The continued importance of comparative auditory research to modern scientific discovery.

A rich history of comparative research in the auditory field has afforded a synthetic view of sound information processing by ears and brains. Some organisms have proven to be powerful models for human hearing due to fundamental similarities (e.g., well-matched hearing ranges), while others feature intriguing differences (e.g., atympanic ears) that invite further study. Work across diverse "non-traditional" organisms, from small mammals to avians to amphibians and beyond, continues to propel auditory science forward, netting a variety of biomedical and technological advances along the way. In this brief review, limited primarily to tetrapod vertebrates, we discuss the continued importance of comparative studies in hearing research from the periphery to central nervous system with a focus on outstanding questions such as mechanisms for sound capture, peripheral and central processing of directional/spatial information, and non-canonical auditory processing, including efferent and hormonal effects.

An evaluation of the CARL manikin for use in "patient-free" real ear measurement: consistency and comparison to normative data.

OBJECTIVE: Simulation-based learning experiences provide low-risk opportunities for procedural training and practice in audiology. A series of real ear measurements (REM) were completed using Clinical Assistant for Research and Learning (CARL) manikins to determine expected responses and to compare to normative data. DESIGN: (1) Real-ear Unaided Response (REUR) curves were measured with one CARL and each of three ear styles. (2) Test/retest reliability was evaluated by repeating each REUR. (3) Real ear to coupler difference (RECD) values for foam-tip and custom earmolds were calculated. (4) The reliability across copies of the CARL heads was evaluated by comparing REUR measurement from one set of ears on 4 heads. STUDY SAMPLE: Four adult CARL manikins and thirty ears (5 sets of large, small, and bent). RESULTS: Within each ear category, the average difference across frequencies from one ear to the next was less than 2.5 dB with no significant individual difference more than 5.8 dB. Test/retest reliability was excellent. Typical REUR and RECD curves were created for each ear style and compared to published data on human ears. CONCLUSIONS: REM using the adult CARL head are predictable and repeatable making this simulator a good tool for audiological training.

Transcutaneous auricular vagus nerve stimulation cannot modulate the P3b event-related potential in healthy volunteers.

OBJECTIVE: The release of cortical norepinephrine is one of the possible mechanisms of action of vagus nerve stimulation (VNS), a neuromodulatory treatment currently under investigation for cognitive impairment. Transcutaneous auricular VNS (taVNS) may be able to activate vagal nerve branches ending in the brainstem's locus coeruleus (LC) non-invasively. The aim was to investigate if acute taVNS can modulate the P3b, a cognitive event-related potential (ERP) reflecting noradrenergic brain activation under control of the LC. METHODS: Thirty-nine healthy volunteers performed an auditory oddball task during no stimulation, sham stimulation and taVNS in a randomized order. P3b amplitude, latency and behavioral outcome parameters were compared between conditions using linear mixed models. RESULTS: P3b amplitude and latency during taVNS did not differ significantly from sham or control. Reaction time shortened and P3b latency prolonged with repetition of the oddball task. CONCLUSIONS: We were unable to modulate cognitive ERPs by means of acute taVNS in a large group of healthy volunteers. SIGNIFICANCE: Targeting vagal nerve fibres via a transcutaneous approach did not alter the P3b in healthy participants. The stimulation parameters used and transient delivery of taVNS might be insufficient to adequately modulate the LC. Also, a disbalanced locus coeruleus - norepinephrine system in patients may be more prone for improvement.

Neuroauriculotherapy: Framework and Remarks for a possible use in Voice Medicine / Neuroauriculoterapia: marco y observaciones para un posible uso en medicina de la voz

Aim. Neuroauriculotherapy (NAT) is a branch of medicine, which, thanks to its diagnostic and therapeutic value, is a powerful tool at the service of both physician and patient. In our experience, as it is discussed in this article, neuroauriculotherapy can have successful applications in voice science and in phoniatrics. The aim of this article is to open a discussion about possible applications of neuroauriculotherapy in voice medicine. Introduction. From the diagnostic point of view, it is possible to explore, with a palpeur (i.e., a tool that provides a constant pressure) or a "spot-hunter", the presence of a perturbation into a particular organ or area, and its return to normal during treatment. Indeed, at the level of the ear auricle, representations of an organ, its in-nervation, its muscular components, etc., are fixed. These spots or voxels correspond absolutely to the respective sensory, motor, visceral, among other spots. Therefore, if any abnormal potential comes from the periphery, it will illuminate the spots both at the cortical level and in the pavilion ­a real display with a constantly active touch screen. The spot can be treated with needles in the context of a neurophysiological strategy to send a message to the brain.Reflection. NAT appears to be a good method to improve the treatment of voice problems, enhancing the results of other therapies based on drugs or rehab and in-ducing relaxation. In neuroauriculotherapy, the ear is used to give the brain orders in a process which has a logical basis in neurophysiology.Conclusion. Diseases of the vocal tract can be dysfunctional or organic. According to our clinical experience, we can say that neuroauriculotherapy can be used in both cases. Neuroauriculotherapy is also extremely effective in voice therapy, both alone and in combination with other therapies, as there is no conflict among them

Objetivo. La neuroauriculoterapia (NAT) es una rama de la medicina que, gracias a su valor diagnóstico y terapéutico, constituye una poderosa herramienta al servicio del médico y del paciente. En nuestra experiencia, como se comenta en este artículo, la neuroauriculoterapia puede tener aplicaciones exitosas en la ciencia de la voz y en foniatría. El objetivo de este artículo es abrir una discusión sobre las posibles aplica-ciones de la neuroauriculoterapia en la medicina de la voz.Introducción. Desde el punto de vista del diagnóstico, es posible explorar, con un palpeur (i.e., una herramienta que proporciona una presión constante) o un "spot-hunter", la presencia de una perturbación en un órgano o área en particular, y su retorno a la normalidad durante el tratamiento. En efecto, a nivel del pabellón auricular se fijan representaciones de un órgano, su inervación, sus componentes musculares, etc. Estos puntos o vóxeles corresponden absolutamente a los respectivos puntos sensoriales, motores, viscerales, entre otros. Por lo tanto, si algún potencial anormal proviene de la periferia, iluminará los puntos tanto a nivel cortical como en el pabellón ­una pantalla real con una pantalla táctil constantemente activa. El punto se puede tratar con agujas en el contexto de una estrategia neurofisiológica para enviar un mensaje al cerebro.Reflexión. NAT parece ser un buen método para mejorar el tratamiento de los problemas de voz, potenciando los resultados de otras terapias basadas en fármacos o rehabilitación e induciendo a la relajación. En neuroauriculoterapia se utiliza el oído para dar órdenes al cerebro en un proceso que tiene una base lógica en la neurofisiología.Conclusión. Las enfermedades del tracto vocal pueden ser disfuncionales u orgáni-cas. Según nuestra experiencia clínica, podemos decir que la neuroauriculoterapia se puede utilizar en ambos casos. La neuroauriculoterapia también es extremadamente eficaz en la terapia de la voz, tanto sola como en combinación con otras terapias, ya que no existe conflicto entre ellas

Acoustic wave response to groove arrays in model ears.

Many mammals and some owls have parallel grooved structures associated with auditory structures that may be exploiting acoustic products generated by groove arrays. To test the hypothesis that morphological structures in the ear can manipulate acoustic information, we expose a series of similar-sized models with and without groove arrays to different sounds in identical conditions and compare their amplitude and frequency responses. We demonstrate how two different acoustic signals are uniquely influenced by the models. Depending on multiple factors (i.e., array characteristics, acoustic signal used, and distance from source) the presence of an array can increase the signal strength of select spectral components when compared to a model with no array. With few exceptions, the models with arrays increased the total amplitude of acoustic signals over that of the smooth model at all distances we tested up to 160 centimeters. We conclude that the ability to uniquely alter the signal based on an array's characteristics is evolutionarily beneficial and supports the concept that different species have different array configurations associated with their biological needs.

Estimation of the time since death based on body cooling: a comparative study of four temperature-based methods.

The estimation of the time since death is an important task in forensic medicine that mainly relies on body cooling in the early post-mortem period. The rectum has been traditionally used to determine the central core temperature after death, though the external auditory canal has been proposed as an alternative site by several authors. The objective of this study was to assess the ability of four body temperature-based methods (Henssge's rectal nomogram, Henssge's brain nomogram, and Baccino's both interval and global formulae based on ear temperature) to estimate the post-mortem interval (PMI). PMI calculations were carried out based on ear and rectal temperature measurements performed with a reference metal probe on 100 inpatient bodies with an average PMI of 4.5 ± 2.5 h. For practical purposes, ear temperature measurements were applied to Henssge's brain nomogram. All methods could be applied to 81 cases, since high body temperatures prevented the rectal nomogram method from being used in most of the remaining cases. The actual PMI was within the time interval (95% CI) provided by the rectal nomogram method in 72.8% of cases, and in 63.0% to 76.5% of cases when using ear temperature-based methods. The proportions of adequate estimates did not differ statistically between the different methods. When the methods failed to provide a reliable time interval, all except the brain nomogram tended to underestimate the PMI. Similar results were obtained in the subgroup of normothermic patients at the time of death (n = 63), confirming that the PMI calculations had not been biased by the inclusion of patients with thermoregulation disorders. Our findings are in accordance with the published literature which suggests that ear temperature-based methods are as reliable as those based on rectal temperature for estimating the early PMI and that they may be used as quick, simple, and non-invasive methods at the scene, although caution should be taken in interpreting their results given their high error rates. However, further research including field studies is recommended to confirm their practical relevance in forensic casework.

Is infrared thermometry suitable for the determination of the time since death based on ear temperature? A comparative study of two measurement methods.

Infrared thermometry has been proposed as an interesting alternative to probe thermometers for recording ear temperature in cadavers to estimate the postmortem interval (PMI), but it has still to be validated in this setting. Our objective was to compare the performance of an infrared thermometer to that of a reference probe thermometer for measuring ear temperature. Temperature measurements were performed on 100 cadavers (mean PMI: 4.5 ± 2.5 h) using the infrared and the probe thermometers. The repeatability of the measurements, their correlation, and the agreement between both methods were evaluated. We showed a good repeatability of the measurements with the infrared thermometer (Lin's concordance correlation coefficient (CCC) = 0.93 [0.72;0.98] for the right ear; CCC = 0.94 [0.75;0.98] for the left ear), and there was a strong and significant correlation between measurements provided by the two instruments (p < 0.001). However, a poor agreement was found between both methods, with a systematic underestimation of about 2 °C of the ear temperature when measured with the infrared thermometer. Data from auricular infrared thermometry should not be applied to algorithms developed for probe thermometers to estimate the PMI. Further research is needed to develop a reliable algorithm specifically based on infrared thermometry.

Horizontal nystagmus is gravity-dependent in patients with vestibular neuritis.

OBJECTIVE: Horizontal nystagmus can be observed in the acute stage of vestibular neuritis, Although the direction of the nystagmus is gravity independent, its intensity can be influenced by gravity. In this study, we compared the slow phase velocity (SPV) of horizontal nystagmus in different head positions in patients with vestibular neuritis to analyze the static effects of gravity on horizontal nystagmus. METHODS: The study enrolled 22 vestibular neuritis patients with spontaneous horizontal nystagmus (9 men, 13 women; median age 40 years). The deficits were right-sided in 9 patients and left-sided in 13. The nystagmus was recorded in the sitting, supine, right and left ear down positions. The intensity of spontaneous nystagmus in the sitting versus while supine position, and SPV in affected ear down (AED), healthy ear down (HED), and supine positions were compared. The position-induced nystagmus was calculated to quantify the effect of head positions on nystagmus. RESULTS: The nystagmus intensity in the supine position had no statistic difference than when sitting, with a median value of 6.3°/s and 5.6°/s, respectively(P = 0.355). SPV in AED had a median value of 7.8°/s, which was greater than when supine (P = 0.008) and HED (4.8°/s) (P < 0.001). Position-induced nystagmus in left and right ear-down positions were 1.4°/s and -1.4°/s respectively, which were significantly correlated (Spearman's ρ = -0.848, P < 0.001). CONCLUSIONS: The nystagmus intensity in vestibular neuritis is gravity dependent; it's greater in AED than in supine and HED, and the effect of head position on nystagmus was nearly symmetrical in left and right ear-down positions.

Immediate effect of non-invasive auricular acupoint stimulation on the performance and meridian activities of archery athletes: A protocol for randomized controlled trial.

BACKGROUND: Archery has existed in human history for millenniums. Being a unique exercise and precision sport, the keys to performance are emotional control, attention, and concentration rather than explosive force, muscle power, and endurance. During the execution of archery, attention is the key to performance in elite players, especially in the initial period while drawing the bow. Auricular acupoint stimulation is one of the therapeutic methods of traditional Chinese medicine and has been reported for its use in amplifying the anesthesia effect, weight reduction, cessation of substance abuse, and autonomic nervous modulation. METHODS: The study will recruit archery players in school teams among junior and senior high schools and colleges. The subjects will be randomly assigned to the ear and sham acupressure groups. This is a randomized controlled trial with crossover design. The outcome measures will be obtained, including the meridian activities and balance index with Ryodoraku device, the movement stability with WIMU tracking system, the continuous heart rate record, and the scores of the 2 sections as the performance. The subjects will rate their attention and fatigue levels through self-reported questionnaires. OBJECTIVES: This study aims to investigate the immediate effect of non-invasive auricular acupoint stimulation on the performance and meridian activities of archery athletes. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04637607.

Thermal infrared imaging based facial temperature in comparison to ear temperature during a real-driving scenario.

Motion Sickness is associated with a variety of symptoms, which differ in occurrence rate and intensity between individuals. In order to research the cause of car sickness and develop countermeasures, it is important to determine symptoms and their severity objectively. A tool for this purpose could be the assessment of physiological reactions due to motion sickness. This paper describes and discusses a methodology to identify changes in facial skin temperatures in a real-driving study. Common techniques had to be adjusted in order to meet the requirements given by the challenges of in-car-recording. The examined data was generated in a previous study, which was designed to research motion sickness in a driving environment. A pre-processing technique had to be developed to magnify features on the face and subsequently improve the tracking in thermal imagery. After the pre-processing, regions of interest (ROI) were manually marked and tracked in thermal images. The thereby assessed facial skin temperatures were compared to tympanic temperatures. Derived temperatures from the forehead as well as from the 20 hottest pixels within the face indicated a better tracking, while the nose tip was more affected by detection errors. The correlation of the three features with the tympanic temperature showed remarkable differences between a baseline measurement and the actual driving. Less than 10% of the data derived during the driving and up to 30% of the data during the baseline measurement correlated highly. It is concluded that detecting changes in facial skin temperature using thermal infrared imaging in a moving car is challenging and results are hardly comparable to tympanic temperatures. Future research should aim at the different influencing factors of skin and tympanic temperature, while enhancing tracking or detection of ROI could be achieved by reducing the passengers' movements or choosing the target area more carefully.

Ear-EEG for sleep assessment: a comparison with actigraphy and PSG.

PURPOSE: To assess automatic sleep staging of three ear-EEG setups with different electrode configurations and compare performance with concurrent polysomnography and wrist-worn actigraphy recordings. METHODS: Automatic sleep staging was performed for single-ear, single-ear with ipsilateral mastoid, and cross-ear electrode configurations, and for actigraphy data. The polysomnography data were manually scored and used as the gold standard. The automatic sleep staging was tested on 80 full-night recordings from 20 healthy subjects. The scoring performance and sleep metrics were determined for all ear-EEG setups and the actigraphy device. RESULTS: The single-ear, the single-ear with ipsilateral mastoid setup, and the cross-ear setup performed five class sleep staging with kappa values 0.36, 0.63, and 0.72, respectively. For the single-ear with mastoid electrode and the cross-ear setup, the performance of the sleep metrics, in terms of mean absolute error, was better than the sleep metrics estimated from the actigraphy device in the current study, and also better than current state-of-the-art actigraphy studies. CONCLUSION: A statistically significant improvement in both accuracy and kappa was observed from single-ear to single-ear with ipsilateral mastoid, and from single-ear with ipsilateral mastoid to cross-ear configurations for both two and five-sleep stage classification. In terms of sleep metrics, the results were more heterogeneous, but in general, actigraphy and single-ear with ipsilateral mastoid configuration were better than the single-ear configuration; and the cross-ear configuration was consistently better than both the actigraphy device and the single-ear configuration.

Effects of noise on integration of acoustic and electric hearing within and across ears.

In bimodal listening, cochlear implant (CI) users combine electric hearing (EH) in one ear and acoustic hearing (AH) in the other ear. In electric-acoustic stimulation (EAS), CI users combine EH and AH in the same ear. In quiet, integration of EH and AH has been shown to be better with EAS, but with greater sensitivity to tonotopic mismatch in EH. The goal of the present study was to evaluate how external noise might affect integration of AH and EH within or across ears. Recognition of monosyllabic words was measured for normal-hearing subjects listening to simulations of unimodal (AH or EH alone), EAS, and bimodal listening in quiet and in speech-shaped steady noise (10 dB, 0 dB signal-to-noise ratio). The input/output frequency range for AH was 0.1-0.6 kHz. EH was simulated using an 8-channel noise vocoder. The output frequency range was 1.2-8.0 kHz to simulate a shallow insertion depth. The input frequency range was either matched (1.2-8.0 kHz) or mismatched (0.6-8.0 kHz) to the output frequency range; the mismatched input range maximized the amount of speech information, while the matched input resulted in some speech information loss. In quiet, tonotopic mismatch differently affected EAS and bimodal performance. In noise, EAS and bimodal performance was similarly affected by tonotopic mismatch. The data suggest that tonotopic mismatch may differently affect integration of EH and AH in quiet and in noise.

Improved binaural speech reception thresholds through small symmetrical separation of speech and noise.

Speech perception in noise is challenging and is improved by binaural hearing. Since signal processing of assistive hearing devices often modifies or masks the peripheral binaural head-shadow or better-ear effects, central binaural processing should be measured separately. In a prospective study, 10 listeners with normal hearing were tested with the German matrix sentence test in a set-up with two loudspeakers located at opposite angles in the horizontal plane with respect to S0N0. The speech reception threshold (SRT) was investigated depending on the separation angle between speech and noise. The lowest (best) SRT was obtained for a separation of target and interfering source from S0N0 at an angle of about S±60°N∓60°. The derived normative curve was comparable to SRTs predicted by the binaural-speech-intelligibility-model. The systematic separation of signal and noise showed a significant improvement in speech intelligibility for normal-hearing people even for small separation angles. This experimental setting was verified. This study aimed to assess the effect of small sound source separation on binaural hearing and speech perception.

Evaluation of wearing comfort of dust masks.

Dust masks are widely used to prevent the inhalation of particulate matter into the human respiratory organs in polluted air environments. The filter of a dust mask inherently obstructs the natural respiratory air flows, and this flow resistance is mainly responsible for the discomfort experienced when wearing a dust mask. In atmospheric conditions seriously contaminated with fine dust, it is recommended that common citizens wear a dust mask in their everyday lives, yet many people are reluctant to wear a dust mask owing to the discomfort experienced when wearing it for a long time. Understanding of physical reasons for the discomfort is thus crucial in designing a dust mask, but remains far from clear. This study presents a technique to quantify the wearing comfort of dust masks. By developing a respiration simulator to measure the pressure loss across a dust mask, we assessed the energy costs to overcome flow resistance when breathing through various types of dust masks. The energy cost for a single inhalation varies with the mask type in a range between 0 and 10 mJ. We compared the results with the survey results of 40 people about the wearing comfort of the dust masks, which revealed that the wearing comfort crucially depends on the energy cost required for air inhalation though the dust mask. Using the measured energy cost during inhalation as a parameter to quantify the wearing comfort, we present a comprehensive evaluation of the performance of dust masks in terms of not only the filtering performance but also the wearing comfort. Our study suggests some design principles for dust mask filters, auxiliary electric fans, and check valves.

Wireless User-Generic Ear EEG.

In the past few years it has been demonstrated that electroencephalography (EEG) can be recorded from inside the ear (in-ear EEG). To open the door to low-profile earpieces as wearable brain-computer interfaces (BCIs), this work presents a practical in-ear EEG device based on multiple dry electrodes, a user-generic design, and a lightweight wireless interface for streaming data and device programming. The earpiece is designed for improved ear canal contact across a wide population of users and is fabricated in a low-cost and scalable manufacturing process based on standard techniques such as vacuum forming, plasma-treatment, and spray coating. A 2.5 × 2.5 cm2 wireless recording module is designed to record and stream data wirelessly to a host computer. Performance was evaluated on three human subjects over three months and compared with clinical-grade wet scalp EEG recordings. Recordings of spontaneous and evoked physiological signals, eye-blinks, alpha rhythm, and the auditory steady-state response (ASSR), are presented. This is the first wireless in-ear EEG to our knowledge to incorporate a dry multielectrode, user-generic design. The user-generic ear EEG recorded a mean alpha modulation of 2.17, outperforming the state-of-the-art in dry electrode in-ear EEG systems.

Vestigial auriculomotor activity indicates the direction of auditory attention in humans.

Unlike dogs and cats, people do not point their ears as they focus attention on novel, salient, or task-relevant stimuli. Our species may nevertheless have retained a vestigial pinna-orienting system that has persisted as a 'neural fossil' within in the brain for about 25 million years. Consistent with this hypothesis, we demonstrate that the direction of auditory attention is reflected in sustained electrical activity of muscles within the vestigial auriculomotor system. Surface electromyograms (EMGs) were taken from muscles that either move the pinna or alter its shape. To assess reflexive, stimulus-driven attention we presented novel sounds from speakers at four different lateral locations while the participants silently read a boring text in front of them. To test voluntary, goal-directed attention we instructed participants to listen to a short story coming from one of these speakers, while ignoring a competing story from the corresponding speaker on the opposite side. In both experiments, EMG recordings showed larger activity at the ear on the side of the attended stimulus, but with slightly different patterns. Upward movement (perking) differed according to the lateral focus of attention only during voluntary orienting; rearward folding of the pinna's upper-lateral edge exhibited such differences only during reflexive orienting. The existence of a pinna-orienting system in humans, one that is experimentally accessible, offers opportunities for basic as well as applied science.

Dogs, cats, monkeys and other animals perk their ears in the direction of sounds they are interested in. Humans and their closest ape relatives, however, appear to have lost this ability. Some humans are able to wiggle their ears, suggesting that some of the brain circuits and muscles that allow automatic ear movements towards sounds are still present. This may be a 'vestigial feature', an ability that is maintained even though it no longer serves its original purpose. Now, Strauss et al. show that vestigial movements of muscles around the ear indicate the direction of sounds a person is paying attention to. In the experiments, human volunteers tried to read a boring text while surprising sounds like a traffic jam, a baby crying, or footsteps played. During this exercise, Strauss et al. recorded the electrical activity in the muscles of their ears to see if they moved in response to the direction the sound came from. In a second set of experiments, the same electrical recordings were made as participants listened to a podcast while a second podcast was playing from a different direction. The individuals' ears were also recorded using high resolution video. Both sets of experiments revealed tiny involuntary movements in muscles surrounding the ear closest to the direction of a sound the person is listening to. When the participants tried to listen to one podcast and tune out another, they also made ear 'perking' movements in the direction of their preferred podcast. The results suggest that movements of the vestigial muscles in the human ear indicate the direction of sounds a person is paying attention to. These tiny movements could be used to develop better hearing aids that sense the electrical activity in the ear muscles and amplify sounds the person is trying to focus on, while minimizing other sounds.

An advanced prosthetic manufacturing framework for economic personalised ear prostheses.

Craniofacial prostheses are commonly used to restore aesthetics for those suffering from malformed, damaged, or missing tissue. Traditional fabrication is costly, uncomfortable for the patient, and laborious; involving several hours of hand-crafting by a prosthetist, with the results highly dependent on their skill level. In this paper, we present an advanced manufacturing framework employing three-dimensional scanning, computer-aided design, and computer-aided manufacturing to efficiently fabricate patient-specific ear prostheses. Three-dimensional scans were taken of ears of six participants using a structured light scanner. These were processed using software to model the prostheses and 3-part negative moulds, which were fabricated on a low-cost desktop 3D printer, and cast with silicone to produce ear prostheses. The average cost was approximately $3 for consumables and $116 for 2 h of labour. An injection method with smoothed 3D printed ABS moulds was also developed at a cost of approximately $155 for consumables and labour. This contrasts with traditional hand-crafted prostheses which range from $2,000 to $7,000 and take around 14 to 15 h of labour. This advanced manufacturing framework provides potential for non-invasive, low cost, and high-accuracy alternative to current techniques, is easily translatable to other prostheses, and has potential for further cost reduction.

Investigation of Photoplethysmography Behind the Ear for Pulse Oximetry in Hypoxic Conditions with a Novel Device (SPYDR).

Photoplethysmography (PPG) is a valuable technique for noninvasively evaluating physiological parameters. However, traditional PPG devices have significant limitations in high-motion and low-perfusion environments. To overcome these limitations, we investigated the accuracy of a clinically novel PPG site using SPYDR®, a new PPG sensor suite, against arterial blood gas (ABG) measurements as well as other commercial PPG sensors at the finger and forehead in hypoxic environments. SPYDR utilizes a reflectance PPG sensor applied behind the ear, between the pinna and the hairline, on the mastoid process, above the sternocleidomastoid muscle, near the posterior auricular artery in a self-contained ear cup system. ABG revealed accuracy of SPYDR with a root mean square error of 2.61% at a 70-100% range, meeting FDA requirements for PPG sensor accuracy. Subjects were also instrumented with SPYDR, as well as finger and forehead PPG sensors, and pulse rate (PR) and oxygen saturation (SpO2) were measured and compared at various reduced oxygen profiles with a reduced oxygen breathing device (ROBD). SPYDR was shown to be as accurate as other sensors in reduced oxygen environments with a Pearson's correlation >93% for PR and SpO2. In addition, SPYDR responded to changes in SpO2 up to 50 s faster than PPG measurements at the finger and forehead.

Equivalent threshold sound pressure levels (ETSPLs) for RadioEar DD65v2 circumaural audiometric headphones.

Objective: Equivalent threshold sound pressure levels (ETSPLs) were determined for RadioEar DD65v2 audiometric headphones.Design: The pure-tone hearing threshold levels were measured for 11 audiometric frequencies between 0.125 and 8 kHz, according to the conditions specified in ISO 389-9. ETSPLs are provided for an ear simulator according to IEC 60318-1, complemented by a comprehensive uncertainty budget.Study sample: The study was based on 25 otologically normal test subjects.Results: ETSPL values are provided with expanded measurement uncertainty. The data are compared for left/right ears as well as male/female test subjects.Conclusions: The results of both studies may be used to update ISO 389-8, the RETSPL standard for circumaural audiometric headphones.

Model systems for regeneration: the spiny mouse, Acomys cahirinus.

The spiny mouse, Acomys spp., is a recently described model organism for regeneration studies. For a mammal, it displays surprising powers of regeneration because it does not fibrose (i.e. scar) in response to tissue injury as most other mammals, including humans, do. In this Primer article, we review these regenerative abilities, highlighting the phylogenetic position of the spiny mouse relative to other rodents. We also briefly describe the Acomys tissues that have been used for regeneration studies and the common features of their regeneration compared with the typical mammalian response. Finally, we discuss the contribution that Acomys has made in understanding the general principles of regeneration and elaborate hypotheses as to why this mammal is successful at regenerating.