This work was supported in part by the GIST Research Institute (GRI), the GIST-Caltech Research Collaboration Project through a grant provided by GIST in 2017. Also supported by research grant (NRF-2016R1A2B4015381) of the National Research Foundation (NRF) funded by the Korean government (MEST), and by KBRI basic research program through Korea Brain Research Institute funded by the Ministry of Science, ICT, and Future Planning (17-BR-04).

Animal care and handling followed the institutional guideline of the Gwangju Institute of Science and Technology (GIST).
NOTE: The procedure for acquiring the VEP signal from a mouse in vivo consists of four steps: (1) sensor assembly, (2) animal preparation, (3) VEP measurement, and (4) signal processing.
1. Sensor Assembly
<ol>
	<li>Prepare sixteen pins for one non-invasive electrode. 
	NOTE: Each pin-type electrode consists of three parts: a probe head plunger, an internal spring, and a barrel as shown in Figure 1a. The length of each pin is 13 mm, and the adjustable spring pre-load length is 1 mm.</li>
	<li>Cut two pieces of glass fiber substrates (thickness: 1.5 mm) with the size of 15 mm &#215; 17 mm (width &#215; height). 
	NOTE: The non-conducting fiberglass substrate functions as an insulator, which separates the multiple signals acquired simultaneously from the mouse&#39;s scalp.</li>
	<li>Make sixteen holes of diameter 1.2 mm each using a precision engraving machine, as shown in Figure 1c.
	<ol>
		<li>Spread out the probe coordination evenly at an interval of 2 mm onto the flat substrate: +7/0, +2/-2, +2/0, +2/+2, 0/-4, 0/-2, 0/0 (bregma), 0/+2, 0/+4, -2/-3, -2/-1, -2/+1, -2/+3, -4/-2, -4/0, -4/+2 (anteroposterior/lateral with basis of bregma, in mm)24,25,26.</li>
	</ol>
	</li>
	<li>Stack two substrates and apply one drop of fast-acting adhesive glue between substrate layers, producing a double-layer of 3 mm thickness supporting sixteen stable and parallel electrodes during signal acquisition.</li>
	<li>Assemble the sixteen electrodes onto the substrate one-by-one manually. 
	NOTE: The smaller hole diameter stops each electrode at the same length. Each hole diameter is slightly smaller than the thickest diameter of a barrel within the single pin (1.3 mm) which enables the tight fixing of electrodes without any loosening.</li>
	<li>Solder and link each electrode&#39;s ending solder-cup part to the touch proof connector.</li>
	<li>Cover and hide the naked junctions with heat-shrink tubing for electrical insulation.</li>
</ol>
2. Animal Preparation
<ol>
	<li>Anesthetize the mouse with an intraperitoneal (i.p.) injection of ketamine:xylazine 100:10 (100 mg/mL:10 mg/mL) mixture with the amount of 10 &#181;L/g of body weight. 
	NOTE: Check the animal&#39;s anesthesia is adequate by pulling one leg or tweaking the tail before starting preparation.</li>
	<li>Apply eye ointment to keep the mouse&#39;s cornea moist with a cotton swab.</li>
	<li>Remove the hairs around the head and shoulders with a hair-clipper, and then spread commercially available depilatory cream and keep it on this area for 3-4 min.</li>
	<li>Remove the applied depilatory with a spatula, and then wipe up the rest with wet wipes applying water several times.</li>
</ol>
3. VEP Measurement
NOTE: The whole VEP measuring process took place in a dark Faraday cage (width &#215; depth &#215; height: 61 &#215; 61 &#215; 60 cm).
<ol>
	<li>Mount the mouse&#39;s head onto the stereotaxic frame by placing ear bars into the mouse&#39;s ear canals and tightening them precisely in place.</li>
	<li>Mount the sensor into the custom-made electrode holder (Figure 1b) and fix the sensor holder onto the stereotaxic frame, as shown in Figure 1d.</li>
	<li>Locate the flexible EEG sensor, considering both the reference electrode position and the bregma position27. After that, very carefully lower the sensor in the vertical direction so that the arrayed electrode plungers contact the mouse&#39;s scalp evenly onto the curved margin. 
	NOTE: The lowered distance is smaller than 1 mm, which is the adjustable length of the plunger.</li>
	<li>Check that the impedances are within the proper range from 100 k&#937; to 2 M&#937;. Reposition the electrode when any impedance value of the pin is out of the range28.</li>
	<li>Position the photo stimulator 20 cm away from the mouse&#39;s eyes.</li>
	<li>Before starting the experiment, adapt the mouse for 10 min in the dark cage for dark visual adaptation.
	<ol>
		<li>Set the parameters of the experimental devices as follows: Sampling frequency: 500 Hz; Notch filtering: 60 Hz; Inter-stimulus interval: 10 s; Flash duration: 10 ms; number of flash stimuli: 100 trials/subject. 
		NOTE: The flash light is a white light LED illumination which has 550 &#177; 20 % lx with a distance of 20 cm.</li>
	</ol>
	</li>
</ol>
4. VEP Responses Signal Processing Procedures
<ol>
	<li>Epoching
	<ol>
		<li>For continuously measuring serial data, extract each epoch to create single-trial VEP segments from the pre-stimulus period (-300 ms) to the post-stimulus period (600 ms), based on the flash stimulus onset. 
		NOTE: Since we repeatedly provide flash stimulation over 100 trials for each subject, a total of 100 VEP epochs for each mouse are extracted in this step. EEG epoching is a process in which specific time-windows are extracted from the continuously measured EEG signal data.</li>
	</ol>
	</li>
	<li>Re-reference (average reference)
	<ol>
		<li>Compute the average of EEG signals across all fourteen electrode channels at each time point and then subtract the averaged value from each channel. Repeat this procedure for all the VEP epochs.</li>
	</ol>
	</li>
	<li>Perform band-pass filtering of signal from ~1-100 Hz using a finite impulse response (FIR) filter.</li>
	<li>Baseline correction
	<ol>
		<li>Calculate the average of the EEG signals in the pre-stimulus period (baseline period, -300 ~ 0 ms) for each channel, then subtract this average from each point in the waveform (-300 ~ 600 ms). This adjusts the amplitude axis of VEP responses to facilitate the observation of brain wave changes after stimulation. Repeat this step for all of the VEP epochs.</li>
	</ol>
	</li>
	<li>Grand VEP Responses
	<ol>
		<li>Average the single-trial VEP epochs to create single-subject averaged VEP waveforms for each channel. Then, calculate the grand ensemble average of VEP responses for each channel with respect to all the subjects.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Alzheimer's Association. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alzheimer's+disease+facts+and+figures.">Alzheimer's disease facts and figures.</a> Alzheimers Dement. 12 (4), 459-509 (2016).</li><li>Birbeck, G. L., Meyer, A. C., Ogunniyi, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nervous+system+disorders+across+the+life+course+in+resource-limited+settings.">Nervous system disorders across the life course in resource-limited settings.</a> Nature. 527 (7578), S167-S171 (2015).</li><li>World Health Organization. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Neurological disorders: public health challenges. , (2006).</li><li>Meyer, U., Feldon, J., Dammann, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Schizophrenia+and+Autism:+Both+Shared+and+Disorder-Specific+Pathogenesis+Via+Perinatal+Inflammation?.">Schizophrenia and Autism: Both Shared and Disorder-Specific Pathogenesis Via Perinatal Inflammation?.</a> Pediatr Res. 69 (5), 26r-33r (2011).</li><li>Freedman, L. P., Cockburn, I. M., Simcoe, T. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Economics+of+Reproducibility+in+Preclinical+Research.">The Economics of Reproducibility in Preclinical Research.</a> PLoS Biol. 13 (6), e1002165 (2015).</li><li>Cummings, J. 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=Alzheimer's+disease+drug+development:+translational+neuroscience+strategies.">Alzheimer's disease drug development: translational neuroscience strategies.</a> CNS Spectr. 18 (3), 128-138 (2013).</li><li>Roelfsema, P. R., Treue, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Basic+neuroscience+research+with+nonhuman+primates:+a+small+but+indispensable+component+of+biomedical+research.">Basic neuroscience research with nonhuman primates: a small but indispensable component of biomedical research.</a> Neuron. 82 (6), 1200-1204 (2014).</li><li>Wu, C., Wais, M., Sheppy, E., del Campo, M., Zhang, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+glue-based,+screw-free+method+for+implantation+of+intra-cranial+electrodes+in+young+mice.">A glue-based, screw-free method for implantation of intra-cranial electrodes in young mice.</a> J Neurosci Methods. 171 (1), 126-131 (2008).</li><li>Yu, F. H., 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=Reduced+sodium+current+in+GABAergic+interneurons+in+a+mouse+model+of+severe+myoclonic+epilepsy+in+infancy.">Reduced sodium current in GABAergic interneurons in a mouse model of severe myoclonic epilepsy in infancy.</a> Nat Neurosci. 9 (9), 1142-1149 (2006).</li><li>Parmentier, 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=Anatomical,+physiological,+and+pharmacological+characteristics+of+histidine+decarboxylase+knock-out+mice:+evidence+for+the+role+of+brain+histamine+in+behavioral+and+sleep-wake+control.">Anatomical, physiological, and pharmacological characteristics of histidine decarboxylase knock-out mice: evidence for the role of brain histamine in behavioral and sleep-wake control.</a> J Neurosci. 22 (17), 7695-7711 (2002).</li><li>Handforth, A., Delorey, T. M., Homanics, G. E., Olsen, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pharmacologic+evidence+for+abnormal+thalamocortical+functioning+in+GABA+receptor+beta3+subunit-deficient+mice,+a+model+of+Angelman+syndrome.">Pharmacologic evidence for abnormal thalamocortical functioning in GABA receptor beta3 subunit-deficient mice, a model of Angelman syndrome.</a> Epilepsia. 46 (12), 1860-1870 (2005).</li><li>Wu, C., Wais, M., Zahid, T., Wan, Q., Zhang, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+improved+screw-free+method+for+electrode+implantation+and+intracranial+electroencephalographic+recordings+in+mice.">An improved screw-free method for electrode implantation and intracranial electroencephalographic recordings in mice.</a> Behav Res Methods. 41 (3), 736-741 (2009).</li><li>Garner, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Significance+of+Meaning:+Why+Do+Over+90%+of+Behavioral+Neuroscience+Results+Fail+to+Translate+to+Humans,+and+What+Can+We+Do+to+Fix+It?.">The Significance of Meaning: Why Do Over 90% of Behavioral Neuroscience Results Fail to Translate to Humans, and What Can We Do to Fix It?.</a> Ilar Journal. 55 (3), 438-456 (2014).</li><li>Naylor, E., Harmon, H., Gabbert, S., Johnson, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automated+sleep+deprivation:+simulated+gentle+handling+using+a+yoked+control.">Automated sleep deprivation: simulated gentle handling using a yoked control.</a> Sleep. 12 (1), 5-12 (2010).</li><li>Naylor, E., 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=Simultaneous+real-time+measurement+of+EEG/EMG+and+L-glutamate+in+mice:+A+biosensor+study+of+neuronal+activity+during+sleep.">Simultaneous real-time measurement of EEG/EMG and L-glutamate in mice: A biosensor study of neuronal activity during sleep.</a> J Electroanal Chem (Lausanne). 656 (1-2), 106-113 (2011).</li><li>Naylor, E., 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=Molecules+in+Neuroscience.">Molecules in Neuroscience.</a> , 12-16 (2010).</li><li>Choi, J. H., 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+flexible+microelectrode+for+mouse+EEG.">A flexible microelectrode for mouse EEG.</a> , 1600-1603 (2009).</li><li>Choi, J. H., Koch, K. P., Poppendieck, W., Lee, M., Shin, H. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+resolution+electroencephalography+in+freely+moving+mice.">High resolution electroencephalography in freely moving mice.</a> J Neurophysiol. 104 (3), 1825-1834 (2010).</li><li>Lee, M., Shin, H. S., Choi, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+recording+of+brain+activity+and+functional+connectivity+in+the+mouse+brain.">Simultaneous recording of brain activity and functional connectivity in the mouse brain.</a> , 2934-2936 (2009).</li><li>Lee, M., Kim, D., Shin, H. S., Sung, H. G., Choi, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-density+EEG+recordings+of+the+freely+moving+mice+using+polyimide-based+microelectrode.">High-density EEG recordings of the freely moving mice using polyimide-based microelectrode.</a> JoVE-J Vis Exp. (47), e2562 (2011).</li><li>M&#233;gevand, P., Quairiaux, C., Lascano, A. M., Kiss, J. Z., Michel, C. 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+mouse+model+for+studying+large-scale+neuronal+networks+using+EEG+mapping+techniques.">A mouse model for studying large-scale neuronal networks using EEG mapping techniques.</a> Neuroimage. 42 (2), 591-602 (2008).</li><li>Megevand, P., 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=Long-term+plasticity+in+mouse+sensorimotor+circuits+after+rhythmic+whisker+stimulation.">Long-term plasticity in mouse sensorimotor circuits after rhythmic whisker stimulation.</a> J Neurosci. 29 (16), 5326-5335 (2009).</li><li>Troncoso, E., Muller, D., Czellar, S., Zoltan Kiss, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epicranial+sensory+evoked+potential+recordings+for+repeated+assessment+of+cortical+functions+in+mice.">Epicranial sensory evoked potential recordings for repeated assessment of cortical functions in mice.</a> J Neurosci Methods. 97 (1), 51-58 (2000).</li><li>Keith, B., Franklin, G. P., Paxinos, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The mouse brain in stereotaxic coordinates. , (2008).</li><li>Kawakami, M., Yamamura, K. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cranial+bone+morphometric+study+among+mouse+strains.">Cranial bone morphometric study among mouse strains.</a> Bmc Evol Biol. 8, (2008).</li><li>Strain, G. M., Tedford, B. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flash+and+pattern+reversal+visual+evoked+potentials+in+C57BL/6J+and+B6CBAF1/J+mice.">Flash and pattern reversal visual evoked potentials in C57BL/6J and B6CBAF1/J mice.</a> Brain Res Bull. 32 (1), 57-63 (1993).</li><li>Schalk, G., McFarland, D. J., Hinterberger, T., Birbaumer, N., Wolpaw, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BCI2000:+A+general-purpose,+brain-computer+interface+(BCI)+system.">BCI2000: A general-purpose, brain-computer interface (BCI) system.</a> Ieee Transactions on Biomedical Engineering. 51 (6), 1034-1043 (2004).</li><li>Kim, D., Yeon, C., Kim, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+Experimental+Validation+of+a+Dry+Non-Invasive+Multi-Channel+Mouse+Scalp+EEG+Sensor+through+Visual+Evoked+Potential+Recordings.">Development and Experimental Validation of a Dry Non-Invasive Multi-Channel Mouse Scalp EEG Sensor through Visual Evoked Potential Recordings.</a> Sensors. 17 (2), 326 (2017).</li><li>Yeon, C., Kim, D., Kim, K., Chung, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> SENSORS, 2014 IEEE. , 519-522 (2014).</li><li>Kim, D., Yeon, C., Chung, E., Kim, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> SENSORS, 2015 IEEE. , 1-4 (2015).</li><li>Lin, C. T., 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=Novel+dry+polymer+foam+electrodes+for+long-term+EEG+measurement.">Novel dry polymer foam electrodes for long-term EEG measurement.</a> IEEE Trans Biomed Eng. 58 (5), 1200-1207 (2011).</li><li>Lopez-Gordo, M. A., Sanchez-Morillo, D., Pelayo Valle, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dry+EEG+electrodes.">Dry EEG electrodes.</a> Sensors (Basel). 14 (7), 12847-12870 (2014).</li><li>Fang, Q., Bedi, R., Ahmed, B., Cosic, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+in+Medicine+and+Biology+Society,+2004.+IEMBS'04.">Engineering in Medicine and Biology Society, 2004. IEMBS'04.</a> , 2995-2998 (2004).</li><li>Maffei, L., Fiorentini, A., Bisti, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+correlate+of+perceptual+adaptation+to+gratings.">Neural correlate of perceptual adaptation to gratings.</a> Science. 182 (4116), 1036-1038 (1973).</li><li>Ernst, M., Lee, M. H., Dworkin, B., Zaretsky, H. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pain+perception+decrement+produced+through+repeated+stimulation.">Pain perception decrement produced through repeated stimulation.</a> Pain. 26 (2), 221-231 (1986).</li></ol>

The authors have nothing to disclose.

We firstly focused on the design of the sensor, prioritizing practicality by minimizing complex surgical procedures. The deformable EEG sensor is comprised of sixteen pins: fourteen for recording, one for ground, and the last one for reference electrodes. Each electrode has the plunger-spring-barrel structure, which applies deformability onto the electrode's contact surface, so they facilitate uniform and stable signal acquisition from the curved and tender mouse's scalp. Considering the welfare of the animals, we tried to minimize the pain incurred by the spring force by alleviating pressure applied to the skin by widening the contact area of the skin-electrode interface29. 
The individual pins composed of the whole multi-channel electrode can have varying specifications for thickness, length, plunger types, and spring strength. These various options should be contemplated to design the electrode to relieve the subject's suffering. In addition, the pin map array and the number of electrodes can be modified according to the purpose of the experiment. The electrode holder and fiberglass substrate can be made by other methodologies and different designs, such as a 3D printing method30,31. 
In general, the impedance of a dry electrode has shown higher impedance, and causing a lowered signal quality compared to a wet electrode32,33. We could confirm the appropriate locations of the sixteen electrodes under the even force on the scalp through checking the impedance within a proper range from 100 k&#937; to 2 M&#937;: the range was comparable with the commercialized dry-type EEG electrode for a human33. The impedance values range from 296.2 K&#937; to 1,522.6 K&#937; (mean &plusmn; SD: 825.2 &plusmn; 443.2 K&#937;). Meanwhile, the mechanical pressure to the scalp caused by internal springs possibly lowered the electrode's impedance, therefore, this may affect the signal improvement34. Although it is possible to enhance signal quality through applying conducting gel onto the pin heads' surface, this can cause signal interference among adjacent pins because of the confined mouse's scalp area.
In order to prove the in vivo utility of the newly designed EEG sensor, we implemented the event-related potential recording paradigm VEP, which is one of the typical passive EEG paradigms. Although we measured VEP signals onto the mouse's scalp without any conducting wet gel, the signal was comparable to the previous VEP result of the epicranial EEG from the same mouse species27. During the VEP measuring process, the grounding of all the individual parts, such as the stereotaxic frame and electrode holder, is an essential process to minimize electrical noise from outside. We also maintained mice for 10 min before starting the VEP experiment, for dark visual adaptation and primary sensory adaptation35,36.
In conclusion, we demonstrate a repeatable experimental protocol to provide visual evoked potential using the non-invasive dry multi-channel mouse scalp EEG sensor. The method described here is non-invasive, thus it does not require any additional surgical preparation, as well as reducing the time for preparing conducting gel, if dry-type electrodes are used. Moreover, a sensor possessing multiple electrodes enables us to measure the brain waves from different scalp areas simultaneously. The proposed method for a non-invasive scalp EEG sensor may contribute to translational research areas connecting basic science results to human studies with comparable, reliable, and efficient results. Ultimately, an approach with these significant characteristics provides convenience and safety both to users and subjects. Still, there are further research issues, such as enhancing the signal quality, comparing signal quality with other brain wave acquisition methodologies, and applying these methods into the freely moving mouse. Moreover, the presented method has further possibilities for application to preclinical small animal EEG studies in vivo, large scale brain network analysis, sensory evoked potential recordings, and combinations with brain stimulation or surface-deep electrophysiological recording methods.

As the number of patients with senile degenerative brain diseases such as dementia, Alzheimer&#39;s, Parkinsonian syndromes, and stroke have increased with an aging population and an increasing life expectancy, the long-term societal burden of these diseases has also increased1,2,3. In addition, most neurodevelopmental diseases, such as Schizophrenia and autism, are accompanied by cognitive and behavioral disorders which affect a patient&#39;s whole life2,3,4. For this reason, researchers have been struggling to improve the diagnosis, prevention, pathological understanding, long-term observation, and treatment of brain diseases. However, problems remain stemming from the brain&#39;s complexity and unrevealed disease pathologies. Translational research may be a promising tool for identifying solutions because it enables the transfer of basic research to clinical applications within a shorter time frame, at lower cost, and with a higher success rate in neuroscience fields5,6,7. Another goal of translational research is to examine applicability in human subjects, which requires non-invasive experimental approaches in animals that allow comparisons to the same method for humans. These conditions have led to several significant needs for developing non-invasive animal preparation methods. One method is electroencephalography (EEG), which reveals cortical brain connectivity and activity two-dimensionally with high temporal resolution, and which benefits from a non-invasive protocol. The event-related potential recording (ERP) is one of the typical experimental paradigms that utilize EEG.
Numerous previous studies employed non-invasive EEG methods for targeting humans subjects, whereas invasive methods, such as implant screws and pole type electrodes, have been used in animal studies8,9,10,11,12. The signal quality and characteristics of these methods are significantly reliant on the invasiveness of the sensor placement. For successful translational research, Garner emphasized using the same conditions for animal study as those used for human research13. For basic research using animals, however, non-invasive EEG methodologies are not prevalent. A novel approach using a non-invasive scalp EEG sensor system focusing on laboratory mice would be a reliable and efficient tool for translational research that can be applied to the non-invasive paradigms for human beings, as well.
Numerous mouse EEG studies led the way by commercializing PCB (printed circuit board) based multi-channel electrodes14,15,16. Although they adopted an invasive method, they had a restricted number of channels (3-8), which made it harder to observe large-scale brain dynamics. Furthermore, applications can be restricted by their invasiveness and high cost. In another research study, the KIST (Korea Institute of Science and Technology) developed a 40 channel polyimide-based thin-film electrode and attached it to a mouse&#39;s skull17,18,19,20. This work acquired the highest number of mouse EEG channels. It was, however, mechanically weak and not easy to reuse; therefore, it was inappropriate for long-term observations, leading to a weakened signal, possibly caused by an immune reaction. Meanwhile, Troncoso and M&#233;gevand acquired a sensory evoked potential (SEP) on rodents&#39; skulls with thirty-two stainless steel electrodes secured by a perforated Poly(methyl methacrylate) (PMMA, acrylic glass) grid21,22,23. Despite their high signal quality, the electrodes were mechanically flexible and tender; therefore, they had difficulties being applied to multiple experiments. In addition, this method was still minimally invasive. Although these methods provide good signal quality, the surface area of a mouse&#39;s skull is limited, therefore the number of electrodes is restricted using a stainless pole-type electrode. A number of previous EEG studies for mice showed several limitations. In this study, we will show a new method for measuring EEG applicable in pre-clinical translational research using a non-invasive dry-type multi-channel sensor.
In order to overcome the limitations of previous animal EEG methodologies, which included the intrinsic complexity of animal preparation, invasiveness, high cost, wastefulness, and weak mechanical strength, we sought to develop a new electrode which exhibits flexibility, dry type status, multi-channel capabilities, non-invasiveness, and re-usability. In the following protocol, we will describe the process of measuring visual evoked potential (VEP) recordings on a mouse scalp using a dry, non-invasive, multi-channel EEG sensor. This method utilizes easily available resources, therefore lowering the barrier to entry into animal experimentation in the biomedical engineering field.

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visual evoked potential recordings in mice using a dry non-invasive multi-channel scalp eeg sensor

For scalp EEG research environments with laboratory mice, we designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable because of the plunger-spring-barrel structural facet and mechanical strengths resulting from metal materials. The whole process for acquiring the VEP responses in vivo from a mouse consists of four steps: (1) sensor assembly, (2) animal preparation, (3) VEP measurement, and (4) signal processing. This paper presents representative measurements of VEP responses from multiple mice with a submicro-voltage signal resolution and sub-hundred millisecond temporal resolution. Although the proposed method is safer and more convenient compared to other previously reported animal EEG acquiring methods, there are remaining issues including how to enhance the signal-to-noise ratio and how to apply this technique with freely moving animals. The proposed method utilizes easily available resources and shows a repetitive VEP response with a satisfactory signal quality. Therefore, this method could be utilized for longitudinal experimental studies and reliable translational research exploiting non-invasive paradigms.

We calculated the ensemble average of VEP responses from eleven mice as shown in Figure 2. This result shows the VEP responses obtained through this experiment from the pre-stimulation period (-300 ms) to the post-stimulation period (600 ms), as the stimulation is given at time 0 s. It is noticeable that the signal fluctuates only for a while (less than 300 ms) after the stimulation, while the signal steadily stabilizes over time during the post-stimulation period. Furthermore, the fourteen channels can be categorized into several groups based on the VEP responses, revealing similar morphologies and patterns29. This method provides insights into the comprehension of brain wave dynamics with respects to temporal and spatial qualities.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56927/56927fig1.jpg" /> 
Figure 1: Mouse EEG sensor description and instructions for using the mouse EEG sensor. (a) 16 pin EEG electrode (b) the customized electrode holder (c) the sixteen electrodes array pin map; the ground electrode (GND) and the reference electrode (Ref) is highlighted in black (d), in vivo mouse EEG measurement using the proposed sensor and the customized holder on the stereotaxic frame. This figure has been modified from 29. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56927/56927fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56927/56927fig2.jpg" /> 
Figure 2: Representative visual evoked potential experimental results from the fourteen channels. Grand averaged visual evoked potential signals of all eleven subjects and all trials from the pre-stimulation period (-300 ms) to the post-stimulation period (600 ms). <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56927/56927fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Visual Evoked Potential Recordings in Mice Using a Dry Non-invasive Multi-channel Scalp EEG Sensor at JoVE.com

Visual Evoked Potential Recordings in Mice Using a Dry Non-invasive Multi-channel Scalp EEG Sensor

We designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable. This paper describes the whole process from manufacturing the proposed EEG electrode to signal processing of visual evoked potential (VEP) signals measured on a mouse scalp using a dry non-invasive multi-channel EEG sensor.

For scalp EEG research environments with laboratory mice, we designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable ...

visual-evoked-potential-recordings-mice-using-dry-non-invasive-multi

Nanyang Technological University

Research

JoVE Journal

Neuroscience

8.8K Views.  Gwangju Institute of Science and Technology (GIST). We designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable. This paper describes the whole process from manufacturing the proposed EEG electrode to signal processing of visual evoked potential (VEP) signals measured on a mouse scalp using a dry non-invasive multi-channel EEG sensor.

Video: Visual Evoked Potential Recordings in Mice Using a Dry Non-invasive Multi-channel Scalp EEG Sensor

Electrode Fabrication and Implantation in Aplysia californica for Multi-channel Neural and Muscular Recordings in Intact, Freely Behaving Animals

Recording from key nerves and muscles of Aplysia during feeding behavior allows us to study the patterns of neural control in an intact animal. Simultaneously recording from multiple nerves and muscles gives us precise information about the timing of neural activity. Previous recording methods have worked for two electrodes, but the study of additional nerves or muscles required combining and averaging the recordings of multiple animals, which made it difficult to determine fine details of timing and phasing, because of variability from response to response, and from animal to animal. Implanting four individual electrodes has a very low success rate due to the formation of adhesions that prevent animals from performing normal feeding movements. We developed a new method of electrode fabrication that reduces the bulk of the electrodes inside the animal allowing for normal feeding movements. Using a combination of glues to attach the electrodes results in a more reliable insulation of the electrode which lasts longer, making it possible to record for periods as long as a week. The fabrication technique that we describe could be extended to incorporate several additional electrodes, and would be applicable to vertebrate animals.

Electrode Fabrication and Implantation in Aplysia californica for Multi-channel Neural and Muscular Recordings in Intact, Freely Behaving Animals

A technique is described for implanting four in vivo electrodes to monitor the neuromuscular control of feeding behavior in Aplysia californica.

Recording from key nerves and muscles of Aplysia during feeding behavior allows us to study the patterns of neural control in an intact animal.  ...

High-density EEG Recordings of the Freely Moving Mice using Polyimide-based Microelectrode

Electroencephalogram (EEG) indicates the averaged electrical activity of the neuronal populations on a large-scale level. It is widely utilized as a noninvasive brain monitoring tool in cognitive neuroscience as well as a diagnostic tool for epilepsy and sleep disorders in neurology. However, the underlying mechanism of EEG rhythm generation is still under the veil. Recently introduced polyimide-based microelectrode (PBM-array) for high resolution mouse EEG1 is one of the trials to answer the neurophysiological questions on EEG signals based on a rich genetic resource that the mouse model contains for the analysis of complex EEG generation process. This application of nanofabricated PBM-array to mouse skull is an efficient tool for collecting large-scale brain activity of transgenic mice and accommodates to identify the neural correlates to certain EEG rhythms in conjunction with behavior. However its ultra-thin thickness and bifurcated structure cause a trouble in handling and implantation of PBM-array. In the presented video, the preparation and surgery steps for the implantation of PBM-array on a mouse skull are described step by step. Handling and surgery tips to help researchers succeed in implantation are also provided.

In this article, we described the surgery procedure and handling tips for implantation of ultra-thin polyimide-based microelectrode array (PBM-array) on the mouse skull for acquisition of high-density encephalography (EEG) in a mouse model.

Electroencephalogram (EEG) indicates the averaged electrical activity of the neuronal populations on a large-scale level. It is widely utilized as a ...

Dual Electrophysiological Recordings of Synaptically-evoked Astroglial and Neuronal Responses in Acute Hippocampal Slices

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs through activation of their ion channels and neurotransmitter receptors, and process information in part through activity-dependent release of gliotransmitters. Furthermore, astrocytes constitute the main uptake system for glutamate, contribute to potassium spatial buffering, as well as to GABA clearance. These cells therefore constantly monitor synaptic activity, and are thereby sensitive indicators for alterations in synaptically-released glutamate, GABA and extracellular potassium levels. Additionally, alterations in astroglial uptake activity or buffering capacity can have severe effects on neuronal functions, and might be overlooked when characterizing physiopathological situations or knockout mice. Dual recording of neuronal and astroglial activities is therefore an important method to study alterations in synaptic strength associated to concomitant changes in astroglial uptake and buffering capacities. Here we describe how to prepare hippocampal slices, how to identify stratum radiatum astrocytes, and how to record simultaneously neuronal and astroglial electrophysiological responses. Furthermore, we describe how to isolate pharmacologically the synaptically-evoked astroglial currents.

The preparation of acute brain slices from isolated hippocampi, as well as the simultaneous electrophysiological recordings of astrocytes and neurons in stratum radiatum during stimulation of schaffer collaterals is described. The pharmacological isolation of astroglial potassium and glutamate transporter currents is demonstrated.

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs ...

Extracting Visual Evoked Potentials from EEG Data Recorded During fMRI-guided Transcranial Magnetic Stimulation

Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological effects. Specifically, by creating a transient interference with the normal activity of a target region and measuring changes in an electrophysiological signal, we can establish a causal link between the stimulated brain area or network and the electrophysiological signal that we record. If target brain areas are functionally defined with prior fMRI scan, TMS could be used to link the fMRI activations with evoked potentials recorded. However, conducting such experiments presents significant technical challenges given the high amplitude artifacts introduced into the EEG signal by the magnetic pulse, and the difficulty to successfully target areas that were functionally defined by fMRI. Here we describe a methodology for combining these three common tools: TMS, EEG, and fMRI. We explain how to guide the stimulator&#39;s coil to the desired target area using anatomical or functional MRI data, how to record EEG during concurrent TMS, how to design an ERP study suitable for EEG-TMS combination and how to extract reliable ERP from the recorded data. We will provide representative results from a previously published study, in which fMRI-guided TMS was used concurrently with EEG to show that the face-selective N1 and the body-selective N1 component of the ERP are associated with distinct neural networks in extrastriate cortex. This method allows us to combine the high spatial resolution of fMRI with the high temporal resolution of TMS and EEG and therefore obtain a comprehensive understanding of the neural basis of various cognitive processes.

This paper describes a method for collecting and analyzing electroencephalography (EEG) data during concurrent transcranial magnetic stimulation (TMS) guided by activations revealed with functional magnetic resonance imaging (fMRI). A method for TMS artifact removal and extraction of event related potentials is described as well as considerations in paradigm design and experimental setup.

Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological ...

Visual Evoked Potential Recording in a Rat Model of Experimental Optic Nerve Demyelination

The visual evoked potential (VEP) recording is widely used in clinical practice to assess the severity of optic neuritis in its acute phase, and to monitor the disease course in the follow-up period. Changes in the VEP parameters closely correlate with pathological damage in the optic nerve. This protocol provides a detailed description about the rodent model of optic nerve microinjection, in which a partial demyelination lesion is produced in the optic nerve. VEP recording techniques are also discussed. Using skull implanted electrodes, we are able to acquire reproducible intra-session and between-session VEP traces. VEPs can be recorded on individual animals over a period of time to assess the functional changes in the optic nerve longitudinally. The optic nerve demyelination model, in conjunction with the VEP recording protocol, provides a tool to investigate the disease processes associated with demyelination and remyelination, and can potentially be employed to evaluate the effects of new remyelinating drugs or neuroprotective therapies.

Focal demyelination is induced in the optic nerve using lysolecithin microinjection. Visual evoked potentials are recorded via skull electrodes implanted over the visual cortex to examine the signal conduction along the visual pathway in vivo. This protocol details the surgical procedures underlying electrode implantation and optic nerve microinjection.

The visual evoked potential (VEP) recording is widely used in clinical practice to assess the severity of optic neuritis in its acute phase, and to ...

Simultaneous Recording of Electroretinography and Visual Evoked Potentials in Anesthetized Rats

The electroretinogram (ERG) and visual evoked potential (VEP) are commonly used to assess the integrity of the visual pathway. The ERG measures the electrical responses of the retina to light stimulation, while the VEP measures the corresponding functional integrity of the visual pathways from the retina to the primary visual cortex following the same light event. The ERG waveform can be broken down into components that reflect responses from different retinal neuronal and glial cell classes. The early components of the VEP waveform represent the integrity of the optic nerve and higher cortical centers. These recordings can be conducted in isolation or together, depending on the application. The methodology described in this paper allows simultaneous assessment of retinal and cortical visual evoked electrophysiology from both eyes and both hemispheres. This is a useful way to more comprehensively assess retinal function and the upstream effects that changes in retinal function can have on visual evoked cortical function.

This protocol describes simultaneous measurement of electroretinogram and visual evoked potentials in anesthetized rats.

The electroretinogram (ERG) and visual evoked potential (VEP) are commonly used to assess the integrity of the visual pathway. The ERG measures the ...

A Visual Guide to Sorting Electrophysiological Recordings Using 'SpikeSorter'

Few stand-alone software applications are available for sorting spikes from recordings made with multi-electrode arrays. Ideally, an application should be user friendly with a graphical user interface, able to read data files in a variety of formats, and provide users with a flexible set of tools giving them the ability to detect and sort extracellular voltage waveforms from different units with some degree of reliability. Previously published spike sorting methods are now available in a software program, SpikeSorter, intended to provide electrophysiologists with a complete set of tools for sorting, starting from raw recorded data file and ending with the export of sorted spikes times. Procedures are automated to the extent this is currently possible. The article explains and illustrates the use of the program. A representative data file is opened, extracellular traces are filtered, events are detected and then clustered. A number of problems that commonly occur during sorting are illustrated, including the artefactual over-splitting of units due to the tendency of some units to fire spikes in pairs where the second spike is significantly smaller than the first, and over-splitting caused by slow variation in spike height over time encountered in some units. The accuracy of SpikeSorter's performance has been tested with surrogate ground truth data and found to be comparable to that of other algorithms in current development.

The article shows how to use the program SpikeSorter to detect and sort spikes in extracellular recordings made with multi-electrode arrays.

Few stand-alone software applications are available for sorting spikes from recordings made with multi-electrode arrays. Ideally, an application should be ...

Investigating Object Representations in the Macaque Dorsal Visual Stream Using Single-unit Recordings

Previous studies have shown that neurons in parieto-frontal areas of the macaque brain can be highly selective for real-world objects, disparity-defined curved surfaces, and images of real-world objects (with and without disparity) in a similar manner as described in the ventral visual stream. In addition, parieto-frontal areas are believed to convert visual object information into appropriate motor outputs, such as the pre-shaping of the hand during grasping. To better characterize object selectivity in the cortical network involved in visuomotor transformations, we provide a battery of tests intended to analyze the visual object selectivity of neurons in parieto-frontal regions.

A detailed protocol to analyze object selectivity of parieto-frontal neurons involved in visuomotor transformations is presented.

Previous studies have shown that neurons in parieto-frontal areas of the macaque brain can be highly selective for real-world objects, disparity-defined ...

Cochlear Implant Surgery and Electrically-evoked Auditory Brainstem Response Recordings in C57BL/6 Mice

Cochlear implants (CIs) are neuroprosthetic devices that can provide a sense of hearing to deaf people. However, a CI cannot restore all aspects of hearing. Improvement of the implant technology is needed if CI users are to perceive music and perform in more natural environments, such as hearing out a voice with competing talkers, reflections, and other sounds. Such improvement requires experimental animals to better understand the mechanisms of electric stimulation in the cochlea and its responses in the whole auditory system. The mouse is an increasingly attractive model due to the many genetic models available. However, the limited use of this species as a CI model is mainly due to the difficulty of implanting small electrode arrays. More details about the surgical procedure are therefore of great interest to expand the use of mice in CI research.
In this report, we describe in detail the protocol for acute deafening and cochlear implantation of an electrode array in the C57BL/6 mouse strain. We demonstrate the functional efficacy of this procedure with electrically-evoked auditory brainstem response (eABR) and show examples of facial nerve stimulation. Finally, we also discuss the importance of including a deafening procedure when using a normally hearing animal. This mouse model provides a powerful opportunity to study genetic and neurobiological mechanisms that would be of relevance for CI users.

Animal models of cochlear implants can advance knowledge of the technological bases of treating permanent sensorineural hearing loss with electrical stimulation. This study presents a surgical protocol for acute deafening and cochlear implantation of an electrode array in mice as well as the functional assessment with auditory brainstem response.

Cochlear implants (CIs) are neuroprosthetic devices that can provide a sense of hearing to deaf people. However, a CI cannot restore all aspects of ...

Noninvasive EEG Recordings from Freely Moving Piglets

The method allows the recording of high-quality electroencephalograms (EEGs) from freely moving piglets directly in the pigpen. We use a one-channel telemetric electroencephalography system in combination with standard self-adhesive hydrogel electrodes. The piglets are calmed down without the use of sedatives. After their release into the pigpen, the piglets behave normally&#8212;they drink and sleep in the same cycle as their siblings. Their sleep phases are used for the EEG recordings.

Here, we present a protocol to record telemetric electroencephalograms (EEGs) from freely moving piglets directly in the pigpen without the use of a sedative, making it possible to record typical EEG patterns during non-REM sleep, like spindle bursts.

The method allows the recording of high-quality electroencephalograms (EEGs) from freely moving piglets directly in the pigpen. We use a one-channel ...