We would like to thank Andrew Cripps and the BioResource Unit at the University of Reading. This research was funded by the BBSRC (Grant number: BB/K010123/1). Data associated with this work is freely available from Y.Z. (ying.zheng@reading.ac.uk).

<ol><li>Mitzdorf, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Current+source-density+method+and+application+in+cat+cerebral+cortex%3A+investigation+of+evoked+potentials+and+EEG+phenomena%5BTitle%5D)+AND+%22Physiol+Rev%22%5BJournal%5D)">Current source-density method and application in cat cerebral cortex: investigation of evoked potentials and EEG phenomena.</a> Physiol Rev. 65 (1), 37-100 (1985).</li>
<li>Logothetis, N. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+Underpinnings+of+the+BOLD+Functional+Magnetic+Resonance+Imaging+Signal%5BTitle%5D)+AND+%22J+Neurosci%22%5BJournal%5D)">The Underpinnings of the BOLD Functional Magnetic Resonance Imaging Signal.</a> J Neurosci. 23 (10), 3963-3971 (2003).</li>
<li>Buzsáki, G., Anastassiou, C. A., Koch, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+origin+of+extracellular+fields+and+currents+%E2%80%94+EEG%2C+ECoG%2C+LFP+and+spikes%5BTitle%5D)+AND+%22Nat+Rev+Neurosci%22%5BJournal%5D)">The origin of extracellular fields and currents — EEG, ECoG, LFP and spikes.</a> Nat Rev Neurosci. 13 (6), 407-420 (2012).</li>
<li>Einevoll, G. T., Kayser, C., Logothetis, N. K., Panzeri, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Modelling+and+analysis+of+local+field+potentials+for+studying+the+function+of+cortical+circuits%5BTitle%5D)+AND+%22Nat+Rev+Neurosci%22%5BJournal%5D)">Modelling and analysis of local field potentials for studying the function of cortical circuits.</a> Nat Rev Neurosci. 14 (11), 770-785 (2013).</li>
<li>Zheng, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Balanced+excitation+and+inhibition%3A+Model+based+analysis+of+local+field+potentials%5BTitle%5D)+AND+%22Neuroimage%22%5BJournal%5D)">Balanced excitation and inhibition: Model based analysis of local field potentials.</a> Neuroimage. 63 (1), 81-94 (2012).</li>
<li>Bruyns-Haylett, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+neurogenesis+of+P1+and+N1%3A+A+concurrent+EEG%2FLFP+study%5BTitle%5D)+AND+%22Neuroimage%22%5BJournal%5D)">The neurogenesis of P1 and N1: A concurrent EEG/LFP study.</a> Neuroimage. 146, 575-588 (2017).</li>
<li>Nunez, P. L. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aNunez%2C+PL+%22Electric+Fields+of+the+Brain%3A+The+Neurophysics+of+EEG%22">Electric Fields of the Brain: The Neurophysics of EEG</a>. , Oxford University Press. (1981).</li>
<li>Jackson, A. F., Bolger, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+neurophysiological+bases+of+EEG+and+EEG+measurement%3A+A+review+for+the+rest+of+us%5BTitle%5D)+AND+%22Psychophysiology%22%5BJournal%5D)">The neurophysiological bases of EEG and EEG measurement: A review for the rest of us.</a> Psychophysiology. 51 (11), 1061-1071 (2014).</li>
<li>Cohen, M. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Where+Does+EEG+Come+From+and+What+Does+It+Mean%3F%5BTitle%5D)+AND+%22Trends+Neurosci%22%5BJournal%5D)">Where Does EEG Come From and What Does It Mean?</a> Trends Neurosci. 40 (4), 208-218 (2017).</li>
<li>Bojak, I., Oostendorp, T., Reid, A., Kötter, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Connecting+Mean+Field+Models+of+Neural+Activity+to+EEG+and+fMRI+Data%5BTitle%5D)+AND+%22Brain+Topogr%22%5BJournal%5D)">Connecting Mean Field Models of Neural Activity to EEG and fMRI Data.</a> Brain Topogr. 23 (2), 139-149 (2010).</li>
<li>Coombes, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Large-scale+neural+dynamics%3A+Simple+and+complex%5BTitle%5D)+AND+%22Neuroimage%22%5BJournal%5D)">Large-scale neural dynamics: Simple and complex.</a> Neuroimage. 52 (3), 731-739 (2010).</li>
<li>Deco, G., Jirsa, V. K., Robinson, P. A., Breakspear, M., Friston, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+dynamic+brain%3A+from+spiking+neurons+to+neural-masses+and+cortical+fields%5BTitle%5D)+AND+%22PLoS+Comput.+Biol%22%5BJournal%5D)">The dynamic brain: from spiking neurons to neural-masses and cortical fields.</a> PLoS Comput. Biol. 4 (8), e1000092(2008).</li>
<li>Pinotsis, D. A., Friston, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Neural+fields%2C+spectral+responses+and+lateral+connections%5BTitle%5D)+AND+%22Neuroimage%22%5BJournal%5D)">Neural fields, spectral responses and lateral connections.</a> Neuroimage. 55 (1), 39-48 (2011).</li>
<li>Riera, J. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Pitfalls+in+the+dipolar+model+for+the+neocortical+EEG+sources%5BTitle%5D)+AND+%22J+Neurophysiol%22%5BJournal%5D)">Pitfalls in the dipolar model for the neocortical EEG sources.</a> J Neurophysiol. 108 (4), 956-975 (2012).</li>
<li>Valdes, P. A., Jimenez, J. C., Riera, J., Biscay, R., Ozaki, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Nonlinear+EEG+analysis+based+on+a+neural+mass+model%5BTitle%5D)+AND+%22Biol+Cybern%22%5BJournal%5D)">Nonlinear EEG analysis based on a neural mass model.</a> Biol Cybern. 81 (5), 415-424 (1999).</li>
<li>Musall, S., von Pföstl, V., Rauch, A., Logothetis, N. K., Whittingstall, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effects+of+Neural+Synchrony+on+Surface+EEG%5BTitle%5D)+AND+%22Cereb+Cortex%22%5BJournal%5D)">Effects of Neural Synchrony on Surface EEG.</a> Cereb Cortex. 24 (4), 1045-1053 (2014).</li>
<li>Snyder, A. C., Morais, M. J., Willis, C. M., Smith, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Global+network+influences+on+local+functional+connectivity%5BTitle%5D)+AND+%22Nat+Neurosci%22%5BJournal%5D)">Global network influences on local functional connectivity.</a> Nat Neurosci. 18 (5), 736-743 (2015).</li>
<li>Mayhew, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Spectroscopic+analysis+of+neural+activity+in+brain%3A+Increased+oxygen+consumption+following+activation+of+barrel+cortex%5BTitle%5D)+AND+%22Neuroimage%22%5BJournal%5D)">Spectroscopic analysis of neural activity in brain: Increased oxygen consumption following activation of barrel cortex.</a> Neuroimage. 12 (6), 664-675 (2000).</li>
<li>Paxinos, G., Watson, C. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aPaxinos%2C+G+%22The+Rat+Brain+in+Stereotaxic+Coordinates%22">The Rat Brain in Stereotaxic Coordinates</a>. , Elsevier Academic Press. (2005).</li>
<li>Martindale, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+hemodynamic+impulse+response+to+a+single+neural+event%5BTitle%5D)+AND+%22J+Cereb+Blood+Flow+Metab%22%5BJournal%5D)">The hemodynamic impulse response to a single neural event.</a> J Cereb Blood Flow Metab. 23 (5), 546-555 (2003).</li>
<li>Pettersen, K. H., Devor, A., Ulbert, I., Dale, A. M., Einevoll, G. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Current-source+density+estimation+based+on+inversion+of+electrostatic+forward+solution%3A+Effects+of+finite+extent+of+neuronal+activity+and+conductivity+discontinuities%5BTitle%5D)+AND+%22J+Neurosci+Methods%22%5BJournal%5D)">Current-source density estimation based on inversion of electrostatic forward solution: Effects of finite extent of neuronal activity and conductivity discontinuities.</a> J Neurosci Methods. 154 (1-2), 116-133 (2006).</li>
<li>Thomson, D. J., et al. Multitaper analysis of nonstationary and nonlinear time series data. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aThomson%2C+DJ+%22Nonlinear+and+Nonstationary+Signal+Processing%22">Nonlinear and Nonstationary Signal Processing</a>. Fitzgerald, W. J., et al. , 317-394 (2000).</li>
<li>Bae, J., Deshmukh, A., Song, Y., Riera, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Brain+Source+Imaging+in+Preclinical+Rat+Models+of+Focal+Epilepsy+using+High-Resolution+EEG+Recordings%5BTitle%5D)+AND+%22Journal+of+Visualized+Experiments+%3A+JoVE%22%5BJournal%5D)">Brain Source Imaging in Preclinical Rat Models of Focal Epilepsy using High-Resolution EEG Recordings.</a> Journal of Visualized Experiments : JoVE. (100), e52700(2015).</li>
<li>Baumann, S. B., Wozny, D. R., Kelly, S. K., Meno, F. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+electrical+conductivity+of+human+cerebrospinal+fluid+at+body+temperature%5BTitle%5D)+AND+%22IEEE+Trans+Biomed+Eng%22%5BJournal%5D)">The electrical conductivity of human cerebrospinal fluid at body temperature.</a> IEEE Trans Biomed Eng. 44 (3), 220-223 (1997).</li>
<li>Wendel, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+Influence+of+Age+and+Skull+Conductivity+on+Surface+and+Subdermal+Bipolar+EEG+Leads%5BTitle%5D)+AND+%22Computational+Intelligence+and+Neuroscience%22%5BJournal%5D)">The Influence of Age and Skull Conductivity on Surface and Subdermal Bipolar EEG Leads.</a> Computational Intelligence and Neuroscience. 2010, (2010).</li>
<li>Flemming, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Evaluation+of+the+distortion+of+EEG+signals+caused+by+a+hole+in+the+skull+mimicking+the+fontanel+in+the+skull+of+human+neonates%5BTitle%5D)+AND+%22Clin+Neurophysiol%22%5BJournal%5D)">Evaluation of the distortion of EEG signals caused by a hole in the skull mimicking the fontanel in the skull of human neonates.</a> Clin Neurophysiol. 116 (5), 1141-1152 (2005).</li>
</ol>

The authors have nothing to disclose.

We have described an experimental procedure for concurrent recording of co-localized EEG and LFP signals of an isoflurane anesthetized rat in response to whisker pad stimulation. A microelectrode was inserted into the neocortex through an opening in the EEG spider electrode which was aligned with a burr hole drilled into the skull. The electrode was secured to the skull by a conductive and adhesive EEG paste23. The nose cone used for the administration of isoflurane was modified so that stimulating electrodes could be inserted into the whisker pad with ease.
The EEG paste was effective at mounting the spider electrode securely to the skull, while providing excellent electrical conductivity throughout the experimental day without the need for additional application of paste. It replaced the undesirable use of glue to fix the periphery of the spider electrode to the skull, as glue is non-conductive and can increase the impedance of the electrode if it runs between the skull and the electrode. EEG paste has a number of advantages over EEG gel, which is difficult to shape around the burr hole and can dry out during experiment, resulting in poor EEG signals.
As the rat was placed inside a Faraday cage, electrical noise due to the environment was greatly attenuated. However, sometimes the neural signal was still quite noisy. In most cases, this was caused by the reference electrode not securely positioned and therefore needed to be re-adjusted or more EEG paste used. Another common problem was that the evoked LFP was small in amplitude. This could be due to the microelectrode not positioned at the center of the cortical region activated by the stimulating electrodes. Instead of re-inserting the microelectrode, which could cause more damage to the local neurons, we usually adjusted the position of the stimulating electrodes in the whisker pad until a reasonable amplitude of the LFP (&#62;3 mV) could be observed.
One of the limitations of the technique is the poor spatial resolution of the spider electrode, which has a diameter of 6 mm. This is large compared with the size of the rat&#39;s skull. Unfortunately, the spider electrode used here is the smallest available to purchase. It will be desirable to reduce the diameter of the spider electrode to 2-4 mm, thus increasing the spatial specificity of EEG recordings, making the comparison between the EEG signal and the supragranular LFP signal less ambiguous.
Several critical steps in the protocol need special attention. The first is the insertion of the microelectrode through the burr hole. As the dura is otherwise intact, the precision of the insertion is crucial. A slight resistance at the tip of the electrode usually means the electrode is not positioned correctly. It must be raised, position adjusted, and re-inserted. The second is the position of the nose cone on the rat. It must not be too loose, as isoflurane will escape from the cone. It also must not be too tight, as this can obstruct the nostrils of the rat and cause difficulty breathing. Special attention is also required to ensure that the amplitude of the EEG recording is much smaller (usually 5 to 10 times smaller) than the LFP top channel recording. If they are similar, it is an indication that the EEG probe has come into direct or indirect contact with the microelectrode. An indirect contact is usually through the cerebral spinal fluid (CSF) that sometimes fills the hole drilled in the skull. The conductivity of CSF is typically 100 times that of the skull24,25. Thus, if the level of CSF inside the burr hole is sufficiently high, it can make contact with the spider electrode. To avoid this, the hole should be frequently cleaned with super absorbent cotton sponges such as the absorption spears.
The effect of a burr hole (diameter &#60;2 mm) in the skull on the EEG recording surrounding the hole was studied by placing another spider electrode on the intact skull atop the ipsi-lateral barrel cortex so that bilateral EEG recordings could be compared. The results shown in Figure 9 and Figure 10, suggest the effect to be insignificant at the 0.05 level of significance. Other factors affecting the amplitude of the EEG include how well the EEG paste was in contact with the skull, how firm the electrode was pressed to the paste, and the spatial extent of the EEG paste on the skull.
It is also worthwhile to note that the protocol described here recorded skull EEG, which is different from scalp EEG used in human EEG studies. The scalp acts like a resistor or a low-pass filter, which will reduce the signal-to-noise ratio of the EEG recording further.
Finally, comparison of the temporal dynamics of the ERP and that of the evoked LFP across cortical layers suggest that somatosensory evoked potential reflects better the LFP in the supragranular layer of the cortex than that in the granular and infragranular layers. This is in agreement with our earlier work6, demonstrating that the initial segment (P1) of the ERP is related to the return current arising from the inflow of the excitatory synaptic current occurring in the granular layer, while the subsequent decrease (N1) in ERP may be related to the delayed arrival of thalamic afferent to cortical layers II/III and/or feedforward signals from deeper cortical layers. In conclusion, concurrent recordings of EEG/LFP can enhance understanding of the neural genesis of EEG, and facilitate the mathematical modeling of EEG in terms of neural signals across cortical layers.

It is generally accepted that LFPs recorded via microelectrodes primarily reflect the weighted sum of synchronized excitatory and inhibitory synaptic activities of local pyramidal neural populations1,2,3,4. Our recent research demonstrated that the profile of the LFP signal could be separated into components of excitation and inhibition5,6. However, as LFP is normally measured via an invasive procedure, it is not suited for most studies of the human brain.
On the other hand, EEG is a non-invasive technique for measuring the electrical activity of the brain. It is widely used as a diagnostic tool for certain types of neurological diseases such as epilepsy, and as a research tool in human cognitive studies. Despite its popularity, a major limitation of EEG is the inability to interpret its temporal profiles precisely in terms of the underlying neural signals7,8,9.
Increasingly, mathematical models of EEG are developed to enhance understanding of brain function10,11,12,13,14,15. Most of the existing EEG models are developed based on fitting frequency domain characteristics of the model predicted output to the EEG data spectrum during spontaneous activity, and very few EEG models can generate realistic sensory evoked potentials. In this context, concurrent recordings of EEG and LFP will provide important insight and constraints for developing more accurate mathematical models of EEG.
To address this need for concurrent recordings to further explore the neural origin of EEG, we developed a methodology to simultaneously record EEG and multi-laminar LFP signals in the neocortex of the anesthetized rat. The setup is similar to previous concurrent EEG/LFP studies conducted in primates16,17. We further investigated the effect of a burr hole drilled into the skull on EEG recordings surrounding the hole, by comparing bilateral EEG recordings (i.e., one hemisphere with a burr hole, the other hemisphere intact) in the absence of sensory stimulation. Our results demonstrate that concurrent EEG/LFP recordings can be conducted simply and effectively, with little EEG signal distortion from the burr hole in the skull.

<table><tbody><tr><td>Female Lister Hood rats</td><td>Charles Rivers</td><td></td><td></td></tr><tr><td>Spider electrode</td><td>Unimed Electrode Supplies Ltd</td><td>SCS24-426</td><td></td></tr><tr><td>EEG paste: Ten20</td><td>Unimed Electrode Supplies Ltd</td><td>10-20-S</td><td></td></tr><tr><td>Stereotaxic holder with dual micromanipulator arms: Dual Manipulator Stereotaxic Frame with 18&amp;deg; Ear Bars</td><td>WPI (World Precision Instruments)</td><td>502603</td><td></td></tr><tr><td>Isoflurane</td><td>National Vet Services Limited</td><td>50878</td><td></td></tr><tr><td>Hard plastic nose cone: Anasthesia Gas Mask for Rat</td><td>WPI</td><td>502054</td><td></td></tr><tr><td>Small animal isoflurane anaesthetic system</td><td>WPI</td><td>EZ-B800A</td><td></td></tr><tr><td>Thermostatic heating pad: Rat Blanket System 230V</td><td>Harvard Apparatus UK</td><td>50-7221-F</td><td></td></tr><tr><td>Ophthalmic ointment: Optixcare eye lube</td><td>Viovet</td><td>203865</td><td></td></tr><tr><td>Lidocaine Hydrochloride (Injection 2%)</td><td>Larkmead Vets</td><td></td><td></td></tr><tr><td>Jacquette Scaler #1SSE, 18cm, Hollow</td><td>WPI</td><td>503421</td><td></td></tr><tr><td>Serrated and curved dissecting forceps</td><td>WPI</td><td>15915</td><td></td></tr><tr><td>Braided silk, non-absorbable suture: Mersilk Suture W502H</td><td>National Vet Services Limited</td><td>153746</td><td></td></tr><tr><td>Dental drill: BONE MICRO DRILL SYST 230 VAC</td><td>Harvard Apparatus UK</td><td>72-4860</td><td></td></tr><tr><td>Sterile Saline: Sodium chloride 0.9%</td><td>Animalcare Ltd</td><td>14K26BT</td><td></td></tr><tr><td>Drill bit #4 : Ball Mill, Carbide, #4</td><td>Harvard Apparatus UK</td><td>72-4958</td><td></td></tr><tr><td>Drill bit #4 : Ball Mill, Carbide, #1/4</td><td>Harvard Apparatus UK</td><td>72-4962</td><td></td></tr><tr><td>Faraday cage</td><td>Newport Corporation</td><td>VIS-FDC-3600</td><td></td></tr><tr><td>Vibration isolation workstation: Vision IsoStation</td><td>Newport Corporation</td><td>M-VIS3660-RG4-325A</td><td></td></tr><tr><td>Oximeter Control Unit and sensor: MouseOxPlus, Starr Life Sciences Corp.</td><td>WPI</td><td>O15001</td><td></td></tr><tr><td>Transparent soft nose cone: Microflex Non-Rebreathing Unit with a Rat Nosecone</td><td>WPI</td><td>EZ-103A</td><td></td></tr><tr><td>Stainless steel stimulating electrodes</td><td>PlasticsOne</td><td>E363/1/SPC</td><td></td></tr><tr><td>Isolated current stimulator</td><td>Made in House</td><td></td><td></td></tr><tr><td>16-channel micro-electrode, 100 &amp;mu;m spacing, area of each site 177 &amp;mu;m&lt;sup&gt;2&lt;/sup&gt;</td><td>NeuroNexus</td><td>A1x16-10mm-100-177-A16</td><td></td></tr><tr><td>16-channel acute headstage</td><td>Tucker David Technologies Inc., TDT</td><td>RA16AC-Z</td><td></td></tr><tr><td>Pre-Amplifier: Z-Series 64-Channel Neuro-Digitizing Preamp</td><td>TDT</td><td>PZ5-64</td><td></td></tr><tr><td>Passive signal splitter: 32-Channel Splitter Box for PZ5</td><td>TDT</td><td>S-BOX_PZ5</td><td></td></tr><tr><td>Data acquisition unit: RZ2 BioAmp Processor. Z-Series 4-DSP ultra high performance processor</td><td>TDT</td><td>RZ2-4</td><td></td></tr><tr><td>Software for Neurophysiology: OpenEX</td><td>TDT</td><td></td><td></td></tr><tr><td>Matlab</td><td>MathWorks</td><td></td><td></td></tr><tr><td>Absorption spears</td><td>Fine Sicence Tools</td><td>18105-01</td><td></td></tr></tbody></table>

concurrent recording of co-localized electroencephalography and local field potential in rodent

Although electroencephalography (EEG) is widely used as a non-invasive technique for recording neural activities of the brain, our understanding of the neurogenesis of EEG is still very limited. Local field potentials (LFPs) recorded via a multi-laminar microelectrode can provide a more detailed account of simultaneous neural activity across different cortical layers in the neocortex, but the technique is invasive. Combining EEG and LFP measurements in a pre-clinical model can greatly enhance understanding of the neural mechanisms involved in the generation of EEG signals, and facilitate the derivation of a more realistic and biologically accurate mathematical model of EEG. A simple procedure for acquiring concurrent and co-localized EEG and multi-laminar LFP signals in the anesthetized rodent is presented here. We also investigated whether EEG signals were significantly affected by a burr hole drilled in the skull for the insertion of a microelectrode. Our results suggest that the burr hole has a negligible impact on EEG recordings.

Data from 4 rats were averaged to obtain mean time series where applicable. The amplitude of the evoked EEG response, also known as the event related potential (ERP), is typically much smaller than that of the LFP. Figure 6 shows the average ERP and LFP in the supragranular, granular, and infragranular layers of the barrel cortex, respectively. The error band in each plot is the corresponding standard error. It can be seen that ERP is approximately 10 times smaller than the evoked LFP.
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/56447/56447fig6.jpg" /> 
Figure 6: Mean (n = 4) neural signals of ERP, supragranular, granular, and infragranular LFP. Shadow indicates standard error. <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/56447/56447fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Comparisons of the temporal dynamics of ERP and LFP are shown in Figure 7. Direct superposition of ERP and the supragranular LFP in Figure 7A illustrates the order of amplitude differences between these two types of neural signals. To compare the temporal dynamics, both ERP and LFP are normalized with respect to their negative peak amplitude. Figure 7B and 7C show the normalized ERP superimposed with the normalized supragranular LFP and normalized granular LFP, respectively.
It can be seen from Figure 7B that the peaks of P1 and N1 for ERP are more delayed than the corresponding peaks of LFP in the supragranular layer. However, the temporal profiles of these two neural signals are similar, with P1 preceding N1. On the other hand, the temporal profile of ERP is markedly different from that of the granular (layer IV of the barrel cortex) LFP (Figure 7C). Importantly they are not mirror images of each other, with granular LFP dominated by a single negative peak (reflecting a major sink in cortical layer IV), whereas ERP consisted primarily of two peaks with opposite polarity.
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/56447/56447fig7.jpg" /> 
Figure 7: Comparison of the temporal dynamics of ERP and LFP. (A) ERP (solid line) superimposed with supragranular LFP (dashed line). Shadow indicates standard error. (B) Normalized ERP (solid line) superimposed with normalized supragranular LFP (dashed line). (C) Normalized ERP (solid line) superimposed with normalized granular LFP (dashed line). <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/56447/56447fig7large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The ERP signal was measured via a spider electrode placed on the skull with a burr hole drilled into it. To investigate the effect of the hole on EEG recordings, another spider electrode was placed on the intact skull above the ipsi-lateral barrel cortex. Care was taken to ensure that the impedances of the two spider electrodes were comparable in magnitude by adjusting the amount of EEG paste used. Data from four rats (which were not the same rats used above) are presented here.
Figure 8 shows the concurrent resting state EEG recordings from both electrodes of one rat, with 100 s data displayed in Figure 8A, and the data in the rectangular frame (20 s) are expanded in Figure 8B. The two EEG signals largely co-vary, within similar range of amplitude. Figure 9 shows the PSD of the four rats, with the top row using a linear scale on the frequency axis, and the bottom row using a logarithmic scale on the frequency axis to provide an expanded view in the lower frequency range. From Figure 9, there does not appear to be consistent bias in the PSD across subjects. This was confirmed by performing one-sample t-tests on the normalized differences in the averaged PSD in the five frequency bands, shown in Figure 10. None of the normalized PSD differences in these frequency bands were significantly different from zero (p = 0.32, 0.46, 0.85, 0.69, and 0.97, respectively).
<img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/56447/56447fig8.jpg" /> 
Figure 8: Bilateral EEG recordings. (A) Skull EEG recording during resting state with a burr hole in the skull (black) and a simultaneous EEG recording on the opposite hemisphere with the skull intact (grey). (B) Expanded view of the waveforms within the rectangular frame in (A). <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/56447/56447fig8large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 9" class="xfigimg" src="/files/ftp_upload/56447/56447fig9.jpg" /> 
Figure 9: Power spectral density (PSD) of the contra- (blue) and the ipsi-lateral (red) EEG. Each column shows the PSD for one rat. The top panels use linear frequency scale, while the bottom panels use logarithmic frequency scale to allow the PSD in the lower frequency range to be visualized. <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/56447/56447fig9large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 10" class="xfigimg" src="/files/ftp_upload/56447/56447fig10.jpg" /> 
Figure 10: Group analysis. Normalized difference between the contra- and the ipsi-lateral PSD with the five frequency bands: Delta, Theta, Alpha, Beta, and Gamma. Each bar shows the mean normalized differences within the frequency band, with the standard error shown as the error bar. <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/56447/56447fig10large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Concurrent Recording of Co-localized Electroencephalography and Local Field Potential in Rodent at JoVE.com

Concurrent Recording of Co-localized Electroencephalography and Local Field Potential in Rodent

This protocol describes a simple method for concurrent recording of co-localized electroencephalography (EEG) and multi-laminar local field potential in an anesthetized rat. A burr hole drilled in the skull for the insertion of a microelectrode is shown to produce negligible distortion of the EEG signal.

Although electroencephalography (EEG) is widely used as a non-invasive technique for recording neural activities of the brain, our understanding of the ...

concurrent-recording-co-localized-electroencephalography-local-field

Universidad San Sebastian

Research

JoVE Journal

Neuroscience

12.3K Views.  University of Reading. Dit protocol beschrijft een eenvoudige methode voor gelijktijdige opname van co gelokaliseerde elektro-encefalografie (EEG) en multi-laminaire lokale veld potentieel in een narcose rat. Een burr gat geboord in de schedel voor het inbrengen van een micro-elektrode is aangetoond dat het te verwaarlozen vervorming van het EEG signaal veroorzaken.

Video: Concurrent Recording of Co-localized Electroencephalography and Local Field Potential in Rodent

Simultaneous fMRI and Electrophysiology in the Rodent Brain

To examine the neural basis of the blood oxygenation level dependent (BOLD) magnetic resonance imaging (MRI) signal, we have developed a rodent model in which functional MRI data and in vivo intracortical recording can be performed simultaneously. The combination of MRI and electrical recording is technically challenging because the electrodes used for recording distort the MRI images and the MRI acquisition induces noise in the electrical recording. To minimize the mutual interference of the two modalities, glass microelectrodes were used rather than metal and a noise removal algorithm was implemented for the electrophysiology data. In our studies, two microelectrodes were separately implanted in bilateral primary somatosensory cortices (SI) of the rat and fixed in place. One coronal slice covering the electrode tips was selected for functional MRI. Electrode shafts and fixation positions were not included in the image slice to avoid imaging artifacts. The removed scalp was replaced with toothpaste to reduce susceptibility mismatch and prevent Gibbs ringing artifacts in the images. The artifact structure induced in the electrical recordings by the rapidly-switching magnetic fields during image acquisition was characterized by averaging all cycles of scans for each run. The noise structure during imaging was then subtracted from original recordings. The denoised time courses were then used for further analysis in combination with the fMRI data. As an example, the simultaneous acquisition was used to determine the relationship between spontaneous fMRI BOLD signals and band-limited intracortical electrical activity. Simultaneous fMRI and electrophysiological recording in the rodent will provide a platform for many exciting applications in neuroscience in addition to elucidating the relationship between the fMRI BOLD signal and neuronal activity.

We have developed a method for simultaneous functional magnetic resonance imaging and electrophysiological recording in the rodent brain, providing a platform for the investigation of the relationship between neural activity and the blood oxygenation level dependent (BOLD) MRI signal.

To examine the neural basis of the blood oxygenation level dependent (BOLD) magnetic resonance imaging (MRI) signal, we have developed a rodent model in ...

Simultaneous Recordings of Cortical Local Field Potentials and Electrocorticograms in Response to Nociceptive Laser Stimuli from Freely Moving Rats

Electrocortical responses, elicited by laser heat pulses that selectively activate nociceptive free nerve endings, are widely used in many animal and human studies to investigate the cortical processing of nociceptive information. These laser-evoked brain potentials (LEPs) consist of several transient responses that are time-locked to the onset of laser stimuli. However, the functional properties of the LEP responses are still largely unknown, due to the lack of a sampling technique that can simultaneously record neural activities at the surface of the cortex (i.e., electrocorticogram [ECoG] and scalp electroencephalogram [scalp EEG]) and inside the brain (i.e., local field potential [LFP]). To address this issue, we present here an animal protocol using freely moving rats. This protocol is composed of three main procedures: (1) animal preparation and surgical procedures, (2) a simultaneous recording of ECoG and LFP in response to nociceptive laser stimuli, and (3) data analysis and feature extraction. Specifically, with the help of a 3D-printed protective shell, both ECoG and LFP electrodes implanted on the rat&#39;s skull were securely held together. During data collection, laser pulses were delivered on the rat&#39;s forepaws through gaps in the bottom of the chamber when the animal was in spontaneous stillness. Ongoing white noise was played to avoid the activation of the auditory system by the laser-generated ultrasounds. As a consequence, only nociceptive responses were selectively recorded. Using the standard analytical procedures (e.g., band-pass filtering, epoch extraction, and baseline correction) to extract stimulus-related brain responses, we obtained results showing that LEPs with a high signal-to-noise ratio were simultaneously recorded from ECoG and LFP electrodes. This methodology makes the simultaneous recording of ECoG and LFP activities possible, which provides a bridge of electrocortical signals at the mesoscopic and macroscopic levels, thereby facilitating the investigation of nociceptive information processing in the brain.

We developed a technique that simultaneously records both electrocorticography and local field potentials in response to nociceptive laser stimuli from freely moving rats. This technique helps establish a direct relationship of electrocortical signals at the mesoscopic and macroscopic levels, which facilitates the investigation of nociceptive information processing in the brain.

Electrocortical responses, elicited by laser heat pulses that selectively activate nociceptive free nerve endings, are widely used in many animal and ...

Behavior

Simultaneous Recordings of Cortical Local Field Potentials, Electrocardiogram, Electromyogram, and Breathing Rhythm from a Freely Moving Rat

Monitoring the physiological dynamics of the brain and peripheral tissues is necessary for addressing a number of questions about how the brain controls body functions and internal organ rhythms when animals are exposed to emotional challenges and changes in their living environments. In general experiments, signals from different organs, such as the brain and the heart, are recorded by independent recording systems that require multiple recording devices and different procedures for processing the data files. This study describes a new method that can simultaneously monitor electrical biosignals, including tens of local field potentials in multiple brain regions, electrocardiograms that represent the cardiac rhythm, electromyograms that represent awake/sleep-related muscle contraction, and breathing signals, in a freely moving rat. The recording configuration of this method is based on a conventional micro-drive array for cortical local field potential recordings in which tens of electrodes are accommodated, and the signals obtained from these electrodes are integrated into a single electrical board mounted on the animal's head. Here, this recording system was improved so that signals from the peripheral organs are also transferred to an electrical interface board. In a single surgery, electrodes are first separately implanted into the appropriate body parts and the target brain areas. The open ends of all of these electrodes are then soldered to individual channels of the electrical board above the animal's head so that all of the signals can be integrated into the single electrical board. Connecting this board to a recording device allows for the collection of all of the signals into a single device, which reduces experimental costs and simplifies data processing, because all data can be handled in the same data file. This technique will aid the understanding of the neurophysiological correlates of the associations between central and peripheral organs.

This study introduces a method for the simultaneous recording of local field potentials in the brain, electrocardiograms, electromyograms, and breathing signals of a freely moving rat. This technique, which reduces experimental costs and simplifies data analysis, will contribute to the understanding of the interactions between the brain and peripheral organs.

Monitoring the physiological dynamics of the brain and peripheral tissues is necessary for addressing a number of questions about how the brain controls ...

Recording Spatially Restricted Oscillations in the Hippocampus of Behaving Mice

The local field potential (LFP) emerges from ion movements across neural membranes. Since the voltage recorded by LFP electrodes reflects the summed electrical field of a large volume of brain tissue, extracting information about local activity is challenging. Studying neuronal microcircuits, however, requires a reliable distinction between truly local events and volume-conducted signals originating in distant brain areas. Current source density (CSD) analysis offers a solution for this problem by providing information about current sinks and sources in the vicinity of the electrodes. In brain areas with laminar cytoarchitecture such as the hippocampus, one-dimensional CSD can be obtained by estimating the second spatial derivative of the LFP. Here, we describe a method to record multilaminar LFPs using linear silicon probes implanted into the dorsal hippocampus. CSD traces are computed along individual shanks of the probe. This protocol thus describes a procedure to resolve spatially restricted neuronal network oscillations in the hippocampus of freely moving mice.

This protocol describes the recording of local field potentials with multi-shank linear silicon probes. Conversion of the signals using current source density analysis allows the reconstruction of local electrical activity in the mouse hippocampus. With this technique, spatially restricted brain oscillations can be studied in freely moving mice.

The local field potential (LFP) emerges from ion movements across neural membranes. Since the voltage recorded by LFP electrodes reflects the summed ...

Evaluation of Hemisphere Lateralization with Bilateral Local Field Potential Recording in Secondary Motor Cortex of Mice

This article demonstrates complete, detailed procedures for both in vivo bilateral recording and analysis of local field potential (LFP) in the cortical areas of mice, which are useful for evaluating possible laterality deficits, as well as for assessing brain connectivity and coupling of neural network activities in rodents. The pathological mechanisms underlying Alzheimer&#39;s disease (AD), a common neurodegenerative disease, remain largely unknown. Altered brain laterality has been demonstrated in aging people, but whether or not abnormal lateralization is one of the early signs of AD has not been determined. To investigate this, we recorded bilateral LFPs in 3-5-month-old AD model mice, APP/PS1, together with littermate wild type (WT) controls. The LFPs of the left and right secondary motor cortex (M2), specifically in the gamma band, were more synchronized in APP/PS1 mice than in WT controls, suggesting a declined hemispheric asymmetry of bilateral M2 in this AD mouse model. Notably, the recording and data analysis processes are flexible and easy to carry out, and can also be applied to other brain pathways when conducting experiments that focus on neuronal circuits.

We present in vivo electrophysiological recording of the local field potential (LFP) in bilateral secondary motor cortex (M2) of mice, which can be applied to evaluate hemisphere lateralization. The study revealed altered levels of synchronization between the left and right M2 in APP/PS1 mice compared to WT controls.

This article demonstrates complete, detailed procedures for both in vivo bilateral recording and analysis of local field potential (LFP) in the cortical ...

Extracellular Electrophysiological Recording in the Motor Cortex of Mice

Multichannel Extracellular Recording in Freely Moving Mice

The protocol aims to uncover the properties of neuronal firing and network local field potentials (LFPs) in behaving mice carrying out specific tasks by correlating the electrophysiological signals with spontaneous and/or specific behavior. This technique represents a valuable tool in studying the neuronal network activity underlying these behaviors. The article provides a detailed and complete procedure for electrode implantation and consequent extracellular recording in free-moving conscious mice. The study includes a detailed method for implanting the microelectrode arrays, capturing the LFP and neuronal spiking signals in the motor cortex (MC) using a multichannel system, and the subsequent offline data analysis. The advantage of multichannel recording in conscious animals is that a greater number of spiking neurons and neuronal subtypes can be obtained and compared, which allows the evaluation of the relationship between a specific behavior and the associated electrophysiological signals. Notably, the multichannel extracellular recording technique and the data analysis procedure described in the present study can be applied to other brain areas when conducting experiments in behaving mice.

Author Spotlight: Advancements in Multichannel Extracellular Recording for Studying Neuronal Activity in Freely Moving Mice 

The protocol describes the methodology of extracellular recording in the motor cortex (MC) to reveal extracellular electrophysiological properties in freely moving conscious mice, as well as the data analysis of local field potentials (LFPs) and spikes, which is useful for evaluating the network neural activity underlying behaviors of interest.

The protocol aims to uncover the properties of neuronal firing and network local field potentials (LFPs) in behaving mice carrying out specific tasks by ...

LFP Recording in Mouse Brain for Cognitive Research and Drug Analysis

Dual Extracellular Recordings in the Mouse Hippocampus and Prefrontal Cortex

The technique of recording local field potentials (LFPs) is an electrophysiological method used to measure the electrical activity of localized neuronal populations. It serves as a crucial tool in cognitive research, particularly in brain regions like the hippocampus and prefrontal cortex. Dual LFP recordings between these areas are of particular interest as they allow the exploration of interregional signal communication. However, methods for performing these recordings are rarely described, and most commercial recording devices are either expensive or lack adaptability to accommodate specific experimental designs. This study presents a comprehensive protocol for performing dual-electrode LFP recordings in the mouse hippocampus and the prefrontal cortex to investigate the effects of antipsychotic drugs and potassium channel modulators on LFP properties in these areas. The technique enables the measurement of LFP properties, including power spectra within each brain region and coherence between the two. Additionally, a low-cost, custom-designed recording device has been developed for these experiments. In summary, this protocol provides a means to record signals with high signal-to-noise ratios in different brain regions, facilitating the investigation of interregional information communication within the brain.

Author Spotlight: Studying Drug Impacts on Brain Signals Using Dual LFP Recording Protocol in Mice

This protocol outlines the use of a custom-designed recording device and electrodes to record local field potentials and investigate information flow in the mouse hippocampus and prefrontal cortex.

The technique of recording local field potentials (LFPs) is an electrophysiological method used to measure the electrical activity of localized neuronal ...

Recording of Local Field Potential in Mouse Hippocampal-Entorhinal Cortex Slices

Source: Whitebirch, A. C. <a href="https://app-jove-com.bdigitaluss.remotexs.co/v/61704">Acute Mouse Brain Slicing to Investigate Spontaneous Hippocampal Network Activity.</a> J. Vis. Exp. (2020)
The video demonstrates a procedure to record the local field potential (LFP) in mouse hippocampal-entorhinal cortex slices. Electrical stimulation is provided at the CA3 stratum radiatum of the hippocampus, which causes changes in the postsynaptic potential at the CA1 stratum pyramidale. The combined change in the membrane potential of CA1 neurons, termed the local field potential, is recorded.

All procedures involving sample collection have been performed in accordance with the institute&#39;s IRB guidelines.
1. Transcardial perfusion

	Suspend ...

JoVE Encyclopedia of Experiments

Neurophysiology

Electrophysiology Techniques

Recording of Local Field Potential from Both Hemispheres of the Mouse Brain

Source: Chen, Y., et al. <a href="https://app-jove-com.bdigitaluss.remotexs.co/v/59310">Evaluation of Hemisphere Lateralization with Bilateral Local Field Potential Recording in Secondary Motor Cortex of Mice.</a> J. Vis. Exp. (2019).
This video demonstrates in vivo recording of local field potential (LFP) from bilateral M2 areas of the mouse brain. An anesthetized mouse is secured and prepared for the procedure. To record LFPs, insert microelectrodes into the target coordinates of the bilateral M2 areas, which are responsible for complex motor movements.

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
1. Animal ...

A Micro-drive Array Method for Electrophysiological Recording from Multiple Brain Regions

Source: Shikano, Y., et al. <a href="https://app-jove-com.bdigitaluss.remotexs.co/v/56980">Simultaneous Recordings of Cortical Local Field Potentials, Electrocardiogram, Electromyogram, and Breathing Rhythm from a Freely Moving Rat.</a> J. Vis. Exp. (2018).
The video demonstrates simultaneous electrophysiological recording from multiple brain regions in a rat using an integrative micro-drive array. Recording electrodes are placed in the olfactory bulb, reference electrodes in the frontal cortex, and micro-drive array electrodes in the hippocampus. The rat is allowed to forage freely, and simultaneous recording from all the implanted electrodes is recorded using the array.

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
1. ...

Concurrent Recording of Co-localized Electroencephalography and Local Field Potential in Rodent

Samenvatting

Meer video's verkennen