Name: generation of local ca1 &#947; oscillations by tetanic stimulation
Uploaded: 2015-08-14T13:00:00
Description: Watch this Scientific Journal Video about Generation of Local CA1 Î³ Oscillations by Tetanic Stimulation at JoVE.com

Supported by APA to RJH, NHMRC program grant 400121 to SP, and NMHRC fellowship 1005050 to SP. CAR acknowledges the support of the ARC (FT0990628) and the DOWD fellowship scheme. The Florey Institute of Neuroscience and Mental Health is supported by Victorian State Government infrastructure funds.

All experiments on mice were approved by the Florey Institute animal ethics committee.
1. Setup for Cutting Brain Slices
<ol>
	<li>Prepare a cutting solution comprised of (mM) 125 Choline-Cl, 2.5 KCl, 0.4 CaCl2, 6 MgCl2, 1.25 NaH2PO4, 26 NaHCO3, 20 D-glucose saturated with carbogen gas (95% O2&#8211;5% CO2) and an artificial cerebrospinal fluid (aCSF) recording solution comprised of (mM) 125 NaCl, 2.5 KCl, 2&#160;Ca...

<ol>
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Brain Res. 87 (2), 145-152 (1995).</li><li>McLeod, F., Ganley, R., Williams, L., Selfridge, J., Bird, A., Cobb, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduced+seizure+threshold+and+altered+network+oscillatory+properties+in+a+mouse+model+of+Rett+syndrome.">Reduced seizure threshold and altered network oscillatory properties in a mouse model of Rett syndrome.</a> Neuroscience. 231, 195-205 (2013).</li><li>Bracci, E., Vreugdenhil, M., Hack, S. P., Jefferys, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+synchronizing+mechanisms+of+tetanically+induced+hippocampal+oscillations.">On the synchronizing mechanisms of tetanically induced hippocampal oscillations.</a> J. Neurosci. 19 (18), 8104-8113 (1999).</li><li>Main, M. J., Cryan, J. E., Dupere, J. R., Cox, B., Clare, J. 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A., Petrou, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+in+vitro+CA1+network+activity+in+a+sodium+channel+&#946;1(C121W)+subunit+model+of+genetic+epilepsy.">Enhanced in vitro CA1 network activity in a sodium channel &#946;1(C121W) subunit model of genetic epilepsy.</a> Epilepsia. 55 (4), 601-608 (2014).</li><li>Lord, L. -. D., Expert, P., Huckins, J. F., Turkheimer, F. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cerebral+energy+metabolism+and+the+brain/'s+functional+network+architecture:+an+integrative+review.">Cerebral energy metabolism and the brain/'s functional network architecture: an integrative review.</a> J. Cereb. Blood Flow Metab. 33 (9), 1347-1354 (2013).</li><li>H&#225;jos, 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=Maintaining+network+activity+in+submerged+hippocampal+slices:+importance+of+oxygen+supply.">Maintaining network activity in submerged hippocampal slices: importance of oxygen supply.</a> Eur. J. Neurosci. 29 (2), 319-327 (2009).</li><li>H&#225;jos, N., Mody, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishing+a+physiological+environment+for+visualized+in+vitro+brain+slice+recordings+by+increasing+oxygen+supply+and+modifying+aCSF+content.">Establishing a physiological environment for visualized in vitro brain slice recordings by increasing oxygen supply and modifying aCSF content.</a> J. Neurosci. Methods. 183 (2), 107-113 (2009).</li><li>Boido, D., Jesuthasan, N., de Curtis, M., Uva, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Network+Dynamics+During+the+Progression+of+Seizure-Like+Events+in+the+Hippocampal-Parahippocampal+Regions.">Network Dynamics During the Progression of Seizure-Like Events in the Hippocampal-Parahippocampal Regions.</a> Cereb Cortex. 24 (1), 163-173 (2012).</li><li>Antuono, M., K&#246;hling, R., Ricalzone, S., Gotman, J., Biagini, G., Avoli, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antiepileptic+drugs+abolish+ictal+but+not+interictal+epileptiform+discharges+in+vitro.">Antiepileptic drugs abolish ictal but not interictal epileptiform discharges in vitro.</a> Epilepsia. 51 (3), 423-431 (2010).</li><li>Stenkamp, K., 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=Enhanced+temporal+stability+of+cholinergic+hippocampal+gamma+oscillations+following+respiratory+alkalosis+in+vitro.">Enhanced temporal stability of cholinergic hippocampal gamma oscillations following respiratory alkalosis in vitro.</a> J. Neurophysiol. 85 (5), 2063-2069 (2001).</li></ol>

A robust method to generate CA1 &#947; oscillations in acute brain slices is described. The oscillations generated arise from a local circuit enabling a better opportunity for controlling and understanding the neurophysiological basis of network oscillations12. AMPA receptors, GABAA receptors, Ih and T-type Ca2+ channels are all required for &#947; oscillations in this model. While the local CA1 oscillations described here can be robustly generated this is dependent on ensuring...

Brain network oscillations occur within distinct frequency bands that correlate to behavioral states. In rodents, hippocampal &#952; oscillations (5 - 10 Hz) are observed during exploratory behaviors1,2, while &#947; oscillations (20 - 80 Hz) associate with various cognitive processes, including perception and attention3,4. Synchronous &#947; network activity is also implicated in the pathology of disorders such as epilepsy and schizophrenia5,6. For example, &#947; oscillations are thought to correspond to areas of cortical epileptic foci5,7,8 and could be used as markers of pharmacosensitivity or resistance, two important areas of investigation in epilepsy research9.
The hippocampal brain slice is a model that has been widely used to investigate network activity10-12. Various protocols have been developed to generate &#947; oscillations in brain slices that typically involve pharmacological modulation such as low Mg2+, 4-aminopyridine (4AP), bicuculline, and kainic acid12-17. Shortcomings of pharmacologically triggered oscillations are that they occur randomly after drug application and are not reliably generated or stable over time. Electrically triggered &#947; oscillations overcome many of these problems and also have the advantage of being temporally locked to the stimulating event allowing for episodic recording and analysis. Here a protocol is described for generating CA1 &#947; oscillations by delivering a tetanic stimulation to the stratum oriens in the hippocampal slice.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>4-(N-Ethyl-N-phenylamino)-1,2- dimethyl-6-(methylamino) pyrimidinium chloride (ZD7288)</td>
			<td>Sigma-Aldrich</td>
			<td>Z3777</td>
			<td></td>
		</tr>
		<tr>
			<td>Biuculline</td>
			<td>Sigma-Aldrich</td>
			<td>14340</td>
			<td></td>
		</tr>
		<tr>
			<td>6-cyano-7-nitroquinoxa- line-2,3-dione (CNQX)</td>
			<td>Sigma-Aldrich</td>
			<td>C127</td>
			<td></td>
		</tr>
		<tr>
			<td>Nickel</td>
			<td>Sigma-Aldrich</td>
			<td>266965</td>
			<td></td>
		</tr>
		<tr>
			<td>Carbamazepine</td>
			<td>Sigma-Aldrich</td>
			<td>C4024</td>
			<td></td>
		</tr>
		<tr>
			<td>(2R)-amino-5-phosphonopentano-ate (APV)</td>
			<td>Tocris Bioscience</td>
			<td>0105</td>
			<td></td>
		</tr>
		<tr>
			<td>Retigabine</td>
			<td>ChemPacific</td>
			<td>150812-12-7</td>
			<td></td>
		</tr>
		<tr>
			<td>Choline-Cl</td>
			<td>Sigma Aldrich</td>
			<td>C1879-5KG</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma Aldrich</td>
			<td>P9333-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>NaH2PO4</td>
			<td>Sigma Aldrich</td>
			<td>S9638-250G</td>
			<td></td>
		</tr>
		<tr>
			<td>NaHCO3</td>
			<td>Sigma Aldrich</td>
			<td>S6297-250G</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma Aldrich</td>
			<td>S7653-5KG</td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma Aldrich</td>
			<td>G8270-1KG</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2.2H2O</td>
			<td>Sigma Aldrich</td>
			<td>223506-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2.6H2O</td>
			<td>Sigma Aldrich</td>
			<td>M2670-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Electrode glass</td>
			<td>Harvard Apparatus&#160;</td>
			<td>GC150F-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Concentric bipolar stimulating metal electrode&#160;</td>
			<td>FHC</td>
			<td>CBBPF75</td>
			<td></td>
		</tr>
		<tr>
			<td>Digital Isolator</td>
			<td>Getting Instruments</td>
			<td>Model BJN8-9V1&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Model 1800 amplifier</td>
			<td>A-M systems</td>
			<td>Model 1800 amplifier</td>
			<td></td>
		</tr>
		<tr>
			<td>Digitizer</td>
			<td>National Intruments</td>
			<td>NI USB-6211</td>
			<td></td>
		</tr>
		<tr>
			<td>Vibrotome</td>
			<td>Leica</td>
			<td>VT1200s</td>
			<td></td>
		</tr>
	</tbody>
</table>

generation of local ca1 &#947; oscillations by tetanic stimulation

Neuronal network oscillations are important features of brain activity in health and disease and can be modulated by a range of clinically used drugs. A protocol is provided to generate a model for studying CA1 &#947; oscillations (20 - 80 Hz). These &#947; oscillations are stable for at least 30 min&#160;and depend upon excitatory and inhibitory synaptic activity in addition to activation of pacemaker currents. Tetanically stimulated oscillations have a number of reproducible and easily quantifiable characteristics including spike count, oscillation duration, latency and frequency that report upon the network state. The advantages of the electrically stimulated oscillations include stability, reproducibility and episodic acquisition enabling robust characterization of network function. This model of CA1 &#947; oscillations can be used to study cellular mechanisms and to systematically investigate how neuronal network activity is altered in disease and by drugs. Disease state pharmacology can be readily incorporated by the use of brain slices from genetically modified or interventional animal models to enable selection of drugs that specifically target disease mechanisms.

Tetanic stimulation of the stratum oriens generated robust and reproducible &#947; oscillations (35.4 &#177; 2.2&#160;Hz), see Figure 3B. To demonstrate that the oscillations were generated within the local CA1 network the inputs from CA3 were severed by cutting the slice in the CA2 region using a bent 32&#160;G needle. The oscillation properties in the cut slices did not differ from the uncut slices (p = 0.85; cut slices 6.16 &#177; 1.1 spikes, n = 6; uncut slices 5.89 &#177; 0.8 spikes, n = 6), indicat...

Watch this Scientific Journal Video about Generation of Local CA1 Î³ Oscillations by Tetanic Stimulation at JoVE.com

Generation of Local CA1 &#947; Oscillations by Tetanic Stimulation

Oscillations are fundamental network properties and are modulated by disease and drugs. Studying brain-slice oscillations allows characterization of isolated networks under controlled conditions. Protocols are provided for the preparation of acute brain slices for evoking CA1 &#947; oscillations.

Neuronal network oscillations are important features of brain activity in health and disease and can be modulated by a range of clinically used drugs. A ...

generation-of-local-ca1-oscillations-by-tetanic-stimulation

Research

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Neuroscience

A Novel Approach for Documenting Phosphenes Induced by Transcranial Magnetic Stimulation

Stimulation of the human visual cortex produces a transient perception of light, known as a phosphene. Phosphenes are induced by invasive electrical stimulation of the occipital cortex, but also by non-invasive Transcranial Magnetic Stimulation (TMS)1 of the same cortical regions. The intensity at which a phosphene is induced (phosphene threshold) is a well established measure of visual cortical excitability and is used to study cortico-cortical interactions, functional organization 2, susceptibility to pathology 3,4 and visual processing 5-7. Phosphenes are typically defined by three characteristics: they are observed in the visual hemifield contralateral to stimulation; they are induced when the subject s eyes are open or closed, and their spatial location changes with the direction of gaze 2. Various methods have been used to document phosphenes, but a standardized methodology is lacking. We demonstrate a reliable procedure to obtain phosphene threshold values and introduce a novel system for the documentation and analysis of phosphenes. We developed the Laser Tracking and Painting system (LTaP), a low cost, easily built and operated system that records the location and size of perceived phosphenes in real-time. The LTaP system provides a stable and customizable environment for quantification and analysis of phosphenes.

Phosphenes are transient percepts of light that can be induced by applying Transcranial Magnetic Stimulation (TMS) to visually sensitive regions of cortex. We demonstrate a standard protocol for determining the phosphene threshold value and introduce a novel method for quantifying and analyzing perceived phosphenes.

Stimulation of the human visual cortex produces a transient perception of light, known as a phosphene. Phosphenes are induced by invasive electrical ...

Combining Transcranial Magnetic Stimulation and fMRI to Examine the Default Mode Network

The default mode network is a group of brain regions that are active when an individual is not focused on the outside world and the brain is at "wakeful rest."1,2,3 It is thought the default mode network corresponds to self-referential or "internal mentation".2,3
It has been hypothesized that, in humans, activity within the default mode network is correlated with certain pathologies (for instance, hyper-activation has been linked to schizophrenia 4,5,6 and autism spectrum disorders 7 whilst hypo-activation of the network has been linked to Alzheimer's and other neurodegenerative diseases 8). As such, noninvasive modulation of this network may represent a potential therapeutic intervention for a number of neurological and psychiatric pathologies linked to abnormal network activation. One possible tool to effect this modulation is Transcranial Magnetic Stimulation: a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability (either increasing or decreasing it) via the application of localized magnetic field pulses.9
In order to explore the default mode network's propensity towards and tolerance of modulation, we will be combining TMS (to the left inferior parietal lobe) with functional magnetic resonance imaging (fMRI). Through this article, we will examine the protocol and considerations necessary to successfully combine these two neuroscientific tools.

In this article, we examine the methodology and considerations relevant to the combination of TMS and fMRI to examine the effects of brain stimulation on the default network.

The default mode network is a group of brain regions that are active when an individual is not focused on the outside world and the brain is at "wakeful ...

TMS: Using the Theta-Burst Protocol to Explore Mechanism of Plasticity in Individuals with Fragile X Syndrome and Autism

Fragile X Syndrome (FXS), also known as Martin-Bell Syndrome, is a genetic abnormality found on the X chromosome.1,2 Individuals suffering from FXS display abnormalities in the expression of FMR1 - a protein required for typical, healthy neural development.3 Recent data has suggested that the loss of this protein can cause the cortex to be hyperexcitable thereby affecting overall patterns of neural plasticity.4,5
In addition, Fragile X shows a strong comorbidity with autism: in fact, 30% of children with FXS are diagnosed with autism, and 2 - 5% of autistic children suffer from FXS.6
Transcranial Magnetic Stimulation (a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability via the application of localized magnetic field pulses 7,8) represents a unique method of exploring plasticity and the manifestations of FXS within affected individuals. More specifically, Theta-Burst Stimulation (TBS), a specific stimulatory protocol shown to modulate cortical plasticity for a duration up to 30 minutes after stimulation cessation in healthy populations, has already proven an efficacious tool in the exploration of abnormal plasticity.9,10 
Recent studies have shown the effects of TBS last considerably longer in individuals on the autistic spectrum - up to 90 minutes.11 This extended effect-duration suggests an underlying abnormality in the brain's natural plasticity state in autistic individuals - similar to the hyperexcitability induced by Fragile X Syndrome.
In this experiment, utilizing single-pulse motor-evoked potentials (MEPs) as our benchmark, we will explore the effects of both intermittent and continuous TBS on cortical plasticity in individuals suffering from FXS and individuals on the Autistic Spectrum.

In this article, we examine the effects of Theta-Burst TMS stimulation on cortical plasticity in individuals suffering from Fragile X syndrome and individuals on the autistic spectrum.

Fragile X Syndrome (FXS), also known as Martin-Bell Syndrome, is a genetic abnormality found on the X chromosome.1,2 Individuals suffering from FXS ...

The NeuroStar TMS Device: Conducting the FDA Approved Protocol for Treatment of Depression

The Neuronetics NeuroStar Transcranial Magnetic Stimulation (TMS) System is a class II medical device that produces brief duration, pulsed magnetic fields. These rapidly alternating fields induce electrical currents within localized, targeted regions of the cortex which are associated with various physiological and functional brain changes.1,2,3
In 2007, O'Reardon et al., utilizing the NeuroStar device, published the results of an industry-sponsored, multisite, randomized, sham-stimulation controlled clinical trial in which 301 patients with major depression, who had previously failed to respond to at least one adequate antidepressant treatment trial, underwent either active or sham TMS over the left dorsolateral prefrontal cortex (DLPFC). The patients, who were medication-free at the time of the study, received TMS five times per week over 4-6 weeks.4
The results demonstrated that a sub-population of patients (those who were relatively less resistant to medication, having failed not more than two good pharmacologic trials) showed a statistically significant improvement on the Montgomery-Asberg Depression Scale (MADRS), the Hamilton Depression Rating Scale (HAMD), and various other outcome measures. In October 2008, supported by these and other similar results5,6,7, Neuronetics obtained the first and only Food and Drug Administration (FDA) approval for the clinical treatment of a specific form of medication-refractory depression using a TMS Therapy device (FDA approval K061053).
In this paper, we will explore the specified FDA approved NeuroStar depression treatment protocol (to be administered only under prescription and by a licensed medical profession in either an in- or outpatient setting).

In this article, we examine the methodology and considerations relevant to the FDA approved depression treatment protocol using the Neuronetics NeuroStar TMS device.

The Neuronetics NeuroStar Transcranial Magnetic Stimulation (TMS) System is a class II medical device that produces brief duration, pulsed magnetic ...

Effects of Transcranial Alternating Current Stimulation on the Primary Motor Cortex by Online Combined Approach with Transcranial Magnetic Stimulation

Transcranial Alternating Current Stimulation (tACS) is a neuromodulatory technique able to act through sinusoidal electrical waveforms in a specific frequency and in turn modulate ongoing cortical oscillatory activity. This neurotool allows the establishment of a causal link between endogenous oscillatory activity and behavior. Most of the tACS studies have shown online effects of tACS. However, little is known about the underlying action mechanisms of this technique because of the AC-induced artifacts on Electroencephalography (EEG) signals. Here we show a unique approach to investigate online physiological frequency-specific effects of tACS of the primary motor cortex (M1) by using single pulse Transcranial Magnetic Stimulation (TMS) to probe cortical excitability changes. In our setup, the TMS coil is placed over the tACS electrode while Motor Evoked Potentials (MEPs) are collected to test the effects of the ongoing M1-tACS. So far, this approach has mainly been used to study the visual and motor systems. However, the current tACS-TMS setup can pave the way for future investigations of cognitive functions. Therefore, we provide a step-by-step manual and video guidelines for the procedure.

Transcranial Alternating Current Stimulation (tACS) allows the modulation of cortical excitability in a frequency-specific fashion. Here we show a unique approach which combines online tACS with single pulse Transcranial Magnetic Stimulation (TMS) in order to "probe" cortical excitability by means of Motor Evoked Potentials.

Transcranial Alternating Current Stimulation (tACS) is a neuromodulatory technique able to act through sinusoidal electrical waveforms in a specific ...

Ocular Kinematics Measured by In Vitro Stimulation of the Cranial Nerves in the Turtle

After animals are euthanized, their tissues begin to die. Turtles offer an advantage because of a longer survival time of their tissues, especially when compared to warm-blooded vertebrates. Because of this, in vitro experiments in turtles can be performed for extended periods of time to investigate the neural signals and control of their target actions. Using an isolated head preparation, we measured the kinematics of eye movements in turtles, and their modulation by electrical signals carried by cranial nerves. After the brain was removed from the skull, leaving the cranial nerves intact, the dissected head was placed in a gimbal to calibrate eye movements. Glass electrodes were attached to cranial nerves (oculomotor, trochlear, and abducens) and stimulated with currents to evoke eye movements. We monitored eye movements with an infrared video tracking system and quantified rotations of the eyes. Current pulses with a range of amplitudes, frequencies, and train durations were used to observe effects on responses. Because the preparation is separated from the brain, the efferent pathway going to muscle targets can be examined in isolation to investigate neural signaling in the absence of centrally processed sensory information.

Ocular Kinematics Measured by In Vitro Stimulation of the Cranial Nerves in the Turtle

This protocol describes how to use an in vitro isolated turtle head preparation to measure the kinematics of their eye movements. After removal of the brain from the cranium, cranial nerves can be stimulated with currents to quantify rotations of the eye and changes in pupil sizes.

After animals are euthanized, their tissues begin to die. Turtles offer an advantage because of a longer survival time of their tissues, especially when ...

Optogenetic Entrainment of Hippocampal Theta Oscillations in Behaving Mice

Extensive data on relationships of neural network oscillations to behavior and organization of neuronal discharge across brain regions call for new tools to selectively manipulate brain rhythms. Here we describe an approach combining projection-specific optogenetics with extracellular electrophysiology for high-fidelity control of hippocampal theta oscillations (5-10 Hz) in behaving mice. The specificity of the optogenetic entrainment is achieved by targeting channelrhodopsin-2 (ChR2) to the GABAergic population of medial septal cells, crucially involved in the generation of hippocampal theta oscillations, and a local synchronized activation of a subset of inhibitory septal afferents in the hippocampus. The efficacy of the optogenetic rhythm control is verified by a simultaneous monitoring of the local field potential (LFP) across lamina of the CA1 area and/or of neuronal discharge. Using this readily implementable preparation we show efficacy of various optogenetic stimulation protocols for induction of theta oscillations and for the manipulation of their frequency and regularity. Finally, a combination of the theta rhythm control with projection-specific inhibition addresses the readout of particular aspects of the hippocampal synchronization by efferent regions.

We describe the use of optogenetics and electrophysiological recordings for selective manipulations of hippocampal theta oscillations (5-10 Hz) in behaving mice. The efficacy of the rhythm entrainment is monitored using local field potential. A combination of opto- and pharmacogenetic inhibition addresses the efferent readout of hippocampal synchronization.

Extensive data on relationships of neural network oscillations to behavior and organization of neuronal discharge across brain regions call for new tools ...

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 ...

Dissection of Local Ca2+ Signals in Cultured Cells by Membrane-targeted Ca2+ Indicators

Calcium ion (Ca2+) is a universal intracellular messenger molecule that drives multiple signaling pathways, leading to diverse biological outputs. The coordination of two Ca2+ signal sources&#8212;&#8220;Ca2+ influx&#8221; from outside the cell and &#8220;Ca2+ release&#8221; from the intracellular Ca2+ store endoplasmic reticulum (ER)&#8212;is considered to underlie the diverse spatio-temporal patterns of Ca2+ signals that cause multiple biological functions in cells. The purpose of this protocol is to describe a new Ca2+ imaging method that enables monitoring of the very moment of &#8220;Ca2+ influx&#8221; and &#8220;Ca2+ release&#8221;. OER-GCaMP6f is a genetically encoded Ca2+ indicator (GECI) comprising GCaMP6f, which is targeted to the ER outer membrane. OER-GCaMP6f can monitor Ca2+ release at a higher temporal resolution than conventional GCaMP6f. Combined with plasma membrane-targeted GECIs, the spatio-temporal Ca2+ signal pattern can be described at a subcellular resolution. The subcellular-targeted Ca2+ indicators described here are, in principle, available for all cell types, even for the in vivo imaging of Caenorhabditis elegans neurons. In this protocol, we introduce Ca2+ imaging in cells from cell lines, neurons, and glial cells in dissociated primary cultures, and describe the preparation of frozen stock of rat cortical neurons.

Dissection of Local Ca2+ Signals in Cultured Cells by Membrane-targeted Ca2+ Indicators

Here we present a protocol for Ca2+ imaging in neurons and glial cells, which enables the dissection of Ca2+ signals at subcellular resolution. This process is applicable to all cell types that allow the expression of genetically encoded Ca2+ indicators.

Calcium ion (Ca2+) is a universal intracellular messenger molecule that drives multiple signaling pathways, leading to diverse biological outputs. The ...

Investigating Long-term Synaptic Plasticity in Interlamellar Hippocampus CA1 by Electrophysiological Field Recording

The study of synaptic plasticity in the hippocampus has focused on the use of the CA3-CA1 lamellar network. Less attention has been given to the longitudinal interlamellar CA1-CA1 network. Recently however, an associational connection between CA1-CA1 pyramidal neurons has been shown. Therefore, there is the need to investigate whether the longitudinal interlamellar CA1-CA1 network of the hippocampus supports synaptic plasticity.
We designed a protocol to investigate the presence or absence of long-term synaptic plasticity in the interlamellar hippocampal CA1 network using electrophysiological field recordings both in vivo and in vitro. For in vivo extracellular field recordings, the recording and stimulation electrodes were placed in a septal-temporal axis of the dorsal hippocampus at a longitudinal angle, to evoke field excitatory postsynaptic potentials. For in vitro extracellular field recordings, hippocampal longitudinal slices were cut parallel to the septal-temporal plane. Recording and stimulation electrodes were placed in the stratum oriens (S.O) and the stratum radiatum (S.R) of the hippocampus along the longitudinal axis. This enabled us to investigate the directional and layer specificity of evoked excitatory postsynaptic potentials. Already established protocols were used to induce long-term potentiation (LTP) and long-term depression (LTD) both in vivo and in vitro. Our results demonstrated that the longitudinal interlamellar CA1 network supports N-methyl-D-aspartate (NMDA) receptor-dependent long-term potentiation (LTP) with no directional or layer specificity. The interlamellar network, however, in contrast to the transverse lamellar network, did not present with any significant long-term depression (LTD).

We used recording and stimulation electrodes in longitudinal hippocampal brain slices and longitudinally positioned recording and stimulation electrodes in the dorsal hippocampus in vivo to evoke extracellular postsynaptic potentials and demonstrate long-term synaptic plasticity along the longitudinal interlamellar CA1.