Multipulse Train Research Articles

Spiders manipulate and exploit bioluminescent signals of fireflies

Predators often search for prey while moving through the environment, but there are important exceptions, including the way sedentary predators sometimes rely on signals for drawing prey to within striking distance1,2. Some spiders, for instance, leave the remnants of previously-captured prey in their webs where they function as static lures that effectively attract a diverse array of additional prey3456. However, important questions remain concerning how specific the targeted prey may be and how dynamic, instead of static, signalling might be. With these questions as our rationale, we initiated research on Araneus ventricosus (L. Koch, 1878), an orb-weaving spider, as the predator and the firefly Abscondita terminalis males as the prey (Figure 1A-C). Using two lanterns situated on their abdomen (Figure 1D,F), A. terminalis males make female-attracting multi-pulse flash trains (Figure 1J), whereas sedentary females attract males by making single-pulse signals (Figure 1C,K) with a single lantern (Figure 1E,G). Drawing from extensive field observations, we propose that A. ventricosus practices deceptive interspecific communication by first ensnaring firefly males in its web and then predisposing the entrapped male fireflies to broadcast bioluminescent signals that deviate from female-attracting signals typically made by A. terminalis males and instead mimic the male-attracting signals typically made by females. The outcome is that the entrapped male fireflies broadcast false signals that lure more male fireflies into the web.

The feasibility and technical aspects of trigemino-cervical reflex elicitation in humans under general anesthesia

ObjectiveTo analyze the feasibility, neurophysiological aspects, stimulation patterns, and topographic distribution of trigemino-cervical reflex (TCR) components in humans under general anesthesia. MethodsThis prospective observational study enrolled 20 participants who underwent posterior fossa surgery, surgical proceduresin thecraniovertebral junction,or spinal cord surgery. TCR responses were simultaneously recorded in the sternocleidomastoid (SCM) and trapezius muscles after electrical stimulation of the supraorbital and infraorbital nerves. TCR responses were recorded preoperatively and intraoperatively using single-pulse and multipulse (trains of 2–7 electrical stimuli) stimulation, respectively. Two stimulus duration patterns were evaluated: 0.2–0.5 ms and 0.5–1.0 ms. ResultsIntraoperatively, short- and long-latency TCR components were obtained in the SCM ipsilateral to the stimulation with variable recordability. Short-latency responses were the most commonly recorded components. A longer stimulus duration (0.5–1.0 ms) seems to favor the elicitation of TCR responses under general anesthesia. ConclusionsShort-latency components recorded in the SCM ipsilateral to the stimulation could be regularly elicited under general anesthesia when a larger stimulus duration (0.5–1.0 ms) was applied. SignificanceThis is the first study to demonstrate the elicitation of TCR components in humans under general anesthesia. This neurophysiological technique can potentially optimize intraoperative neurophysiological monitoring during brainstem surgery.

Neurophysiologic cut off values for safe resection of patients with supratentorial gliomas.

Gliomas have infiltrative nature and tumor volume has direct prognostic value. Optimal resection limits delineated by high-frequency monopolar stimulation with multipulse short train technique is still a matter of debate for safe surgery without (or with acceptable) neurological deficits. It is also an enigma whether the same cut-off values are valid for high and low grades. We aimed to analyze the value of motor mapping/monitoring findings on postoperative motor outcome in diffuse glioma surgery. Patients who were operated on due to glioma with intraoperative neuromonitorization at our institution between 2017 and 2021 were analyzed. Demographic information, pre- and post-operative neurological deficit, magnetic resonance images, resection rates, and motor evoked potential (MEP) findings were analyzed. Eighty-seven patients of whom 55 had high-grade tumors were included in the study. Total/near-total resection was achieved in 85%. Subcortical motor threshold (ScMTh) from resection cavity to the corticospinal tract was ≤ 2mA in 17; 3 mA in 14; 4 mA in 6; 5 mA in 7, and ≥5mA in 50 patients. On the 6th month examination, six patients (5 with high-grade tumor) had motor deficits. These patients had changes in MEP that exceeded critical threshold during monitoring. Receiver operating characteristic analysis revealed 2.5 mA ScMTh as the cut-off point for limb paresis after awakening and 6 months for the groups. Subcortical mapping with MEP monitoring helps to achieve safe wider resection. The optimal safe limit for SCMTh was determined as 2.5 mA. Provided that safe threshold values are maintained in MEP, surgeon may force the functional limits by lowering the SCMTh to 1 mA, especially in low-grade gliomas.

Matched filter processing to improve measuring accuracy of interferometric fringe analysis using a multi-pulse train interferometer

We propose a novel approach to address the problem of measurement accuracy in analyzing the distance between the peak positions of interference envelopes in multi-pulse train (MPT) interferometry. In the frequency domain, a bandpass filter cannot remove all noise since the deterministic signal and noise overlap in the frequency domain. In the proposed method, by focusing on the differences in the statistical properties of deterministic signal and noise, matched filter processing eliminates any uncorrelated noise signals, thereby achieving noise reduction. This paper describes the procedure of the proposed method and its development based on a simple interference fringe model. The proposed approach is introduced within the framework of a MPT interferometer, and the experimental results demonstrate its superiority in determining the distance between peaks over the conventional Fourier transform method. This technique can be useful for high-precision measurement of distances for scientific purposes as well as industrial applications.

Altered Accumbal Dopamine Terminal Dynamics Following Chronic Heroin Self-Administration.

Administration of heroin results in the engagement of multiple brain regions and the rewarding and addictive effects are mediated, at least partially, through activation of the mesolimbic dopamine system. However, less is known about dopamine system function following chronic exposure to heroin. Withdrawal from chronic heroin exposure is likely to drive a state of low dopamine in the nucleus accumbens (NAc), as previously observed during withdrawal from other drug classes. Thus, we aimed to investigate alterations in NAc dopamine terminal function following chronic heroin self-administration to identify a mechanism for dopaminergic adaptations. Adult male Long Evans rats were trained to self-administer heroin (0.05 mg/kg/inf, IV) and then placed on a long access (FR1, 6-h, unlimited inf, 0.05 mg/kg/inf) protocol to induce escalation of intake. Following heroin self-administration, rats had decreased basal extracellular levels of dopamine and blunted dopamine response following a heroin challenge (0.1 mg/kg/inf, IV) in the NAc compared to saline controls. FSCV revealed that heroin-exposed rats exhibited reduced stimulated dopamine release during tonic-like, single-pulse stimulations, but increased phasic-like dopamine release during multi-pulse stimulation trains (5 pulses, 5–100 Hz) in addition to an altered dynamic range of release stimulation intensities when compared to controls. Further, we found that presynaptic D3 autoreceptor and kappa-opioid receptor agonist responsivity were increased following heroin self-administration. These results reveal a marked low dopamine state following heroin exposure and suggest the combination of altered dopamine release dynamics may contribute to increased heroin seeking.

Noise reduction method in both time and frequency domains for envelope peak position extraction of pulse-train interferometry measuring distance between interference fringes

Multi-pulse train interferometry is used to measure distance for meter-scale/nanometer-resolution geometric measurements. The core of multi-pulse train interferometry is object positioning accuracy, which is limited by the ability to position the interference fringe envelope peak. The Fourier fringe analysis method, optical Hilbert transform method, and other methods are used in the envelope demodulation of multi-pulse train interferometry. The matched filter, which provides good noise reduction capability in the time domain, is widely used in radar signal processing. In this study, a matched filter is combined with the Fourier fringe analysis method and used to demodulate the envelopes of a fringe in a multi-pulse train interferometry because the proposed combined method performs noise reduction in both the time and frequency domains for fringe envelope signal processing. Compared with two conventional methods, the proposed combined method was proven to be feasible for envelope demodulation of multi-pulse train interferometry.

Photon energy transfer on titanium targets for laser thrusters

Abstract Using two infrared pulsed lasers systems, a picosecond solid-state Nd:YAG laser with tuneable repetition rate (400 kHz–1 MHz) working in the burst mode of a multi-pulse train and a femtosecond Ti:sapphire laser amplifier with tuneable pulse duration in the range of tens of femtoseconds up to tens of picoseconds, working in single-shot mode (TEWALASS facility from CETAL-NILPRP), we have investigated the optimal laser parameters for kinetic energy transfer to a titanium target for laser-thrust applications. In the single-pulse regime, we controlled the power density by changing both the duration and pulse energy. In the multi-pulse regime, the train’s number of pulses (burst length) and the pulse energy variation were investigated. Heat propagation and photon reflection-based models were used to simulate the obtained experimental results. In the single-pulse regime, optimal kinetic energy transfer was obtained for power densities of about 500 times the ablation threshold corresponding to the specific laser pulse duration. In multi-pulse regimes, the optimal number of pulses per train increases with the train frequency and decreases with the pulse power density. An ideal energy transfer efficiency resulting from our experiments and simulations is close to about 0.0015%.

SY5.2. Intraoperative monitoring and mapping during brain tumor surgery

The aggressive removal of a glioma is expected to improve long-term patient survival and quality of life. However, removal of a supratentorial glioma, particularly in proximity to the eloquent cortex, poses a great risk of creating new functional deficits. Thus, it is critical to consider functional and oncological outcomes simultaneously when treating patients with supratentorial glioma. Neurophysiological intraoperative monitoring (NIOM) has long been regarded as the “gold standard” for glioma resection, allowing for maximal resection of lesions while preserving sensorimotor function. NIOM during surgery involves the use of both mapping and monitoring strategies with multiple modalities. Brain mapping is necessary due to individual variability in cortical organization and the unexpected displacement of normal anatomic landmarks by tumor growth. Typically, the median somatosensory evoked potential phase reversal technique is used to localize the central sulcus, followed by direct cortical stimulation with a monopolar electrode and multipulse train stimulation, to confirm the location of the eloquent motor cortex. During resection, motor and somatosensory evoked potentials (MEP and SSEP) from the contralateral hemibody and direct waves (d waves), if indicated, are monitored to safeguard the integrity of functional structures. If resection extends beyond the cortical boundary, subcortical mapping can be used to confirm the approximate distance from the resection cavity to the corticospinal tract. Concomitant use of subcortical mapping and MEP monitoring is believed to be associated with more extensive resection and fewer severe late functional deficits. In addition, a meta-analysis indicated that use of intraoperative brain mapping during glioma surgery resulted in a 2-fold reduction of long term neurological deficits. Further, this was not at the expense of extent of resection. In conclusion, while functional deficits are still possible even with NIOM during the surgical procedure, in most cases, the use of this technique significantly improves patient outcomes.

Neurophysiologic Mapping of Thalamocortical Tract in Asleep Craniotomies: Promising Results From an Early Experience.

Subcortical mapping of the corticospinal tract has been extensively used during craniotomies under general anesthesia to achieve maximal resection while avoiding postoperative motor deficits. To our knowledge, similar methods to map the thalamocortical tract (TCT) have not yet been developed. To describe a neurophysiologic technique for TCT identification in 2 patients who underwent resection of frontoparietal lesions. The central sulcus (CS) was identified using the somatosensory evoked potentials (SSEP) phase reversal technique. Furthermore, monitoring of the cortical postcentral N20 and precentral P22 potentials was performed during resection. Subcortical electrical stimulation in the resection cavity was done using the multipulse train (case #1) and Penfield (case #2) techniques. Subcortical stimulation within the postcentral gyrus (case #1) and in depth of the CS (case #2), resulted in a sudden drop in amplitudes in N20 (case #1) and P22 (case #2), respectively. In both patients, the potentials promptly recovered once the stimulation was stopped. These results led to redirection of the surgical plane with avoidance of damage of thalamocortical input to the primary somatosensory (case #1) and motor regions (case #2). At the end of the resection, there were no significant changes in the median SSEP. Both patients had no new long-term postoperative sensory or motor deficit. This method allows identification of TCT in craniotomies under general anesthesia. Such input is essential not only for preservation of sensory function but also for feedback modulation of motor activity.

Continuous-wave stability and multipulse structures in a universal complex Ginzburg–Landau model for passively mode-locked lasers with a saturable absorber

The stability of continuous waves and the dynamics of multipulse structures are studied theoretically for a generic model of passively mode-locked fiber lasers with arbitrary nonlinearity. The model is characterized by a complex Ginzburg–Landau equation with a nonlinear term I m / ( 1 + Γ I ) n , where I is the field intensity, m and n are real numbers, and Γ is the saturation power. Fixed-point solutions of the governing equations reveal an interesting loci of singular points in the amplitude-frequency plane consisting of zero, one, or two fixed points, depending on the values of m and n . The continuous-wave stability is analyzed within the framework of the modulational-instability theory, and the results demonstrate a bifurcation in the continuous-wave amplitude growth rate and propagation constant characteristic of multiperiodic wave structures. In the full nonlinear regime, these multiperiodic wave structures turn out to be multipulse trains, unveiled via numerical simulations of the model nonlinear equation, the rich variety of which is highlighted by considering different combinations of values for the pair ( m , n ). The results are consistent with previous analyses of the dynamics of multipulse structures in several contexts of passively mode-locked lasers with a saturable absorber, as well as with predictions about the existence of multipulse structures and bound-state solitons in optical fibers with strong optical nonlinearity, such as cubic-quintic and saturable nonlinearities.

Reconstruction of partial envelope of interference pattern based on chirp Z-transform

This paper presents a novel algorithm for the partial reconstruction of interference pattern envelopes. In multi-pulse train interferometers, the exact determination of the peak position of the envelope of interference fringes is of paramount importance. The estimation of the interference pattern envelope usually involves the use of discrete Fourier transform (DFT). The proposed algorithm is based on the chirp Z-transform (CZT) instead of DFT and avoids estimating the entire envelope of the interference pattern. It is sufficient for determining part of the envelope around the peak value position. The proposed approach is presented and illustrated for the first time by means of optical fringes. The experimental results demonstrate that this approach is reliable for partial envelope determination.

Factors that modify the risk of intraoperative seizures triggered by electrical stimulation during supratentorial functional mapping

ObjectiveIntraoperative mapping via electrical stimulation is the gold standard technique for surgeries close to the eloquent cortex. However, it can trigger seizures which immediately impact patient’s safety. We studied whether administration of antiepileptic drugs (AED) prior to and/or at the beginning of the surgery decreases the probability of triggering seizures, while adjusting for other risk factors. Methods544 consecutive intraoperative mapping cases performed at a tertiary care center for epilepsy and brain tumor surgery were included in the study. Using a multivariate logistic regression analysis, we analyzed the independent impacts of AED loading at time of surgery, preoperative AED maintenance, history of seizures, type of stimulation paradigm, lobar location of stimulation, age, opioid administration and pathology on the probability of triggering seizures. ResultsSeizures were identified in 135 patients. Intravenous loading with AED decreased the odds of triggering seizures by 45% (OR = 0.55, p = 0.01), Penfield (versus multipulse train) stimulation and diffuse (versus well circumscribed) pathology increased it twice (OR = 1.97, p = 0.01) and 2.4 times (OR = 2.42, p = 0.003) respectively. No other factors had a significant impact. ConclusionsSeizures triggered during mapping occur frequently and are multifactorial. SignificanceLoading with AED independently reduces the risk of their occurrence.

Transcranial motor evoked potentials electrically elicited by multi-train stimulation can reflect isolated nerve root injury more precisely than those by conventional multi-pulse stimulation: an experimental study in rats.

Nerve root injury can occur in complex spine surgeries. Recording transcranial motor-evoked potentials (TcMEPs) has been the most popular method to monitor motor function during surgery. However, TcMEPs cannot detect single nerve root injury satisfactorily. Recently, multi-train stimulation (MTS) was demonstrated to effectively enhance TcMEPs. The aim of this study was to investigate the utility of TcMEPs elicited by MTS for intraoperative nerve root monitoring. TcMEPs were recorded from the quadriceps femoris (QF) and gastrocnemius (GC) muscles in the hindlimbs of 20 rats before and after transection of the nerve root at L6 (dominant root innervating the GC). For MTS, a multipulse (train) stimulus was delivered repeatedly at 5Hz. The change ratio of the amplitude after transection of the nerve root was compared between MTS and conventional single-train stimulation (STS). The change in TcMEP amplitudes for QF after transection of the nerve root at L6 was 97.8 ± 12.2% with MTS and 100.1 ± 7.2% with STS (p = 0.496), whereas that for GC was 40.6 ± 11.5% with MTS and 64.8 ± 8.8% with STS (p<0.001). MTS could improve the ability to detect isolated nerve root injury in intraoperative TcMEP monitoring.

Platform Session – Evoked potentials & NIOM: Factors that modify the risk of intraoperative seizures triggered by electrical stimulation during supratentorial functional mapping

Introduction Neurophysiologic mapping via electrical stimulation is the gold standard for intraoperative functional mapping during surgeries in close proximity to eloquent cortical and subcortical regions. While it’s temporal and spatial resolution are far superior to other intraoperative and extraoperative techniques, the method carries a relatively high risk for triggering after discharges and seizures. These can not only lead to inaccurate mapping results but also pose an immediate safety risk to the patient. In the current study we aim to identify factors that impact this risk. Particularly, we are aim to study whether administration of antiepileptic (AED) drugs prior to and/or at surgery decrease the probability of triggering seizures. Methods We studied 544 consecutive mapping cases performed at an institution with tertiary care centers for epilepsy and brain tumor surgery. Applying a multivariate logistic regression model, we analyzed whether certain stimulation paradigms, patient’s state (awake versus general anesthesia), history of epilepsy, maintenance AED administration prior to surgery, and loading with AED at the beginning of the surgery do impact the risk of triggering seizures, after adjusting for potential confounders. Results Seizures were triggered in 135 patients. Penfield method of stimulation independently increased the odds of triggering seizures 5.5 times, when compared to high frequency anodal stimulation (OR = 5.6, p = 0.03) while diffuse pathology increased this risk 2.7 times (OR = 2.7. p Conclusion Intravenous administration of a loading dose of AED at the beginning of the surgery does reduce the risk of stimulation triggering intraoperative seizures, regardless of whether patient has had preoperative seizures or not. Penfield method is more epileptogenic than multipulse train technique and thus the latter should be used preferentially. Prior history of epilepsy does not increase the risk of triggering seizures, while preoperative administration of maintenance AEDs does not decrease it. Mapping in proximity to poorly defined lesions carries a significantly higher risk for triggering seizures.

Multi-operational tuneable Q-switched mode-locking Er fibre laser

A wavelength-spacing tuneable, Q-switched mode-locking (QML) erbium-doped fibre laser based on non-linear polarization rotation controlled by four waveplates and a cube polarizer is proposed. A mode-locked pulse train using two quarter-wave plates and a half-wave plate (HWP) is obtained first, and then an extra HWP is inserted into the cavity to produce different operation regimes. The evolutions of temporal and spectral dynamics with different orientation angles of the extra HWP are investigated. A fully modulated stable QML pulse train is observed experimentally. This is, to the author’s best knowledge, the first experimental work reporting QML operation without adding an extra saturable absorber inside the laser cavity. Multi-wavelength pulse laser operation, multi-pulse train continuous-wave mode-locking operation and pulse-splitting operations are also reported at certain HWP angles. The observed operational dynamics are interpreted as a mutual interaction of dispersion, non-linear effect and insertion loss. This work provides a new mechanism for fabricating cheap tuneable multi-wavelength lasers with QML pulses.

Spin echo processor in functional electronic devices: Control of responses in processing of multipulse trains

A specific analog device (spin echo processor) is proposed for processing of pulsed data in functional electronic devices under certain conditions. It is shown that a disadvantage of such devices related to generation of multiple noise signals upon processing of multipulse trains can be eliminated with the aid of magnetically ordered working substance using an additional channel that forms magnetic field in the working substance.

Multi Pulse Train Modeling of Piezo-Drop-on-Demand Inkjet Print-Head Response

Resonant oscillations set up internal fluid waves within a piezo-drop-on-demand (DoD) print-head channel as a result of actuation drive pulses. Such waves will persist for some time after droplet ejection from the nozzle, and the residual wave amplitude can interfere (constructively or destructively) with all succeeding actuation drive pulses, potentially altering the speed and volume of successive droplets. As uncontrolled interference would worsen printing quality, residual waves are usually reduced by a combination of print-head design and waveform optimization for better performance at continuous (steady state) printing frequencies. However, the residual waves following any changes of printing frequency can influence &#x201C;first&#x201D; drops and short bursts of drops. Exact analytic expressions are provided here for the N-pulse burst DoD print-head response function with fixed printing frequency. This article explains the purpose and application of the model predictions to published piezo-driven DoD data. An examination of the effect of fluid properties, the identification of unexpected jetting behavior and some issues with manufacturing prototype quality, tests of assumptions made in the simple model and extensions to the prediction of print-head performance using realistic complex waveforms are also discussed. An earlier shorter article, mainly introducing the multi pulse train modeling approach and some applications within Xaar, was first presented at NIP31/DF2015 [S. D. Hoath, A simple model for DoD inkjet frequency response, Proc. IS&amp;Ts 31st Int'l. Conf. on Digital Printing Technologies (IS&amp;T, Springfield, VA 2015), 8&#x2013;12]. &#xA9; 2016 Society for Imaging Science and Technology.

Transcranial Electrical Stimulation (TES) as a Possible Novel Alternative to Transcranial Magnetic Stimulation (TMS) to Assess the Motor Function of the Spinal Cord for Clinical Diagnosis in Horses

Reasons for performing studyTo introduce and assess the feasibility of multipulse transcranial electrical stimulation (TES) in horses.ObjectivesTo assess latency times of muscular motor evoked potentials (MEP) in the m. extensor carpi radialis (ECR) and the m. tibialis cranialis (TC), elicited by transcranially applied multipulse stimulation in 12 healthy horses.Study designProspective observational study applied in 12 healthy horses.MethodsHorses with a mean age of 11.0 (range 3.6–20.5) years and a height of 160 (s.d. ± 10.0) cm were studied. Horses were sedated with detomidin (1.5 μg/kg bwt) and butorphanol (1.5 μg/kg bwt) i.v. A subcutaneous ring block with lidocaine 2% + adrenaline was placed on the forehead. TES was performed using biphasic high frequency multipulse voltage trains (pulse width: 0.1 ms, interpulse interval: 1.3 ms, 3 pulses/train) applied to 2 subcutaneous needle electrodes bilateral from the centre of the forehead. Latency times (30 V above motor threshold (MT) and amplitude of MEP were recorded bilaterally at the ECR and the TC muscles. Motor latency times are expressed as mean ± 2 s.d.ResultsMean latency times (at MT + 30 V) for the ECR muscles were respectively 20.18 ± 1.85 ms (left side) and 19.7 ± 1.69 ms (right side) and for the TC muscles respectively: 34.6 ± 2.01 ms (left) and 34.9 ± 2.43 ms (right).ConclusionsTES is well tolerated. Interestingly, recorded motor latency times at the level of front and hind legs appear to be shorter for TES when compared to TMS from literature data [1].Ethical animal research: Ethical approval was granted by the animal ethics committee of the Groningen University. Sources of funding: JS Center and Wolvega Equine Clinic. Competing interests: None.

Intraoperative brain mapping to identify corticospinal projections during resective epilepsy surgery in children with congenital hemiparesis.

The purpose of the study is to determine corticospinal organization using intraoperative neurophysiologic monitoring (IONM) during resective epilepsy surgery for patients with congenital hemiparesis and intractable epilepsy. Ten patients, aged 3-17, with intractable epilepsy underwent resective surgery. Transcranial stimulation (TCS) was achieved using a pair of cork screws at Cz and C3/C4, respectively. A 1 × 4 stimulating electrode strip was placed on the presumed motor cortex of the affected hemisphere for direct cortical stimulation (DCS) after craniotomy. Multipulse TCS and DCS train stimulation was delivered, with simultaneous recordings from bilateral abductor pollicis brevis and abductor halluces, to determine the corticospinal projection pattern of the paretic limbs. The above mapping techniques revealed ipsilateral corticospinal projections from the contralesional hemisphere to target muscles in the paretic limbs in three patients, projections from both hemispheres to target muscles in three, and preserved crossed projections from the affected hemisphere in four. Nine patients were seizure free after surgery. Five had unchanged postoperative functional status, and three showed minimally improved use of the paretic hand. Two developed new motor deficits after surgery, which may have been due to a premotor syndrome in one patient, since it completely resolved within 2 weeks. The other experienced increased weakness of the paretic lower limb because a small part of the eloquent cortex was removed for better seizure control. Using IONM to define the corticospinal projection pattern is a valuable technique that can potentially replace preoperative fMRI and transcranial magnetic stimulation in resective epilepsy surgery, particularly for younger patients.

11. Evoked movements in transcranial electrical stimulation on 4 locations of the body at different stimulation electrode montages and stimulation paradigms

Introduction Muscle contraction from transcranial electrical stimulation (TES) induces seismic potentials: sMEP. These movements may be of discomfort to the surgeon or address safety issues. In this study sMEPs at the chin, occiput, at mid thoracic and thoracic-lumbar levels are studied at single and multipulse TES with 2 TES montage pairs. Methods Eight patients (5f/3 m, 22 ± 12 y) underwent TES-mMEP monitoring during spinal deformity surgery. sMEPs were recorded by 2-vector accelero transducers on 4 locations during the set-up procedure for TES-mMEP monitoring at the selected TES voltage for monitoring. The sMEPampl vector pairs were summed before analysis. Single and multi-pulse trains (1 or 5 ppt) TES was performed at Cz- Fz and C3-C4 montages. Results At CzFz (Cz anode), the latencies increase from chin and occiput to mid thoracic and thoraco-lumbar from 3.8 ± 0.6 ms to 12.4 ± 2.3 ms when 1 ppt is used. sMEPampl decrease from 1.7 ± 1.3 mV (chin) to 0.087 ± 0.008 mV (thoraco-lumbar). When using 5 ppt, latencies increase from 4.1 ± 0.6 ms (chin) to 12.9 ± 2.30 ms (thoraco-lumbar). sMEPampl decrease from 2.3 ± 1.0 mV (chin) to 0.05 ± 0.03 mV (thoraco-lumbar). At C3C4, latencies are similar to CzFz. sMEPampl at the chin is higher at C3C4 than at CzFz, where sMEPampl at the chin is 2.0 ± 1.6 mV and at thoraco-lumbar level 0.058 ± 0.021 mV for 1ppt, and 2.9 ± 2.1 (chin) to 0.42 ± 0.44(thoraco-lumbar) for 55pt. The higher sMEP amplitudes at the chin could result from stronger electrical fields from the C3/C4 electrodes close to the masseter muscle. Conclusion Because of the short latency times at 1 and 5 ppt, the movements of the jaw and head most likely result from extracranial stimulation, while sMEPampl at thoracic and lumbar locations apparently originate from the cortico-spinal route.