The authors would like to acknowledge Caroline Hartley and Rebeccah Slater (Department of Paediatrics, University of Oxford, UK) for critical reviewing our paper and Walter Magerl (Department of Neurophysiology, Center of Biomedicine and Medical Technology Mannheim (CBTM), University of Heidelberg, Germany) for supporting us with technical equipment and knowledge.

The study was approved by the Competent Ethics Committee of Northwestern Switzerland (EKNZ 2015-079) and informed written parental consent for the participant was obtained before the measurement.
1. Preparation
<ol>
	<li>Make sure the baby is settled. It should be quiet and settled, without sucking motions during the recording because of movement artefacts. The baby can be asleep9.</li>
	<li>Measure the neonate&#39;s head circumference with a measuring tape to define the size of the EEG cap.</li>
	<li>Identify the active electrode position: Cz / vertex position by marking the middle point between nasion and inion and the middle point between the left and right preaurical point with a skin marker pencil. For positioning the electrodes see also Figure 1.</li>
	<li>Identify the positions of the ground electrode: right forehead (Fp2), and the reference electrode: left mastoid (A1).</li>
	<li>Clean the electrode sites (Cz, Fp2 and A1) with disinfectant using a cotton swab. In case of a lot of hair, separate the hair to visualize the scalp.</li>
	<li>Gently scrub the electrode sites with EEG prepping paste, using a cotton swab, to lower the impedance.</li>
	<li>Place the EEG cap with the electrodes attached on the neonate&#39;s head.</li>
	<li>Inject conductive EEG gel into the electrodes using a syringe with a short plastic needle to optimize the contact between the electrodes and the scalp.</li>
	<li>Adjust the electrodes until the impedance is below 50 k&#937; as described in the manufacturer&#39;s recommendations and in published guidelines12.</li>
	<li>Position a camera to record the neonate&#39;s facial expressions.</li>
	<li>Connect the flat-tip probe to the contact trigger device, which is fixed to the EEG recording device. When the flat-tip probe reaches the nominal force on the skin, a trigger signal is generated by the contact trigger device. This signal is sent to the computer, tagging the EEG recording with a trigger mark.</li>
</ol>
2. Measurement
<ol>
	<li>Select a study name to store the data.</li>
	<li>Add online band pass filters:
	<ol>
		<li>Display filters: 
		Low cutoff filter: Frequency: 1 Hz 
		High cutoff filter: Frequency: 70 Hz 
		Notch filter: 50 Hz 
		Sampling rate: 2000 Hz</li>
	</ol>
	</li>
	<li>Start the EEG and video recording.</li>
	<li>Hold the neonate&#39;s right hand in a horizontal position. The stimulus can also be applied on a different site, e.g. the foot, which will result in longer latency than from hand, please see for details 3.7.</li>
	<li>First record background EEG activity. Whilst the neonate&#39;s hand is held, annotate the EEG recording manually to record periods where no stimuli are applied and the infant is resting.</li>
	<li>Conduct the required amount of flat-tip probe stimuli according to the study design on the neonate&#39;s right hand. In our experimental design, set the the number of flat-tip probe stimuli at 50. Be careful to use the flat-tip probe perpendicularly to the neonate&#39;s hand so the tip does not bend and the correct force is applied. Perform the flat-tip probe stimuli using a minimum of a 2 to 3 s inter-stimulus interval (ISI)6 to avoid summation.</li>
	<li>Stop all the recordings.</li>
	<li>Document the experimental setting details.</li>
</ol>
3. Data Analysis
<ol>
	<li>Filter the raw EEG data offline using a high pass filter at 1 Hz and a low pass filter at 30 Hz.</li>
	<li>Segment the data in epochs of 1,500 ms (500 ms before to 1,000 ms after stimulus onset).</li>
	<li>Perform a baseline correction to the pre-stimulus interval.</li>
	<li>Manually reject the EEG epochs containing artefacts, such as movement artefacts and noise, after visual inspection. Please see also the tutorial outline: https://sccn.ucsd.edu/wiki/Chapter_01:_Rejecting_Artifacts</li>
	<li>Average the EEG epochs (for the background and stimulus response separately).</li>
	<li>Woody filter the data with a maximum jitter of &#177; 50 ms in the time window 0 - 1,000 ms post stimulus onset. This allows for latency differences between the infants. Do this for the background and stimulus responses separately.</li>
	<li>Project a template of noxious-evoked brain activity, that was defined in an independent dataset and has been described in detail elsewhere11 on to the data to ascertain the magnitude of the noxious-evoked response within each individual trial. The template describes a characteristic waveform of the noxious-evoked response and the magnitude reflects the amount of this noxious-evoked response within the individual trial. 
	NOTE: The time window on which to project the template is dependent on the age of the infant and the stimulus position. If stimuli are applied to the hand then the time window of interest is 200 - 500 ms post stimulus11. If the stimuli are applied to the foot then the time window of interest is 400 - 700 ms post stimulus11. Note that this template has only currently been validated for infants between 34 - 43 weeks&#39; gestation. For detailed methods associated with using this template, and a discussion of the limitations, please see Hartley et al. 201711.</li>
	<li>Check that the magnitude of the noxious-evoked brain activity calculated using the template is significantly higher following the stimulus, compared with in the background EEG.</li>
	<li>Analyze the behavioral facial expression afterwards (camera is linked to the EEG recording) using the Neonatal Facial Coding System2,13.</li>
</ol>

<ol>
	<li>Bonica, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+need+of+a+taxonomy.">The need of a taxonomy.</a> Pain. 6 (3), 247-248 (1979).</li><li>Duhn, L. J., Medves, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+systematic+integrative+review+of+infant+pain+assessment+tools.">A systematic integrative review of infant pain assessment tools.</a> Adv Neonatal Care. 4 (3), 126-140 (2004).</li><li>Witt, N., Coynor, S., Edwards, C., Bradshaw, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Guide+to+Pain+Assessment+and+Management+in+the+Neonate.">A Guide to Pain Assessment and Management in the Neonate.</a> Curr Emerg Hosp Med Rep. 4, 1-10 (2016).</li><li>Hummel, P., van Dijk, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pain+assessment:+current+status+and+challenges.">Pain assessment: current status and challenges.</a> Semin Fetal Neonatal Med. 11 (4), 237-245 (2006).</li><li>Slater, R., Fitzgerald, M., Meek, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Can+cortical+responses+following+noxious+stimulation+inform+us+about+pain+processing+in+neonates?.">Can cortical responses following noxious stimulation inform us about pain processing in neonates?.</a> Semin Perinatol. 31 (5), 298-302 (2007).</li><li>Hartley, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+relationship+between+nociceptive+brain+activity,+spinal+reflex+withdrawal+and+behaviour+in+newborn+infants.">The relationship between nociceptive brain activity, spinal reflex withdrawal and behaviour in newborn infants.</a> Sci Rep. , 31 (2015).</li><li>Iannetti, G. D., Baumg&#228;rtner, U., Tracey, I., Treede, R. D., Magerl, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pinprick-evoked+brain+potentials:+a+novel+tool+to+assess+central+sensitization+of+nociceptive+pathways+in+humans.">Pinprick-evoked brain potentials: a novel tool to assess central sensitization of nociceptive pathways in humans.</a> J Neurophysiol. 110 (5), 1107-1116 (2013).</li><li>Ziegler, E. A., Magerl, W., Meyer, R. A., Treede, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Secondary+hyperalgesia+to+punctate+mechanical+stimuli.+Central+sensitization+to+A-fibre+nociceptor+input.">Secondary hyperalgesia to punctate mechanical stimuli. Central sensitization to A-fibre nociceptor input.</a> Brain. 122 (Pt 12), 2245-2257 (1999).</li><li>Slater, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evoked+potentials+generated+by+noxious+stimulation+in+the+human+infant+brain.">Evoked potentials generated by noxious stimulation in the human infant brain.</a> Eur J Pain. 14 (3), 321-326 (2010).</li><li>Fabrizi, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+shift+in+sensory+processing+that+enables+the+developing+human+brain+to+discriminate+touch+from+pain.">A shift in sensory processing that enables the developing human brain to discriminate touch from pain.</a> Curr Biol. 21 (18), 1552-1558 (2011).</li><li>Hartley, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nociceptive+brain+activity+as+a+measure+of+analgesic+efficacy+in+infants.">Nociceptive brain activity as a measure of analgesic efficacy in infants.</a> Sci Transl Med. 9 (388), (2017).</li><li>Keil, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Committee+report:+publication+guidelines+and+recommendations+for+studies+using+electroencephalography+and+magnetoencephalography.">Committee report: publication guidelines and recommendations for studies using electroencephalography and magnetoencephalography.</a> Psychophysiology. 51 (1), 1-21 (2014).</li><li>Grunau, R. V., Johnston, C. C., Craig, K. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neonatal+facial+and+cry+responses+to+invasive+and+non-invasive+procedures.">Neonatal facial and cry responses to invasive and non-invasive procedures.</a> Pain. 42 (3), 295-305 (1990).</li><li>van den Broeke, E. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterizing+pinprick-evoked+brain+potentials+before+and+after+experimentally+induced+secondary+hyperalgesia.">Characterizing pinprick-evoked brain potentials before and after experimentally induced secondary hyperalgesia.</a> J Neurophysiol. 114 (5), 2672-2681 (2015).</li><li>Verriotis, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cortical+activity+evoked+by+inoculation+needle+prick+in+infants+up+to+one-year+old.">Cortical activity evoked by inoculation needle prick in infants up to one-year old.</a> Pain. 156 (2), 222-230 (2015).</li><li>Rolke, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+sensory+testing+in+the+German+Research+Network+on+Neuropathic+Pain+(DFNS):+standardized+protocol+and+reference+values.">Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): standardized protocol and reference values.</a> Pain. 123 (3), 231-243 (2006).</li><li>Moultrie, F., Slater, R., Hartley, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improving+the+treatment+of+infant+pain.">Improving the treatment of infant pain.</a> Curr Opin Support Palliat Care. 11 (2), 112-117 (2017).</li><li>Hu, L., Zhang, Z. G., Mouraux, A., Iannetti, G. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiple+linear+regression+to+estimate+time-frequency+electrophysiological+responses+in+single+trials.">Multiple linear regression to estimate time-frequency electrophysiological responses in single trials.</a> Neuroimage. 111, 442-453 (2015).</li><li>Hartley, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changing+Balance+of+Spinal+Cord+Excitability+and+Nociceptive+Brain+Activity+in+Early+Human+Development.">Changing Balance of Spinal Cord Excitability and Nociceptive Brain Activity in Early Human Development.</a> Curr Biol. 26 (15), 1998-2002 (1998).</li><li>Evers, K. S., Wellmann, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Arginine+Vasopressin+and+Copeptin+in+Perinatology.">Arginine Vasopressin and Copeptin in Perinatology.</a> Front Pediatr. 4 (75), (2016).</li><li>Slater, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oral+sucrose+as+an+analgesic+drug+for+procedural+pain+in+newborn+infants:+a+randomised+controlled+trial.">Oral sucrose as an analgesic drug for procedural pain in newborn infants: a randomised controlled trial.</a> Lancet. 376 (9748), 1225-1232 (2010).</li></ol>

The authors have nothing to disclose.

The approach presented here shows how noxious-evoked brain activity in neonates can be measured in an objective way using EEG recording and flat-tip probe stimulators to apply experimental noxious stimuli. This technique can be used in various clinical settings to detect nociception, e.g. in non-verbal persons such as neonates. The complete study can be done within 15 min, including placing the baby, identifying, preparing and mounting the electrodes, and finally applying and recording the 50 noxious stimuli. The stimuli do not cause the infant behavioral distress, and this approach provides an objective method with which to assess nociception in infants.
In this study, we used a flat-tip probe stimulus with a mild force of 32 mN. Higher forces of 64 mN or 128 mN can also be applied in neonates but may lead to increased movements artefacts due to limb withdrawal. We noticed that in our study neonates accepted a force of 32 mN very well and did not withdraw their limbs, whereas a stimulus with 128 mN force leads to bilateral reflex withdrawal6. It has been shown that the noxious-evoked potential is greater depending on the force of the flat-tip probe stimulus (32 vs. 64 mN)6,14. Verriotis et al. showed that children at the age of 1 year have higher amplitude in their event-related vertex potential and higher pain scores than newborn infants15. Therefore, the force of the flat-tip probe stimulus can be adapted depending on the age of the patient16.
Previous studies recorded nociception from neonates being nursed supine or prone or even on their side. To keep experimental settings constant, we recommend keeping one position especially when performing a study with several participants. We found that performing the measurement in a supine position worked well. We performed the flat-tip probe stimuli on the neonate&#39;s hand. Positioning and handling of the neonate may be easier if applying the stimuli to the hand compared to the foot. The foot in fact is more commonly used in studies, however, we found that stimulating the back of the hand can be easier than accessing the foot. Reflex withdrawal is a useful additional measure of nociceptive activity, which can be incorporated into a multidimensional assessment of pain in this challenging non-verbal population17.
Despite avoiding any discomfort and movement artefacts there is always spontaneous neuronal activity. Thus filtering and averaging is important in order to attenuate the background noise and visualize the event related potential. Also, repetition of flat-tip probe stimuli, e.g. 50, strongly improves the signal-to-noise ratio. To analyze the data, time-locking of all the measurements is crucial.
A further technical challenge in neonates shortly after birth is the presence of vernix caseosa coating the skin of newborn infants including the head, which is why their skin needs to be cleaned carefully with an extra prepping paste even when active electrodes are used. In our opinion, active electrodes are better suited for this method than passive electrodes because they are less sensitive to external movement on the wires. Also, they are easier to use since they accept higher impedances due to the inbuilt pre-amplifier. However, passive electrodes can be used as well.
For data analysis, we used the method described by Hartley et al.6,11. Another method is the time-frequency analysis demonstrated by Hu et al.18.
Taken together, the technical methods, setup, and interpretation of the results require a trained team with preferably two people doing the measurement, one applying the stimuli while the other is checking the EEG. If the neonate is unsettled, the EEG will be contaminated with movement artifacts and it is not possible to perform the measurements. Also, because of validity, it is mandatory to have a certain number of stimuli, which can be challenging.
Nociception matures in early life and as early as 34 weeks&#39; gestation the neonates&#39; brain can distinguish between touch and nociception17. Under the age of 34 weeks&#39; gestation infants are more likely to generate nonspecific neuronal bursts19 whereas in late-preterm infants starting at 34 weeks&#39; gestation the here described method can be used11. This method opens the door for a variety of research investigations. For example, it could be used to test the impact of birth-related stress on nociception20 or to test the specific impact of various analgesic drugs in neonates and infants6,21. For example, the protocol presented here has been recently used in a study demonstrating the efficacy of topical local anesthetics in significantly reducing the noxious-evoked potential when a noxious stimulus was applied to a treated foot as compared to background activity or to the untreated foot11.
In conclusion, noxious-evoked brain potentials in EEG recordings make it possible to objectively investigate surrogate measures of pain perception in non-verbal patients. This method is applicable for use in the clinical setting in research investigations. By time-locking the flat-tip probe stimuli to the EEG recording it is possible to reliably evaluate the electrophysiological nociceptive response.

Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage1. The inability to communicate verbally does not negate the possibility that an individual is experiencing pain but makes it very challenging to assess pain-relieving treatment, for example in newborn infants2. Several behavioral and physiological indicators are used to assess pain in non-verbal patients. Different scales have been developed over the years, the choice depends on the type of stimulus, gestational age and the environment in which the neonates are embeded3,4,5. These pain assessment tools either rely on the rater&#39;s interpretation or they demand secondary physiological indicators.
In this video, we present a method to assess nociception with electrophysiological recordings optimized for use in newborn infants. Nociception is defined as the neural process of encoding noxious stimuli. Thus, quantitating nociception is an elegant and objective method to determine the neural input in a non-verbal person. Moreover, cortical activity detected by electroencephalography (EEG) is correlated with the intensity of noxious events5,6.
The method presented here combines EEG recording with noxious stimuli produced by a mechanical stimulation with a flat-tip probe, also called a pinprick7, which is not skin-breaking and does not cause behavioral distress6. It has been shown, that nociception following punctuate stimulation is predominantly mediated by A&#948;-fibers, does not need a skin breaking lesion8 and the magnitude of the nociceptive-specific potential is not dependent on sleep state9. The probe is well accepted also by parents when applying this method in a study setting with neonates. The probe is electronically linked to the EEG recording system enabling the EEG recording to be precisely tagged when the probe contacts the skin. This greatly simplifies the process of time locking and is the premise for all subsequent EEG analyses. In order to minimize preparation time of the infant EEG recording we used a modified international 10/20 electrode placement system where we reduced the number of electrodes to the minimum requirement of three electrodes (Figure 1). The central vertex Cz electrode, where the noxious-evoked brain activity is maximal9,10,11, was used together with one reference and one ground electrode.

<table><tbody><tr><td>Easycap</td><td>EASYCAP GmbH</td><td>AC-32-C</td><td>EEG caps for infants sizes 34 and 36</td></tr><tr><td>actiCAP</td><td>Brain Products GmbH</td><td>BP-04243-SIG</td><td>active electrodes</td></tr><tr><td>ImpBox</td><td>Brain Products GmbH</td><td></td><td>impedance measurement</td></tr><tr><td>V-Amp</td><td>Brain Products GmbH</td><td></td><td>EEG recording device</td></tr><tr><td>Contact trigger for pinprick stimulation</td><td>MRC Systems GmbH</td><td></td><td></td></tr><tr><td>PinPrick stimulator set</td><td>MRC Systems GmbH</td><td></td><td></td></tr><tr><td>EEG prepping paste</td><td>USB Pharmacy</td><td></td><td>contains sodium chloride, pumice stone, propylene glycol</td></tr><tr><td>SuperVisc</td><td>EASYCAP GmbH</td><td></td><td>Electrolyte-Gel for active electrodes</td></tr><tr><td>Brain Vision Recorder</td><td>Brain Products GmbH</td><td></td><td></td></tr><tr><td>Brain Vision Analyzer</td><td>Brain Products GmbH</td><td></td><td></td></tr><tr><td>MATLAB using EEGLAB &lt;p&gt;&lt;/p&gt; &lt;p&gt;&lt;/p&gt; &lt;p&gt;&lt;/p&gt; &lt;p&gt;&lt;/p&gt; &lt;p&gt;&lt;/p&gt; </td><td>Swartz Center for Computational Neuroscience, University of California San Diego</td><td></td><td>For EEG processing, including averaging of all EEG epochs &lt;p&gt;&lt;/p&gt; &lt;p&gt;&lt;/p&gt; &lt;p&gt;&lt;/p&gt; </td></tr></tbody></table>

electrophysiological measurement of noxious-evoked brain activity in neonates using a flat-tip probe coupled to electroencephalography

Pain is an unpleasant sensory and emotional experience. In non-verbal patients, it is very difficult to measure pain, even with pain assessment tools. Those tools are subjective or determine secondary physiological indicators which also have certain limitations particularly when exploring the effectiveness of analgesia. As cortical processing is essential for pain perception, brain activity measures may provide a useful approach to assess pain in infants. Here we present a method to assess nociception with electrophysiological brain activity recordings optimized for the use in newborn infants. To produce highly standardized and reproducible noxious stimuli we applied mechanical stimulation with a flat-tip probe, e.g., PinPrick, which is not skin-breaking and does not cause behavioral distress. The noxious-evoked potential allows the objective measurement of nociception in non-verbal patients. This method can be used in newborn infants as early as 34 weeks of gestational age. Moreover, it could be applied in different situations such as measuring the efficacy of analgesic or anesthetic drugs.

Figure 1 is the diagrammatic representation of the electrode positioning using the modified international 10/20 electrode placement system. Figure 2 shows the EEG activity recorded shortly before and after application of one single noxious stimulus using a flat-tip probe with 32 mN force, stimulation occurred as described in the protocol to the neonate&#39;s right hand (Figure 2A). The noxious-evoked response is visible at approximately 300 ms post stimulus onset (time 0). Figure 2B demonstrates the average response of 50 stimuli applied with a force of 32 mN to the same patient. Note that the noxious-evoked potential is more clearly if more stimuli are applied. Woody filtering, as shown in Figure 2C, can be used to adjust for slight variability in the response latency. The predefined template11, shown in red, is projected onto the EEG to calculate the magnitude of the noxious-evoked response.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56531/56531fig1.jpg" /> 
Figure 1: Diagrammatic representation of the electrode positioning using the modified international 10/20 electrode placement system.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56531/56531fig2.jpg" /> 
Figure 2: EEG activity recorded in response to the experimental noxious stimulation. A flat-tip probe stimulus (32 mN) was applied to the right hand of one patient, the time window of interest 200 - 500 ms after the stimulus is shaded. Panel A: EEG activity after one single stimulus, the principal peak at 250 ms is marked with an arrow. Panel B: Averaged response following 50 stimuli. Panel C: Woody filtered data with projected template (red). <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56531/56531fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Electrophysiological Measurement of Noxious-evoked Brain Activity in Neonates Using a Flat-tip Probe Coupled to Electroencephalography at JoVE.com

Electrophysiological Measurement of Noxious-evoked Brain Activity in Neonates Using a Flat-tip Probe Coupled to Electroencephalography

Measuring pain in non-verbal patients is a challenge. In this study we combine EEG recording with stimulation using a flat-tip probe to detect noxious-evoked brain activity in an objective manner.

Pain is an unpleasant sensory and emotional experience. In non-verbal patients, it is very difficult to measure pain, even with pain assessment tools. ...

electrophysiological-measurement-noxious-evoked-brain-activity

Nanyang Technological University

Research

JoVE Journal

Medicine

6.5K Views.  University of Basel Children's Hospital. Measuring pain in non-verbal patients is a challenge. In this study we combine EEG recording with stimulation using a flat-tip probe to detect noxious-evoked brain activity in an objective manner.

Video: Electrophysiological Measurement of Noxious-evoked Brain Activity in Neonates Using a Flat-tip Probe Coupled to Electroencephalography

Infant Auditory Processing and Event-related Brain Oscillations

Rapid auditory processing and acoustic change detection abilities play a critical role in allowing human infants to efficiently process the fine spectral and temporal changes that are characteristic of human language. These abilities lay the foundation for effective language acquisition; allowing infants to hone in on the sounds of their native language. Invasive procedures in animals and scalp-recorded potentials from human adults suggest that simultaneous, rhythmic activity (oscillations) between and within brain regions are fundamental to sensory development; determining the resolution with which incoming stimuli are parsed. At this time, little is known about oscillatory dynamics in human infant development. However, animal neurophysiology and adult EEG data provide the basis for a strong hypothesis that rapid auditory processing in infants is mediated by oscillatory synchrony in discrete frequency bands. In order to investigate this, 128-channel, high-density EEG responses of 4-month old infants to frequency change in tone pairs, presented in two rate conditions (Rapid: 70 msec ISI and Control: 300 msec ISI) were examined. To determine the frequency band and magnitude of activity, auditory evoked response averages were first co-registered with age-appropriate brain templates. Next, the principal components of the response were identified and localized using a two-dipole model of brain activity. Single-trial analysis of oscillatory power showed a robust index of frequency change processing in bursts of Theta band (3 - 8 Hz) activity in both right and left auditory cortices, with left activation more prominent in the Rapid condition. These methods have produced data that are not only some of the first reported evoked oscillations analyses in infants, but are also, importantly, the product of a well-established method of recording and analyzing clean, meticulously collected, infant EEG and ERPs. In this article, we describe our method for infant EEG net application, recording, dynamic brain response analysis, and representative results.

High-density electroencephalography (dEEG) is being used increasingly to study brain development and plasticity in the early years of life. Here we present an application of sophisticated analysis techniques that builds on traditional EEG recording to understand the oscillatory dynamics of rapid auditory processing in the infant brain.

Rapid auditory processing and acoustic change detection abilities play a critical role in allowing human infants to efficiently process the fine spectral ...

Behavior

Electrophysiological Measurements and Analysis of Nociception in Human Infants

Pain is an unpleasant sensory and emotional experience. Since infants cannot verbally report their experiences, current methods of pain assessment are based on behavioural and physiological body reactions, such as crying, body movements or changes in facial expression. While these measures demonstrate that infants mount a response following noxious stimulation, they are limited: they are based on activation of subcortical somatic and autonomic motor pathways that may not be reliably linked to central sensory processing in the brain. Knowledge of how the central nervous system responds to noxious events could provide an insight to how nociceptive information and pain is processed in newborns.
The heel lancing procedure used to extract blood from hospitalised infants offers a unique opportunity to study pain in infancy. In this video we describe how electroencephalography (EEG) and electromyography (EMG) time-locked to this procedure can be used to investigate nociceptive activity in the brain and spinal cord.
This integrative approach to the measurement of infant pain has the potential to pave the way for an effective and sensitive clinical measurement tool.

The assessment and treatment of pain in infants is difficult because infants cannot verbally report their experience. In this video we describe quantitative electrophysiological methods and analysis techniques that can be used to measure the response to noxious events from the infant nervous system.

Pain is an unpleasant sensory and emotional experience. Since infants cannot verbally report their experiences, current methods of pain assessment are ...

Neuroscience

Preterm EEG: A Multimodal Neurophysiological Protocol

Since its introduction in early 1950s, electroencephalography (EEG) has been widely used in the neonatal intensive care units (NICU) for assessment and monitoring of brain function in preterm and term babies. Most common indications are the diagnosis of epileptic seizures, assessment of brain maturity, and recovery from hypoxic-ischemic events. EEG recording techniques and the understanding of neonatal EEG signals have dramatically improved, but these advances have been slow to penetrate through the clinical traditions. The aim of this presentation is to bring theory and practice of advanced EEG recording available for neonatal units. 
In the theoretical part, we will present animations to illustrate how a preterm brain gives rise to spontaneous and evoked EEG activities, both of which are unique to this developmental phase, as well as crucial for a proper brain maturation. Recent animal work has shown that the structural brain development is clearly reflected in early EEG activity. Most important structures in this regard are the growing long range connections and the transient cortical structure, subplate. Sensory stimuli in a preterm baby will generate responses that are seen at a single trial level, and they have underpinnings in the subplate-cortex interaction. This brings neonatal EEG readily into a multimodal study, where EEG is not only recording cortical function, but it also tests subplate function via different sensory modalities. Finally, introduction of clinically suitable dense array EEG caps, as well as amplifiers capable of recording low frequencies, have disclosed multitude of brain activities that have as yet been overlooked.
In the practical part of this video, we show how a multimodal, dense array EEG study is performed in neonatal intensive care unit from a preterm baby in the incubator. The video demonstrates preparation of the baby and incubator, application of the EEG cap, and performance of the sensory stimulations.

This video explains the background theory of the neonatal EEG activity and the sensory responses, followed by a live demonstration of their recording in neonatal intensive care unit.

Since its introduction in early 1950s, electroencephalography (EEG) has been widely used in the neonatal intensive care units (NICU) for assessment and ...

Neonatal Pial Surface Electroporation

Over the past several years the pial surface has been identified as a germinal niche of importance during embryonic, perinatal and adult neuro- and gliogenesis, including after injury. However, methods for genetically interrogating these progenitor populations and tracking their lineages had been limited owing to a lack of specificity or time consuming production of viruses. Thus, progress in this region has been relatively slow with only a handful of investigations of this location. Electroporation has been used for over a decade to study neural stem cell properties in the embryo, and more recently in the postnatal brain. Here we describe an efficient, rapid, and simple technique for the genetic manipulation of pial surface progenitors based on an adapted electroporation approach. Pial surface electroporation allows for facile genetic labeling and manipulation of these progenitors, thus representing a time-saving and economical approach for studying these cells.

The pial surface is a unique progenitor zone in the CNS that is receiving increasing attention. Herein, we detail a method for rapid genetic manipulation of this progenitor zone using a modified electroporation method. This procedure can be used for cellular and molecular investigations of cell lineages and signaling pathways involved in cell differentiation and to elucidate the fate and properties of daughter cells.

Over the past several years the pial surface has been identified as a germinal niche of importance during embryonic, perinatal and adult neuro- and ...

Recording EEG in Freely Moving Neonatal Rats Using a Novel Method

EEG is a useful method to detect electrical activity in the brain. Moreover, it is a widely used diagnostic tool for various neurological conditions, such as epilepsy and neurodegenerative disorders. However, it is technically difficult to obtain EEG recordings in neonates as it requires specialized handling and great care. Here, we present a novel method to record EEG in neonatal rat pups (P8-P15). We designed a simple and reliable electrode using computer pin loci; it can be easily implanted into the skull of a rat pup to record high-quality EEG signals in the normal and epileptic brain. Pups were given an intraperitoneal (i.p.) injection of the neurotoxin kainic acid (KA) to induce epileptic seizures. The surgical implantation performed in this procedure is less expensive than other EEG procedures for neonates. This method allows one to record high-quality and stable EEG signals for more than 1 week. Furthermore, this procedure can also be applied to adult rats and mice to study epilepsy or other neurological disorders.

Here, we introduce a novel technique designed to record electroencephalography (EEG) in freely moving neonatal epileptic pups and describe its procedures, features, and applications. This method allows one to record EEG for more than 1 week.

EEG is a useful method to detect electrical activity in the brain. Moreover, it is a widely used diagnostic tool for various neurological conditions, such ...

Application of an Amplitude-integrated EEG Monitor (Cerebral Function Monitor) to Neonates

Amplitude-integrated EEG (aEEG) is an easily accessible technique to monitor the electrocortical activity in preterm and term infants in neonatal intensive care units (NICUs). This method was first used to monitor newborns after asphyxia, providing information about future neurological outcomes. The aEEG is also helpful to select newborns who benefit from cooling. The aEEG monitoring of preterm infants is becoming more widespread, as various studies have shown that neurodevelopmental outcome is related to early aEEG tracings. Here, we demonstrate the application of the aEEG monitoring system and present typical patterns that depend upon gestational age and pathophysiological conditions. Furthermore, we mention pitfalls in the interpretation of the aEEG, as this method requires accurate fixation and localization of the electrodes. Additionally, the raw EEG can be used to detect neonatal seizures or to identify aEEG application problems. In conclusion, aEEG is a safe and generally well-tolerated method for the bedside monitoring of neonatal cerebral function; it can even provide information about long-term outcome.

Application of an Amplitude-integrated EEG Monitor Cerebral Function Monitor to Neonates

Here, we show how to apply amplitude-integrated electroencephalography to monitor cerebral function in neonates.

Amplitude-integrated EEG (aEEG) is an easily accessible technique to monitor the electrocortical activity in preterm and term infants in neonatal ...

Objective Nociceptive Assessment in Ventilated ICU Patients: A Feasibility Study Using Pupillometry and the Nociceptive Flexion Reflex

The concept of objective nociceptive assessment and optimal pain management have gained increasing attention. Despite the known negative short- and long-term consequences of unresolved pain or excessive analgosedation, adequate nociceptive monitoring remains challenging in non-communicative, critically ill adults. In the intensive care unit (ICU), routine nociceptive evaluation is carried out by the attending nurse using the Behavior Pain Scale (BPS) in mechanically ventilated patients. This assessment is limited by medication use (e.g., neuromuscular blocking agents) and the inherent subjective character of nociceptive evaluation by third parties.
Here, we describe the use of two nociceptive reflex testing devices as tools for objective pain evaluation: the pupillary dilation reflex (PDR) and nociception flexion reflex (NFR). These measurement tools are non-invasive and well tolerated, providing clinicians and researchers with objective information regarding two different nociceptive processing pathways: (1)&#160;the pain-related autonomic reactivity&#160;and (2) the ascending component of the somatosensory system. The use of PDR and NFR measurements are currently limited to specialized pain clinics and research institutions because of impressions that these are technically demanding or time-consuming procedures, or even because of a lack of knowledge regarding their existence.
By focusing on the two abovementioned nociceptive reflex assessments, this study evaluated their feasibility as a physiological pain measurement method in daily practice. Pursuing novel technologies for evaluating the analgesia level in unconscious patients may further improve individual pharmacological treatment and patient related outcome measures. Therefore, future research must include large well-designed clinical trials in a real-life environment.

Pain assessment in anesthetized patients who cannot communicate with the outside world in any way remains challenging despite the development of innovative objective pain evaluation tools. In this project, the pupillary dilation reflex and the nociception flexion reflex are assessed in critically ill, mechanically ventilated adult patients.

The concept of objective nociceptive assessment and optimal pain management have gained increasing attention. Despite the known negative short- and ...

How to Obtain Reliable Visual Event-related Potentials in Newborns

The present study discusses the characteristics of visual event-related potentials (VEPs) and outlines methodological steps for obtaining reliable measurements in newborns. Obtaining high-quality, reliable VEPs is crucial for the early detection of abnormal development of the central nervous system in at-risk newborns, and for implementing successful early interventions. Recommendations are based on a previous study which showed that when post-conceptional age, polysomnography-identified sleep stages, and light-emitting diodes (LEDs) googles as the luminous source are controlled, no more than 4 repetitions of VEP averages are required to obtain replicable recordings, variability decreases, and reliable VEPs can be obtained. By controlling for these sources of variability and using statistical analyses, we were able to clearly and reliably identify the amplitude and latency of three main components (NII, PII and NIII) present in 100% of newborns (n = 20) during active sleep. Recording VEPs during awake states, quiet sleep and transitional sleep is not recommended because VEP morphology may differ significantly from one average to the next, leading to the risk of misleading clinical prognoses. Moreover, it is easier to obtain VEPs during active sleep because this state can be clearly and reliably identified at this stage of development, sleep cycles are short enough to allow measurements to be taken in a reasonable time, and the method does not require new o expensive equipment.

Several important points for obtaining high-quality reliable visual evoked potentials (VEPs) in newborns while minimizing variability and the risk of misleading prognoses are presented.

The present study discusses the characteristics of visual event-related potentials (VEPs) and outlines methodological steps for obtaining reliable ...

Using a Portable Amplitude-Integrated Electroencephalogram for Infant Transport

Amplitude-Integrated EEG in Infants at Risk of Hypoxic-Ischemic Encephalopathy: A Feasibility Study in Road and Air Transport in Western Australia

Infants at risk of HIE require early identification and initiation of therapeutic hypothermia (TH). Earlier treatment with TH is associated with better outcomes. aEEG is frequently used when making the decision whether to commence TH. As this is often limited to tertiary centers, TH may be delayed if the infant requires transport to a center that provides it. We aimed to provide a method for the application of amplitude-integrated electroencephalogram (aEEG) and to determine the feasibility of acquiring clinically meaningful information during transport. All infants &#8805;35 weeks, at risk of HIE at referral, were eligible for inclusion. Scalp electrodes were placed in the C3-C4; P3-P4 position on the infant&#39;s scalp and connected to the aEEG amplifier. The aEEG amplifier was, in turn, connected to a clinical tablet computer with EEG software to collect and analyze aEEG information. Recordings were reviewed by the chief principal investigator and two independent reviewers (blinded) for background trace and artifact. Predefined criteria for data quality were set to movement artifacts and software impedance notifications. Surveys were completed by healthcare staff and parents for acceptability and ease of use.

Author Spotlight: Assessing the Feasibility of Using Amplitude-Integrated EEG During Neonatal Transport

Here, we present a feasibility study to assess a portable amplitude-integrated electroencephalogram (aEEG) recording system during the transport of infants with suspected hypoxic ischemic encephalopathy (HIE).

Infants at risk of HIE require early identification and initiation of therapeutic hypothermia (TH). Earlier treatment with TH is associated with better ...

Measuring Pain-Evoked Brain Activity in Neonates Using a Flat-Tip Probe Coupled to EEG

Source: Klarer, N. et al., <a href="https://app-jove-com.remotexs.ntu.edu.sg/v/56531">Electrophysiological Measurement of Noxious-evoked Brain Activity in Neonates Using a Flat-tip Probe Coupled to Electroencephalography.</a>&#160;J. Vis. Exp. (2017).
This video demonstrates a method for measuring pain-evoked brain activity in infants. It outlines the procedure for positioning electrodes on the infant&#39;s head and applying pain stimuli to the infant&#39;s hand using a flat-tip probe. The video also shows the EEG recording process to identify brain activity in response to the stimuli.

All procedures involving human participants have been performed in compliance with the institutional, national, and international guidelines for human ...