Name: whisker-signaled eyeblink classical conditioning in head-fixed mice
Uploaded: 2016-03-30T14:00:00
Description: Watch this Scientific Journal Video about Whisker-signaled Eyeblink Classical Conditioning in Head-fixed Mice at JoVE.com

This work was funded by the Department of Defense (W81XWH-13-01-0243) and the National Institutes of Health (R37 AG008796). We thank Alan Baker in Northwestern University&#39;s machine shop for building the head-fixed cylinder apparatus. We thank Dr. Shoai Hattori for his guidance in MATLAB and Solidworks. We thank Dr. John Power for the LabView software that controlled the experiment.

All procedures involving mice were performed in accordance with protocols approved by Northwestern University&#39;s Institutional Animal Care and Use Committee based on guidelines issued by the National Institute of Health.
1. The Cylinder (Figure 2A)
<ol>
	<li>Construct the cylinder as described by Chettih et al. and Heiney et al. from a long foam cylinder14-15. Cut a 10 cm length of cylinder and drill a hole through the center to fit the axle, a metal rod 12.7 ...

<ol>
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F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adaptive+timing+of+motor+output+in+the+mouse:+the+role+of+movement+oscillations+in+eyelid+conditioning.">Adaptive timing of motor output in the mouse: the role of movement oscillations in eyelid conditioning.</a> Front in Integ Neurosci. 5 (72), (2011).</li><li>Heiney, S. A., Wohl, M. P., Chettih, S. N., Ruffolo, L. I., Medina, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cerebellar-Dependent+Expression+of+Motor+Learning+during+Eyeblink+Conditioning+in+Head-Fixed+Mice.">Cerebellar-Dependent Expression of Motor Learning during Eyeblink Conditioning in Head-Fixed Mice.</a> J Neurosci. 34 (45), 14845-14853 (2014).</li><li>Siegel, J. 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=Trace+Eyeblink+Conditioning+in+Mice+is+Dependent+upon+the+Dorsal+Medial+Prefrontal+Cortex,+Cerebellum,+and+Amygdala:+Behavioral+Characterization+and+Functional+Circuity.">Trace Eyeblink Conditioning in Mice is Dependent upon the Dorsal Medial Prefrontal Cortex, Cerebellum, and Amygdala: Behavioral Characterization and Functional Circuity.</a> eNeuro. , (2015).</li><li>Galvez, R., Weiss, C., Cua, S., Disterhoft, J. <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+method+for+precisely+timed+stimulation+of+mouse+whiskers+in+a+freely+moving+preparation:+application+for+delivery+of+the+conditioned+stimulus+in+trace+eyeblink+conditioning.">A novel method for precisely timed stimulation of mouse whiskers in a freely moving preparation: application for delivery of the conditioned stimulus in trace eyeblink conditioning.</a> J Neurosci Meth. 177 (2), 434-439 (2009).</li><li>Gruart, A., S&#225;nchez-Campusano, R., Fern&#225;ndez-Guiz&#225;n, A., Delgado-Garc&#236;a, J. 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F., Weiss, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trace+eyeblink+conditioning+is+hippocampally+dependent+in+mice.">Trace eyeblink conditioning is hippocampally dependent in mice.</a> Hippocampus. 14 (1), 58-65 (2004).</li><li>Joachimsthaler, B., Brugger, D., Skodras, A., Schwarz, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spine+loss+in+primary+somatosensory+cortex+during+trace+eyeblink+conditioning.">Spine loss in primary somatosensory cortex during trace eyeblink conditioning.</a> J Neurosci. 35 (9), 3772-3781 (2015).</li><li>Boele, H. 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Classical eyeblink conditioning is a form of associative learning that is a useful tool for understanding the neural substrates underlying learning and memory. Previous methods employed for eyeblink conditioning in rodents such as mice involved a chamber that allowed for the animal to move about freely. A head-fixed preparation for eyeblink conditioning in mice, using the apparatus described by Chettih et al. and Heiney et al. and most recently utilized in light-evoked trace eyeblink conditioning in Sie...

Eyeblink conditioning is a form of Pavlovian conditioning and a model system for investigating the neural mechanisms of associative learning and memory. It has been investigated in various species, including humans, rabbits, cats, rats, and mice. The paradigm involves the presentation of two paired stimuli: a neutral conditioned stimulus (CS; e.g., a tone, a flash of light, or whisker stimulation), and a salient unconditioned stimulus (US; e.g., an air puff to the eye, or periorbital shock). The US elicits an unconditioned, reflexive eyeblink response (i.e., UR). Eventually, after several presentations of the paired CS-US, the subject learns to associate the CS with the US. This learning manifests itself in the form of a conditioned response (CR), an eyeblink elicited by the CS alone that precedes the presentation of the US.
Eyeblink conditioning in the trace form includes a stimulus-free interval of a few hundred milliseconds that separates the CS and the US (Figure 1). Trace conditioning is a form of declarative learning since it requires awareness of the stimulus contingencies1. The temporal gap requires the animal to keep a neural &#39;trace&#39; of the CS in forebrain regions such as the hippocampus in order for the US and the CS to become associated1-6. Along with the forebrain regions, trace conditioning is also dependent on the cerebellum7.
Eyeblink conditioning is, therefore, a useful paradigm for the investigation of the multiple facets of memory, including acquisition, consolidation, and retrieval. During eyeblink conditioning, a control group of animals is presented with unpaired stimuli in random order to test for pseudoconditioning or sensitized responses to the CS that may be caused by US presentation alone rather than a learned CS-US association.
A commonly used apparatus for the investigation of eyeblink conditioning in rodents is a chamber in which the rodents are allowed to move about freely during the training process8-10. With this type of apparatus, a tether is normally attached to a headpiece that is affixed to the rodent&#39;s skull. The tether allows for the delivery of the US (and sometimes the CS) and for transmitting the animal&#39;s response to those stimuli (i.e., the eyeblink response)10. The tether itself may be modified based on the type of stimuli delivered and how the eyeblink response is recorded.
The reason for using &#34;freely-moving&#34; tethered mice for eyeblink conditioning is that mice struggle against restraint. Though other species may be more amenable to restraint, the major advantage of using mice in eyeblink conditioning experiments is that the majority of available genetically modified mutant strains are mouse strains. In addition to struggling, complete restraint of mice results in acute distress. A head-fixed mouse preparation that minimizes stress would increase the physiological information that can be obtained during eyeblink conditioning. For example, this system would allow imaging of cortical neurons with 2-photon microscopy11.
Head-fixed preparations have been used in previous experiments for optical imaging of the cortex through removable cranial implants, in vivo electrophysiological recordings of the rodent brain with tetrode arrays, two-photon calcium imaging, and also as a platform for eyeblink conditioning in mice11-16.
In the head-fixed system, reliable stimulation and recordings are ensured without complete restraint of the mouse (Figure 2). A headpiece like the one used in the freely moving system is affixed to the mouse&#39;s skull. During training, the headpiece is affixed to a connector that is attached to bars over a cylindrical treadmill in order to stabilize the rodent&#39;s head (Figure 2A). The cylindrical treadmill allows the mouse to rest comfortably, but if the mouse so wishes, also allows it to run or to walk. With the use of this system, mice can be trained with a whisker vibration as the CS and a mild periorbital electrical shock as the US (Figure 1). The US is delivered through wires surgically placed underneath the skin lateral to the eye. The CS is delivered via a comb that is attached to a 2-layer rectangular bending actuator (Figure 2B). The comb and bending actuator are then attached to a magnetic base that is moved to the proper position during training and is adjusted for optimal delivery for each individual animal. The comb is positioned to straddle the selected whiskers. During delivery of the CS, a signal is sent to the bending actuator that displaces the comb and leads to vibration of the whiskers17.
Other stimuli such as a tone or a flash of light have been used as effective conditioned stimuli in mice in the past16,18,19. The reason whisker stimulation is chosen for the CS in this experimental paradigm is the dependence of murine animals on their vibrissae for somatosensory information input during exploration. Whisker stimulation has been shown to be a reliable and effective CS20. Furthermore, given the well-established and organized cortical substrate of the vibrissae system (i.e., the barrel cortex), whisker stimulation as the CS provides an elegant tool for mapping cortical changes and plasticity associated with learning eyeblink conditioning20,21. A head-fixed system allows for the precise stimulation of selected whiskers to compare responses between stimulated neurons and neurons receiving inputs from non-stimulated whiskers. Finally, many strains of mice exhibit age-related hearing loss as relatively young adults22, and eyelid closure during the conditioned blink alters a visual CS (although a visual CS does ameliorate issues with startle responses16). Whisker stimulation is not affected by either of these complications.
Presented here are unique and important modifications upon other head-fixed preparations for eyeblink conditioning, including methods for CS and US delivery, and the acquisition of the eyeblink response. The reliability of this apparatus and the training paradigm in eyeblink conditioning is demonstrated by learning curves from conditioned mice and a relatively flat learning curve from pseudoconditioned control animals (Figure 7A).

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			<td height="21" style="height:21px;width:436px;">Exervo TeraNova Foam Roller 36&#34; x 6&#34;&#160;</td>
			<td style="width:357px;">Amazon</td>
			<td style="width:181px;">B002ONUM0E</td>
			<td style="width:377px;">For cylinder</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:436px;">Plexiglas</td>
			<td style="width:357px;"></td>
			<td></td>
			<td>Custom-made; 1 cm thick</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:436px;">Metal Rods (12.7mm diameter)</td>
			<td style="width:357px;"></td>
			<td></td>
			<td>Custom-made</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:436px;">4-40 machine screw (.25 in long)</td>
			<td style="width:357px;">Amazon Supply</td>
			<td>&#160;B00F33Q8QO</td>
			<td>For cylinder</td>
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		<tr height="22">
			<td height="22" style="height:22px;width:436px;">Classic Design Hair Comb</td>
			<td style="width:357px;">Conair</td>
			<td style="width:181px;">93505WG-320</td>
			<td>For whisker stimulation</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">2-Layer Rectangular Bending Actuator</td>
			<td style="width:357px;">Piezo Systems</td>
			<td>T220-A4-303X&#160;</td>
			<td>For whisker stimulation</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Solder and Flux Kit</td>
			<td style="width:357px;">Piezo Systems</td>
			<td>MSF-003-NI</td>
			<td>For whisker stimulation</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Magnetic Base</td>
			<td style="width:357px;">Thor Labs</td>
			<td style="width:181px;">MB175</td>
			<td>For whisker stimulation</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Threaded rod for magnetic base</td>
			<td style="width:357px;"></td>
			<td style="width:181px;"></td>
			<td>Custom-made</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:436px;">Strips based on 221 series nylon strip connectors from Electronic Connector Corp.</td>
			<td style="width:357px;"></td>
			<td style="width:181px;"></td>
			<td>Custom-made, based on Weiss and Disterhoft, 2008</td>
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		<tr height="20">
			<td height="20" style="height:20px;width:436px;">TO-220 Style Transistor</td>
			<td style="width:357px;">Amazon Supply</td>
			<td>B0002ZPZYO&#160;</td>
			<td>For connector; for the wings</td>
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			<td height="20" style="height:20px;width:436px;">Relia-Tac Sockets</td>
			<td style="width:357px;">Electronic Connector Corp.</td>
			<td style="width:181px;">220-S02</td>
			<td>For connector</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Relia-Tac Pins</td>
			<td style="width:357px;">Electronic Connector Corp.</td>
			<td style="width:181px;">220-P02</td>
			<td>For headpiece</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">0-80 stainless steel machine screw (1 in. long)</td>
			<td>Amazon Supply</td>
			<td>B000FN68EE</td>
			<td>Locking Screw</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">0-80 stainless steel machine screw hex nut (5/32 in. thick)</td>
			<td>Amazon Supply</td>
			<td>B000N2TK7Y</td>
			<td>Locking Screw Head</td>
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			<td height="20" style="height:20px;width:436px;">Loctite Super Glue-Liquid</td>
			<td>Loctite</td>
			<td>1365896</td>
			<td>Cyanoacrylic glue; for the locking screw</td>
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		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Quick Setting Epoxy</td>
			<td style="width:357px;">Ace Hardware</td>
			<td>18613</td>
			<td>For connector and whisker stimulation system</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Ethernet Cable Wires</td>
			<td style="width:357px;"></td>
			<td></td>
			<td>Ethernet cable can be taken apart to use the individual wires for the connector</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:436px;">Polyimide coated stainless steel wires (2 in. long, .005 in. diameter)</td>
			<td style="width:357px;">PlasticsOne</td>
			<td>005sw/2.0 37365 S-S&#160;</td>
			<td>For headpiece, EMG and shock wires</td>
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		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Stainless steel uncoated wire (.005 in. diameter)</td>
			<td style="width:357px;">AM Systems</td>
			<td>792800</td>
			<td>For headpiece, ground wires</td>
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			<td height="20" style="height:20px;width:436px;">Tenma Variable Autotransformer</td>
			<td style="width:357px;">Tenma</td>
			<td>72-110</td>
			<td>For the whisker stimulation; rheostat to adjust current to the bending actuator</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Amplifier</td>
			<td style="width:357px;">A-M Systems</td>
			<td>1700</td>
			<td>Amplifier for filtering and amplifying EMG signals</td>
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			<td height="20" style="height:20px;width:436px;">WPI A385R stimulus isolator</td>
			<td style="width:357px;">World Precision Instruments</td>
			<td>31405</td>
			<td>For the electrical shock</td>
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		<tr height="18">
			<td height="18" style="height:18px;width:436px;">Isothesia (Isoflurane)</td>
			<td style="width:357px;">Henry Schein: Animal Health</td>
			<td style="width:181px;">50031</td>
			<td>For surgery; anesthesia</td>
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		<tr height="18">
			<td height="18" style="height:18px;width:436px;">Buprenex Injectable CIII</td>
			<td style="width:357px;">Reckett Benckiser Pharmaceuticals Inc</td>
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		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Akwa Tears: Lubricant Ophthalmic Ointment&#160;</td>
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			<td style="width:181px;">NDC 17478-062-35</td>
			<td>Artificial tear ointment to prevent dry eyes while under anesthesia</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Povidine-Iodine Prep Pads</td>
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		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Alcohol Prep Pads</td>
			<td style="width:357px;"></td>
			<td style="width:181px;"></td>
			<td>May be purchased from any standard pharmacy</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Stainless steel surgical scalpel handles (no.3)</td>
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			<td>4-7.</td>
			<td>For surgery</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Stainless steel surgical scalpel blades</td>
			<td style="width:357px;">Integra Miltex</td>
			<td style="width:181px;">4-310 or 4-315</td>
			<td>For surgery; number 10 or 15 scalpel blade</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">3% Hydrogen Peroxide</td>
			<td style="width:357px;"></td>
			<td style="width:181px;"></td>
			<td>May be purchased from any standard pharmacy</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Micro Clip</td>
			<td style="width:357px;">Roboz</td>
			<td style="width:181px;">RS-5459</td>
			<td>For surgery, to hold back skin</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">00-90 stainless steel machine screw (0.0625 in. long)&#160;</td>
			<td style="width:357px;">Amazon Supply</td>
			<td>B002SG89X4&#160;</td>
			<td>For surgery, to wrap ground wire around</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Professional Rotary Tool</td>
			<td style="width:357px;">Walnut Hollow</td>
			<td>29637</td>
			<td>Hand drill for surgery, to drill holes in skull</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Inverted Cone Burr</td>
			<td style="width:357px;">Roboz</td>
			<td>RS-6282C-34</td>
			<td>Inverted cone burr size 34; for surgery, to drill holes in skull</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Engraving Cutter Drill Bit</td>
			<td style="width:357px;">Dremel</td>
			<td>106</td>
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		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">C&#38;B Metabond-Quick! Cement System &#34;B&#34; Quick Base</td>
			<td style="width:357px;">Parkell</td>
			<td style="width:181px;">S398</td>
			<td>For surgery; adhesive luting cement system; important to prevent headpiece avulsion</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">C&#38;B Metabond-Quick! Cement System Clear L-Powder</td>
			<td style="width:357px;">Parkell</td>
			<td style="width:181px;">S399</td>
			<td>For surgery; adhesive luting cement system; important to prevent headpiece avulsion</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:436px;">C&#38;B Metabond-Quick! Cement System &#34;C&#34; Universal TBB Catalyst 0.7 ml</td>
			<td style="width:357px;">Parkell</td>
			<td style="width:181px;">S371</td>
			<td>For surgery; adhesive luting cement system; important to prevent headpiece avulsion</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:436px;">C&#38;B Metabond-Quick! Cement System Ceramic Mixing Dish with temperature strip</td>
			<td style="width:357px;">Parkell</td>
			<td style="width:181px;">S387</td>
			<td>For surgery; adhesive luting cement system; important to prevent headpiece avulsion</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:436px;">Swiss Tweezers, style #5</td>
			<td style="width:357px;">World Precision Instruments</td>
			<td style="width:181px;">504506</td>
			<td>For surgery</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Puritan Cotton-Tipped Applicators</td>
			<td style="width:357px;">VWR International</td>
			<td>10806-005&#160;</td>
			<td>For surgery</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:436px;">Dental Caulk Grip Cement Kit</td>
			<td style="width:357px;">Dentsply</td>
			<td>675570</td>
			<td>For surgery; dental cement</td>
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	</tbody>
</table>

whisker-signaled eyeblink classical conditioning in head-fixed mice

Eyeblink conditioning is a common paradigm for investigating the neural mechanisms underlying learning and memory. To better utilize the extensive repertoire of scientific techniques available to study learning and memory at the cellular level, it is ideal to have a stable cranial platform. Because mice do not readily tolerate restraint, they are usually trained while moving about freely in a chamber. Conditioned stimulus (CS) and unconditioned stimulus (US) information are delivered and eyeblink responses recorded via a tether connected to the mouse's head. In the head-fixed apparatus presented here, mice are allowed to run as they desire while their heads are secured to facilitate experimentation. Reliable conditioning of the eyeblink response is obtained with this training apparatus, which allows for the delivery of whisker stimulation as the CS, a periorbital electrical shock as the US, and analysis of electromyographic (EMG) activity from the eyelid to detect blink responses.

8-10 week old male C57Bl6/J mice were trained on trace eyeblink conditioning on the head-fixed cylindrical treadmill apparatus. 8 mice were trained with paired CS-US presentations (conditioned group) and 9 mice were trained with unpaired CS and US presentations (pseudoconditioned group).
Example EMG recordings of a conditioned response from a conditioned mouse are shown in Figures 3 and 4. EMG r...

Watch this Scientific Journal Video about Whisker-signaled Eyeblink Classical Conditioning in Head-fixed Mice at JoVE.com

Whisker-signaled Eyeblink Classical Conditioning in Head-fixed Mice

The preparation presented here for whisker-signaled eyeblink conditioning in head-fixed mice precisely stimulates specific whiskers while allowing mice to ambulate on a cylindrical treadmill. A whisker stimulation conditioned stimulus (CS) paired with a periorbital shock unconditioned stimulus (US) results in reliable associative learning on this apparatus.

Eyeblink conditioning is a common paradigm for investigating the neural mechanisms underlying learning and memory. To better utilize the extensive ...

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