported measures, indicating the importance of physical functioning measures in classification systems.

Speech signal modification to increase intelligibility in noisy environments.

The role of transient speech components on speech intelligibility was investigated. Speech was decomposed into two components--quasi-steady-state (QSS) and transient--using a set of time-varying filters whose center frequencies and bandwidths were controlled to identify the strongest formant components in speech. The relative energy and intelligibility of the QSS and transient components were compared to original speech. Most of the speech energy was in the QSS component, but this component had low intelligibility. The transient component had much lower energy but was almost as intelligible as the original speech, suggesting that the transient component included speech elements important to speech perception. A modified version of speech was produced by amplifying the transient component and recombining it with the original speech. The intelligibility of the modified speech in background noise was compared to that of the original speech, using a psychoacoustic procedure based on the modified rhyme protocol. Word recognition rates for the modified speech were significantly higher at low signal-to-noise ratios (SNRs), with minimal effect on intelligibility at higher SNRs. These results suggest that amplification of transient information may improve the intelligibility of speech in noise and that this improvement is more effective in severe noise conditions.

Towards the development of a pediatric ventricular assist device.

The very limited options available to treat ventricular failure in children with congenital and acquired heart diseases have motivated the development of a pediatric ventricular assist device at the University of Pittsburgh (UoP) and University of Pittsburgh Medical Center (UPMC). Our effort involves a consortium consisting of UoP, Children's Hospital of Pittsburgh (CHP), Carnegie Mellon University, World Heart Corporation, and LaunchPoint Technologies, Inc. The overall aim of our program is to develop a highly reliable, biocompatible ventricular assist device (VAD) for chronic support (6 months) of the unique and high-risk population of children between 3 and 15 kg (patients from birth to 2 years of age). The innovative pediatric ventricular assist device we are developing is based on a miniature mixed flow turbodynamic pump featuring magnetic levitation, to assure minimal blood trauma and risk of thrombosis. This review article discusses the limitations of current pediatric cardiac assist treatment options and the work to date by our consortium toward the development of a pediatric VAD.

The PediaFlow pediatric ventricular assist device.

The very limited options available to treat ventricular failure in patients with congenital and acquired heart diseases have motivated the development of a pediatric ventricular assist device (VAD). Our effort involves a consortium consisting of the University of Pittsburgh, Carnegie Mellon University, Children's Hospital of Pittsburgh, World Heart Corporation, and LaunchPoint Technologies, LLC. The overall aim of our program is to develop a highly reliable, biocompatible VAD for chronic support (6 months) of the unique and high-risk population of children between 3 kg and 15 kg (patients from birth to 2 years of age). The innovative pediatric VAD we are developing (PediaFlow) is based on a miniature mixed-flow turbodynamic pump featuring magnetic levitation, with the design goal being to assure minimal blood trauma and risk of thrombosis. This article discusses the limitations of current pediatric cardiac assist treatment options and the work to date by our consortium toward the development of a pediatric VAD.

The use of splines to calculate jerk for a lifting task involving chronic lower back pain patients.

Motion differences in a repetitive lifting task have been described previously using differences in the timing of body angle changes during the lift. These timing changes relied on small differences of motion and are difficult to measure. The purpose of this study was to evaluate shoulder jerk (rate of change of acceleration) in a repetitive lifting task as an alternative parameter to detect differences of motion between controls and chronic lower back pain (CLBP) patients and to measure the impact of a rehabilitation program on jerk. The jerk calculation was a noisy measure, since jerk is the third derivative of position; consequently a simulation was performed to evaluate smoothing methods. Woltring's generalized cross-validation spline produced the best estimates of the third derivative and was fit to subject data. The root mean square (rms) amplitude of jerk was used for comparison. Significant group differences were found. CLBP patients performed lifts with lower jerk values than controls and, as the task progressed, both groups increased jerk. After completion of a rehabilitation program, CLBP patients performed lifts with greater rms jerk. In general, patients performed lifts with lower jerk values than controls, suggesting that pain impacts lifting style.

In vitro evaluation of multiobjective hemodynamic control of a heart-assist pump.

Ventricular assist devices now clinically used for treatment of end-stage heart failure require responsive and reliable hemodynamic control to accommodate the continually changing demands of the body. This is an essential ingredient to maintaining a high quality of life. To satisfy this need, a control algorithm involving a trade-off between optimal perfusion and avoidance of ventricular collapse has been developed. An optimal control strategy has been implemented in vitro that combines two competing indices: representing venous return and prevalence of suction. The former is derived from the first derivative of diastolic flow with speed, and the latter derived from the harmonic spectra of the flow signal. The responsiveness of the controller to change in preload and afterload were evaluated in a mock circulatory simulator using a HeartQuest centrifugal blood pump (CF4b, MedQuest Products, Salt Lake City, UT). To avoid the need for flow sensors, a state estimator was used, based on the back-EMF of the actuator. The multiobjective algorithm has demonstrated more robust performance as compared with controllers relying on individual indices.

Body motion during repetitive isodynamic lifting: a comparative study of normal subjects and low-back pain patients.

To quantify performance differences between patients with low-back pain (LBP) and a control group during their performance of a repetitive isodynamic lifting task. Case-control study was done. LBP patients were recruited and tested at an outpatient ambulatory chronic pain rehabilitation program before treatment was begun. Fifty-three LBP patients who had prolonged back pain and 53 age and gender matched pain-free control subjects. Overall lifting performance measures included weight lifting and number of lifts completed; kinematic measures of hip and knee movements during lifting were described by hyperbolic tangent models, and included static measures of starting and ending angles, and dynamic measures of midpoint, falltime, and lift speed. Control subjects completed significantly more lifts and lifted more weight than patients. Starting hip flexion was greater for controls and starting knee flexion was greater for patients, indicating that patients used more of a leg lift. Patients and controls also differed significantly on dynamic measures, particularly lifting speed and hip and knee temporal midpoints. Major static and dynamic motion differences were found between LBP patients and controls as they performed repetitive lifting under a constant load. These findings indicate that body motion parameters, in addition to more common strength and endurance measures, are necessary to describe the impact of persistent LBP on a person's lifting abilities.

Efficacy of percutaneous electrical nerve stimulation for the treatment of chronic low back pain in older adults.

OBJECTIVES: To determine the efficacy of a complementary analgesic modality, percutaneous electrical nerve stimulation (PENS), for the treatment of chronic low back pain (CLBP) in community-dwelling older adults. DESIGN: Randomized, controlled clinical trial. SETTING: University of Pittsburgh Pain Evaluation and Treatment Institute. PARTICIPANTS: Thirty-four English speaking, community-dwelling adults aged 65 and older with CLBP of at least moderate intensity experienced every day or almost every day. INTERVENTION: Subjects were randomized to receive twice-weekly PENS and physical therapy (PT) or sham PENS and physical therapy for 6 weeks. MEASUREMENTS: At baseline, immediately after the 6-week intervention period, and 3 months later, the primary outcome measures pain intensity and pain-related disability were assessed. The secondary outcome measures physical performance (timed chair rise, functional reach, gait speed, static and isoinertial lifting), psychosocial factors (mood, sleep, and life control), and cognitive function (measures of attention, concentration, and mental flexibility) were also collected. RESULTS: Subjects randomized to PENS plus PT displayed significant reductions in pain intensity measures from pre- to posttreatment (P <.001), but the sham PENS plus PT group did not (P =.94). These pain reduction effects were maintained at 3-month follow-up. Similarly, significant reductions in pain-related disability were observed at posttreatment (P =.002) for the PENS plus PT group and were maintained at follow-up, but the sham PENS plus PT group did not show reductions in pain-related disability (P =.81). Of the secondary outcome measures, psychosocial function, timed chair rise, and isoinertial lifting endurance also improved significantly at posttreatment for the PENS plus PT group, and their improvement was sustained at 3-month follow-up, but the sham PENS plus PT did not display significant changes on these measures after treatment. CONCLUSION: This preliminary study suggests that PENS may be a promising treatment modality for community-dwelling older adults with CLBP, as demonstrated by reduction in pain intensity and self-reported disability, and improvement in mood, life control, and physical performance. Larger studies with longer duration of follow-up are needed to validate these findings and support the use of PENS in clinical practice.

The influence of weight and starting height on lifting mechanics in lower extremity amputees.

This study compares the lifting mechanics of lower extremity amputees to controls and describes the influence of weight lifted and starting height on lifting style. Subjects included three individuals with transtibial amputation (TTA), two individuals with transfemoral amputation (TFA), and three able-bodied controls (CO). Amputee subjects performed six repetitions of six weights, randomly ordered, from two starting heights. TTA lifted from 30 cm and knee height, TFA from knee and thigh height, and controls from all three heights. Data were obtained from a work simulator, force plate, and a motion analysis system, with starting posture index, lateral sway index, lift duration, synchrony index, and hip moments and elbow moments as dependent measures. The results for each lifting height were analyzed using a mixed model repeated measures MANOVA to test for group and weight differences and post hoc tests were applied when appropriate. Results suggest that healthy lower extremity amputees who have had a number of years to adjust to their prosthesis and develop compensatory strategies can complete a repetitive lifting task at a performance level very similar to able-bodied controls. The most consistent group differences detected were in the timing parameters: synchrony and duration. TTA and TFA tended to lift with less synchronization of hip and knee movements than able-bodied controls and to initiate the lift with their upper bodies. In contrast, able-bodied controls tended to move their upper and lower bodies more synchronously during the lift. TTA had longer lift durations than CO. In terms of stability and moments generated, TTA lifted very similarly to controls. TFA used a different lifting style that involved higher moments and more use of the upper body, particularly for lifts of heavier weights. TFA appeared to be less stable than CO, while TTA did not appear to be less stable than CO.

Psychosocial predictors of physical performance in disabled individuals with chronic pain.

OBJECTIVES: First, to identify what physical performance differences existed between a group of disabled individuals with chronic pain and a control group of pain-free individuals with comparable disabilities; and second, to test a psychosocial model designed to evaluate which psychosocial constructs were predictive of performance in disabled individuals with chronic pain. DESIGN: Case-comparison study. SETTING: Ambulatory university laboratory. PARTICIPANTS: A community sample of 62 individuals with lower limb amputations or paraplegia, 31 with chronic pain and 31 pain-free. INTERVENTION: Standardized lifting and wheel-turning tasks. MAIN OUTCOME MEASURES: Static strength, endurance, lifting speed, lateral and anterior-posterior sway, and multidimensional psychosocial measures. RESULTS Disabled individuals with chronic pain had decreased endurance for both the lifting (p <0.001) and the wheel-turning (p <0.05) tasks. A psychosocial model of physical performance also was evaluated. Using confirmatory factor analysis, 31 measures were used to validate 8 theoretical constructs: emotional functioning, pain intensity, pain cognitions, physical functioning, social functioning, task-specific self-efficacy, performance outcome, and performance style. Regression analyses indicated that more than 90% of the variance in performance was predicted by psychosocial factors, with self-efficacy, perceived emotional and physical functioning, pain intensity, and pain cognitions showing the highest associations. CONCLUSIONS: Chronic pain was found to significantly reduce the performance in individuals with lower limb amputations and paraplegia. A strong association was found between performance and psychosocial factors in disabled individuals with chronic pain. These findings extend the existing literature by validating that psychosocial models of chronic pain can be applied to the disabled population, with results similar to those of other chronic pain samples.

Mandibular kinematics represented by a non-orthogonal floating axis joint coordinate system.

There are many methods used to represent joint kinematics (e.g., roll, pitch, and yaw angles; instantaneous center of rotation; kinematic center; helical axis). Often in biomechanics internal landmarks are inferred from external landmarks. This study represents mandibular kinematics using a non-orthogonal floating axis joint coordinate system based on 3-D geometric models with parameters that are "clinician friendly" and mathematically rigorous. Kinematics data for two controls were acquired from passive fiducial markers attached to a custom dental clutch. The geometric models were constructed from MRI data. The superior point along the arc of the long axis of the condyle was used to define the coordinate axes. The kinematic data and geometric models were registered through fiducial markers visible during both protocols. The mean absolute maxima across the subjects for sagittal rotation, coronal rotation, axial rotation, medial-lateral translation, anterior-posterior translation, and inferior-superior translation were 34.10 degrees, 1.82 degrees, 1.14 degrees, 2.31, 21.07, and 6.95 mm, respectively. All the parameters, except for one subject's axial rotation, were reproducible across two motion recording sessions. There was a linear correlation between sagittal rotation and translation, the dominant motion plane, with approximately 1.5 degrees of rotation per millimeter of translation. The novel approach of combining the floating axis system with geometric models succinctly described mandibular kinematics with reproducible and clinician friendly parameters.

Relation of jaw sounds and kinematics visualized and quantified using 3-D computer animation.

The management of jaw pain or temporomandibular disorders (TMD) has been controversial regarding temporomandibular joint (TMJ) sounds and their implication regarding TMD prognosis. 3-D computer animation was used to visualize and quantify the internal mechanics of natural mandibular motion synchronized with TMJ sounds. Mandibular movements of four TMD patients and two healthy subjects were recorded using CCD cameras and reflective markers. Sounds were recorded with electret microphones. Magnetic resonance imaging was used to create 3-D geometric models. Visualization of the internal anatomy, mandibular condyle and glenoid fossa, revealed that the condyle initially rotated within the fossa and then moved out of the fossa along, and well beyond, the articular eminence. Power in the opening sound recordings after the condyle moved out of the fossa was significantly greater than when the condyle was within the fossa (p<0.001). The louder opening sounds were often classified as TMJ clicks, implying that clicks occur after the condyle moves out of the fossa. The 3-D computer animation should help resolve the implication of TMJ sounds regarding TMD prognosis by providing visualization and quantization of the TMJ internal mechanics during sound production.

A control system for rotary blood pumps based on suction detection.

A control system for rotary ventricular assist devices was developed to automatically regulate the pumping speed of the device to avoid ventricular suction. The control system comprises a suction detector and a fuzzy logic controller (FLC). The suction detector can correctly classify pump flow patterns, using a discriminant analysis (DA) model that combines several indices derived from the pump flow signal, to classify the pump status as one of the following: no suction (NS), moderate suction (MS), and severe suction (SS). The discriminant scores, which are the output of the suction detector, were used as inputs to the FLC. Based on this information, the controller updates pump speed, providing adequate flow and pressure perfusion to the patient. The performance of the control system was tested in simulations over a wide range of physiological conditions, including hypertension, exercise, and strenuous exercising for healthy, sick, and very sick hearts, using a lumped parameter model of the circulatory system coupled with a left ventricular assist device. The controller was able to maintain cardiac output and mean arterial pressure within acceptable physiologic ranges, while avoiding suction, demonstrating the feasibility of the proposed control system.

Hemodynamic controller for left ventricular assist device based on pulsatility ratio.

Hemodynamic control of left ventricular assist devices (LVADs) is generally a complicated problem due to diverse operating environments and the variability of the patients: both the changes in the circulatory and metabolic parameters as well as disturbances that require adjustment to the operating point. This challenge is especially acute with control of turbodynamic blood pumps. This article presents a pulsatility ratio controller for LVAD that provides a proper perfusion according to the physiological demands of the patient, while avoiding adverse conditions. It utilizes the pulsatility ratio of the flow through the pump and pressure difference across the pump as a control index and adjusts the pump speed according to the reference pulsatility ratio under the different operating conditions. The simulation studies were performed to evaluate the controller in consideration of the sensitivity to afterload and preload, influence of the contractility, and effect of suction sensitivity. The controller successfully adjusts the pump speed according to the reference pulsatility ratio, and supports the natural heart under diverse pump operating conditions. The resulting safe pump operations demonstrate the solid performance of the controller in terms of sensitivity to afterload and preload, influence of the contractility, and effect of suction sensitivity.

A rule-based controller based on suction detection for rotary blood pumps.

A rule-based controller for rotary ventricular assist devices was developed to automatically regulate the pumping speed of the device without introducing suction in the ventricle. The control approach is based on a discriminant analysis function that detects the occurrence of suction, providing the input for the rule-based controller. This controller has been tested in simulations showing the ability to autonomously adjust pump flow according to the patient's level of activity, while sustaining adequate perfusion pressures. The performance of the system (suction detector and controller) was tested for several levels of activity and contractility state of the left ventricle, using a lumped parameter model of the circulatory system coupled with a left ventricular assist device. In all cases, the controller kept cardiac output and mean arterial pressure within acceptable physiologic ranges.

Evaluating reliability of hidden Markov models that describe the lifting patterns of chronic lower back pain patients and controls.

Two hidden Markov models (HMMs) were designed to identify sub-groups of chronic lower back pain (CLBP) subjects based on time series of lifting parameters obtained during a repetitive lifting task. Two simulation studies were conducted to determine the reliability of this approach, using data from the repetitive lifting study. The first simulation verifies that control and CLBP HMMs based on these data can reliably identify sequences that were generated from that model. The second simulation determines whether the HMMs can reliably identify sequences that are intentionally misclassified (CLBP lifting sequences included in the control group and visa versa). The kappa statistic is used to quantify reliability. The simulation results show that the HMMs provide a reliable technique to analyze time series of lifting patterns and can be used to identify misclassified subjects as a subgroup.