Name: optogenetic manipulation of neural circuits during monitoring sleep/wakefulness states in mice
Uploaded: 2019-06-19T12:30:00
Description: Watch this Scientific Journal Video about Optogenetic Manipulation of Neural Circuits During Monitoring Sleep/wakefulness States in Mice at JoVE.com

This study was supported by the Merck Investigator Studies Program (#54843), a KAKENHI Grant-in-Aid for Scientific Research on Innovative Areas, &#34;WillDynamics&#34; (16H06401) (T.S.), and a KAKENHI Grant-in-Aid for Exploratory Research on Innovative Areas (T.S.) (18H02595).

All experiments here were approved by the Animal Experiment and Use Committee of the University of Tsukuba, complying with NIH guidelines.
1. Animal Surgery, Virus Injection, Electrode for EEG/EMG, and Optical Fiber Implantation
CAUTION: Appropriate protection and handling techniques should be selected based on the biosafety level of the virus to be used. AAV should be used in an isolated P1A graded room for injection, and the tube carrying AA...

<ol>
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We here presented a method to evaluate the effect of optogenetic stimulation of neurons with particular chemical identities on state transitions of sleep/wakefulness and gave an example of manipulation of GABABNST neurons. Our data showed that optogenetic excitation of GABABNST neurons results in immediate transition from NREM sleep to wakefulness.
Various experimental designs are available because of the development of numerous types of optogenetic tools. It is possible ...

Sleep is essential for optimal cognitive function.Recent findings also suggest that disturbances in sleep are associated with a wide range of diseases1,2,3. Although the functions of sleep are as yet largely unresolved, substantial progress has been made recently in understanding the neural circuits and mechanisms that control sleep/wakefulness states4. In mammals, there are three states of vigilance: wakefulness, non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep. Wakefulness is characterized by fast EEG oscillations (5-12 Hz) of low amplitude with purposeful and sustained motor activity. NREM sleep is defined by slow oscillations (1-4 Hz) of high amplitude (delta waves), with lack of consciousness and purposeful motor activity. REM sleep is characterized by relatively fast oscillations (6-12 Hz) of low amplitude and almost complete bilateral muscle atonia5.
Borbely proposed a theory of sleep-wakefulness regulation known as the two process model6,7. A homeostatic process, also referred to as process S, represents sleep pressure that accumulates during wakefulness and dissipates during sleep. Another process, referred to as process C, is a circadian process, which explains why vigilance levels fluctuate in the 24 h cycle. In addition to these two processes, allostatic factors are also important for regulation of sleep/wakefulness8,9. Allostatic factors include nutritional states and emotion. Fear and anxiety are usually accompanied by an increase in arousal along with autonomic and neuroendocrine responses10,11,12. The limbic system is believed to play a role in regulation of fear and anxiety, and mechanisms underlying autonomic and neuroendocrine responses have been studied extensively, but the pathway by which the limbic system influences sleep/wakefulness states has not yet been revealed. A large number of recent studies using opto- and pharmacogenetics have suggested that neurons and neuronal circuits that regulate sleep/wakefulness states are distributed throughout the brain, including the cortices, basal forebrain, thalamus, hypothalamus, and brain stem. In particular, recent advances in optogenetics have allowed us to stimulate or inhibit specific neural circuits in vivo with high spatial and temporal resolutions. This technique will allow progress in our understanding of the neural substrates of sleep and wakefulness, and how sleep/wakefulness states are regulated by circadian processes, sleep pressure, and allostatic factors, including emotion. This paper aims to introduce how to use optogenetic manipulation combined with sleep/wake recording, which could have the potential to update our understanding of the connectomes and mechanisms in the brain that play a role in the regulation of NREM sleep, REM sleep, and wakefulness. Understanding of this mechanism by which the limbic system regulates sleep/wakefulness states is of paramount importance to health, because insomnia is usually associated with anxiety or fear of being unable to sleep (somniphobia).
The BNST is thought to play an essential role in anxiety and fear. GAD 67-expressing GABAergic neurons are a major population of the BNST12,13. We examined the effect of optogenetic manipulation of these neurons (GABABNST) on sleep/wakefulness states. One of the greatest advances in neuroscience in recent years has been methods that enable manipulation of neurons with particular chemical identities in vivo, with high spatial and temporal resolutions. Optogenetics is highly useful for demonstrating causal links between neural activity and specific behavioral responses14. We describe optogenetics as a method to examine the functional connectivity of defined neural circuits in the regulation of sleep/wakefulness states. By utilizing this technique, great progress has been achieved in understanding the neuronal circuits that regulate sleep/wakefulness states15,16,17,18,19. In many cases, opsins are specifically introduced in&#160;neurons with particular chemical identities in selective brain regions by a combination of Cre-driver mice and Cre-inducible AAV-mediated gene transfer.&#160;Further, focal expression of photo-sensitive opsins such as channelrhodopsin 2 (ChR2)20 or archaerhodopsin (ArchT)21 combined with a Cre-loxP or Flp-FRT system allows us to manipulate a selective neuronal population and specific neural pathway22.
We describe here experiments on GABAergic neurons in the BNST as an example. To express opsins in a designated neuronal population, appropriate Cre driver mice and Cre-dependent virus vectors are most frequently used. Transgenic or knock-in lines in which opsins are expressed in particular neuronal populations are also useful. In the following experiments, we used GAD67-Cre knock-in mice23 in which only GABAergic neurons express Cre recombinase with a C57BL/6J genetic background, and an AAV vector which contains ChR2 (hChR2 H134R) fused with EYFP or EYFP as a control with a &#34;FLEx (Flip-excision) switch&#34;24. The procedure specifically describes optogenetic excitation of GABAergic neurons in the BNST during monitoring of sleep/wakefulness states25.

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			<td height="19" style="height:19px;width:375px;">1x1 Fiber-optic Rotary Joints</td>
			<td style="width:191px;">Doric</td>
			<td style="width:177px;">FRJ 1x1 FC-FC</td>
			<td style="width:437px;">for optogenetics</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">6-pin header</td>
			<td style="width:191px;">KEL corporation</td>
			<td style="width:177px;">DSP02-006-431G</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">6-pin socket</td>
			<td style="width:191px;">Hirose</td>
			<td style="width:177px;">21602X3GSE</td>
			<td></td>
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		<tr height="19">
			<td height="19" style="height:19px;width:375px;">A/D converter</td>
			<td style="width:191px;">Nippon koden</td>
			<td style="width:177px;">N/A</td>
			<td>Analog to digital converter</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:375px;">AAV10-EF1a-DIO-ChR2-EYFP</td>
			<td style="width:191px;"></td>
			<td style="width:177px;"></td>
			<td>3.70&#215;1013(genomic copies/ml)</td>
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		<tr height="22">
			<td height="22" style="height:22px;width:375px;">AAV10-EF1a-DIO-EYFP</td>
			<td style="width:191px;"></td>
			<td style="width:177px;"></td>
			<td>5.82&#215;1013(genomic copies/ml)</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Ampicillin</td>
			<td style="width:191px;">Fuji film</td>
			<td style="width:177px;">014-23302</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Amplifier</td>
			<td style="width:191px;">Nippon koden</td>
			<td style="width:177px;">N/A</td>
			<td>for EEG/EMG recording</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Anesthetic vaporizer</td>
			<td style="width:191px;">Muromachi</td>
			<td style="width:177px;">MK-AT-210D</td>
			<td></td>
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		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Automatic injecter</td>
			<td style="width:191px;">KD scientific</td>
			<td style="width:177px;">780311</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Carbide cutter</td>
			<td style="width:191px;">Minitor</td>
			<td style="width:177px;">B1055</td>
			<td>&#966;0.7 mm. Reffered as dental drill, used with high speed rotary micromotor&#160;</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Cyanoacrylate adhesion&#160; (Aron alpha A) and acceleration</td>
			<td style="width:191px;">Konishi</td>
			<td>#30533</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Dental curing light</td>
			<td style="width:191px;">3M</td>
			<td style="width:177px;">Elipar S10</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Epoxy adhesive</td>
			<td style="width:191px;">Konishi</td>
			<td>#04888</td>
			<td>insulation around the solder of 6-pin and shielded cable</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Fiber optic patch cord (branching)</td>
			<td style="width:191px;">Doric</td>
			<td>BFP(#)_50/125/900-0.22</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Gad67-Cre mice</td>
			<td style="width:191px;">provided by Dr. Kenji Sakimura</td>
			<td></td>
			<td>Cre recombinase gene is knocked-in in the Gad67 allele</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Hamilton syringe</td>
			<td style="width:191px;">Hamilton</td>
			<td>65461-01</td>
			<td></td>
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		<tr height="19">
			<td height="19" style="height:19px;width:375px;">High speed rotary micromotor kit</td>
			<td style="width:191px;">FOREDOM</td>
			<td style="width:177px;">K.1070</td>
			<td>Used with carbide cutter</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Interconnecting sleeve</td>
			<td style="width:191px;">Thorlab</td>
			<td>ADAF1</td>
			<td>&#966;2.5 mm Ceramic&#160;</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Isoflurane</td>
			<td style="width:191px;">Pfizer</td>
			<td>871119</td>
			<td></td>
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			<td height="19" style="height:19px;width:375px;">Laser&#160;&#160;</td>
			<td style="width:191px;">Rapp OptoElectronic</td>
			<td style="width:177px;">N/A</td>
			<td>473nm wave length</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Laser intesity checker</td>
			<td style="width:191px;">COHERENT</td>
			<td style="width:177px;">1098293</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Laser stimulator</td>
			<td style="width:191px;">Bio research center</td>
			<td style="width:177px;">STO2</td>
			<td>reffered as pulse generator in text</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Optic fiber with ferrule&#160;</td>
			<td style="width:191px;">Thorlab</td>
			<td>FP200URT-CANNULA-SP-JP</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">pAAV2-rh10</td>
			<td style="width:191px;">provided by PennVector Core</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">pAAV-EF1a-DIO-EYFP-WPRE-HGHpA</td>
			<td style="width:191px;">Addgene</td>
			<td>plasimid # 20296</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">pAAV-EF1a-DIO-hChR2(H134R)-EYFP-WPRE-HGHpA</td>
			<td style="width:191px;">provided by Dr. Karl Deisseroth</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Patch cord</td>
			<td style="width:191px;">Doric</td>
			<td>D202-9089-0.4</td>
			<td>0.4m length, laser conductor between laser and rotary joint</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">pHelper</td>
			<td style="width:191px;">Stratagene</td>
			<td style="width:177px;"></td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Photocurable dental cement</td>
			<td style="width:191px;">3M</td>
			<td style="width:177px;">56846</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Serafin clamp</td>
			<td style="width:191px;">Stoelting</td>
			<td style="width:177px;">52120-43P</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Shielded cable</td>
			<td style="width:191px;">mogami</td>
			<td style="width:177px;">W2780</td>
			<td>Soldering to 6-pin socket for EEG/EMG recording</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Sleep recording chamber</td>
			<td style="width:191px;">N/A</td>
			<td style="width:177px;">N/A</td>
			<td style="width:437px;">Custum-made (21cm&#215; 29cm &#215; 19cm) with water tank holder</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Sleep sign software</td>
			<td style="width:191px;">KISSEI COMTEC</td>
			<td style="width:177px;">N/A</td>
			<td>for EEG/EMG analysis</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Slip ring</td>
			<td style="width:191px;">neuroscience,inc</td>
			<td style="width:177px;">N/A</td>
			<td>for EEG/EMG analysis</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Stainless screw</td>
			<td style="width:191px;">Yamazaki</td>
			<td style="width:177px;">N/A</td>
			<td>&#966;1.0 x 2.0</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Stainless wire</td>
			<td style="width:191px;">Cooner wire</td>
			<td style="width:177px;">AS633</td>
			<td>&#160;0.0130 inch diameter</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Stereotaxic frame with digital console</td>
			<td style="width:191px;">Koph</td>
			<td style="width:177px;">N/A</td>
			<td>Model 940</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Syringe needle</td>
			<td style="width:191px;">Hamilton</td>
			<td>7803-05</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:375px;">Vital recorder software</td>
			<td style="width:191px;">KISSEI COMTEC</td>
			<td style="width:177px;">N/A</td>
			<td>for EEG/EMG recording</td>
		</tr>
	</tbody>
</table>

optogenetic manipulation of neural circuits during monitoring sleep/wakefulness states in mice

In recent years, optogenetics has been widely used in many fields of neuroscientific research. In many cases, an opsin, such as channel rhodopsin 2 (ChR2), is expressed by a virus vector in a particular type of neuronal cells in various Cre-driver mice. Activation of these opsins is triggered by application of light pulses which are delivered by laser or LED through optic cables, and the effect of activation is observed with very high time resolution. Experimenters are able to acutely stimulate neurons while monitoring behavior or another physiological outcome in mice. Optogenetics can enable useful strategies to evaluate function of neuronal circuits in the regulation of sleep/wakefulness states in mice. Here we describe a technique for examining the effect of optogenetic manipulation of neurons with a specific chemical identity during electroencephalogram (EEG) and electromyogram (EMG) monitoring to evaluate the sleep stage of mice. As an example, we describe manipulation of GABAergic neurons in the bed nucleus of the stria terminalis (BNST). Acute optogenetic excitation of these neurons triggers a rapid transition to wakefulness when applied during NREM sleep. Optogenetic manipulation along with EEG/EMG recording can be applied to decipher the neuronal circuits that regulate sleep/wakefulness states.

The present study showed the effect of optogenetic excitation of GABABNST neurons on sleep state transition. ChR2-EYFP was focally expressed in GABA neurons in the BNST. An in situ hybridization histochemical study showed that ChR2-EYFP was colocalized in neurons expressing GAD 67 mRNA signals, indicating that these are GABAergic neurons. Immunohistochemical slice samples confirmed the position of the optic fiber, whose tip was just above the BNST25....

Watch this Scientific Journal Video about Optogenetic Manipulation of Neural Circuits During Monitoring Sleep/wakefulness States in Mice at JoVE.com

Optogenetic Manipulation of Neural Circuits During Monitoring Sleep/wakefulness States in Mice

Here, we describe methods of optogenetic manipulation of particular types of neurons during monitoring of sleep/wakefulness states in mice, presenting our recent work on the bed nucleus of the stria terminalis as an example.

In recent years, optogenetics has been widely used in many fields of neuroscientific research. In many cases, an opsin, such as channel rhodopsin 2 ...

This procedure can help us identify the function of specific neuro circuit that are involved in the sleep wakefulness regulation with less invasive manipulation and high temporal resolution. This method allows us the monitoring surface EEG in real time in conjunction with manipulation of a specific neuro circuit to examine the causal relationship between circuits and sleep wakefulness states. Shota Kodani is going to demonstrate the procedure.After confirming a lack of response to toe pinch, apply ointment to the animal's eyes and use the ear bars and nose pin to the stereotactic apparatus to stabilize the head of the anesthetized mouse on an absorbent pad. When the head is fixed in position, make a mid-sagittal incision in the scalp to confirm that the intersection between the sutura sagittalis and sutura coronalis or sutura lambdoidea are in a horizontal line at the same level. To avoid a positioning gap, adjust the nose pinch and ear bars as necessary.Then using serafin clamps to the hold the skin open disinfect the exposed surface of the skull to enable the cranial sutures to be visualized more clearly. To inject the adeno-associated virus vector, load an ethanol sterilized 10 milliliter syringe with two microliters of mineral oil, followed by the experimental volume of virus to be injected. Use the microinjection pump to adjust the tip of the microinjection needle onto the bregma and note the coordinates as the point of origin.Then move the tip to the designated injection site and place the tip of the needle onto the position. Mark the skull at the injection site and use a dental drill equipped with a 0.7 millimeter carbide cutter to drill an approximately two millimeter diameter hole into the skull. After removing blood from around the hole with a cotton swab, slowly move the needle to the bed nucleus of the stria terminalis or BSNT and slowly inject the designated volume of virus solution.Then leave the needle in place for five minutes to allow the solution to sufficiently infiltrate the BNST tissue before carefully retracting the needle. For electroencephalogram, or EEG, and electromyogram, or EMG, electrode implantation, first solder two stainless steel wires from which one millimeter of insulation has been stripped from both ends to the EMG electrodes and place the center of the electrodes onto the bregma. Then mark the position for each EEG electrode.To determine the position of the optical fiber implant, attach an optic fiber ferrule to the manipulator and rotate the manipulator arm to a plus or minus 30 degree angle against a horizontal line. Put the fiber tip on the bregma and record the coordinates. Move the tip to the targeted insertion line and mark the position on the skull and the position for the anchor screw next to the insertion site.Use the dental drill to drill the skull at each site and use the manipulator to gently insert the optic fiber until it reaches above the BNST. The ferrule should rest on the remaining cranium. Secure the fiber to the skull with an anchor screw, taking care not to break the dura or damage any tissue.Then cover the fiber and screw with photo-curable dental cement. Next, drill holes for EEG/EMG electrodes and insert the tip of the first electrode into one hole. Holding the implant with one hand, apply cyanoacrylate adhesive to the space between the skull and the electrode and insert the electrode the rest of the way, taking care not to damage any tissue.When all of the electrodes have been placed, cover the circumference of the electrodes and the optic fibers with additional cyanoacrylate adhesive and cyanoacrylate accelerant to avoid causing any interruption at the ferrule to optic cable and electrode to lead wire connecting zones. Now expose the neck muscles, and insert the wires for the EMG electrode under the muscle. Adjust the length of the EMG electrode so that it fits just under the nuchal muscles and fill the implants with more cyanoacrylate adhesive and accelerant.Then place the mouse on a heat pad with monitoring until full recompensy. For EEG/EMG monitoring during the photo-excitation of targeted neurons, first use a scalar to adjust the laser intensity and use a ferrule to tether the tip of the laser cable to an unused optic fiber. Confirm that there is no space at the junction between the fiber and the cable.After 20 minutes, emit the warmed up laser to the intensity checker and adjust the intensity to 10 milliwatts per millimeter squared. Set the light pulse duration to 10 milliseconds, the rest period to 40 milliseconds, the cycle to 20, and the repeat to 20. Change the laser mode to transistor logic and confirm that light pulses are emitted from the fiber controlled by the pattern regulator.Connect the implanted electrode and cable adapter, then cover the junction with light impermeable material to prevent laser leakage. And when the laser is ready, move the mice to the experimental chamber for EEG/EMG recording. To assess the latency to wakefulness from non rapid eye movement or rapid eye movement sleep, limit the recording time and optimized site gain time and let the mice move freely in the experimental chamber for at least one hour.During the experimental period, monitor the EEG and EMG signals in the same recording screen. Evaluate the mouse's state as wakefulness, non rapid eye movement sleep, or rapid eye movement sleep using the gain control for each wave for ease of distinguishing each state. For measurement of the non rapid eye movement sleep to wakefulness latency, observe stable non rapid eye movement sleep for 40 seconds, then turn on the pattern generator for photo stimulation and confirm laser emission to the implanted optic fibers.Then record the EEG/EMG signals until the sleep state changes to wakefulness. Here represented EEG/EMG traces before and after photo stimulation during non rapid eye movement sleep are shown. A high voltage and slow frequency EEG with no EMG signals, represents non rapid eye movement sleep.Photo stimulation triggered an acute transition to wakefulness about two seconds after stimulation in channelrhodopsin-2 expressing mice while control mice did not demonstrate this transition, suggesting that the excitation of BNST GABA neurons during non rapid eye movement sleep triggers a rapid induction of wakefulness. Conversely, photo stimulation during rapid eye movement sleep had no effect so a transition effect only emerged in non rapid eye movement sleep. It is important to take care to precise coordinations for the virus injection and optic fiber implantation steps.The EEG/EMG traces captured during the sleep analysis can be used to assess the consequences of the photo manipulation on the different vigilant states in mice. This technique will also help us identify other components and circuits involved in regulating the sleep wakefulness states. Use protective goggles to avoid laser damage to the eye and be sure to always autoclave sterilize the adeno-associated virus vector container after use.

optogenetic-manipulation-neural-circuits-during-monitoring

Research

JoVE Journal

Neuroscience

Extinction Training During the Reconsolidation Window Prevents Recovery of Fear

Fear is maladaptive when it persists long after circumstances have become safe. It is therefore crucial to develop an approach that persistently prevents the return of fear. Pavlovian fear-conditioning paradigms are commonly employed to create a controlled, novel fear association in the laboratory. After pairing an innocuous stimulus (conditioned stimulus, CS) with an aversive outcome (unconditioned stimulus, US) we can elicit a fear response (conditioned response, or CR) by presenting just the stimulus alone1,2 . Once fear is acquired, it can be diminished using extinction training, whereby the conditioned stimulus is repeatedly presented without the aversive outcome until fear is no longer expressed3. This inhibitory learning creates a new, safe representation for the CS, which competes for expression with the original fear memory4. Although extinction is effective at inhibiting fear, it is not permanent. Fear can spontaneously recover with the passage of time. Exposure to stress or returning to the context of initial learning can also cause fear to resurface3,4.
Our protocol addresses the transient nature of extinction by targeting the reconsolidation window to modify emotional memory in a more permanent manner. Ample evidence suggests that reactivating a consolidated memory returns it to a labile state, during which the memory is again susceptible to interference5-9. This window of opportunity appears to open shortly after reactivation and close approximately 6hrs later5,11,16, although this may vary depending on the strength and age of the memory15. By allowing new information to incorporate into the original memory trace, this memory may be updated as it reconsolidates10,11. Studies involving non-human animals have successfully blocked the expression of fear memory by introducing pharmacological manipulations within the reconsolidation window, however, most agents used are either toxic to humans or show equivocal effects when used in human studies12-14. Our protocol addresses these challenges by offering an effective, yet non-invasive, behavioral manipulation that is safe for humans.
By prompting fear memory retrieval prior to extinction, we essentially trigger the reconsolidation process, allowing new safety information (i.e., extinction) to be incorporated while the fear memory is still susceptible to interference. A recent study employing this behavioral manipulation in rats has successfully blocked fear memory using these temporal parameters11. Additional studies in humans have demonstrated that introducing new information after the retrieval of previously consolidated motor16, episodic17, or declarative18 memories leads to interference with the original memory trace14. We outline below a novel protocol used to block fear recovery in humans.

Conditioned fear can be diminished through an inhibitory process called extinction, but can resurface under conditions such as the passage of time or exposure to stress. Our protocol presents a novel way of preventing fear recovery by introducing extinction during the reconsolidation window (the re-storage phase of a reactivated memory).

Fear is maladaptive when it persists long after circumstances have become safe. It is therefore crucial to develop an approach that persistently prevents ...

Simultaneous Electroencephalography, Real-time Measurement of Lactate Concentration and Optogenetic Manipulation of Neuronal Activity in the Rodent Cerebral Cortex

Although the brain represents less than 5% of the body by mass, it utilizes approximately one quarter of the glucose used by the body at rest1. The function of non rapid eye movement sleep (NREMS), the largest portion of sleep by time, is uncertain. However, one salient feature of NREMS is a significant reduction in the rate of cerebral glucose utilization relative to wakefulness2-4. This and other findings have led to the widely held belief that sleep serves a function related to cerebral metabolism. Yet, the mechanisms underlying the reduction in cerebral glucose metabolism during NREMS remain to be elucidated.
	One phenomenon associated with NREMS that might impact cerebral metabolic rate is the occurrence of slow waves, oscillations at frequencies less than 4 Hz, in the electroencephalogram5,6. These slow waves detected at the level of the skull or cerebral cortical surface reflect the oscillations of underlying neurons between a depolarized/up state and a hyperpolarized/down state7. During the down state, cells do not undergo action potentials for intervals of up to several hundred milliseconds. Restoration of ionic concentration gradients subsequent to action potentials represents a significant metabolic load on the cell8; absence of action potentials during down states associated with NREMS may contribute to reduced metabolism relative to wake.
	Two technical challenges had to be addressed in order for this hypothetical relationship to be tested. First, it was necessary to measure cerebral glycolytic metabolism with a temporal resolution reflective of the dynamics of the cerebral EEG (that is, over seconds rather than minutes). To do so, we measured the concentration of lactate, the product of aerobic glycolysis, and therefore a readout of the rate of glucose metabolism in the brains of mice. Lactate was measured using a lactate oxidase based real time sensor embedded in the frontal cortex. The sensing mechanism consists of a platinum-iridium electrode surrounded by a layer of lactate oxidase molecules. Metabolism of lactate by lactate oxidase produces hydrogen peroxide, which produces a current in the platinum-iridium electrode. So a ramping up of cerebral glycolysis provides an increase in the concentration of substrate for lactate oxidase, which then is reflected in increased current at the sensing electrode. It was additionally necessary to measure these variables while manipulating the excitability of the cerebral cortex, in order to isolate this variable from other facets of NREMS.
	We devised an experimental system for simultaneous measurement of neuronal activity via the elecetroencephalogram, measurement of glycolytic flux via a lactate biosensor, and manipulation of cerebral cortical neuronal activity via optogenetic activation of pyramidal neurons. We have utilized this system to document the relationship between sleep-related electroencephalographic waveforms and the moment-to-moment dynamics of lactate concentration in the cerebral cortex. The protocol may be useful for any individual interested in studying, in freely behaving rodents, the relationship between neuronal activity measured at the electroencephalographic level and cellular energetics within the brain.

A procedure is described for manipulating the activity of cerebral cortical pyramidal neurons optogenetically while the electroencephalogram, electromyogram, and cerebral lactate concentration are monitored. Experimental recordings are performed on cable-tethered mice while they undergo spontaneous sleep/wake cycles. Optogenetic equipment is assembled in our laboratory; recording equipment is commercially available.

Although the brain represents less than 5% of the body  by mass, it utilizes approximately one quarter of the glucose used by the body  at rest1. The ...

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 ...

In Vivo Two-photon Imaging Of Experience-dependent Molecular Changes In Cortical Neurons

The brain's ability to change in response to experience is essential for healthy brain function, and abnormalities in this process contribute to a variety of brain disorders1,2. To better understand the mechanisms by which brain circuits react to an animal's experience requires the ability to monitor the experience-dependent molecular changes in a given set of neurons, over a prolonged period of time, in the live animal. While experience and associated neural activity is known to trigger gene expression changes in neurons1,2, most of the methods to detect such changes do not allow repeated observation of the same neurons over multiple days or do not have sufficient resolution to observe individual neurons3,4. Here, we describe a method that combines in vivo two-photon microscopy with a genetically encoded fluorescent reporter to track experience-dependent gene expression changes in individual cortical neurons over the course of day-to-day experience. 
One of the well-established experience-dependent genes is Activity-regulated cytoskeletal associated protein (Arc)5,6. The transcription of Arc is rapidly and highly induced by intensified neuronal activity3, and its protein product regulates the endocytosis of glutamate receptors and long-term synaptic plasticity7. The expression of Arc has been widely used as a molecular marker to map neuronal circuits involved in specific behaviors3. In most of those studies, Arc expression was detected by in situ hybridization or immunohistochemistry in fixed brain sections. Although those methods revealed that the expression of Arc was localized to a subset of excitatory neurons after behavioral experience, how the cellular patterns of Arc expression might change with multiple episodes of repeated or distinctive experiences over days was not investigated. 
In vivo two-photon microscopy offers a powerful way to examine experience-dependent cellular changes in the living brain8,9. To enable the examination of Arc expression in live neurons by two-photon microscopy, we previously generated a knock-in mouse line in which a GFP reporter is placed under the control of the endogenous Arc promoter10. This protocol describes the surgical preparations and imaging procedures for tracking experience-dependent Arc-GFP expression patterns in neuronal ensembles in the live animal. In this method, chronic cranial windows were first implanted in Arc-GFP mice over the cortical regions of interest. Those animals were then repeatedly imaged by two-photon microscopy after desired behavioral paradigms over the course of several days. This method may be generally applicable to animals carrying other fluorescent reporters of experience-dependent molecular changes4.

In Vivo Two-photon Imaging Of Experience-dependent Molecular Changes In Cortical Neurons

Experience-dependent molecular changes in neurons are essential for the brain's ability to adapt in response to behavioral challenges. An in vivo two-photon imaging method is described here that allows the tracking of such molecular changes in individual cortical neurons through genetically encoded reporters.

The brain's ability to change in response to experience is essential for healthy brain function, and abnormalities in this process contribute to a variety ...

Optogenetic Perturbation of Neural Activity with Laser Illumination in Semi-intact Drosophila Larvae in Motion

Drosophila larval locomotion is a splendid model system in developmental and physiological neuroscience, by virtue of the genetic accessibility of the underlying neuronal components in the circuits1-6. Application of optogenetics7,8 in the larval neural circuit allows us to manipulate neuronal activity in spatially and temporally patterned ways9-13. Typically, specimens are broadly illuminated with a mercury lamp or LED, so specificity of the target neurons is controlled by binary gene expression systems such as the Gal4-UAS system14,15. In this work, to improve the spatial resolution to "sub-genetic resolution", we locally illuminated a subset of neurons in the ventral nerve cord using lasers implemented in a conventional confocal microscope. While monitoring the motion of the body wall of the semi-intact larvae, we interactively activated or inhibited neural activity with channelrhodopsin16,17 or halorhodopsin18-20, respectively. By spatially and temporally restricted illumination of the neural tissue, we can manipulate the activity of specific neurons in the circuit at a specific phase of behavior. This method is useful for studying the relationship between the activities of a local neural assembly in the ventral nerve cord and the spatiotemporal pattern of motor output.

Optogenetic Perturbation of Neural Activity with Laser Illumination in Semi-intact Drosophila Larvae in Motion

Here we describe a protocol for optogenetic manipulation of motoneuronal activity while monitoring changes in motor output (muscle contraction) in semi-intact Drosophila larvae using lasers within a conventional confocal microscope. This technique enables researchers to achieve local perturbation of neural activity in a few neuromeres to elucidate the dynamics of motor circuits.

Drosophila larval locomotion is a splendid model system in developmental and physiological neuroscience, by virtue of the genetic accessibility of the ...

Ex Vivo Optogenetic Dissection of Fear Circuits in Brain Slices

Optogenetic approaches are now widely used to study the function of neural populations and circuits by combining targeted expression of light-activated proteins and subsequent manipulation of neural activity by light. Channelrhodopsins (ChRs) are light-gated cation-channels and when fused to a fluorescent protein their expression allows for visualization and concurrent activation of specific cell types and their axonal projections in defined areas of the brain. Via stereotactic injection of viral vectors, ChR fusion proteins can be constitutively or conditionally expressed in specific cells of a defined brain region, and their axonal projections can subsequently be studied anatomically and functionally via ex vivo optogenetic activation in brain slices. This is of particular importance when aiming to understand synaptic properties of connections that could not be addressed with conventional electrical stimulation approaches, or in identifying novel afferent and efferent connectivity that was previously poorly understood. Here, a few examples illustrate how this technique can be applied to investigate these questions to elucidating fear-related circuits in the amygdala. The amygdala is a key region for acquisition and expression of fear, and storage of fear and emotional memories. Many lines of evidence suggest that the medial prefrontal cortex (mPFC) participates in different aspects of fear acquisition and extinction, but its precise connectivity with the amygdala is just starting to be understood. First, it is shown how ex vivo optogenetic activation can be used to study aspects of synaptic communication between mPFC afferents and target cells in the basolateral amygdala (BLA). Furthermore, it is illustrated how this ex vivo optogenetic approach can be applied to assess novel connectivity patterns using a group of GABAergic neurons in the amygdala, the paracapsular intercalated cell cluster (mpITC), as an example.

Ex Vivo Optogenetic Dissection of Fear Circuits in Brain Slices

Optogenetic approaches are widely used to manipulate neural activity and assess the consequences for brain function. Here, a technique is outlined that&#160;upon in vivo expression of the optical activator Channelrhodopsin, allows for ex vivo analysis of synaptic properties of specific long range and local neural connections in fear-related circuits.

Optogenetic approaches are now widely used to study the function of neural populations and circuits by combining targeted expression of light-activated ...

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 ...

Disruption of Frontal Lobe Neural Synchrony During Cognitive Control by Alcohol Intoxication

Decision making relies on dynamic interactions of distributed, primarily frontal brain regions. Extensive evidence from functional magnetic resonance imaging (fMRI) studies indicates that the anterior cingulate (ACC) and the lateral prefrontal cortices (latPFC) are essential nodes subserving cognitive control. However, because of its limited temporal resolution, fMRI cannot accurately reflect the timing and nature of their presumed interplay. The present study combines distributed source modeling of the temporally precise magnetoencephalography (MEG) signal with structural MRI in the form of &#34;brain movies&#34; to: (1) estimate the cortical areas involved in cognitive control (&#34;where&#34;), (2) characterize their temporal sequence (&#34;when&#34;), and (3) quantify the oscillatory dynamics of their neural interactions in real time. Stroop interference was associated with greater event-related theta (4 - 7 Hz) power in the ACC during conflict detection followed by sustained sensitivity to cognitive demands in the ACC and latPFC during integration and response preparation. A phase-locking analysis revealed co-oscillatory interactions between these areas indicating their increased neural synchrony in theta band during conflict-inducing incongruous trials. These results confirm that theta oscillations are fundamental to long-range synchronization needed for integrating top-down influences during cognitive control. MEG reflects neural activity directly, which makes it suitable for pharmacological manipulations in contrast to fMRI that is sensitive to vasoactive confounds. In the present study, healthy social drinkers were given a moderate alcohol dose and placebo in a within-subject design. Acute intoxication attenuated theta power to Stroop conflict and dysregulated co-oscillations between the ACC and latPFC, confirming that alcohol is detrimental to neural synchrony subserving cognitive control. It interferes with goal-directed behavior that may result in deficient self-control, contributing to compulsive drinking. In sum, this method can provide insight into real-time interactions during cognitive processing and can characterize the selective sensitivity to pharmacological challenge across relevant neural networks.

This experiment uses an anatomically-constrained magnetoencephalography (aMEG) method to examine brain oscillatory dynamics and long-range functional synchrony during engagement of cognitive control as a function of acute alcohol intoxication.

Decision making relies on dynamic interactions of distributed, primarily frontal brain regions. Extensive evidence from functional magnetic resonance ...

The Detection of 5-Hydroxymethylcytosine in Neural Stem Cells and Brains of Mice

Multiple&#160;DNA modifications have been identified in the mammalian genome. Of that, 5-methylcytosine and 5-hydroxymethylcytosine-mediated epigenetic mechanisms have been intensively studied. 5-hydroxymethylcytosine displays dynamic features during embryonic and postnatal development of the brain, plays a regulatory function in gene expression, and is involved in multiple neurological disorders. Here, we describe the detailed methods including immunofluorescence staining and&#160;DNA dot-blot to detect 5-hydroxymethylcytosine in cultured cells and brain tissues of mouse.

Here, we present a protocol to detect 5-hydroxymethylcytosine in cells and brain tissues, utilizing immunofluorescence staining and DNA dot-blot methods.

Multiple&#160;DNA modifications have been identified in the mammalian genome. Of that, 5-methylcytosine and 5-hydroxymethylcytosine-mediated epigenetic ...

Measuring Neural Mechanisms Underlying Sleep-Dependent Memory Consolidation During Naps in Early Childhood

Sleep is critical for daily functioning. One important function of sleep is the consolidation of memories, a process that makes them stronger and less vulnerable to interference. The neural mechanisms underlying the benefit of sleep for memory can be investigated using polysomnography (PSG). PSG is a combination of physiological recordings including signals from the brain (EEG), eyes (EOG), and muscles (EMG) that are used to classify sleep stages. In this protocol, we describe how PSG can be used in conjunction with behavioral memory assessments, actigraphy, and parent-report to examine sleep-dependent memory consolidation. The focus of this protocol is on early childhood, a period of significance as children transition from biphasic sleep (consisting of a nap and overnight sleep) to monophasic sleep (overnight sleep only). The effects of sleep on memory performance are measured using a visuospatial memory assessment across periods of sleep and wakeful-rest. A combination of actigraphy and parent report is used to assess sleep rhythms (i.e., characterizing children as habitual or non-habitual nappers). Finally, PSG is used to characterize sleep stages and qualities of those stages (such as frequencies and the presence of spindles) during naps. The advantage of using PSG is that it is the only tool currently available to assess sleep quality and sleep architecture, pointing to the relevant brain state that supports memory consolidation. The main limitations of PSG are the length of time it takes to prepare the recording montage and that recordings are typically taken over one sleep bought. These limitations can be overcome by engaging young participants in distracting tasks during application and combining PSG with actigraphy and self/parent-report measures to characterize sleep cycles. Together, this unique combination of methods allows for investigations into how naps support learning in preschool children.

This protocol describes methods used to examine neural mechanisms underlying sleep-dependent memory consolidation during naps in early childhood. It includes procedures for examining the effect of sleep on behavioral memory performance, as well as the application and recording of both polysomnography and actigraphy.

Sleep is critical for daily functioning. One important function of sleep is the consolidation of memories, a process that makes them stronger and less ...