Posterior Auricular Muscle Research Articles

Electro-Stimulation System with Artificial-Intelligence-Based Auricular-Triggered Algorithm to Support Facial Movements in Peripheral Facial Palsy: A Simulation Pilot Study.

Facial palsy causes severe functional disorders and impairs quality of life. Disturbing challenges for patients with acute facial palsy, but also with those with chronic facial palsy with synkinesis, are the loss of the ability to smile and insufficient eyelid closure. A potential treatment for these conditions could be a closed-loop electro-stimulation system that stimulates the facial muscles on the paretic side as needed to elicit eye closure, eye blink and smile in a manner similar to the healthy side. This study focuses on the development and evaluation of such a system. An artificial intelligence (AI)-based auricular-triggered algorithm is used to classify the intended facial movements. This classification is based on surface electromyography (EMG) recordings of the extrinsic auricular muscles, specifically the anterior, superior, and posterior auricular muscle on the paretic side. The system then delivers targeted surface electrical stimulation to contract the appropriate facial muscles. The evaluation of the system was conducted with 17 patients with facial synkinesis, who performed various facial movements according to a paradigm video. The system's performance was evaluated through a simulation, using previously captured data as the inputs. The performance was evaluated by means of the median macro F1-score, which was calculated based on the stimulation signal (output of the system) and the actual movements the patients performed. This study showed that such a system, using an AI-based auricular-triggered algorithm, can support with a median macro F1-score of 0.602 for the facial movements on the synkinetic side in patients with unilateral chronic facial palsy with synkinesis.

Myogenic artifacts masquerade as neuroplasticity in the auditory frequency-following response.

The frequency-following response (FFR) is an evoked potential that provides a neural index of complex sound encoding in the brain. FFRs have been widely used to characterize speech and music processing, experience-dependent neuroplasticity (e.g., learning and musicianship), and biomarkers for hearing and language-based disorders that distort receptive communication abilities. It is widely assumed that FFRs stem from a mixture of phase-locked neurogenic activity from the brainstem and cortical structures along the hearing neuraxis. In this study, we challenge this prevailing view by demonstrating that upwards of ~50% of the FFR can originate from an unexpected myogenic source: contamination from the postauricular muscle (PAM) vestigial startle reflex. We measured PAM, transient auditory brainstem responses (ABRs), and sustained frequency-following response (FFR) potentials reflecting myogenic (PAM) and neurogenic (ABR/FFR) responses in young, normal-hearing listeners with varying degrees of musical training. We first establish that PAM artifact is present in all ears, varies with electrode proximity to the muscle, and can be experimentally manipulated by directing listeners' eye gaze toward the ear of sound stimulation. We then show this muscular noise easily confounds auditory FFRs, spuriously amplifying responses 3-4-fold with tandem PAM contraction and even explaining putative FFR enhancements observed in highly skilled musicians. Our findings expose a new and unrecognized myogenic source to the FFR that drives its large inter-subject variability and cast doubt on whether changes in the response typically attributed to neuroplasticity/pathology are solely of brain origin.

The vestigial pinna-orienting system in humans briefly suppresses superior auricular muscle activity during reflexive orienting toward auditory stimuli.

The vestigial pinna-orienting system in humans is capable of increasing the activity of several auricular muscles in response to lateralized transient auditory stimuli. For example, transient increases in electromyographic activity in the posterior auricular muscle (PAM) to an attention-capturing stimulus have been documented. For the current study, surface electromyograms (EMGs) were recorded from the PAMs and superior auricular muscles (SAMs) of 10 normal-hearing participants. During the experiments, lateralized transient auditory stimuli, such as a crying baby, a shattering vase, or the participant's first names, were presented. These transient stimuli were either presented in silence or when participants actively listened to a podcast. Although ipsilateral PAM activity increased in response to transient stimuli, the SAM displayed the opposite behavior, i.e., a brief, ipsilateral suppression of activity. This suppression of ipsilateral SAM activity was more frequent on the right (75%) than left side (35%), whereas an ipsilateral PAM increase was roughly equal in prevalence on the two sides (left: 90%, right: 95%). During the active listening task, SAM suppression on the right ear was significantly larger in response to ipsilateral stimuli, compared with contralateral ones (P = 0.002), whereas PAM activity increased significantly (P = 0.002). Overall, this study provides evidence of a systematic transient suppression of the SAM during exogenous attention. This could suggest a more complex system than previously assumed, as the presence of synchronized excitatory and inhibitory components in different auricular muscles points toward a coordinated attempt at reflexively orienting the pinna toward a sound.NEW & NOTEWORTHY This study provides evidence that two auricular muscles in humans, the posterior and superior auricular muscles (PAM, SAM), react fundamentally different to lateralized transient auditory stimuli, especially during active listening. Although the PAM reacts with a transient increase in ipsilateral activity, ongoing ipsilateral SAM activity is briefly suppressed at the same time. This indicates the presence of a more complex and nuanced pinna-orienting system, with synchronized excitatory and inhibitory components in humans, than previously suspected.

Post-auricular orientation of auditory attention in sound field versus virtual sound space

The post-auricular muscle in many species’ changes orientation of external ears to improve hearing for biologically relevant sounds. The muscle exists in humans but cannot similarly change direction of their ears. Objectives focused on measuring activity of muscle during speech-in-noise task where orientations of speaker and noise were controlled experimentally to determine how signal-to-noise varies as function of presentation mode and azimuth (target speech and noise co-localized, 45°, or spatially separated, 135° and 45°, respectively). It was hypothesized that activity would be elicited in same proportion of subjects when evoked via earphones compared to speakers; there would be no significant differences in magnitude between conditions; maximum engagement would be observed with speech 135°, noise 45°. Activity was recorded with electrodes affixed around ears, outer canthi and neck, while listeners completed a spatialized listening test (locations of speaker/noise controlled experimentally). There was significant main effect of channel; significant interaction between presentation mode and channel; no significant differences between presentation modes for other muscles; no significant effect of azimuth. Engagement in virtual sound-space suggests that muscle activation occurs consequently of spatially directed attention, even when changes in pinna orientation are unlikely to have effect on sound heard.

The posterior auricular muscle complex graft as a porous orbital implant wrap: long-term follow-up over a 31-year period

ABSTRACT Purpose Orbital implant exposures, infections, and extrusions can occur many years following enucleation or evisceration. This study analyzes complication rates following porous orbital implant wrapped with a posterior auricular muscle complex graft (PAMCG). Methods This is a retrospective study of patients who underwent orbital implantation following enucleation using this technique between 1992 and 2013. Only cases with a minimum of 18 months of follow-up were included. No patients underwent peg implantation. Patient’s demographics, follow-up time, type of implant, complications including wound dehiscence, exposure, postoperative infection, and extrusion were recorded. Results This study included 36 orbits of 36 patients with a mean age of 39.3 ± 23.2 years (range, 3–84 years). Thirty patients had hydroxyapatite implants and six had porous polyethylene. The average follow-up time was 12.6 ± 5.6 years (range, 1.5–31.0 years). There were no implant extrusions, and only one exposure resulting in orbital infection that necessitated implant removal (2.8%). Conclusion Wrapping porous orbital implants with PAMCG had favorable long-term outcomes over a thirty-one-year period.

Facial expression detection using posterior-auricular muscle surface-electromyographic activity

IntroductionFollowing Bell's palsy, 25% of sufferers are left with chronic, difficult to treat involuntary muscle movements (synkinesis). Surface-electromyography (sEMG) biofeedback has an established role in improving muscular coordination. The vestigial posterior auricular muscle (PAM) is the first muscle re-innervated by the facial nerve. This study measured the sEMG signal from PAM in facial animation in healthy subjects and explored the possibility of using PAM in a wearable rehabilitative device. Material and methodsPAMs activity was recorded using sEMG in 41 healthy volunteers during the performance of a set range of facial expressions. To compare results between participants and expressions, the percentage increase from baseline were used. ResultsPAMs activity increased significantly from baseline in response to smiling (110.98%) compared with other facial expressions: closing eyes (7.85%); blowing out cheeks (39.35%); whistling (11.84%), and showing lower teeth (38.24%). PAMs activity increased in proportion to smile intensity: lips together smile (55.18%); open smile (111.98%); full denture smile (130.07%); and, laughing (269.42%). ConclusionThis study demonstrates that measurement of smile intensity is possible via the sEMG signal from the PAM. Further studies investigating the applicability of measuring PAM activity during smiling to enhance and guide facial palsy rehabilitation are ongoing.

Machine-Learning-Based Detecting of Eyelid Closure and Smiling Using Surface Electromyography of Auricular Muscles in Patients with Postparalytic Facial Synkinesis: A Feasibility Study.

Surface electromyography (EMG) allows reliable detection of muscle activity in all nine intrinsic and extrinsic ear muscles during facial muscle movements. The ear muscles are affected by synkinetic EMG activity in patients with postparalytic facial synkinesis (PFS). The aim of the present work was to establish a machine-learning-based algorithm to detect eyelid closure and smiling in patients with PFS by recording sEMG using surface electromyography of the auricular muscles. Sixteen patients (10 female, 6 male) with PFS were included. EMG acquisition of the anterior auricular muscle, superior auricular muscle, posterior auricular muscle, tragicus muscle, orbicularis oculi muscle, and orbicularis oris muscle was performed on both sides of the face during standardized eye closure and smiling tasks. Machine-learning EMG classification with a support vector machine allowed for the reliable detection of eye closure or smiling from the ear muscle recordings with clear distinction to other mimic expressions. These results show that the EMG of the auricular muscles in patients with PFS may contain enough information to detect facial expressions to trigger a future implant in a closed-loop system for electrostimulation to improve insufficient eye closure and smiling in patients with PFS.

Direct cochlear nerve stimulation monitoring through evoked muscle responses during retrosigmoid vestibular schwannoma resection surgery: technical note.

Cochlear nerve preservation during surgery for vestibular schwannoma (VS) may be challenging. Brainstem auditory evoked potentials and cochlear compound nerve action potentials have clearly shown their limitations in surgeries for large VSs. In this paper, the authors report their preliminary results after direct electrical intraoperative cochlear nerve stimulation and recording of the postauricular muscle response (PAMR) during resection of large VSs. The details for the electrode setup, stimulation, and recording parameters are provided. Data of patients for whom PAMR was recorded during surgery were prospectively collected and analyzed. PAMRs were recorded in all patients at the ipsilateral vertex-earlobe scalp electrode, and in 90% of the patients they were also observed in the contralateral electrode. The optimal stimulation intensity was found to be 1 mA at 1 Hz, with a good cochlear response and an absent response from other nerves. At that intensity, the ipsilateral cochlear response had an initial peak at a mean (± SEM) latency of 11.6 ± 1.5 msec with an average amplitude of 14.4 ± 5.4 µV. One patient experienced a significant improvement in his audition, while that of the other patients remained stable. PAMR monitoring may be useful in mapping the position and trajectory of the cochlear nerve to enable hearing preservation during surgery.

Assessment of Vestigial Auriculomotor Activity to Acoustic Stimuli Using Electrodes In and Around the Ear.

Recently, it has been demonstrated that electromyographic (EMG) activity of auricular muscles in humans, especially the postauricular muscle (PAM), depends on the spatial location of auditory stimuli. This observation has only been shown using wet electrodes placed directly on auricular muscles. To move towards a more applied, out-of-the-laboratory setting, this study aims to investigate if similar results can be obtained using electrodes placed in custom-fitted earpieces. Furthermore, with the exception of the ground electrode, only dry-contact electrodes were used to record EMG signals, which require little to no skin preparation and can therefore be applied extremely fast. In two experiments, auditory stimuli were presented to ten participants from different spatial directions. In experiment 1, stimuli were rapid onset naturalistic stimuli presented in silence, and in experiment 2, the corresponding participant's first name, presented in a "cocktail party" environment. In both experiments, ipsilateral responses were significantly larger than contralateral responses. Furthermore, machine learning models objectively decoded the direction of stimuli significantly above chance level on a single trial basis (PAM: 80%, in-ear: 69%). There were no significant differences when participants repeated the experiments after several weeks. This study provides evidence that auricular muscle responses can be recorded reliably using an almost entirely dry-contact in-ear electrode system. The location of the PAM, and the fact that in-ear electrodes can record comparable signals, would make hearing aids interesting devices to record these auricular EMG signals and potentially utilize them as control signals in the future.

Intra-Operative Cochlear Nerve Function Monitoring in Hearing Preservation Surgery: A Systematic Review of the Literature.

With the recent scientific and technical developments, hearing preservation surgery is becoming a growing objective in inner ear pathologies, especially for vestibular schwannomas. In this review, we aim to describe the pros and cons of the following cochlear nerve monitoring techniques: ABRs (auditory brainstem responses), DENM (direct eighth cranial nerve monitoring), EcochG (electrocochleography), CNAP (cochlear compound nerve action potentials), DPOAE (distortion product otoacoustic emissions), PAMRs (postauricular muscle responses). The Cochrane library, Scopus, DynaMed, and PubMed databases were screened to obtain any relevant papers from October 2009 to the present day. Due to the heterogeneity of the existing studies in the literature, there is no way to tell whether a technique is better than another. All authors reported satisfactory outcomes with the cochlear nerve monitoring techniques tested, either alone or in combination.

Correction of Prominent Ears: Postauricular Muscle Relocation and Fibrofatty Tissue Excision.

In this study, we modified the combined Mustarde and Furnas type otoplasty technique and evaluated the postoperative results of the patients for symmetry and complications. Eighty prominent ears in 42 patients who underwent otoplasty between January 2017 and April 2019 were included in this study. The authors determined the amount of postauricular subcutaneous tissue to be removed according to the shape of skin incision and relocated the postauricular muscle as an adjunct to the Mustarde and Furnas otoplasty technique. All patients were followed-up at least 12 months postoperatively. The patients were also evaluated for early postoperative complications (bleeding, hematoma, perichondritis, wound infection, and skin necrosis), late postoperative complications (asymmetry, hypertrophic scars, suture extrusion, and recurrence), and patient satisfaction using objective and subjective methods.Considering all the patients, early complications consisted of minimal low-flow bleeding (n = 4 ears/4 patients), hematoma (n = 1), and perichondritis (n = 1). Late complications consisted of suture extrusion (n = 2 ears/2 patients), hypertrophic scars (n = 2 ears/2 patients), and asymmetry (n = 1). None of the patients presented with wound infection or skin necrosis. Revision otoplasty was unilaterally performed in only 1 patient with the complaint of asymmetry. A natural-looking, adequate correction, and symmetric ear shape were achieved in all patients except 1. In terms of patient satisfaction, 38 of 42 patients evaluated the outcome as "very good," 3 as "good," and only 1 as "poor." Our modified technique produced very satisfactory results and reduced the postoperative complication and asymmetry rates, as well as eliminating recurrence. The authors recommend this simple and safe procedure with excellent outcomes.

Cartilage-Sparing Otoplasty: The Effects of Adipo-Perichondrial Flap-Assisted Posterior Auricular Muscle Complex Flap Technique on the Repair of Prominent Ear Deformities.

In the repair of prominent ear deformities, the main objectives are to recreate the antihelical fold, reduce projection in patients with a large concha, and normalize the distance between the ear and the cranium. This study evaluated the efficacy of the adipo-perichondrial flap-assisted posterior auricular muscle complex (PAMC) flap technique, which involves a new approach to the repair of prominent ear deformities. A medially based PAMC flap and a laterally based adipo-perichondrial flap were elevated in 22 patients with prominent ear deformities. In order to shape the ear, the PAMC flap was sutured to the transition zone between the helix and antihelix, and the adipo-perichondrial flap to the periosteum of the mastoid bone. The ear-cranium distances were measured preoperatively and at postoperative first and sixth months. Thirteen patients were female and 9 were male. The mean age of the patients was 19.4 years, and the mean follow-up period was 10.6 months. The ear-cranium distance significantly decreased in the postoperative first-month and sixth-month evaluations compared to the preoperative values (P < .05). No relapse, suture exposition, hematoma, keloid scar, or infection was observed. Posterior auricular muscle complex is a strong anatomical structure that includes the trapezius muscle, occipital muscle, extrinsic ear muscles, temporal fascia, and sternocleidomastoid fascia. By elevating this structure as a flap and combining it with an adipo-perichondrial flap, successful results can be achieved in the repair of prominent ear deformities, which prevents relapses and maintains the shape of the ear in the long term.

Evidence of a Vestibular Origin for Crossed-Sternocleidomastoid Muscle Responses to Air-Conducted Sound.

Small, excitatory surface potentials can sometimes be recorded from the contralateral sternocleidomastoid muscle (SCM) following monaural acoustic stimulation. Little is known about the physiological properties of these crossed reflexes. In this study, we sought the properties of crossed SCM responses and through comparison with other cochlear and vestibular myogenic potentials, their likely receptor origin. Surface potentials were recorded from the ipsilateral and contralateral SCM and postauricular (PAM) muscles of 11 healthy volunteers, 4 patients with superior canal dehiscence and 1 with profound hearing loss. Air-conducted clicks of 105 dB nHL and tone bursts (250 to 4000 Hz) of 100 dB nHL were presented monaurally through TDH 49 headphones during head elevation. Click-evoked responses were recorded under two conditions of gaze in random order: gaze straight ahead and rotated hard toward the contralateral recording electrodes. Amplitudes (corrected and uncorrected) and latencies for crossed SCM responses were compared with vestibular (ipsilateral SCM) and cochlear (PAM) responses between groups and across the different recording conditions. Surface waveforms were biphasic; positive-negative for the ipsilateral SCM, and negative-positive for the contralateral SCM and PAM. There were significant differences in the amplitudes and latencies (p = 0.004) for click responses of healthy controls across recording sites. PAM responses had the largest mean-corrected amplitudes (2.3 ± 2.8) and longest latencies (13.0 ± 1.2 msec), compared with ipsilateral (1.6 ± 0.5; 12.0 ± 0.7 msec) and contralateral (0.8 ± 0.3; 10.4 ± 1.0 msec) SCM responses. Uncorrected amplitudes and muscle activation for PAM increased by 104.4% and 46.8% with lateral gaze respectively, whereas SCM responses were not significantly affected. Click responses of patients with superior canal dehiscence followed a similar latency, amplitude, and gaze modulation trend as controls. SCM responses were preserved in the patient with profound hearing loss, yet all PAM were absent. There were significant differences in the frequency tuning of the three reflexes (p < 0.001). Tuning curves of healthy controls were flat for PAM and down sloping for ipsilateral and contralateral SCM responses. For superior canal dehiscence, they were rising for PAM and slightly down sloping for SCM responses. Properties of crossed SCM responses were similar, though not identical, to those of ipsilateral SCM responses and are likely to be predominantly vestibular in origin. They are unlikely to represent volume conduction from the PAM as they were unaffected by lateral gaze, were shorter in latency, and had different tuning properties. The influence of crossed vestibulo-collic pathways should be considered when interpreting cervical vestibular-evoked myogenic potentials recorded under conditions of binaural stimulation.

Development and growth of auricular cartilage and muscles: A study using human fetuses

ObjectivesThe auricle is a key target in pediatric plastic surgery and is considered to develop from a ring- or funnel-like arrangement of six hillocks in the embryo. However, there has been no report showing the morphologies of the auricular muscle and cartilage after midterm in humans. MethodsWe examined histological sections of 20 near-term human fetuses (29–40 weeks) and those from 7 midterm fetuses (15–16 weeks). ResultsAt midterm, the auricular cartilage was a single wavy plate with the helicis major muscle (HMM). The superior and posterior auricular muscles (SAM, PAM) were inserted into the middle parts, and the anterior auricular muscle (AAM) was inserted into the lowest part of the cartilage plate, while the tragus and antitragus were not clearly identified. In near-term fetuses, the cartilage plate varied in size and shape between specimens. The scapha and antihelix were separated from the cartilage plate with major or minor involvement of the HMM from the initial mass along the helix. The SAM inserted to the crus helix or the developing scapha, while the insertion sites of the AAM and PAM into the helix were stable. The tragus–antitragus cartilages were well-developed and they sandwiched a deep notch of skin below the helix tail. The antitragicus muscle was more evident than the tragicus muscle. An unnamed muscle was evident along the external acoustic meatus. The other intrinsic muscles, including the transverse and oblique muscles, might develop from the HMM after birth. ConclusionsDevelopment of the auricle was advanced after midterm. However, a single wavy plate-like cartilage was maintained until late-stage. Near term, the antihelix and scapha developed from the plate-like core of the auricle and the tragus and antitragus were added in the antero-inferior side of the cartilage plate. Establishment of muscle arrangements was markedly delayed compared to cartilage development. Altogether, the classical concept of an initial funnel-like arrangement of cartilage anlagen might have been biased by studies of adult morphology.

Auricular cartilage multi-point suspension fixed to craniofacial deep fascia in correcting mild to moderate cupped ear malformation

To explore the feasibility and effectiveness of using auricular cartilage multi-point suspension fixed on deep craniofacial fascia in correcting mild to moderate cupped ear malformation. Between January 2014 and March 2016, 22 patients (12 males and 10 females) with mild to moderate cupped ear malformation were admitted, aged from 6 to 28 years, with an average age of 15 years. Sixteen cases were unilateral and 6 cases were bilateral. According to Tanzer classification, there were 18 sides of type Ⅰ and 10 sides of type Ⅱ. The otocranial groove incision was selected to expose and release the posterior auricular muscles and ligaments. The abnormal structure of auricle subunits was remolded. The auricle cartilage was suspended and fixed on the deep craniofacial fascia with non absorbable line to remodel the shape and position of auricle. The incision healed by first intention, without hematoma, infection, and skin necrosis. All the patients were followed up 3-48 months, with an average of 12 months. In addition to 1 case of slippage of the fixed line knot, the effect was good after being suspended and fixed again, the auricles of the other patients were not drooping and tilted forward, the shape of the outer ear was good, the ear boat was obvious, the shape of the upper and lower feet of the ear wheel and the pair of ears was natural, the bilateral symmetry was good, and the patients and their families were satisfied. Auricular cartilage multi-point suspension fixed on deep craniofacial fascia is effective in the treatment of mild to moderate cupped ear malformation.

Role of posterior auricular muscle to prevent protruding ear after retroauricular ear surgery

ObjectiveThe posterior auricular muscle (PAM) functions in ear projection in normal position and is severed during the retroauricular approach, and some patients complain of a protruding ear postoperatively. This study was designed to determine whether suturing of the severed PAM reduces pinna projection after the retroauricular approach. MethodsIn a prospective controlled study, we enrolled 91 patients with chronic otitis media, all of who underwent canal wall up mastoidectomy with tympanoplasty via retroauricular approach. They were randomly assigned to the PAM-sutured (n=45) or PAM-non-sutured (n=46) group. Helical-mastoid distance and concho-mastoid angle were measured serially. ResultsIn both groups, helical-mastoid distance was significantly longer than preoperatively until 1 month postoperatively but was similar to preoperatively by 6 months. Concho-mastoid angle increased significantly until 1 month after surgery in the PAM-non-sutured group but returned to the preoperative value at 6 months postoperatively. In the PAM-sutured group, concho-mastoid angle increased significantly at 3 days postoperatively, was similar to preoperatively at 1 month after surgery, and became narrower than preoperatively at 6 months postoperatively. In both groups, there were significant effects of time on the changes in helical-mastoid distance or concho-mastoid angle. Group assignment did not significantly affect these time-related changes. ConclusionPAM suturing did not affect helical-mastoid distance by 6 months postoperatively, but it did reduce the concho-mastoid angle to below the preoperative value at 6 months. We recommend that PAM be left severed to maintain concho-mastoid angle in the long term when using the retroauricular approach.

The Influence of Stimulus Repetition Rate on Tone-Evoked Post-Auricular Muscle Response (PAMR) Threshold.

Post-auricular muscle response (PAMR) is a large myogenic potential that can be useful in estimating behavioral hearing thresholds when the recording protocol is optimal. The main aim of the present study was to determine the influence of stimulus repetition rate on PAMR threshold. In this repeated-measures study, 20 normally hearing adults aged between 18 and 30 years were recruited. Tone bursts (500, 1000, 2000, and 4000 Hz) were used to record PAMR thresholds at 3 different stimulus repetition rates (6.1/s, 11.1/s, and 17.1/s). Statistically higher PAMR thresholds were found for the faster stimulus rate (17.1/s) compared with the slower stimulus rate (6.1/s) (p < 0.05). For all stimulus rates and frequencies, significant correlations were found between PAMR and pure-tone audiometry thresholds (r = 0.62 to 0.82). Even though the stimulus rate effect was significant at most of the tested frequencies, the differences in PAMR thresholds between the rates were small (<5 dB). Nevertheless, based on the correlation results, we suggest the use of 11.1/s stimulus rate when recording PAMR thresholds.

Gap-induced inhibition of the post-auricular muscle response in humans and guinea pigs

A common method for measuring changes in temporal processing sensitivity in both humans and animals makes use of GaP-induced Inhibition of the Acoustic Startle (GPIAS). It is also the basis of a common method for detecting tinnitus in rodents. However, the link to tinnitus has not been properly established because GPIAS has not yet been used to objectively demonstrate tinnitus in humans. In guinea pigs, the Preyer (ear flick) myogenic reflex is an established method for measuring the acoustic startle for the GPIAS test, while in humans, it is the eye-blink reflex. Yet, humans have a vestigial remnant of the Preyer reflex, which can be detected by measuring skin surface potentials associated with the Post-Auricular Muscle Response (PAMR). A similar electrical potential can be measured in guinea pigs and we aimed to show that the PAMR could be used to demonstrate GPIAS in both species.In guinea pigs, we compare the GPIAS measured using the pinna movement of the Preyer reflex and the electrical potential of the PAMR to demonstrate that the two are at least equivalent. In humans, we establish for the first time that the PAMR provides a reliable way of measuring GPIAS that is a pure acoustic alternative to the multimodal eye-blink reflex. Further exploratory tests showed that while eye gaze position influenced the size of the PAMR response, it did not change the degree of GPIAS.Our findings confirm that the PAMR is a sensitive method for measuring GPIAS and suggest that it may allow direct comparison of temporal processing between humans and animals and may provide a basis for an objective test of tinnitus.

Operational learning with sensory feedback for controlling a robotic thumb using the posterior auricular muscle

Extra robotic limbs in a robotic system that are designed to augment and expand human abilities have received attention in the field of wearable robotics. We aim to develop a robotic system that is controlled by body parts that are not used on a daily basis in order to augment and expand human abilities. This paper presents operational learning experiments for manipulating a robotic thumb using the posterior auricular muscle, a body part that is not used in everyday life. In these experiments, reaching motions were executed using sensory feedback in the robotic thumb through a device that continuously displays its position. The experimental results indicate the proposed operational learning experiments improve the ability to contract the posterior auricular muscles. In addition, the results indicate the operability of a robotic thumb could be improved by acquiring internal models through repetitive operational learning.

Posterior Auricular Muscle Response: Observations in Brainstem Lesions

Posterior Auricular Muscle Response: Observations in Brainstem Lesions