We thank the Deutsche Forschungsgemeinschaft (DFG), KFO 247, for funding our study.

Experimental procedures were conducted in accordance with the German Animal Welfare Act (last revised in 2014) and European regulations (2010/63/EU). Experiments were approved by the local animal welfare authority (LaGeSo, Berlin), and conformed to local department and international guidelines.
NOTE: In the presented method two models of electrodes are used to record from the hyperdirect cortico-basal ganglia pathway that connects the primary motor cortex (M1) with the subthalamic nucleus (STN) and the substantia nigra pars reticulate (SNr). For epidural electrocorticogram (ECoG) recordings from the M1 custom-made low-impedance Ag/AgCl electrodes are used. The recordings from the STN and SNr are performed with commercially available high-impedance tungsten electrodes.
1. Construction of Epidural Ag/AgCl Epidural Electrodes
<ol>
	<li>Take an approx. 5 cm long strip of 99.99% pure silver wire with a diameter of 200 &#181;m and remove any coating if necessary.</li>
	<li>Hold the wire tip with the tip downwards into a flame of a lighter or candle until the tip starts to melt. Wait until the tip is ball-shaped and has a diameter of approximately 1 mm. Cut off the preformed electrode to a total length of 15 mm from the beginning of the ball-shaped tip to the wire end.</li>
	<li>Solder a precision connector to the wire end, which fits the used electrophysiological recording system. Cover the soldering point from the wire end to the connector with conductive silver varnish. This helps conductivity and results in a better signal quality.</li>
	<li>After the conductive varnish has dried, cover the soldering point with a 3 mm to 1 mm heat shrinking tube. Carefully use a watchmaker&#39;s hammer to flatten the ball-shaped tip to half the thickness.</li>
	<li>Put on examination gloves and take a lint-free cleaning cloth with 100% ethanol to remove any dirt and grease.</li>
	<li>Put the electrodes in a 15 mL centrifuge tube or cell culture tube and fill it up with household chlorine bleach (CAUTION; containing 2.8 g of sodium hypochloride per 100 g solvent) until the ball-shaped tip is fully covered. 
	CAUTION: Chlorine bleach is corrosive; always follow the manufacturer&#39;s safety instructions.</li>
	<li>Take the electrodes out after 23 min and flush them generously with distilled water. The successful application of a silver chloride layer appears as a homogenous purple change in color.</li>
	<li>Dry in air. After fully dried, take the electrodes with fine tweezers. With a fine paintbrush, apply liquid electrical insulation. Start on the wire directly behind the electrode tip and cover everything up to the heat shrinking tube. Let the insulation dry for at least 2 h.</li>
	<li>For quality control, perform a check of electrical conductivity with a multimeter. If available, perform impedance testing at 1 kHz using an appropriate impedance meter, while the electrode and test probe are put together in a 0.9% NaCl containing H2O solution without touching each other. Impedance values at 1 kHz should be approximately 8 k&#937;.</li>
</ol>
2. Affixing the Electrodes to a Stereotaxic Holder
NOTE: To record MUA and LFPs at the same time, use tungsten microwire electrodes with an impedance of 1.5 M&#937;. If the focus of the recordings is on high quality recordings of single units, choose microwire electrodes with a higher impedance (&#62;5 M&#937;). If the aim of the study is solely directed at LFPs, electrodes with lower impedances can be acceptable. For small structures, for which dorsoventral stereotaxic adjustments are often necessary, use pairs of electrodes with a suitable dorsoventral tip separation (in this case 250 &#181;m). Furthermore, this provides the advantage of a more local reference electrode, if needed. The stereotaxic coordinates are always measured from the lowermost electrode and are calculated in reference to the bregma.
<ol>
	<li>Take a standard stereotaxic electrode holder with an acrylic block and clamp and lay it securely on a flat surface in the field of view of a surgical microscope.</li>
	<li>Loosely fix the first pair of electrodes to the acrylic block of the holder with pieces of adhesive tape (3 mm x 8 mm) using fine tweezers. The electrodes should protrude the acrylic block approx. 12 mm.</li>
	<li>Carefully fix the second bipolar electrode next to the first electrode. For targeting the structures of the hyperdirect pathway, the distance should be 2 mm (Figure 1). For most standard stereotaxic electrode holders, this is the adjacent recess. Use a caliper gauge to verify. Different networks can be approached the same way. For this, the acrylic block may be turned to a certain degree.</li>
	<li>Adjust the second pair of electrodes by sliding it carefully to a position, in which the most ventral tip is approximately 200 &#181;m recessed compared to the first electrode (Figure 1). Do this under microscopic vision. For this, use a 30 G cannula (outer diameter 300 &#181;m) to better estimate the distance.</li>
	<li>Press on the adhesive tape, and then secure with the holder&#39;s metal clamp.</li>
</ol>
3. Surgery
<ol>
	<li>For electrophysiological recordings, use urethane (CAUTION) for anesthesia. 
	Caution: Urethane is toxic and carcinogenic, so always adhere to the safety regulations and data sheet given by the substance&#39;s manufacturer.</li>
	<li>Prepare a solution of 200 mg/mL urethane in 0.9% NaCl medical saline solution.</li>
	<li>Administer a total of 1.3 g/kg bodyweight urethane intraperitoneally (IP). Depending on the rat strain it might be reasonable to split the dose into two doses with a 15 min interval in between the injections in order to enhance the safety of the anesthesia.</li>
	<li>Check the depth of anesthesia by using pedal-withdrawal reflex and other suitable reflexes. If the anesthesia is not deep enough to perform surgery, inject 0.15 g/kg bodyweight of urethane IP and wait another 15 min.</li>
	<li>Apply an eye ointment to prevent corneal dehydration.</li>
	<li>Constantly monitor respiratory rate and pedal withdrawal reflex during anesthesia. Use a small animal heating pad with temperature control to ensure that a physiological body temperature is maintained throughout the surgery. Before the start electrophysiological recordings, change to a non-electrical alternative (e.g. sodium acetate head pad).</li>
	<li>Shave the fur alongside the dorsal side of the head to achieve a clean surgical field. Disinfect around the incision site with appropriate surgical disinfectant. Fix the animal in the stereotactic frame.</li>
	<li>Perform a 2-cm long incision of the scalp in sagittal direction with a scalpel. Use a scalpel to slightly scrape off the skull aponeurosis and disinfect the skull. Use cotton buds soaked in 3% H2O2 to remove any remaining tissue.</li>
	<li>Use an electrocauter or thermocauter to control bleeding, if necessary. Stop bleedings from the skull bone and hypoderm, if the bleeding does not stop spontaneously after 1-2 min and hinders sight onto the skull.</li>
	<li>Adjust the incisor bar until the head is positioned in flat skull position, which means the bregma and lambda as stereotaxic reference points are in the same plane. This is most important to achieve high surgical precision. Use a standard stereotaxic rat alignment tool, calibrate the designated tip to the bregma under microscopic vision and adjust the incisor bar until the designated points for the bregma and lambda on the tool touch the skull at the same time. 
	NOTE: A view from one side with focused light from the other may help to determine this condition. Alternatively, take a stereotaxic holder with a fine cannula and measure the dorsoventral coordinates of Bregma and lambda under microscopic vision. Adjust the incisor bar until the dorsoventral coordinates of Bregma and lambda are the same.</li>
	<li>Use a stereotaxic holder with cannula, calibrate to the bregma and then calculate the position of all drill holes on the skull. Using the stereotaxic holder, mark the positions of the holes to be drilled either by carefully scratching the skull or by using a surgical color marker. The coordinates for this depend on the targets, coordinates with reference to the bregma are given for the hyperdirect pathway in Table 1, including the suggested coordinates for cerebellar reference electrodes.</li>
	<li>Using a microdrill carefully drill all holes. For the STN and SNr, drill a common hole (approximately 2 mm x 3 mm in size). All other drill holes should have a diameter of about 1 mm.</li>
	<li>Take two fine cannulas (at least 27 G) and bend their tips to form a hooked shape, using a hard surface or tweezers. Use these to remove any debris from the drill holes, and carefully cut and remove the dura mater in the common STN/SNr hole.</li>
	<li>Flush the drill holes with physiologic saline. Apply a drop of physiologic saline every 15 min to the drill holes to prevent the brain and dura from drying-out.</li>
	<li>Take a microdrill and matching stainless steel micro-screw (e.g. a M 1.2 mm x 2 mm screw), drill a hole and screw in a micro-screw in between the drill holes of the reference epidural electrodes above cerebellum, do the same for the M1 epidural electrodes.</li>
	<li>Slide the self-built Ag/AgCl epidural electrodes into the drill holes for the reference electrodes and M1 electrodes. Guide the electrode tip with fine tweezers and slide it directly below the skull bone into the drill hole.</li>
	<li>Fix all epidural electrodes with two-component dental acrylic. Make sure not to cover the bregma point nor affect the common STN/SNr hole.</li>
	<li>Insert the prepared holder with the tungsten microwire electrodes into the stereotaxic frame.</li>
	<li>Calibrate the most ventral electrode, which is intended to target the STN, to the bregma. Adjust to the calculated position above the common STN/SNr hole and lower the electrodes down to the brain under microscopic vision. Make sure that the tungsten microwire electrodes go inside the brain smoothly.</li>
</ol>
4. Electrophysiological Mapping and Recordings
NOTE: For this step, a Faraday cage and a multi-channel electrophysiological recording system with recording software capable of online-filtering and online spike-sorting is necessary. Preferably use a system that works with a preamplifier positioned near the head of the animals to keep electrical noise and artifacts to an absolute minimum. Besides the tungsten microwire electrodes, at least one epidural and one reference electrode are necessary to perform recordings of the hyperdirect pathway. It is recommended to insert epidural and reference electrodes pairwise without them touching each other, this helps in case of malfunctioning and allows for different types of referencing in data analysis.
<ol>
	<li>Put a mobile Faraday cage above the stereotaxic frame. If only a stationary Faraday cage is available, carefully move the stereotaxic frame into the Faraday cage while making sure deep brain electrodes are not lowered into the brain until the stereotaxic frame is in its final position.</li>
	<li>Connect the electrodes to the headstage of the electrophysiological setup. Make sure the reference electrodes are connected to appropriate reference channels.</li>
	<li>Set up the recording software: Bandpass filter (0.05-8,000 Hz) and amplify (gain 1,500-2,000x) the raw data signal. Use an online LFP and spike filter with appropriate settings (bandpass filter 0.05-250 Hz for LFPs, bandpass filter 300-8,000 Hz for MUA). For all filters, use a butterworth-type filter.</li>
	<li>Set up a spike threshold, if applicable, for online spike sorting. Most recording software allows for setting up of a spike threshold, which is an amplitude value above which a signal is marked as a spike by the software. This threshold can either be determined mathematically as a factor or standard deviation of the mean amplitude of the filtered spike signal, or can preferably be determined by visual inspection of data segments &#60;500 ms and set up as a line above the signal noise in a graphical user interface. 
	NOTE: The intention in setting up a spike threshold is to count spikes and sort units in order to provide information on how many neurons are presently recorded and how their spikes are shaped.</li>
	<li>Slowly lower the tungsten microwire electrodes to 1 mm dorsal of the target, which is STN for hyperdirect pathway. Wait for the signal to stabilize if necessary.</li>
	<li>For the electrophysiological mapping, advance the electrodes ventrally in steps of 100 &#181;m. At each step, evaluate the firing pattern, firing rate and shape of spikes. Compare those with the typical examples given in Figure 2. Commonly, dense nuclei show fast and continuous spiking over several dorsoventral steps, whereas fiber-rich structures show low firing rates and less homogenous spike activity in subsequent ventral steps.</li>
	<li>For the hyperdirect pathway, make sure that the most ventral electrode is inside STN. 
	NOTE: The STN is reached when a considerable increase in MUA is detected ventral of the Zona incerta. Ventral to the STN, spiking stops almost completely because the electrode has reached the internal capsule. When the most ventral electrode is in STN, the configuration of the tungsten microelectrodes ensures the posterior, second electrode is in SNr. Dorsoventral fine-tuning in small increments might be necessary to record typical MUA in STN and SNr at the same time. Note that the frequency of MUA depends on the number of neurons actually recorded and on the level brain activation.</li>
	<li>Once the electrodes are in the desired structures, set up online filtering and spike-sorting (see Figure 4), and then start the recording of the data. Typical examples for the different cortical synchronization states that can be identified in the LFP recordings are shown in Figure 3.</li>
</ol>
5. End of Experiment
<ol>
	<li>When recordings are done, slowly raise the electrodes out of the brain and instantaneously flush them with physiological saline. The electrodes can be reused after thorough flushing and visual inspection. Discharge bend electrodes.</li>
	<li>Euthanize the animals by an IP injection of an overdose of urethane (2.5 g/kg bodyweight). 
	NOTE: Urethane should only be used for final procedures.</li>
	<li>If histological verification of the electrode position or other histological staining procedures is required, remove the brain from the skull and process the tissue appropriately. 
	NOTE: Depending on the intended staining methods, transcardial perfusion may be necessary. For post-mortem verification of the electrode position, a standard Nissl staining is sufficient in most cases to visualize the electrode trajectory in e.g. coronal brain sections. Further approaches to facilitate histological target verification include the use of electrically induced lesions to the brain tissue by applying electrical current via the recording electrodes or the application of biocompatible dye prior to electrode insertion16,17.</li>
</ol>

<ol>
	<li>Lozano, A. M., Lipsman, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+and+regulating+dysfunctional+circuits+using+deep+brain+stimulation.">Probing and regulating dysfunctional circuits using deep brain stimulation.</a> Neuron. 77 (3), 406-424 (2013).</li><li>Mathalon, D. H., Sohal, V. 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+Oscillations+and+Synchrony+in+Brain+Dysfunction+and+Neuropsychiatric+Disorders:+It's+About+Time.">Neural Oscillations and Synchrony in Brain Dysfunction and Neuropsychiatric Disorders: It's About Time.</a> JAMA Psychiatry. 72 (8), 840-844 (2015).</li><li>Uhlhaas, P. J., Singer, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+dynamics+and+neuropsychiatric+disorders:+toward+a+translational+paradigm+for+dysfunctional+large-scale+networks.">Neuronal dynamics and neuropsychiatric disorders: toward a translational paradigm for dysfunctional large-scale networks.</a> Neuron. 75 (6), 963-980 (2012).</li><li>Buzsaki, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Large-scale+recording+of+neuronal+ensembles.">Large-scale recording of neuronal ensembles.</a> Nat Neurosci. 7 (5), 446-451 (2004).</li><li>Buzsaki, G., Anastassiou, C. A., Koch, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+origin+of+extracellular+fields+and+currents--EEG,+ECoG,+LFP+and+spikes.">The origin of extracellular fields and currents--EEG, ECoG, LFP and spikes.</a> Nat Rev Neurosci. 13 (6), 407-420 (2012).</li><li>Brazhnik, E., Novikov, N., McCoy, A. J., Cruz, A. V., Walters, 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=Functional+correlates+of+exaggerated+oscillatory+activity+in+basal+ganglia+output+in+hemiparkinsonian+rats.">Functional correlates of exaggerated oscillatory activity in basal ganglia output in hemiparkinsonian rats.</a> Exp Neurol. 261, 563-577 (2014).</li><li>Avila, I., 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=Beta+frequency+synchronization+in+basal+ganglia+output+during+rest+and+walk+in+a+hemiparkinsonian+rat.">Beta frequency synchronization in basal ganglia output during rest and walk in a hemiparkinsonian rat.</a> Exp Neurol. 221 (2), 307-319 (2010).</li><li>Javor-Duray, B. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early-onset+cortico-cortical+synchronization+in+the+hemiparkinsonian+rat+model.">Early-onset cortico-cortical synchronization in the hemiparkinsonian rat model.</a> J Neurophysiol. 113 (3), 925-936 (2015).</li><li>Beck, M. 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=Short-+and+long-term+dopamine+depletion+causes+enhanced+beta+oscillations+in+the+cortico-basal+ganglia+loop+of+parkinsonian+rats.">Short- and long-term dopamine depletion causes enhanced beta oscillations in the cortico-basal ganglia loop of parkinsonian rats.</a> Exp Neurol. 286, 124-136 (2016).</li><li>Magill, P. J., Bolam, J. P., Bevan, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relationship+of+activity+in+the+subthalamic+nucleus-globus+pallidus+network+to+cortical+electroencephalogram.">Relationship of activity in the subthalamic nucleus-globus pallidus network to cortical electroencephalogram.</a> J Neurosci. 20 (2), 820-833 (2000).</li><li>Magill, P. J., 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=Changes+in+functional+connectivity+within+the+rat+striatopallidal+axis+during+global+brain+activation+in+vivo.">Changes in functional connectivity within the rat striatopallidal axis during global brain activation in vivo.</a> J Neurosci. 26 (23), 6318-6329 (2006).</li><li>Brown, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Abnormal+oscillatory+synchronisation+in+the+motor+system+leads+to+impaired+movement.">Abnormal oscillatory synchronisation in the motor system leads to impaired movement.</a> Curr Opin Neurobiol. 17 (6), 656-664 (2007).</li><li>Stein, E., Bar-Gad, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=beta+oscillations+in+the+cortico-basal+ganglia+loop+during+parkinsonism.">beta oscillations in the cortico-basal ganglia loop during parkinsonism.</a> Exp Neurol. 245, 52-59 (2013).</li><li>Little, S., Brown, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=What+brain+signals+are+suitable+for+feedback+control+of+deep+brain+stimulation+in+Parkinson's+disease?.">What brain signals are suitable for feedback control of deep brain stimulation in Parkinson's disease?.</a> Ann N Y Acad Sci. 1265, 9-24 (2012).</li><li>Priori, A., Foffani, G., Rossi, L., Marceglia, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adaptive+deep+brain+stimulation+(aDBS)+controlled+by+local+field+potential+oscillations.">Adaptive deep brain stimulation (aDBS) controlled by local field potential oscillations.</a> Exp Neurol. , 77-86 (2013).</li><li>Brozoski, T. J., Caspary, D. M., Bauer, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Marking+multi-channel+silicon-substrate+electrode+recording+sites+using+radiofrequency+lesions.">Marking multi-channel silicon-substrate electrode recording sites using radiofrequency lesions.</a> J Neurosci Methods. 150 (2), 185-191 (2006).</li><li>Schjetnan, A. G., Luczak, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recording+large-scale+neuronal+ensembles+with+silicon+probes+in+the+anesthetized+rat.">Recording large-scale neuronal ensembles with silicon probes in the anesthetized rat.</a> J Vis Exp. (56), (2011).</li><li>Mallet, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Disrupted+dopamine+transmission+and+the+emergence+of+exaggerated+beta+oscillations+in+subthalamic+nucleus+and+cerebral+cortex.">Disrupted dopamine transmission and the emergence of exaggerated beta oscillations in subthalamic nucleus and cerebral cortex.</a> J Neurosci. 28 (18), 4795-4806 (2008).</li><li>Steriade, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Corticothalamic+resonance,+states+of+vigilance+and+mentation.">Corticothalamic resonance, states of vigilance and mentation.</a> Neuroscience. 101 (2), 243-276 (2000).</li><li>Maesawa, S., 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+stimulation+of+the+subthalamic+nucleus+in+hemiparkinsonian+rats:+neuroprotection+of+dopaminergic+neurons.">Long-term stimulation of the subthalamic nucleus in hemiparkinsonian rats: neuroprotection of dopaminergic neurons.</a> J Neurosurg. 100 (4), 679-687 (2004).</li><li>Paxinos, G., Watson, C. <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 Rat Brain in Stereotaxic Coordinates. , (1998).</li><li>Oliveira, L. M. O., Dimitrov, D., Nicolelis, M. A. 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> Methods for Neural Ensemble Recordings Frontiers in Neuroscience. , (2008).</li><li>Torres, E. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increased+efficacy+of+the+6-hydroxydopamine+lesion+of+the+median+forebrain+bundle+in+small+rats,+by+modification+of+the+stereotaxic+coordinates.">Increased efficacy of the 6-hydroxydopamine lesion of the median forebrain bundle in small rats, by modification of the stereotaxic coordinates.</a> J Neurosci Methods. 200 (1), 29-35 (2011).</li><li>Hadar, 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=Rats+overexpressing+the+dopamine+transporter+display+behavioral+and+neurobiological+abnormalities+with+relevance+to+repetitive+disorders.">Rats overexpressing the dopamine transporter display behavioral and neurobiological abnormalities with relevance to repetitive disorders.</a> Sci Rep. 6, 39145 (2016).</li><li>Parr-Brownlie, L. C., Poloskey, S. L., Bergstrom, D. A., Walters, 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=Parafascicular+thalamic+nucleus+activity+in+a+rat+model+of+Parkinson's+disease.">Parafascicular thalamic nucleus activity in a rat model of Parkinson's disease.</a> Exp Neurol. 217 (2), 269-281 (2009).</li><li>Steriade, M., Nunez, A., Amzica, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+slow+(&lt;+1+Hz)+oscillation+of+neocortical+neurons+in+vivo:+depolarizing+and+hyperpolarizing+components.">A novel slow (&lt; 1 Hz) oscillation of neocortical neurons in vivo: depolarizing and hyperpolarizing components.</a> J Neurosci. 13 (8), 3252-3265 (1993).</li><li>Maggi, C. A., Meli, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Suitability+of+urethane+anesthesia+for+physiopharmacological+investigations+in+various+systems.+Part+1:+General+considerations.">Suitability of urethane anesthesia for physiopharmacological investigations in various systems. Part 1: General considerations.</a> Experientia. 42 (2), 109-114 (1986).</li><li>Goldberg, J. A., Kats, S. S., Jaeger, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Globus+pallidus+discharge+is+coincident+with+striatal+activity+during+global+slow+wave+activity+in+the+rat.">Globus pallidus discharge is coincident with striatal activity during global slow wave activity in the rat.</a> J Neurosci. 23 (31), 10058-10063 (2003).</li><li>Karain, B., Xu, D., Bellone, J. A., Hartman, R. E., Shi, W. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rat+globus+pallidus+neurons:+functional+classification+and+effects+of+dopamine+depletion.">Rat globus pallidus neurons: functional classification and effects of dopamine depletion.</a> Synapse. 69 (1), 41-51 (2015).</li><li>Paasonen, J., 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=Comparison+of+seven+different+anesthesia+protocols+for+nicotine+pharmacologic+magnetic+resonance+imaging+in+rat.">Comparison of seven different anesthesia protocols for nicotine pharmacologic magnetic resonance imaging in rat.</a> Eur Neuropsychopharmacol. 26 (3), 518-531 (2016).</li><li>Mahmud, M., Vassanelli, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Processing+and+Analysis+of+Multichannel+Extracellular+Neuronal+Signals:+State-of-the-Art+and+Challenges.">Processing and Analysis of Multichannel Extracellular Neuronal Signals: State-of-the-Art and Challenges.</a> Front Neurosci. 10, 248 (2016).</li><li>Hadar, 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=Altered+neural+oscillations+and+elevated+dopamine+levels+in+the+reward+pathway+during+alcohol+relapse.">Altered neural oscillations and elevated dopamine levels in the reward pathway during alcohol relapse.</a> Behav Brain Res. 316, 131-135 (2017).</li><li>Voget, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Altered+local+field+potential+activity+and+serotonergic+neurotransmission+are+further+characteristics+of+the+Flinders+sensitive+line+rat+model+of+depression.">Altered local field potential activity and serotonergic neurotransmission are further characteristics of the Flinders sensitive line rat model of depression.</a> Behav Brain Res. 291, 299-305 (2015).</li></ol>

The authors have nothing to disclose.

In the present study, the method is demonstrated how to record extracellular electrophysiological signals simultaneously from multiple sites of a given network using the example of the hyperdirect cortico-basal ganglia pathway that connects the M1 with the STN and SNr in rodents.
A critical step in the recording of small subcortical structures such as the STN is the precisely guided insertion of the recording electrodes into the target. In the presented method, taking care of two crucial steps...

Recent cumulative evidence on different neuropsychiatric disorders such as Parkinson&#180;s disease (PD) and schizophrenia strongly suggests that their pathophysiology is based on a critical dysfunction of extended neuronal circuits that often involve cortical and subcortical structures1,2,3. According to this theory, the clinical manifestations of the diseases arise as a consequence of an impaired information processing capacity of a network of cells instead of single cells or specific neuronal elements1,2,3. In order to enhance the understanding of this complex group of neuropsychiatric diseases and to find new treatment options, it is mandatory to characterize the neuronal dynamics of those disordered networks in human patients and in animal models in great detail. An excellent method to study large-scale networks in living subjects is multi-site electrophysiological recordings of extracellular potentials4. Using this method, it is possible to simultaneously assess local field potentials (LFPs), that primarily represent the temporal summation of excitatory and inhibitory postsynaptic currents and multi-unit activity (MUA), that is generated by presynaptic potentials5. The recording of extracellular potentials has several advantages over alternative methods to study networks, e.g., functional magnetic resonance imaging and calcium imaging, because it provides a higher temporal and spatial resolution and because it is not dependent on genetically engineered organisms5. However, the use of extracellular in vivo recordings is limited since it is an invasive technique that cannot be universally applied.
In vivo electrophysiological recordings can be performed in awake as well as in anesthetized animals6. Both methods are accompanied by specific pros and cons. Studies in awake animals allow the recording of brain signals during the performance of defined behavioral tasks, but are prone to movement related and other artifacts7,8. Recordings in anesthetized animals on the other hand offer the opportunity to assess LFPs and MUA with a minimum of artifacts at highly defined cortical synchronization states, but the results also differ to some extent to what can be found in awake subjects9,10,11.
In recent years, it has been demonstrated that the sampling of LFPs is especially useful to delineate pathological changes of network activity. A prominent example of this is research on the pathophysiology of PD in human patients and animal models of the disease, where it could be shown that enhanced beta oscillations in the cortico-basal ganglia loop are linked to parkinsonian motor symptoms12,13. As a consequence of this line of research, it is currently investigated if beta oscillations could be used as an online feedback biomarker for closed-loop deep brain stimulation14,15.
In the present study, a detailed description of acute multi-site in vivo electrophysiological recordings of LFPs and MUA in rats anesthetized with urethane is provided. It is demonstrated how a complete network, such as the hyperdirect cortico-basal ganglia pathway can be characterized electrophysiologically using standard and customized electrodes and how those electrodes can be build. It is especially emphasized how a precise targeting of basal ganglia nuclei can be achieved by combining stereotactic surgery together with the online registration of MUAs.

<table>
	<tbody>
		<tr>
			<td>Ag/AgCl custom epidural electrodes</td>
			<td>Goodfellow GmbH 
			D-61213 Bad Nauheim, Germany 
			info@goodfellow.com</td>
			<td>Product-ID AG005127 for 99.99% silver wire</td>
			<td>Ag/AgCl electrodes will allow for better signal quality, but may only be used in acute experiments. Possible replacement: Stainless steel electrodes</td>
		</tr>
		<tr>
			<td>Stereotaxic holder with acrylic block</td>
			<td>David Kopf Instruments, 
			7324 Elmo Street, Tujunga, CA 91042, USA</td>
			<td>Product ID Model 1770 Standard Electrode Holder</td>
			<td>Make sure the acrylic block has recesses which suit the electrode setup for the desired target. Acrylic blocks can easily be modified with a file to obtain the desired configuration. Possible replacement: Self-constructed electrode holders</td>
		</tr>
		<tr>
			<td>Tungsten microwire electrodes 1.5 M&#937; impedance</td>
			<td>Microprobes.com 
			18247-D Flower Hill Way&#160; Gaithersburg, Maryland, 20879 USA</td>
			<td>Product-ID WE3ST31.5A5-250um</td>
			<td>The 1.5 M&#937; is necessary to record MUA and LFP at the same time. Possible replacement: Microelectrodes of different materials can be used. The electrodes have to be straight, robust and as thin as possible.</td>
		</tr>
		<tr>
			<td>Rat alignment tool</td>
			<td>David Kopf Instruments, 
			7324 Elmo Street, Tujunga, CA 91042, USA</td>
			<td>Product ID Model 944 Rat Alignment Tool</td>
			<td>Allows the exact orientation of the brain to match stereotaxic atlases. Possible replacement: Stereotaxic holder with a cannula</td>
		</tr>
		<tr>
			<td>Two-component dental acrylic</td>
			<td>Associated Dental Products Ltd. 
			Kemdent Works, Purton, Swindon 
			Wiltshire, SN5 4HT, United Kingdom</td>
			<td>Simplex Rapid Powder Clear 225g, Product code: ACR803; Simplex Rapid Liquid 150ml, Product code: ACR920</td>
			<td>Depending in the electrodes used, superglue might be an easy alternative, if the electrodes are small and lightweight. Possible replacement: Superglue (Cyanacrylate-based)</td>
		</tr>
		<tr>
			<td>Faraday cage</td>
			<td>Self-construction</td>
			<td></td>
			<td>A proper Faraday cage will be the best protection from electromagnetic artifacts, but everything which can be formed into a box shape or applied to a frame and is made of conductive material may help. Possible replacement: Aluminum foil or copper mesh</td>
		</tr>
		<tr>
			<td>Electrophysiological setup with recording software and online spike-sorting capabilities</td>
			<td>OmniPlex&#174; Neural Data Acquisition System 
			Plexon Inc 
			6500 Greenville Avenue, Suite 700 
			Dallas, Texas 75206 
			USA</td>
			<td></td>
			<td>Offline sorting software is a potential alternative, multiple scripts and softwares can be found for free in the open source community.</td>
		</tr>
	</tbody>
</table>

acute in vivo electrophysiological recordings of local field potentials and multi-unit activity from the hyperdirect pathway in anesthetized rats

Converging evidence shows that many neuropsychiatric diseases should be understood as disorders of large-scale neuronal networks. To better understand the pathophysiological basis of these diseases, it is necessary to precisely characterize in which way the processing of information is disturbed between the different neuronal parts of the circuit. Using extracellular in vivo electrophysiological recordings, it is possible to accurately delineate neuronal activity within a neuronal network. The application of this method has several advantages over alternative techniques, e.g., functional magnetic resonance imaging and calcium imaging, as it allows a unique temporal and spatial resolution and does not rely on genetically engineered organisms. However, the use of extracellular in vivo recordings is limited since it is an invasive technique that cannot be universally applied. In this article, a simple and easy to use method is presented with which it is possible to simultaneously record extracellular potentials such as local field potentials and multiunit activity at multiple sites of a network. It is detailed how a precise targeting of subcortical nuclei can be achieved using a combination of stereotactic surgery and online analysis of multi-unit recordings. Thus, it is demonstrated, how a complete network such as the hyperdirect cortico-basal ganglia loop can be studied in anesthetized animals in vivo.

With the herein used recording electrodes, it is possible to sample LFPs from the primary motor cortex, the subthalamic nucleus and the substantia nigra pars reticulata and MUA from the STN and SNr. Initially, LFPs and multi-unit activity are recorded together in a broad-band signal. Thereafter, LFPs and MUAs are separated by bandpass filters (0.05-250 Hz for LFPs and 300-4,000 Hz for MUA).
For the correct targeting of subcortic...

Watch this Scientific Journal Video about Acute In Vivo Electrophysiological Recordings of Local Field Potentials and Multi-unit Activity from the Hyperdirect Pathway in Anesthetized Rats at JoVE.com

Acute In Vivo Electrophysiological Recordings of Local Field Potentials and Multi-unit Activity from the Hyperdirect Pathway in Anesthetized Rats

In this study, the methodology is presented on how to perform multi-site in vivo electrophysiological recordings from the hyperdirect pathway under urethane anesthesia.

Acute In Vivo Electrophysiological Recordings of Local Field Potentials and Multi-unit Activity from the Hyperdirect Pathway in Anesthetized Rats

Converging evidence shows that many neuropsychiatric diseases should be understood as disorders of large-scale neuronal networks. To better understand the ...

acute-vivo-electrophysiological-recordings-local-field-potentials

Research

JoVE Journal

Neuroscience

15.5K Views.  Charité University Medicine Berlin. In this study, the methodology is presented on how to perform multi-site in vivo electrophysiological recordings from the hyperdirect pathway under urethane anesthesia.

Video: Acute In Vivo Electrophysiological Recordings of Local Field Potentials and Multi-unit Activity from the Hyperdirect Pathway in Anesthetized Rats

Electrophysiological Recordings from the Giant Fiber Pathway of D. melanogaster

When startled adult D. melanogaster react by jumping into the air and flying away. In many invertebrate species, including D. melanogaster, the "escape" (or "startle") response during the adult stage is mediated by the multi-component neuronal circuit called the Giant Fiber System (GFS). The comparative large size of the neurons, their distinctive morphology and simple connectivity make the GFS an attractive model system for studying neuronal circuitry. The GFS pathway is composed of two bilaterally symmetrical Giant Fiber (GF) interneurons whose axons descend from the brain along the midline into the thoracic ganglion via the cervical connective. In the mesothoracic neuromere (T2) of the ventral ganglia the GFs form electro-chemical synapses with 1) the large medial dendrite of the ipsilateral motorneuron (TTMn) which drives the tergotrochanteral muscle (TTM), the main extensor for the mesothoracic femur/leg, and 2) the contralateral peripherally synapsing interneuron (PSI) which in turn forms chemical (cholinergic) synapses with the motorneurons (DLMns) of the dorsal longitudinal muscles (DLMs), the wing depressors. The neuronal pathway(s) to the dorsovental muscles (DVMs), the wing elevators, has not yet been worked out (the DLMs and DVMs are known jointly as indirect flight muscles - they are not attached directly to the wings, but rather move the wings indirectly by distorting the nearby thoracic cuticle) (King and Wyman, 1980; Allen et al., 2006). The di-synaptic activation of the DLMs (via PSI) causes a small but important delay in the timing of the contraction of these muscles relative to the monosynaptic activation of TTM (~0.5 ms) allowing the TTMs to first extend the femur and propel the fly off the ground. The TTMs simultaneously stretch-activate the DLMs which in turn mutually stretch-activate the DVMs for the duration of the flight. The GF pathway can be activated either indirectly by applying a sensory (e.g."air-puff" or "lights-off") stimulus, or directly by a supra-threshold electrical stimulus to the brain (described here). In both cases, an action potential reaches the TTMs and DLMs solely via the GFs, PSIs, and TTM/DLM motoneurons, although the TTMns and DLMns do have other, as yet unidentified, sensory inputs. Measuring "latency response" (the time between the stimulation and muscle depolarization) and the "following to high frequency stimulation" (the number of successful responses to a certain number of high frequency stimuli) provides a way to reproducibly and quantitatively assess the functional status of the GFS components, including both central synapses (GF-TTMn, GF-PSI, PSI-DLMn) and the chemical (glutamatergic) neuromuscular junctions (TTMn-TTM and DLMn-DLM). It has been used to identify genes involved in central synapse formation and to assess CNS function.

Electrophysiological Recordings from the Giant Fiber Pathway of D. melanogaster

The Giant Fiber System is a simple neuronal circuit of adult Drosophila melanogaster containing the largest neurons in the fly. We describe the protocol for monitoring synaptic transmission through this pathway by recording post synaptic potentials in dorsal longitudinal (DLM) and tergotrochanteral (TTM) muscles following direct stimulation of the Giant Fiber interneurons.

When startled adult D. melanogaster react by jumping into the air and flying away. In many invertebrate species, including D. melanogaster, the "escape" ...

Identification of Olfactory Volatiles using Gas Chromatography-Multi-unit Recordings (GCMR) in the Insect Antennal Lobe

All organisms inhabit a world full of sensory stimuli that determine their behavioral and physiological response to their environment. Olfaction is especially important in insects, which use their olfactory systems to respond to, and discriminate amongst, complex odor stimuli. These odors elicit behaviors that mediate processes such as reproduction and habitat selection1-3. Additionally, chemical sensing by insects mediates behaviors that are highly significant for agriculture and human health, including pollination4-6, herbivory of food crops7, and transmission of disease8,9. Identification of olfactory signals and their role in insect behavior is thus important for understanding both ecological processes and human food resources and well-being.
	To date, the identification of volatiles that drive insect behavior has been difficult and often tedious. Current techniques include gas chromatography-coupled electroantennogram recording (GC-EAG), and gas chromatography-coupled single sensillum recordings (GC-SSR)10-12. These techniques proved to be vital in the identification of bioactive compounds. We have developed a method that uses gas chromatography coupled to multi-channel electrophysiological recordings (termed 'GCMR') from neurons in the antennal lobe (AL; the insect's primary olfactory center)13,14. This state-of-the-art technique allows us to probe how odor information is represented in the insect brain. Moreover, because neural responses to odors at this level of olfactory processing are highly sensitive owing to the degree of convergence of the antenna's receptor neurons into AL neurons, AL recordings will allow the detection of active constituents of natural odors efficiently and with high sensitivity. Here we describe GCMR and give an example of its use.
	Several general steps are involved in the detection of bioactive volatiles and insect response. Volatiles first need to be collected from sources of interest (in this example we use flowers from the genus Mimulus (Phyrmaceae)) and characterized as needed using standard GC-MS techniques14-16. Insects are prepared for study using minimal dissection, after which a recording electrode is inserted into the antennal lobe and multi-channel neural recording begins. Post-processing of the neural data then reveals which particular odorants cause significant neural responses by the insect nervous system.
	Although the example we present here is specific to pollination studies, GCMR can be expanded to a wide range of study organisms and volatile sources. For instance, this method can be used in the identification of odorants attracting or repelling vector insects and crop pests. Moreover, GCMR can also be used to identify attractants for beneficial insects, such as pollinators. The technique may be expanded to non-insect subjects as well.

Identification of Olfactory Volatiles using Gas Chromatography-Multi-unit Recordings GCMR in the Insect Antennal Lobe

Olfactory cues mediate many different behaviors in insects, and are often complex mixtures comprised of tens to hundreds of volatile compounds. Using gas chromatography with multi-channel recording in the insect antennal lobe, we describe a method for the identification of bioactive compounds.

All  organisms inhabit a world full of sensory stimuli that determine their  behavioral and physiological response to their environment. Olfaction is ...

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 ...

Multi-unit Recording Methods to Characterize Neural Activity in the Locust (Schistocerca Americana) Olfactory Circuits

Detection and interpretation of olfactory cues are critical for the survival of many organisms. Remarkably, species across phyla have strikingly similar olfactory systems suggesting that the biological approach to chemical sensing has been optimized over evolutionary time1. In the insect olfactory system, odorants are transduced by olfactory receptor neurons (ORN) in the antenna, which convert chemical stimuli into trains of action potentials. Sensory input from the ORNs is then relayed to the antennal lobe (AL; a structure analogous to the vertebrate olfactory bulb). In the AL, neural representations for odors take the form of spatiotemporal firing patterns distributed across ensembles of principal neurons (PNs; also referred to as projection neurons)2,3. The AL output is subsequently processed by Kenyon cells (KCs) in the downstream mushroom body (MB), a structure associated with olfactory memory and learning4,5. Here, we present electrophysiological recording techniques to monitor odor-evoked neural responses in these olfactory circuits.
First, we present a single sensillum recording method to study odor-evoked responses at the level of populations of ORNs6,7. We discuss the use of saline filled sharpened glass pipettes as electrodes to extracellularly monitor ORN responses. Next, we present a method to extracellularly monitor PN responses using a commercial 16-channel electrode3. A similar approach using a custom-made 8-channel twisted wire tetrode is demonstrated for Kenyon cell recordings8. We provide details of our experimental setup and present representative recording traces for each of these techniques.

Multi-unit Recording Methods to Characterize Neural Activity in the Locust Schistocerca Americana Olfactory Circuits

We demonstrate variations of the extracellular multi-unit recording technique to characterize odor-evoked responses in the first three stages of the invertebrate olfactory pathway. These techniques can easily be adapted to examine ensemble activity in other neural systems as well.

Detection and interpretation of olfactory cues are critical for the survival  of many organisms. Remarkably, species across phyla have strikingly similar ...

Electrophysiological and Morphological Characterization of Neuronal Microcircuits in Acute Brain Slices Using Paired Patch-Clamp Recordings

The combination of patch clamp recordings from two (or more) synaptically coupled neurons (paired recordings) in acute brain slice preparations with simultaneous intracellular biocytin filling allows a correlated analysis of their structural and functional properties. With this method it is possible to identify and characterize both pre- and postsynaptic neurons by their morphology and electrophysiological response pattern. Paired recordings allow studying the connectivity patterns between these neurons as well as the properties of both chemical and electrical synaptic transmission. Here, we give a step-by-step description of the procedures required to obtain reliable paired recordings together with an optimal recovery of the neuron morphology. We will describe how pairs of neurons connected via chemical synapses or gap junctions are identified in brain slice preparations. We will outline how neurons are reconstructed to obtain their 3D morphology of the dendritic and axonal domain and how synaptic contacts are identified and localized. We will also discuss the caveats and limitations of the paired recording technique, in particular those associated with dendritic and axonal truncations during the preparation of brain slices because these strongly affect connectivity estimates. However, because of the versatility of the paired recording approach it will remain a valuable tool in characterizing different aspects of synaptic transmission at identified neuronal microcircuits in the brain.

Patch-clamp recordings and simultaneous intracellular biocytin filling of synaptically coupled neurons in acute brain slices allow a correlated analysis of their structural and functional properties. The aim of this protocol is to describe the essential technical steps of electrophysiological recording from neuronal microcircuits and their subsequent morphological analysis.

The combination of patch clamp recordings from two (or more) synaptically coupled neurons (paired recordings) in acute brain slice preparations with ...

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 ...

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 ...

Quantifying Acute Changes in Renal Sympathetic Nerve Activity in Response to Central Nervous System Manipulations in Anesthetized Rats

Renal sympathetic nerve activity (RSNA) and mean arterial pressure are important parameters in cardiovascular and autonomic research; however, there are limited resources directing scientists in the techniques for measuring and analyzing these variables. This protocol describes the methods for measuring RSNA and mean arterial pressure in anesthetized rats. The protocol also includes the approaches for accessing the brain during RSNA recordings for central nervous system (CNS) manipulations. The RSNA recording technique is compatible with pharmacologic, optogenetic, or electrical stimulation of the CNS. The approach is useful when an investigator will measure short-term (min to h) autonomic responses in non-survival experiments to correlate anatomically with CNS nuclei. The approach is not intended to be used to obtain chronic (survival) recordings of RSNA in rats. Discharges in RSNA, averaged rectified RSNA, and mean arterial pressure can be quantified and analyzed further using parametric statistical tests. Methods for obtaining venous access, recording mean arterial pressure telemetrically, and brain fixation for future histological analysis are also described in the article.

Methods for measuring sympathetic and cardiovascular responses to central nervous system (CNS) manipulations are important for advancing neuroscience. This protocol was developed to assist scientists with measuring and quantifying acute changes in renal sympathetic nerve activity (RSNA) in anesthetized rats (non-survival).

Renal sympathetic nerve activity (RSNA) and mean arterial pressure are important parameters in cardiovascular and autonomic research; however, there are ...

Labeling and Imaging of Amyloid Plaques in Brain Tissue Using the Natural Polyphenol Curcumin

Deposition of amyloid beta protein (A&#946;) in extra- and intracellular spaces is one of the hallmark pathologies of Alzheimer&#39;s disease (AD). Therefore, detection of the presence of A&#946; in AD brain tissue is a valuable tool for developing new treatments to prevent the progression of AD. Several classical amyloid binding dyes, fluorochrome, imaging probes, and A&#946;-specific antibodies have been used to detect A&#946; histochemically in AD brain tissue. Use of these compounds for A&#946; detection is costly and time consuming. However, because of its intense fluorescent activity, high-affinity, and specificity for A&#946;, as well as structural similarities with traditional amyloid binding dyes, curcumin (Cur) is a promising candidate for labeling and imaging of A&#946; plaques in postmortem brain tissue. It is a natural polyphenol from the herb Curcuma longa. In the present study, Cur was used to histochemically label A&#946; plaques from both a genetic mouse model of 5x familial Alzheimer&#39;s disease (5xFAD) and from human AD tissue within a minute. The labeling capability of Cur was compared to conventional amyloid binding dyes, such as thioflavin-S (Thio-S), Congo red (CR), and Fluoro-jade C (FJC), as well as A&#946;-specific antibodies (6E10 and A11). We observed that Cur is the most inexpensive and quickest way to label and image A&#946; plaques when compared to these conventional dyes and is comparable to A&#946;-specific antibodies. In addition, Cur binds with most A&#946; species, such as oligomers and fibrils. Therefore, Cur could be used as the most cost-effective, simple, and quick fluorochrome detection agent for A&#946; plaques.

Curcumin is an ideal fluorophore for labeling and imaging of amyloid beta protein plaques in brain tissue due to its preferential binding to amyloid beta protein as well as its structural similarities with other traditional amyloid binding dyes. It can be used to label and image amyloid beta protein plaques more efficiently and inexpensively than traditional methods.

Deposition of amyloid beta protein (A&#946;) in extra- and intracellular spaces is one of the hallmark pathologies of Alzheimer&#39;s disease (AD). ...

Establishment of Acute Pontine Infarction in Rats by Electrical Stimulation

Pontine infarction is the most common stroke subtype in the posterior circulation, while there lacks a rodent model mimicking pontine infarction. Provided here is a protocol for successfully establishing a rat model of acute pontine infarction. Rats weighing about 250 g are used, and a probe with an insulated sheath is injected into the pons using a stereotaxic apparatus. A lesion is produced by the electrical stimulation with a single pulse. The Longa score, Berderson score, and beam balance test are used to assess neurological deficits. Additionally, the adhesive-removal somatosensory test is used to determine sensorimotor function, and the limb placement test is used to evaluate proprioception. MRI scans are then used to assess the infarction in vivo, and TTC staining is used to confirm the infarction in vitro. Here, a successful infarction is identified that is located in the anterolateral basis of the rostral pons. In conclusion, a new method is described to establish an acute pontine infarction rat model.

Presented here is a protocol for establishing acute pontine infarction in a rat model via electrical stimulation with a single pulse.

Pontine infarction is the most common stroke subtype in the posterior circulation, while there lacks a rodent model mimicking pontine infarction. Provided ...