Head Stabilization Research Articles

The startle response during whiplash: a protective or harmful response?

Whiplash injuries are common following rear-end collisions. During such collisions, initially relaxed occupants exhibit brisk, stereotypical muscle responses consisting of postural and startle responses that may contribute to the injury. Using prestimulus inhibition, we sought to determine if the startle response elicited during a rear-end collision contributes to head stabilization or represents a potentially harmful overreaction of the body. Three experiments were performed. In the first two experiments, two groups of 14 subjects were exposed to loud tones (124 dB) preceded by prestimulus tones at either four interstimulus intervals (100-1,000 ms) or five prestimulus intensities (80-124 dB). On the basis of the results of the first two experiments, 20 subjects were exposed to a simulated rear-end collision (peak sled acceleration = 2 g; speed change = 0.75 m/s) preceded by one of the following: no prestimulus tone, a weak tone (85 dB), or a loud tone (105 dB). The prestimulus tones were presented 250 ms before sled acceleration onset. The loud prestimulus tone decreased the amplitude of the sternocleidomastoid (16%) and cervical paraspinal (29%) muscles, and key peak kinematics: head retraction (17%), horizontal head acceleration (23%), and head angular acceleration in extension (23%). No changes in muscle amplitude or kinematics occurred for the weak prestimulus. The reduced muscle and kinematic responses observed with loud tones suggest that the startle response represents an overreaction that increases the kinematics in a way that potentially increases the forces and strains in the neck tissues. We propose that minimizing this overreaction during a car collision may decrease the risk of whiplash injuries.

Optimal Design of the Large-Diameter Spinning Torispherical Head

Two important parameters of torispherical head that are (interior radius of spherical crown area) and r (interior radius of transition corner) have been optimized by the module of the large general-purpose finite-element software ANSYS, targeting the strength and stability of the head. This paper provides an optimized torispherical head, which improves the stability of the edge of the head with acceptable strength of the head. The procedure is generally applicable as a design tool for optimal design.

인공고관절 치환술 후 세라믹 대퇴골두에서 발생하는 응력분포 예측

Ceramic femoral heads are now widely used in Total Hip Replacement (THR). Due to their high biocompatibility and low ductility, ceramic femoral heads are considered to be suitable for young and active patients. However, as in testing the mechanical stability of the femoral head, the conventional proof test (standard ISO 7206-10) has its limit of showing axisymmetric stress distribution on the contact surface, while non-uniformed stress distribution is expected after THR. Since non-uniformed stress distribution can result in the increased probability of ceramic femoral head fracture, it is considerable to evaluate the stress distribution in vivo-like conditions. Therefore, this study simulated the ceramic femoral heads under in vivo-like conditions using finite element method. The maximum stress decreased when increasing the size of the femoral head and stress distribution was concentrated on superior contact surface of the taper region.

Experimental study of plastic optical fiber TNT sensor based on evanescence absorption

Here, the concentration of TNT was detected by using evanescent absorption method, U-shaped plastic optical fiber was used as sensor head and light transmit element. A high brightness blue light-emitting diode with spectrum centered at 470 nm was used as excitation source. The relationship between the transmitted light power of U-shaped sensor head and TNT concentration was linearly and the linear coefficient was 0.944. The system showed excellent reversibility when the sensor tested by alternately cycling between 0 and 25 mg/100 ml TNT solution in five cycles. The stability of the sensor head in 25 mg/100 ml TNT solution was also tested within two hours. The proposed sensor is a cost-effective alternative to traditional TNT sensors and provides a platform for other optically based sensors.

Anatomical Reconstruction of Reverse Hill-Sachs Lesions Using the Underpinning Technique

Posterior glenohumeral joint dislocation is an uncommon injury and is associated with bony and ligamentous disruption. It requires prompt diagnosis and early treatment to prevent acute or recurrent instability and subsequent dysfunction. Reverse Hill-Sachs lesions associated with this injury are challenging to treat, and optimal treatment is controversial. Treatment methods can be divided into those that achieve stability through muscle transfers, osteotomies, or posterior bone-block procedures (glenoid augmentation) and those that restore the sphericity of the humeral head. Joint replacement is often suggested for large head lesions (>50%) considered beyond reconstruction. Restoration of stability, preservation of the proximal humeral anatomy, and salvage of the humeral head sphericity should be the treatment goals in the younger population.This article describes the surgical technique of elevation of the impressed osteochondral fragment followed by filling the lesion with Allomatrix bone graft putty (Wright Medical Technology, Arlington, Tennessee) in 2 patients. The size of the head lesion was ≤35%. Underpinning raft screws were used to provide subchondral support and prevent the collapse of the elevated fragment. Postoperatively, the sphericity of the humeral head and glenohumeral stability were restored. No evidence of collapse, osteonecrosis, or osteoarthritis progression was seen at latest follow-up. Functional results were excellent, with a minimum follow-up of 2 years.This technique is an alternative method of restoring humeral head sphericity in patients with acute posterior glenohumeral joint dislocations with medium (20%-40%) reverse Hill-Sachs lesions.

Analysis on dynamic characteristics in time domain of slider with ultra thin spacing

With increasing recording density in computer hard disks, the flying height of the magnetic head becomes 10 nm or less. The numerical method of the control equations needs to be optimized consistently with the decrease of the flying height. The iterative process is usually divergent with traditional methods which cannot ensure the accuracy of the analysis results and the stability of numerical calculations. Firstly, a new scheme is presented to solve the ultra-thin lubricating control equations in this paper. The equilibrium equation is obtained by taking the Couette flow terms and time term as dominating terms in iterative process. Moreover, the weighting flow factor is introduced for the abrupt change of film thickness in order to reduce calculated deviation. Secondly, the rules for variation of flying pose of the magnetic head with time are obtained by the time domain analysis. The results show that the magnetic head can recover to the equilibrium position after being slightly influenced by outside disturbance. And the dynamic lubrication properties of the head suffer heavily from the vibrations in the height direction and fluctuation in the pitch direction. Finally, the analysis of the sine roughness-passing capacity of the head indicates that the head can surpass small sine waves and the equilibrium position can be retrieved after a period of decaying oscillation. The proposed research ensures the accuracy and stability of the numerical calculation of the control equations, and the dynamic characteristics and flying stability of a magnetic head is studied systematically. It can also be the theoretical basis for the analysis of the flight characteristics of the slider.

Head and body stabilization in blowflies walking on differently structured substrates

Visually guided animals depend heavily on the quality of visual signals in order to obtain functionally relevant information about their environment. To support visual information processing, nature has evolved a large variety of physiological adaptations and behavioral strategies such as compensatory head movements. During self-movement, head rotations compensate for changes in body attitude in order to stabilize gaze. However, how walking animals cope with uneven structured substrates, which may affect body and gaze orientation, is still unknown. We used stereo high-speed video to analyze compensatory head movements of blowflies walking freely on differently structured substrates. We found that even a pronounced asperity of the ground structure, with bumps of almost the size of the animal, was largely compensated by the walking apparatus of the blowfly, which leads to body roll and pitch movements only marginally larger than those on flat substrate. Pitch and roll fluctuations of the head were smaller compared with body fluctuations on all tested substrates, emphasizing the significance of gaze stabilization during walking on structured substrates. Furthermore, we found no impairment in head and body stabilization during walks in darkness, which indicates that the control system mediating compensatory head movements works well without any visual input. Interestingly, blowflies changed their walking style in the dark and seemed to use their forelegs as tactile probes.

The X-Linked Intellectual Disability Protein TSPAN7 Regulates Excitatory Synapse Development and AMPAR Trafficking

SummaryMutations in TSPAN7—a member of the tetraspanin protein superfamily—are implicated in some forms of X-linked intellectual disability. Here we show that TSPAN7 overexpression promotes the formation of filopodia and dendritic spines in cultured hippocampal neurons from embryonic rats, whereas TSPAN7 silencing reduces head size and stability of spines and AMPA receptor currents. Via its C terminus, TSPAN7 interacts with the PDZ domain of protein interacting with C kinase 1 (PICK1), to regulate PICK1 and GluR2/3 association and AMPA receptor trafficking. These findings indicate that, in hippocampal neurons, TSPAN7 regulates AMPA receptor trafficking by limiting PICK1 accessibility to AMPA receptors and suggest an additional mechanism for the functional maturation of glutamatergic synapses, whose impairment is implicated in intellectual disability.

Forehead pressure sore following a prolonged operation and the role of the Mayfield head frame in re-operation

To the Editor: Appropriate intraoperative patient positioning by surgeons and anaesthetists is essential to prevent pressure sores. Facial pressure sores are rare, and their occurrence is possibly underreported [1]. We report a unique case of a stage 2 forehead pressure sore developing after a 21-h operation in the prone position despite full anesthetic precautions, and we advocate use of the Mayfield head frame to prevent deterioration if re-operation is required in the prone position in such scenarios. A 43-year-old overweight gentleman with sacral chondrosarcoma and no other significant medical history underwent hemisacrectomy and two-stage reconstruction with a free latissimus dorsi musculo-osseo-cutaneous flap. He was intubated and lay in the prone position for the duration of the second-stage reconstruction. He was placed on a cami table, with full padding precautions and a head ring. The total duration of the operation was 21 h. Postoperatively the patient was noted to have a 4 9 2 cm grade 2 forehead pressure ulcer (Fig. 1). The patient returned to the operating room for an exploration of the free flap following an absent venous Doppler signal, although clinically the flap appeared viable. On this occasion he was placed in a Mayfield head frame to avoid further pressure on his forehead sore. Intraoperatively the flap was indeed viable, but the internal venous Doppler revealed it required repositioning. This procedure took 2 h. The forehead pressure sore was unchanged postoperatively as a result of the avoidance of pressure on it and the shorter operative period. It was subsequently treated conservatively with regular dressings and healed 2 months later. In our case, the Mayfield head frame was utilized when the patient was taken back to the operating room for flap exploration in the prone position to avoid further facial tissue compromise. This frame is generally used for head stabilization during intracranial surgery. However, there have been reports of hematomas following its use if placed against anatomically thin bone (such as the squamous part of the temporal bone) or pathologically thin bone (as can happen after chronic intracranial hypertension) [2, 3]. Goodwin et al. [4] believe the use of the head frame prevents the development of facial pressure sores in patients undergoing sacrectomy. Facial pressure sores can cause much physical and emotional morbidity, adding to the already appreciable healthcare costs of treating these patients. As the number of prone cases in surgery increases, it is crucial to recognize all patients at risk and to address all contributory factors, particularly if prolonged procedures are anticipated. Established methods to reduce facial pressure sore development include widening of the facial–pillow contact area to disperse the pressure, checking facial skin status frequently, and changing head position regularly (when the H. Sadideen (&) H. Giele Department of Plastic and Reconstructive Surgery, West Wing, John Radcliffe Hospital, Oxford, UK e-mail: hazim.sadideen@doctors.org.uk

Feed-forward and visual feed-back control of head roll orientation in wasps (Polistes humilis, Vespidae, Hymenoptera)

Flying insects keep their visual system horizontally aligned, suggesting that gaze stabilization is a crucial first step in flight control. Unlike flies, hymenopteran insects such as bees and wasps do not have halteres that provide fast, feed-forward angular rate information to stabilize head orientation in the presence of body rotations. We tested whether hymenopteran insects use inertial (mechanosensory) information to control head orientation from other sources, such as the wings, by applying periodic roll perturbations to male Polistes humilis wasps flying in tether under different visual conditions indoors and in natural outdoor conditions. We oscillated the thorax of the insects with frequency-modulated sinusoids (chirps) with frequencies increasing from 0.2 to 2 Hz at a maximal amplitude of 50 deg peak-to-peak and maximal angular velocity of ±245 deg s(-1). We found that head roll stabilization is best outdoors, but completely absent in uniform visual conditions and in darkness. Step responses confirm that compensatory head roll movements are purely visually driven. Modelling step responses indicates that head roll stabilization is achieved by merging information on head angular velocity, presumably provided by motion-sensitive neurons and information on head orientation, presumably provided by light level integration across the compound eyes and/or ocelli (dorsal light response). Body roll in free flight reaches amplitudes of ±40 deg and angular velocities greater than 1000 deg s(-1), while head orientation remains horizontal for most of the time to within ±10 deg. In free flight, we did not find a delay between spontaneous body roll and compensatory head movements, and suggest that this is evidence for the contribution of a feed-forward control to head stabilization.

8B34 外乱に対するヒト立位時の頭部安定性(GS04 ヒューマンダイナミクス1)

8B34 外乱に対するヒト立位時の頭部安定性(GS04 ヒューマンダイナミクス1)

Applying a subtraction technique to minimize cochlear implant artifact with soundfield and direct audio input stimulations

We explored the feasibility of a subtraction technique described by Friesen and Picton to remove the cochlear implant (CI) artifact to long duration stimuli in the soundfield and using direct input all through the participant's preferred MAP. Friesen and Picton previously explored this technique by recording cortical potentials in four CI users with 1000 pulse per second (pps) stimuli, bypassing the speech processor. Cortical auditory evoked potentials (N1–P2) to 1000 Hz tones were recorded from a post-lingually deafened adult with three different stimulus presentation setups: soundfield to processor T-mic (SF), soundfield to lapel mic (SF-LM), and direct input (DI). Stimuli were presented at 65 dB SPL(A). The SF setup required stabilizing the head to minimize changes in magnitude for the CI artifact. The SF-LM and DI setups did not require head stabilization, but were evaluated as alternatives to the SF setup. Clear N1–P2 responses were obtained with comparable waveform morphologies, amplitudes, and latencies despite some differences in the magnitude of the CI artifact for the different stimulus presentation setups. The results of this study demonstrate that subtraction technique is feasible for recording N1–P2 responses in CI users, though further studies are needed for the three stimulation setups.

Arthroscopic Superior Capsular Reconstruction Restores Shoulder Stability and Function in Patients with Irreparable Rotator Cuff Tears: A Prospective Study (SS-15)

Introduction Rotator cuff tears cause severe functional impairment and pain as a result of loss of superior stability of the humeral head. Here, we focused on the treatment of defects in the superior capsule for the stabilization of irreparable tears in the rotator cuff tendon. Our previous biomechanical study in cadaveric shoulders showed that superior capsular reconstruction completely restored the superior stability of a simulated irreparable rotator cuff tear. The objective of this study was to investigate the functional and radiological results of this arthroscopic superior capsular reconstruction in the living body. Methods From 2007 to 2009, twenty-two consecutive patients (12 male and 10 female) (mean age of 65 years; range, 52 to 77 years) with irreparable supraspinatus and infraspinatus tears (9 large and 13 massive) were prospectively enrolled in the study. Mean duration of symptoms before surgery was 20 months (range, 3 to 96 months). The average follow-up was 33 months (range, 24 to 40 months). All patients underwent arthroscopic superior capsular reconstruction using fascia lata. The average dimensions of the grafted fascia lata were 3.2 × 5.9 cm. Suture anchors were used to attach the graft medially to the superior tubercle of the glenoid and laterally to the greater tuberosity. The torn subscapularis tendon in 9 patients was repaired arthroscopically. Finally, side-to-side sutures were added between the graft and the infraspinatus tendon and between the graft and the subscapularis tendon to improve force coupling in the shoulder joint. Physical examination was performed and shoulder radiographs and magnetic resonance images taken before surgery and 3, 6, 12, and 24 months after surgery. Functional outcome was evaluated by using the University of California, Los Angeles (UCLA) score. Results Mean active flexion significantly increased from 66° to 163° (P Conclusion In patients with irreparable rotator cuff tears, including subscapularis tendon tears, our arthroscopic superior capsular reconstruction restored superior stability of the humeral head, resulting in substantial improvements in shoulder function, strength, and pain relief without complications, including graft tears.

Vestibular control of the head: possible functions of the vestibulocollic reflex

Here, we review the angular vestibulocollic reflex (VCR) focusing on its function during unexpected and voluntary head movements. Theoretically, the VCR could (1) stabilize the head in space during body movements and/or (2) dampen head oscillations that could occur as a result of the head's underdamped mechanics. The reflex appears unaffected when the simplest, trisynaptic VCR pathways are severed. The VCR's efficacy varies across species; in humans and monkeys, head stabilization is ineffective during low-frequency body movements in the yaw plan. While the appearance of head oscillations after the attenuation of semicircular canal function suggests a role in damping, this interpretation is complicated by defects in the vestibular input to other descending motor pathways such as gaze premotor circuits. Since the VCR should oppose head movements, it has been proposed that the reflex is suppressed during voluntary head motion. Consistent with this idea, vestibular-only (VO) neurons, which are possible vestibulocollic neurons, respond vigorously to passive, but not active, head rotations. Although VO neurons project to the spinal cord, their contribution to the VCR remains to be established. VCR cancelation during active head movements could be accomplished by an efference copy signal negating afferent activity related to active motion. Oscillations occurring during active motion could be eliminated by some combination of reflex actions and voluntary motor commands that take into account the head's biomechanics. A direct demonstration of the status of the VCR during active head movements is required to clarify the function of the reflex.

Effects of fermentation temperature on the composition of beer volatile compounds, organoleptic quality and spent yeast density

Production of good quality beer is dependent largely on the fermentation temperature and yeast strains employed during the brewing process, among others. In this study, effects of fermentation temperatures and yeast strain type on beer quality and spent yeast density produced after wort fermentation by two commercial yeast strains were investigated. Beer samples were assessed for colour, clarity and foam head stability using standard methods, whilst the compositions and concentration of Beer Volatile Compounds (BVCs) produced were assessed using GC-MS. The spent yeast density, measured as dry cell weight, ranged between 1.84 - 3.157 mg/ml for both yeast strains with the highest yield obtained at room temperature fermentation. A peak viable population of 2.56 x 10 7 cfu/ml was obtained for strain A, also during fermentation at room temperature. The foam head of the beers produced at 22.5oC was most stable, with foam head ratings of 2.66 and 2.50 for yeast strain A and B, respectively. However, there was no significant ( p = 0.242) difference in colour intensity between the beers produced at the different fermentation temperatures. Eight different BVCs were detected in all beer samples and were found to affect the organoleptic properties of the beer produced. Further optimizations are required to determine the effects of other parameters on beer quality.

A novel stereotaxic apparatus for neuronal recordings in awake head-restrained rats

A novel technique for neuronal recordings in awake head-restrained animals is presented. Our setup allows (1) daily repeat microelectrode studies in rats without use of anesthesia, (2) excellent stabilization of head using an eight point fixation, (3) painless head-restraint of the animal, (4) accurate stereotaxic localization during multiple sessions of recording, (5) to considerably reduced surgical time, (6) quick repositioning during chronic recording sessions and (7) high quality stabilized neuronal recordings during periods of rest and active movements.

Nonsensor control of centrifugal water pump with asynchronous electric-drive motor based on extended Kalman filter

An approach is described for estimating the pump’s variables based only on measuring the motor’s electrical variables. The method is based on extended Kalman filter estimation of the pump’s shaft power and velocity and on-line calculation of the head and flow rate using steady-state pump curves. The application of the method for the head and flow-rate stabilization systems is demonstrated in simulations.

Attenuation of trunk acceleration during walking in patients with unilateral vestibular deficiencies

Head stability, central for balance control during locomotion, is associated with attenuation of trunk oscillations. The study aimed at exploring trunk attenuation in patients with unilateral vestibular disorder (UVD) assuming it was compromised, and to see if attenuation could be influenced by vestibular rehabilitation therapy. Patients with UVD (N= 21), mean age (SD): 50.7 (11.5) years, women: 57%, were tested before and after intervention. Patients walked at different velocities with triaxial accelerometers over the lower and upper trunk. Normalization of data allowed comparison across patients over time. Self-reported symptoms and perception of handicap were registered. Acceleration was significantly higher at the lower compared to the upper trunk on both occasions. Increased accelerations at the lower and decreased accelerations at the upper trunk following intervention caused attenuation to increase along the antero-posterior (p=0.05) and medio-lateral axes (p< 0.01). Cadence was reduced (p=0.01), step-length increased (p= 0.01), and self-reported balance (p=0.05) and handicap (p<0.01) improved. More effective attenuation of trunk oscillations was found during walking following intervention. The observed increased stability of the upper trunk is compatible with improved head control, and this was associated with increased mobility of the lower trunk facilitating balance control during ambulation. Trunk accelerations may be useful for identification of balance control in UVD patients.

A channel head stability criterion for first-order catchments

The present analysis derives a stability criterion for long-term equilibrium channel heads. The concept of finite perturbation analysis is presented, during which the surface is subjected to perturbations of a finite amplitude and resulting changes in flow path structure and slope are computed. Based on these quantities the analysis predicts whether the perturbed location is going to erode, be filled in or remain steady. The channel head is defined geometrically as the focus point of converging flow lines at the bottom of hollows. It is demonstrated that stability at the channel head grows out of the competition between the rate of flow path convergence and the degree of profile concavity. Analytical functions are derived to compute channel head-contributing area and -slope, flow path convergence and profile concavity as a function of perturbation depth, distance from the crest and the initial slope. In a numerical model these quantities point to the long-term equilibrium channel head position, which is shown to depend also on the width to length ratio of hollows. It is also demonstrated that the equilibrium channel head position is sensitive to the base-level lowering/non-dimensional slope length ratio and to the slope of the initial topography. Morphometrical measurements both in the field and on simulated topographies were used to test the theoretical predictions.

Updating process of internal model of action as assessed from motor and postural strategies in young adults

Internal models are constantly updated based on the actions and experiences of a person in the world. In the present study, we proposed to assess the updating process of internal models of action by providing new environmental constraints for motor planning, postural control, and execution processes in daily tasks such as STS and BTS. STS and BTS tasks were performed with different inclinations of the support surface on which the participant and the chair were positioned: horizontal support, support tilted 10° to the right, or forward. Twelve healthy adults participated in this experiment. Kinematic characteristics were recorded using an optoelectronic motion analysis system. Movement duration and trunk inclination amplitudes were analyzed for STS and BTS as well as trunk orientation and strategies of head stabilization. Concerning the movement analysis our results showed (1) temporal asymmetry between STS and BTS, attributed mainly to the integration of the mechanical effects of gravity, and (2) a decrease of trunk movements when the support was tilted forward, attesting to an immediate adaptation process. Concerning the postural analysis our study revealed that adults adopted selective head stabilization on space strategy with respect to balance constraints. To conclude, young adults were able to immediately update their internal model of action in order to optimize motor control and vertical body orientation.