On the Immunometabolic Role of NF-κB in Adipocytes.

Two decades of research have established that Nuclear Factor-κB (NF-κB) signaling plays a critical role in reprogramming the fat cell transcriptome towards inflammation in response to overnutrition and metabolic stress. Several groups have suggested that inhibition of NF-κB signaling could have metabolic benefits for obesity-associated adipose tissue inflammation. However, two significant problems arise with this approach. The first is how to deliver general NF-κB inhibitors into adipocytes without allowing these compounds to disrupt normal functioning in cells of the immune system. The second issue is that general inhibition of canonical NF-κB signaling in adipocytes will likely lead to a massive increase in adipocyte apoptosis under conditions of metabolic stress, leading full circle into a secondary inflammation (However, this problem may not be true for non-canonical NF-κB signaling.). This review will focus on the research that has examined canonical and non-canonical NF-κB signaling in adipocytes, focusing on genetic studies that examine loss-of-function of NF-κB specifically in fat cells. Although the development of general inhibitors of canonical NF-κB signaling seems unlikely to succeed in alleviating adipose tissue inflammation in humans, the door remains open for more targeted therapeutics. In principle, these would include compounds that interrogate NF-κB DNA binding, protein-protein interactions, or post-translational modifications that partition NF-κB activity towards some genes and away from others in adipocytes. I also discuss the possibility for inhibitors of non-canonical NF-κB signaling to realize success in mitigating fat cell dysfunction in obesity. To plant the seeds for such approaches, much biochemical "digging" in adipocytes remains; this includes identifying-in an unbiased manner-NF-κB direct and indirect targets, genomic DNA binding sites for all five NF-κB subunits, NF-κB protein-protein interactions, and post-translational modifications of NF-κB in fat cells.

Nipping Adipocyte Inflammation in the Bud.

Adipose tissue inflammation continues to represent a significant area of research in immunometabolism. We have identified a transcription factor, EBF1, which crucially regulates the expression of numerous inflammatory loci in adipocytes. However, EBF1 appears to do so without physically binding to these inflammatory genes. Our research is currently focused on understanding this discrepancy, and we believe that future findings could pave the road for drug development aimed to block adipose inflammation at its source.

Metabolomics and the pig model reveal aberrant cardiac energy metabolism in metabolic syndrome.

Although metabolic syndrome (MS) is a significant risk of cardiovascular disease (CVD), the cardiac response (MR) to MS remains unclear due to traditional MS models' narrow scope around a limited number of cell-cycle regulation biomarkers and drawbacks of limited human tissue samples. To date, we developed the most comprehensive platform studying MR to MS in a pig model tightly related to human MS criteria. By incorporating comparative metabolomic, transcriptomic, functional analyses, and unsupervised machine learning (UML), we can discover unknown metabolic pathways connections and links on numerous biomarkers across the MS-associated issues in the heart. For the first time, we show severely diminished availability of glycolytic and citric acid cycle (CAC) pathways metabolites, altered expression, GlcNAcylation, and activity of involved enzymes. A notable exception, however, is the excessive succinate accumulation despite reduced succinate dehydrogenase complex iron-sulfur subunit b (SDHB) expression and decreased content of precursor metabolites. Finally, the expression of metabolites and enzymes from the GABA-glutamate, GABA-putrescine, and the glyoxylate pathways significantly increase, suggesting an alternative cardiac means to replenish succinate and malate in MS. Our platform discovers potential therapeutic targets for MS-associated CVD within pathways that were previously unknown to corelate with the disease.

Effects of seating on the discomfort caused by mechanical shocks: Measurement and prediction of SEAT values.

Seat effective amplitude transmissibilities (SEAT values) quantify the influence of seats on discomfort caused by vibration. This study investigated SEAT values with vertical mechanical shocks at low, medium, and high magnitudes (0.5, 1.0, and 2.0 ms-1.75) at frequencies between 1.0 and 16 Hz. With 18 subjects sitting on a rigid seat and two foam cushions, SEAT values were measured objectively (from the transmitted vibration), measured subjectively (by the responses of subjects), and predicted (using a model of the seat-passenger system). Except with high magnitude low frequency shocks, predicted SEAT values were similar to measured SEAT values. With shocks causing subjects to rise off a cushion and subsequently impact the cushion (low frequencies around 1 g), subjective SEAT values were better estimated using predicted SEAT values than objectively measured SEAT values, because accelerometers on cushions exaggerated the impact of the falling subject. However, accelerometers on rigid seats will underestimate such impacts.

Postural Stability When Walking and Exposed to Mediolateral Oscillatory Motion: Effect of Oscillation Waveform.

Postural stability can be threatened by the low-frequency motions in transport that are usually quantified by their root-mean-square (r.m.s.) acceleration. This study investigated how the stability of walking people depends on the waveform of 1- and 2-Hz mediolateral oscillations of the surface on which they walk. Walking on a treadmill, 20 subjects were perturbed by random oscillations of the treadmill with one-third octave bandwidths: different waveforms with the same r.m.s. acceleration and different waveforms with the same peak acceleration. Stability was measured subjectively and objectively by the velocity of the center of pressure in the mediolateral direction. Subjective and objective measures of walking instability increased with increasing r.m.s. acceleration of oscillations having the same peak acceleration. These same measures of instability were also affected by the peak acceleration when the r.m.s. magnitude of the oscillations was constant, especially with 1-Hz oscillations. It is concluded that r.m.s. measures of acceleration are insufficient to predict the postural stability of walking passengers exposed to mediolateral oscillations and that peaks in the oscillations should also be taken into account.

Equivalent comfort contours for fore-and-aft, lateral, and vertical whole-body vibration in the frequency range 1.0 to 10 Hz.

Standards assume vibration discomfort depends on the frequency and direction of whole-body vibration, with the same weightings for frequency and direction at all magnitudes. This study determined equivalent comfort contours from 1.0 to 10 Hz in each of three directions (fore-and-aft, lateral, vertical) at magnitudes in the range 0.1 to 3.5 ms-2 r.m.s. Twenty-four subjects sat on a rigid flat seat with and without a beanbag, altering the pressure distribution on the seat but not the transmission of vibration. The rate of growth of vibration discomfort with increasing magnitude of vibration differed between the directions of vibration and varied with the frequency of vibration. The frequency-dependence and direction-dependence of discomfort, therefore, depended on the magnitude of vibration. The beanbag did not affect the frequency-dependence or direction-dependence of vibration discomfort. It is concluded that different weightings for the frequency and direction of vibration are required for low and high magnitude vibration. Practitioner summary: When evaluating whole-body vibration to predict vibration discomfort, the weightings appropriate to different frequencies and different directions of vibration should depend on the magnitude of vibration. This is overlooked in all current methods of evaluating the severity of whole-body vibration.

Transmission of vibration through glove materials: effects of contact force.

This study investigated effects of applied force on the apparent mass of the hand, the dynamic stiffness of glove materials and the transmission of vibration through gloves to the hand. For 10 subjects, 3 glove materials and 3 contact forces, apparent masses and glove transmissibilities were measured at the palm and at a finger at frequencies in the range 5-300 Hz. The dynamic stiffnesses of the materials were also measured. With increasing force, the dynamic stiffnesses of the materials increased, the apparent mass at the palm increased at frequencies greater than the resonance and the apparent mass at the finger increased at low frequencies. The effects of force on transmissibilities therefore differed between materials and depended on vibration frequency, but changes in apparent mass and dynamic stiffness had predictable effects on material transmissibility. Depending on the glove material, the transmission of vibration through a glove can be increased or decreased when increasing the applied force. Practitioner summary: Increasing the contact force (i.e. push force or grip force) can increase or decrease the transmission of vibration through a glove. The vibration transmissibilities of gloves should be assessed with a range of contact forces to understand their likely influence on the exposure of the hand and fingers to vibration.

Frequency-dependence of discomfort caused by vibration and mechanical shocks.

The frequency content of a mechanical shock is not confined to its fundamental frequency, so it was hypothesised that the frequency-dependence of discomfort caused by shocks with defined fundamental frequencies will differ from the frequency-dependence of sinusoidal vibration. Subjects experienced vertical vibration and vertical shocks with fundamental frequencies from 0.5 to 16 Hz and magnitudes from ±0.7 to ±9.5 ms-2. The rate of growth of discomfort with increasing magnitude of motion decreased with increasing frequency of both motions, so the frequency-dependence of discomfort varied with the magnitudes of both motions and no single frequency weighting will be ideal for all magnitudes. At the frequencies of sinusoidal vibration producing greatest discomfort (4-16 Hz), shocks produced less discomfort than vibration with same peak acceleration or unweighted vibration dose value. Frequency-weighted vibration dose values provided the best predictions of the discomfort caused by different frequencies and magnitudes of vibration and shock. Practitioner Summary: Human responses to vibration and shock vary according to the frequency content of the motion. The ideal frequency weighting depends on the magnitude of the motion. Standardised frequency-weighted vibration dose values estimate discomfort caused by vibration and shock but for motions containing very low frequencies the filtering is not optimum.

Assessment of thermotactile and vibrotactile thresholds for detecting sensorineural components of the hand-arm vibration syndrome (HAVS).

BACKGROUND: Thermotactile thresholds and vibrotactile thresholds are measured to assist the diagnosis of the sensorineural component of the hand-arm vibration syndrome (HAVS). OBJECTIVES: This study investigates whether thermotactile and vibrotactile thresholds distinguish between fingers with and without numbness and tingling. METHODS: In 60 males reporting symptoms of the hand-arm vibration syndrome, thermotactile thresholds for detecting hot and cold temperatures and vibrotactile thresholds at 31.5 and 125 Hz were measured on the index and little fingers of both hands. RESULTS: In fingers reported to suffer numbness or tingling, hot thresholds increased, cold thresholds decreased, and vibrotactile thresholds at both 31.5 and 125 Hz increased. With sensorineural symptoms on all three phalanges (i.e. numbness or tingling scores of 6), both thermotactile thresholds and both vibrotactile thresholds had sensitivities greater than 80% and specificities around 90%, with areas under the receiver operating characteristic curves around 0.9. There were correlations between all four thresholds, but cold thresholds had greater sensitivity and greater specificity on fingers with numbness or tingling on only the distal phalanx (i.e. numbness or tingling scores of 1) suggesting cold thresholds provide better indications of early sensorineural disorder. CONCLUSIONS: Thermotactile thresholds and vibrotactile thresholds can provide useful indications of sensorineural function in patients reporting symptoms of the sensorineural component of HAVS.

Dynamic forces over the interface between a seated human body and a rigid seat during vertical whole-body vibration.

Biodynamic responses of the seated human body are usually measured and modelled assuming a single point of vibration excitation. With vertical vibration excitation, this study investigated how forces are distributed over the body-seat interface. Vertical and fore-and-aft forces were measured beneath the ischial tuberosities, middle thighs, and front thighs of 14 subjects sitting on a rigid flat seat in three postures with different thigh contact while exposed to random vertical vibration at three magnitudes. Measures of apparent mass were calculated from transfer functions between the vertical acceleration of the seat and the vertical or fore-and-aft forces measured at the three locations, and the sum of these forces. When sitting normally or sitting with a high footrest, vertical forces at the ischial tuberosities dominated the vertical apparent mass. With feet unsupported to give increased thigh contact, vertical forces at the front thighs were dominant around 8Hz. Around 3-7Hz, fore-and-aft forces at the middle thighs dominated the fore-and-aft cross-axis apparent mass. Around 8-10Hz, fore-and-aft forces were dominant at the ischial tuberosities with feet supported but at the front thighs with feet unsupported. All apparent masses were nonlinear: as the vibration magnitude increased the resonance frequencies decreased. With feet unsupported, the nonlinearity in the apparent mass was greater at the front thighs than at the ischial tuberosities. It is concluded that when the thighs are supported on a seat it is not appropriate to assume the body has a single point of vibration excitation.

Effect of room temperature on tests for diagnosing vibration-induced white finger: finger rewarming times and finger systolic blood pressures.

PURPOSE: This study investigates the effects of room temperature on two standard tests used to assist the diagnosis of vibration-induced white finger (VWF): finger rewarming times and finger systolic blood pressures. METHODS: Twelve healthy males and twelve healthy females participated in four sessions to obtain either finger skin temperatures (FSTs) during cooling and rewarming of the hand or finger systolic blood pressures (FSBPs) after local cooling of the fingers to 15 and 10 °C. The measures were obtained with the room temperature at either 20 or 28 °C. RESULTS: There were lower baseline finger skin temperatures, longer finger rewarming times, and lower finger systolic blood pressures with the room temperature at 20 than 28 °C. However, percentage reductions in FSBP at 15 and 10 °C relative to 30 °C (i.e. %FSBP) did not differ between the two room temperatures. Females had lower baseline FSTs, longer rewarming times, and lower FSBPs than males, but %FSBPs were similar in males and females. CONCLUSIONS: Finger rewarming times after cold provocation are heavily influenced by room temperature and gender. For evaluating peripheral circulatory function using finger rewarming times, the room temperature must be strictly controlled, and a different diagnostic criterion is required for females. The calculation of percentage changes in finger systolic blood pressure at 15 and 10 °C relative to 30 °C reduces effects of both room temperature and gender, and the test may be used in conditions where the ±1 °C tolerance on room temperature required by the current standard cannot be achieved.

Response of the seated human body to whole-body vertical vibration: discomfort caused by mechanical shocks.

The frequency dependence of discomfort caused by vertical mechanical shocks has been investigated with 20 seated males exposed to upward and downward shocks at 13 fundamental frequencies (1-16 Hz) and 18 magnitudes (±0.12 to ±8.3 ms-2). The rate of growth of discomfort with increasing shock magnitude depended on the fundamental frequency of the shocks, so the frequency dependence of equivalent comfort contours (for both vertical acceleration and vertical force measured at the seat) varied with shock magnitude. The rate of growth of discomfort was similar for acceleration and force, upward and downward shocks, and lower and higher magnitude shocks. The frequency dependence of discomfort from shocks differs from that of sinusoidal vibrations having the same fundamental frequencies. This arises in part from the frequency content of the shock. Frequency weighting Wb in BS 6841:1987 and ISO 2631-1:1997 provided reasonable estimates of the discomfort caused by the shocks investigated in this study. Practitioner Summary: No single frequency weighting can accurately predict the discomfort caused by mechanical shocks over wide ranges of shock magnitude, but vibration dose values with frequency weighting Wb provide reasonable estimates of discomfort caused by shocks similar to those investigated in this study with peak accelerations well below 1 g.

Transmission of vibration through gloves: effects of contact area.

For three samples of material (12.5, 25.0 and 37.5 mm diameter) from each of three gloves, the dynamic stiffnesses and the vibration transmissibilities of the materials (to both the palm of the hand and the thenar eminence) were measured at frequencies from 10 to 300 Hz. Additional measurements showed the apparent masses of the hand at the palm and the thenar eminence were independent of contact area at frequencies less than about 40 Hz, but increased with increasing area at higher frequencies. The stiffness and damping of the glove materials increased with increasing area. These changes caused material transmissibilities to the hand to increase with increasing area. It is concluded that the size of the area of contact has a large influence on the transmission of vibration through a glove to the hand. The area of contact should be well-defined and controlled when evaluating the transmission of vibration through gloves. Practitioner Summary: The transmission of vibration through gloves depends on both the dynamic stiffness of glove material and the dynamic response of the hand. Both of these depend on the size of the contact area between a glove material and the hand, which should be taken into account when assessing glove transmissibility.

Response of the seated human body to whole-body vertical vibration: biodynamic responses to mechanical shocks.

The biodynamic response of the seated human body has been investigated with 20 males exposed to upward and downward shocks at 13 fundamental frequencies (1-16 Hz) and 18 magnitudes (up to ±8.3 ms-2). For 1- and 2- degree-of-freedom models, the stiffness and damping coefficients were obtained by fitting seat acceleration waveforms predicted from the measured force to the measured seat acceleration waveform. Stiffness and damping coefficients were also obtained in the frequency domain with random vibration. The optimum stiffness and damping coefficients varied with the magnitude and the frequency of shocks. With both upward and downward shocks, the resonance frequency of the models decreased from 6.3 to 4 Hz as the vibration dose values of the shocks increased from 0.05 to 2.0 ms-1.75. The stiffness and damping obtained from responses to shocks were correlated with, and similar to, the stiffness and damping obtained with random vibration. Practitioner Summary: When modelling the dynamic response of the seated human body to vertical acceleration less than 1 g, the relation between force and acceleration can be well represented by a single degree-of-freedom model although the optimum stiffness and damping depend on the magnitude and frequency of sinusoidal, random or shock motion.

Assessment of two alternative standardised tests for the vascular component of the hand-arm vibration syndrome (HAVS).

BACKGROUND: Vibration-induced white finger (VWF) is the vascular component of the hand-arm vibration syndrome (HAVS). Two tests have been standardised so as to assist the diagnosis of VWF: the measurement of finger rewarming times and the measurement of finger systolic blood pressures (FSBPs). OBJECTIVES: This study investigates whether the two tests distinguish between fingers with and without symptoms of whiteness and compares individual results between the two test methods. METHODS: In 60 men reporting symptoms of the HAVS, the times for their fingers to rewarm by 4°C (after immersion in 15°C water for 5 min) and FSBPs at 30°C, 15°C and 10°C were measured on the same day. RESULTS: There were significant increases in finger rewarming times and significant reductions in FSBPs at both 15°C and 10°C in fingers reported to suffer blanching. The FSBPs had sensitivities and specificities >90%, whereas the finger rewarming test had a sensitivity of 77% and a specificity of 79%. Fingers having longer rewarming times had lower FSBPs at both temperatures. CONCLUSIONS: The findings suggest that, when the test conditions are controlled according to the relevant standard, finger rewarming times and FSBPs can provide useful information for the diagnosis of VWF, although FSBPs are more sensitive and more specific.

Higher body fat percentage is associated with enhanced temperature perception in NAFLD: results from the randomised Wessex Evaluation of fatty Liver and Cardiovascular markers in NAFLD with OMacor thErapy trial (WELCOME) trial.

AIMS/HYPOTHESIS: The effect of n-3 fatty acid treatment on temperature perception as a sensory nerve function modality is uncertain. In patients with non-alcoholic fatty liver disease (NAFLD) both with and without type 2 diabetes, we: (1) tested whether 15-18 months' treatment with 4 g/day of docosahexaenoic plus eicosapentaenoic acid (DHA+EPA) improved hot (HPT) and cold (CPT) temperature perception thresholds and (2) explored factors associated with HPT and CPT, in a randomised, double-blind, placebo-controlled trial. METHODS: The effect of treatment (n = 44) on HPT, CPT and temperature perception index (TPI: difference between HPT and CPT) was measured at the big toe in 90 individuals without neuropathy (type 2 diabetes; n = 30). Participants were randomised 1:1, using sequential numbering, by personnel independent from the trial team. All participants and all members of the research team were blinded to group assignment. Data were collected in the Southampton National Institute for Health Research Biomedical Research Centre. Treatment effects and the independence of associations were testing by regression modelling. RESULTS: Mean ± SD age was 50.9 ± 10.6 years. In men (n = 53) and women (n = 37), HPTs (°C) were 46.1 ± 5.1 and 43.1 ± 6.4 (p = 0.02), CPTs (°C) were 22.7 ± 3.4 and 24.5 ± 3.6 (p = 0.07) and TPIs (°C) were 23.4 ± 7.4 and 18.7 ± 9.5 (p = 0.008), respectively. In univariate analyses, total body fat percentage (measured by dual-energy x-ray absorptiometry [DXA]) was associated with HPT (r = -0.36 p = 0.001), CPT (r = 0.35 p = 0.001) and TPI (r = 0.39 p = 0.0001). In multivariable-adjusted regression models, adjusting for age, sex and other potential confounders, only body fat percentage was independently associated with HPT, CPT or TPI (p = 0.006, p = 0.006 and p = 0.002, respectively). DHA+EPA treatment did not modify HPT, CPT or TPI (p = 0.93, p = 0.44 and p = 0.67, respectively). There were no important adverse effects or side effects reported. CONCLUSIONS/INTERPRETATION: Higher body fat percentage is associated with enhanced temperature perception. There was no benefit of treatment with high-dose n-3 fatty acids on the thresholds to detect hot or cold stimuli. TRIAL REGISTRATION: ClinicalTrials.gov NCT00760513 FUNDING: This work was supported by the National Institute for Health Research through the NIHR Southampton Biomedical Research Unit grant and by a Diabetes UK allied health research training fellowship awarded to KMcC (Diabetes UK. BDA 09/0003937).

Discomfort of seated persons exposed to low frequency lateral and roll oscillation: Effect of backrest height.

Backrests influence the comfort of seated people. With 21 subjects sitting with three backrest heights (no backrest, short backrest, high backrest) discomfort caused by lateral, roll, and fully roll-compensated lateral oscillation was investigated at frequencies between 0.25 and 1.0 Hz. With lateral oscillation, the short backrest reduced discomfort at frequencies less than 0.63 Hz and the high backrest reduced discomfort at frequencies less than 1.0 Hz. With roll oscillation, the high backrest reduced discomfort at frequencies less than 0.63 Hz, but increased discomfort at 1.0 Hz. With fully roll-compensated lateral oscillation, the short backrest reduced discomfort at 0.4 Hz and the high backrest reduced discomfort at 0.5 and 0.63 Hz. As predicted by current standards, a backrest can increase discomfort caused by high frequencies of vibration. However, a backrest can reduce discomfort caused by low frequencies, with the benefit depending on the frequency and direction of oscillation and backrest height.

Reductions in finger blood flow induced by 125-Hz vibration: effect of location of contact with vibration.

PURPOSE: This study investigated whether the reductions in finger blood flow induced by 125-Hz vibration applied to different locations on the hand depend on thresholds for perceiving vibration at these locations. METHODS: Subjects attended three sessions during which vibration was applied to the right index finger, the right thenar eminence, or the left thenar eminence. Absolute thresholds for perceiving vibration at these locations were determined. Finger blood flow in the middle finger of both hands was then measured at 30-s intervals during five successive 5-min periods: (i) pre-exposure, (ii) pre-exposure with 2-N force, (iii) 2-N force with vibration, (iv) post-exposure with 2-N force, (v) recovery. During period (iii), vibration was applied at 15 dB above the absolute threshold for perceiving vibration at the right thenar eminence. RESULTS: Vibration at all three locations reduced finger blood flow on the exposed and unexposed hand, with greater reductions when vibrating the finger. Vibration-induced vasoconstriction was greatest for individuals with low thresholds and locations of excitation with low thresholds. CONCLUSIONS: Differences in vasoconstriction between subjects and between locations are consistent with the Pacinian channel mediating both absolute thresholds and vibration-induced vasoconstriction.

Transmission of vibration through gloves: effects of material thickness.

It might be assumed that increasing the thickness of a glove would reduce the vibration transmitted to the hand. Three material samples from an anti-vibration glove were stacked to produce three thicknesses: 6.4, 12.8 and 19.2 mm. The dynamic stiffnesses of all three thicknesses, the apparent mass at the palm and the finger and the transmission of vibration to the palm and finger were measured. At frequencies from 20 to 350 Hz, the material reduced vibration at the palm but increased vibration at the finger. Increased thickness reduced vibration at the palm but increased vibration at the finger. The measured transmissibilities could be predicted from the material dynamic stiffness and the apparent mass of the palm and finger. Reducing the dynamic stiffness of glove material may increase or decrease the transmission of vibration, depending on the material, the frequency of vibration and the location of measurement (palm or finger). Practitioner Summary: Transmission of vibration through gloves depends on the dynamic response of the hand and the dynamic stiffness of glove material, which depends on material thickness. Measuring the transmission of vibration through gloves to the palm of the hand gives a misleading indication of the transmission of vibration to the fingers.

Ocular vestibular evoked myogenic potentials elicited with vibration applied to the teeth.

OBJECTIVES: This study investigated whether the method for eliciting vibration-induced oVEMPs could be improved by applying vibration directly to the teeth, and how vibration-induced oVEMP responses depend on the duration of the applied vibration. METHODS: In 10 participants, a hand-held shaker was used to present 100-Hz vibration tone pips to the teeth via a customised bite-bar or to other parts of the head. oVEMP potentials were recorded in response to vibration in three orthogonal directions and five stimulus durations (10-180 ms). The oVEMP responses were analysed in terms of the peak latency onset, peak-to-peak amplitude, and the quality of the trace. RESULTS: Vibration applied to the teeth via the bite-bar produced oVEMPs that were more consistent, of higher quality and of greater amplitude than those evoked by vibration applied to the head. Longer duration stimuli produced longer duration oVEMP responses. One cycle duration stimuli produced responses that were smaller in amplitude and lower quality than the longer stimulus durations. CONCLUSIONS: Application of vibration via the teeth using a bite-bar is an effective means of producing oVEMPs. A 1-cycle stimulus is not optimal to evoke an oVEMP because it produces less robust responses than those of longer stimulus duration. A positive relationship between the duration of the stimulus and the response is consistent with the notion that the vibration-induced oVEMP is an oscillatory response to the motion of the head, rather than being a simple reflex response that occurs when the stimulus exceeds a threshold level of stimulation. SIGNIFICANCE: Applying acceleration to the teeth through a bite-bar elicits clearer oVEMP responses than direct application to other parts of the head and has potential to improve clinical measurements. A 100-Hz 1-cycle stimulus produces less robust oVEMP responses than longer 100-Hz stimuli.