LCA acknowledges funding from an NDSEG fellowship, the NSF GRFP, and the Friends of the McGovern Institute. EP acknowledges funding the Harry and Eunice Nohara UROP Fund, the MIT Class of 1995 UROP Fund, and the MIT UROP Fund. ESB acknowledges funding from NIH 2R44NS070453-03A1, the IET Harvey Prize, and the New York Stem Cell Foundation-Robertson Award. RD acknowledges funding from NIH EY017292. Michael Williams helped the team to organize and gather supplies prior to filming.

Note: All animal procedures were in accordance with the NIH guidelines and were approved by the Massachusetts Institute of Technology Committee on Animal Care.
1. Illuminator Fabrication
<ol>
	<li>Use a pair of sharp shears to cut a section of 250 &#181;m diameter plastic optical fiber that is at least 10 cm longer than the desired total illuminator length.</li>
	<li>Remove 15 - 20 cm of polyethylene jacket from one end of the plastic optical fiber using a 22 gauge wire stripper.</li>
	<li>S...

<ol>
	<li>Herculano-Houzel, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+human+brain+in+numbers:+a+linearly+scaled-up+primate+brain.">The human brain in numbers: a linearly scaled-up primate brain.</a> Front Hum Neurosci. 3, 31 (2009).</li><li>Tamura, 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=A+glass-coated+tungsten+microelectrode+enclosing+optical+fibers+for+optogenetic+exploration+in+primate+deep+brain+structures.">A glass-coated tungsten microelectrode enclosing optical fibers for optogenetic exploration in primate deep brain structures.</a> J Neurosci Meth. 211 (1), 49-57 (2012).</li><li>Diester, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+optogenetic+toolbox+designed+for+primates.">An optogenetic toolbox designed for primates.</a> Nat Neurosci. 14 (3), 387-397 (2011).</li><li>Dai, J., Brooks, D. I., Sheinberg, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optogenetic+and+Electrical+Microstimulation+Systematically+Bias+Visuospatial+Choice+in+Primates.">Optogenetic and Electrical Microstimulation Systematically Bias Visuospatial Choice in Primates.</a> Curr biol. 24 (1), 63-69 (2014).</li><li>Ozden, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+coaxial+optrode+as+multifunction+write-read+probe+for+optogenetic+studies+in+non-human+primates.">A coaxial optrode as multifunction write-read probe for optogenetic studies in non-human primates.</a> J Neurosci Meth. 219 (1), 142-154 (2013).</li><li>Ruiz, O., 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=Optogenetics+through+windows+on+the+brain+in+the+nonhuman+primate.">Optogenetics through windows on the brain in the nonhuman primate.</a> J Neurophysiol. 110 (6), 1455-1467 (2013).</li><li>Chuong, A. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Noninvasive+optical+inhibition+with+a+red-shifted+microbial+rhodopsin.">Noninvasive optical inhibition with a red-shifted microbial rhodopsin.</a> Nat Neurosci. 17 (8), 1123-1129 (2014).</li><li>Acker, L., Pino, E. N., Boyden, E. S., Desimone, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FEF+inactivation+with+improved+optogenetic+methods.">FEF inactivation with improved optogenetic methods.</a> Proc Natl Acad Sci U S A. 113 (46), 7297-7306 (2016).</li><li>Jazayeri, M., Lindbloom-Brown, Z., Horwitz, G. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Saccadic+eye+movements+evoked+by+optogenetic+activation+of+primate+V1.">Saccadic eye movements evoked by optogenetic activation of primate V1.</a> Nat Neurosci. 15 (10), 1368-1370 (2012).</li><li>Gerits, A., 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=Optogenetically+Induced+Behavioral+and+Functional+Network+Changes+in+Primates.">Optogenetically Induced Behavioral and Functional Network Changes in Primates.</a> Curr Biol. 22 (18), 1722-1726 (2012).</li><li>Ohayon, S., Grimaldi, P., Schweers, N., Tsao, D. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Saccade+modulation+by+optical+and+electrical+stimulation+in+the+macaque+frontal+eye+field.">Saccade modulation by optical and electrical stimulation in the macaque frontal eye field.</a> J Neurosci. 33 (42), 16684-16697 (2013).</li><li>Cavanaugh, 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=Optogenetic+inactivation+modifies+monkey+visuomotor+behavior.">Optogenetic inactivation modifies monkey visuomotor behavior.</a> Neuron. 76 (5), 901-907 (2012).</li></ol>

While optogenetic tools are widely used to study disease and physiology in rodents, the technical challenge of illuminating large brain volumes has limited the use of optogenetics in non-human primates. Pioneering studies in monkeys used large light power densities (~100 mW/mm2 to 20 W/mm2) to illuminate small volumes, perhaps &#60; 1 mm3, and reported modest behavioral effects with excitatory opsins in the cortex4,9,<s...

Optogenetic tools, which allow for millisecond-precise, light-driven neuronal control are widely used to study functional physiology and behavior in rodents and invertebrates. However, technical challenges have limited the use of optogenetics in the non-human primate brain, which has a volume ~100x larger than the rodent brain 1.
To facilitate optogenetics studies in non-human primates, an illuminator was designed to address two competing goals: large volume illumination and minimal penetration damage. Previous attempts to address one of these concerns have come at the expensive of the other. Bundles of fibers illuminate larger volumes but with increased diameter, and, thus, damage2,3. Tapered glass fibers reduce penetration damage, but narrowly focus light to light emitting surface areas &#60;100 &#181;m2 4,5. External brain illumination through a window in the dura circumvents the challenge of penetration damage and may allow for large volume illumination, but it can only be used for a few superficial brain areas6.
To create a large-volume, small diameter illuminator (Figure 1a), the tip of a plastic optical fiber is heat tapered and the core and cladding are etched (Figure 1b,c). Unlike other tapered fibers that focus light to a narrow point, the etching allows light to escape evenly out the sides of the tip, thus, distributing light broadly over a large area (Figure 1d,e). Because penetration damage is proportional to penetration diameter, this illuminator has no more penetration damage than a conventional fiber, yet it has &#62;100x the light emitting surface area and delivers light more broadly with 1/100th the light power density in a brain phantom (1.75% agarose) (Figure 1e). A Monte Carlo model (Figure 1f) illustrates the difference in light spread between a conventional fiber and the large volume illuminator when they have equal light power densities as their light emitting surfaces. Each illuminator is individually calibrated using an integrating sphere (Figure 2a,b) to ensure even light distribution along the tip (Figure 2c).
This large volume illuminator has been validated with optogenetic manipulation of both behavior and neuronal firing in non-human primates. The fiber tip length may be customized to any brain area and to each animal&#8217;s individual receptive field map. The illuminator may be paired with a penetrating electrode for neuronal recordings that span the length of illumination. Further, because the fiber can carry any color of visible light, it can be paired with any of the available optogenetic molecules available.

<table border="0" cellpadding="0" cellspacing="0" width="853">
	<tbody>
		<tr height="63">
			<td height="63" style="height:63px;width:403px;">Plastic optical fiber</td>
			<td style="width:323px;">Industrial fiber optics</td>
			<td style="width:64px;">SK-10</td>
			<td style="width:64px;">250 micron diameter, Super Eska line</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:403px;">Wire stripper</td>
			<td style="width:323px;">Klein Tools</td>
			<td align="right" style="width:64px;">11047</td>
			<td>22 gauge</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:403px;">Vise Clamp</td>
			<td style="width:323px;">Wilton</td>
			<td align="right" style="width:64px;">11104</td>
			<td>Generic table mount vice clamp</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">Dual temperature heat gun</td>
			<td style="width:323px;">Milwaukee</td>
			<td style="width:64px;">8975-6</td>
			<td>570 / 1000&#176;F</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:403px;">Lab marker</td>
			<td style="width:323px;">VWR</td>
			<td align="right" style="width:64px;">52877</td>
			<td></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">Dissection microscope</td>
			<td style="width:323px;">VistaVision</td>
			<td style="width:64px;">82027-156</td>
			<td>Stereo microscope w/ dual incandescent light, 2x/4x magnification, available from VWR</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:403px;">Lab tape</td>
			<td style="width:323px;">VWR</td>
			<td style="width:64px;">89097-972</td>
			<td>4 pack of violet color; however, tape color does not matter</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">Silicon carbide lapping sheet</td>
			<td style="width:323px;">ThorLabs</td>
			<td style="width:64px;">LF5P</td>
			<td>5 micron grit, 10 pack</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">Aluminum oxide lapping sheet</td>
			<td style="width:323px;">ThorLabs</td>
			<td style="width:64px;">LF3P</td>
			<td>3 micron grit, 10 pack</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">Aluminum oxide lapping&#160; sheet</td>
			<td style="width:323px;">ThorLabs</td>
			<td style="width:64px;">LF1P</td>
			<td>1 micron grit, 10 pack</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">Calcined alumina lapping sheet</td>
			<td style="width:323px;">ThorLabs</td>
			<td style="width:64px;">LF03P</td>
			<td>0.3 micron grit, 10 pack</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:403px;">Hot knife</td>
			<td style="width:323px;">Industrial fiber optics</td>
			<td style="width:64px;">IF370012</td>
			<td>60 Watt, heavy duty</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">Fiber inspection scope</td>
			<td style="width:323px;">ThorLabs</td>
			<td style="width:64px;">FS201</td>
			<td>optional</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:403px;">Stainless Steel Ferrule</td>
			<td style="width:323px;">Precision fiber optics</td>
			<td style="width:64px;">MM-FER2003SS-265</td>
			<td>265 micron inner diameter</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:403px;">1 mL syringe</td>
			<td style="width:323px;">BD</td>
			<td style="width:64px;">14-823-30</td>
			<td>Luer-lok tip is preferable to reduce risk of leakage, but not strictly needed</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:403px;">Plastic epoxy</td>
			<td style="width:323px;">Industrial fiber optics</td>
			<td>40 0005</td>
			<td></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">18 gauge blunt needle</td>
			<td style="width:323px;">BD</td>
			<td align="right" style="width:64px;">305180</td>
			<td>1.5 inch length</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">Lint-free wipe (KimWipe)</td>
			<td style="width:323px;">ThorLabs</td>
			<td>KW32</td>
			<td>available from many vendors</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:403px;">Light absorbing foil</td>
			<td style="width:323px;">ThorLabs</td>
			<td style="width:64px;">BKF12</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:403px;">Electrical tape</td>
			<td style="width:323px;">3M</td>
			<td style="width:64px;">Temflex 1700</td>
			<td>Optional, may substitute other brands / models</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">26 gauge sharp needle&#160;</td>
			<td style="width:323px;">BD</td>
			<td align="right" style="width:64px;">305111</td>
			<td>0.5 inch length</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:403px;">Micromanipulator</td>
			<td style="width:323px;">Siskiyou</td>
			<td style="width:64px;">70750000E</td>
			<td>may substitute other brands/models</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:403px;">Steretactic arm</td>
			<td style="width:323px;">Kopf</td>
			<td align="right" style="width:64px;">1460</td>
			<td>may substitute other brands/models</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:403px;">Laser safety goggles</td>
			<td style="width:323px;">KenTeK</td>
			<td>KCM-6012</td>
			<td>must be selected based on the color of laser used, example given here</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">Laser or other light source</td>
			<td style="width:323px;">vortran</td>
			<td style="width:64px;">Stradus 473-50</td>
			<td>example of blue laser</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:403px;">Integrating sphere</td>
			<td style="width:323px;">ThorLabs</td>
			<td>S142C</td>
			<td>Attached power meter, also available from ThorLabs, item #PM100D</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:403px;">Ultem recording chamber</td>
			<td style="width:323px;">Crist instrument company</td>
			<td style="width:64px;">6-ICO-J0</td>
			<td>Customized with alignment notch</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">Tower microdrive with clamps</td>
			<td style="width:323px;">NAN</td>
			<td style="width:64px;">DRTBL-CMS</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:403px;">Guide tube</td>
			<td style="width:323px;">Custom</td>
			<td style="width:64px;">N/A</td>
			<td>Made from 25 gauge spinal needle (BD) or blunt tubing</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:403px;">NAN driver system</td>
			<td style="width:323px;">NAN</td>
			<td style="width:64px;">NANDrive</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:403px;">Custom grid design</td>
			<td style="width:323px;">custom</td>
			<td style="width:64px;">custom</td>
			<td>plans available upon request</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:403px;">Blunt forceps</td>
			<td style="width:323px;">FischerScientific</td>
			<td style="width:64px;">08-875-8A</td>
			<td>generic stainless steel blunt forceps</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:403px;">Digital calipers</td>
			<td style="width:323px;">Neiko</td>
			<td style="width:64px;">01407A</td>
			<td>available on amazon.com. May select a finer resolution caliper for more precise measurements.</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:403px;">Patch cable</td>
			<td style="width:323px;">ThorLabs</td>
			<td style="width:64px;">FG200LCC-custom</td>
			<td>This is one example of many possible patch cables. As long as the fiber diameter is less than or equal to the fiber diameter of the large volume illuminator and as long as the connectors interface, any patch cable (glass or plastic, vendor purchased or made in the lab) is fine for this application.</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">Clear plastic dust caps</td>
			<td style="width:323px;">ThorLabs</td>
			<td style="width:64px;">CAPF</td>
			<td>Package of 25</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:403px;">ceramic split mating sleeve</td>
			<td style="width:323px;">Precision Fiber Products, Inc.</td>
			<td style="width:64px;">SM-CS1140S</td>
			<td></td>
		</tr>
	</tbody>
</table>

large volume, behaviorally-relevant illumination for optogenetics in non-human primates

This protocol describes a large-volume illuminator, which was developed for optogenetic manipulations in the non-human primate brain. The illuminator is a modified plastic optical fiber with etched tip, such that the light emitting surface area is &#62; 100x that of a conventional fiber. In addition to describing the construction of the large-volume illuminator, this protocol details the quality-control calibration used to ensure even light distribution. Further, this protocol describes techniques for inserting and removing the large volume illuminator. Both superficial and deep structures may be illuminated. This large volume illuminator does not need to be physically coupled to an electrode, and because the illuminator is made of plastic, not glass, it will simply bend in circumstances when traditional optical fibers would shatter. Because this illuminator delivers light over behaviorally-relevant tissue volumes (&#8776; 10 mm3) with no greater penetration damage than a conventional optical fiber, it facilitates behavioral studies using optogenetics in non-human primates.

The illumination of large brain volumes in non-human primates allows for behaviorally-relevant optogenetic manipulation. Acker et al. (2016) used this large volume illuminator with the red-shifted Halorhodopsin, Jaws 7 to study the temporal contribution of the frontal eye field (FEF) to memory-guided saccades in two rhesus monkeys. Specifically, FEF neurons were injected with a viral vector containing Jaws and then illuminated with red-light using the large volume illuminator during eithe...

Watch this Scientific Journal Video about Large Volume, Behaviorally-relevant Illumination for Optogenetics in Non-human Primates at JoVE.com

Large Volume, Behaviorally-relevant Illumination for Optogenetics in Non-human Primates

A protocol to build a tissue penetrating illuminator for delivering light over large volumes with minimal diameter is presented.

This protocol describes a large-volume illuminator, which was developed for optogenetic manipulations in the non-human primate brain. The illuminator is a ...

The overall goal of this protocol is to create a large volume tissue illuminator that is well suited to optogenetic manipulations in non human primates. This method can help answer key questions in the field of neuroscience, such as how do populations of neurons in the different brain regions contribute to behavior, and how can temporally specific neuronal firing patterns in one region impact another region? The main advantage of this technique is that it uses light, and thus allows optogenetic manipulation of large behaviorally relevant brain volumes with minimal tissue damage.The implications of this technique extend toward translational medicine because of the similarities between the human and non-human primate brains. Generally, individuals new to this method will struggle because it takes some practice to apply the proper amount of pressure when pulling these fibers. To begin this procedure, use a pair of sharp shears to cut a section of 250 micrometer diameter plastic optical fiber that is at least 10 centimeters longer than the desired total illuminator length.Next, remove 15 to 20 centimeter of polyethylene jacket from one end of the plastic optical fiber using a 22-gauge wire stripper. Then, secure the distal-most three to five centimeters of the stripped end of the fiber in a table vice clamp. Hold the jacketed end of the fiber taut in one hand, with a constant steady pull.The fiber should be parallel to the floor, pulled away from the vice. Maintain this constant tension on the fiber throughout heating and cooling, so that the fiber remains straight and taut as it thins. Using the lowest setting of a dual temperature heat gun, heat the stripped section of the fiber until it is thinned to a diameter of 60 to 100 micrometers, or about the diameter of a human hair.Maintain the constant tension on the fiber while allowing it to cool. Failure to maintain tension or overheating the fiber may cause the fiber to curl and or break. To help maintain constant tension on the fiber as you heat it, use your non-dominant hand so you don't have to let go when you're using the heat gun.Also, you can gently wrap the fiber around your palm to get an even better grip. Once the fiber has fully cooled, and the desired diameter has been achieved, pinch the fiber three centimeters from the narrowest point on both sides. With a quick sharp pull along the axis of the fiber, separate the sides to create a tapered tip.Then, examine the tapered tip in low power under a dissection microscope. If the tip is forked or curled, discard the fiber. Even with a lot of practice, about a third of fibers will have forked or curled tips.We just discard those fibers rather than trying to repair them, since it's so quick and inexpensive to pull another one. Prepare to etch the tapered tip by placing a piece of lab tape near the end of the tip, leaving the desired tip length exposed. Here the last five millimeters are exposed.The tape protects the fiber from etching above the desired length of light emission. After that, fold a small square of five micrometer silicon carbide lapping sheet over between the thumb and forefinger. Place the tip of the fiber between the two sides of the lapping sheet, and gently etch the fiber using small circular motions.Frequently rotate the fiber so that all sides are etched evenly. Next, remove about five millimeters of the polyethylene jacket from the opposite end of the illuminator using a 22-gauge wire stripper. Then, cut the opposite end flat with a hot knife to smooth the surface.Affix a connector on the end of the illuminator opposite to the etched tip. This allows the illuminator to connect to an optical cable or laser. Afterward, polish the opposite end flat with successively finer lapping sheets.Subsequently, insert the flat opposite end into a 260 micrometer inner diameter stainless steel ferrule until it is flush with the end of the ferrule. Visually confirm that the opposite end is smoothly and evenly polished with a fiber microscope. Tape the ferrule vertically on the edge of the table with the smaller opening of the ferrule pointing down.Then, fill a one milliliter syringe with plastic epoxy and attach a blunt 18-gauge needle to the syringe. Following this, use the needle to apply epoxy down into the ferrule. Fill the ferrule completely with epoxy.Insert fiber into the ferrule so that it is flush with the bottom of the ferrule. If needed, wipe any excess epoxy from the polished surface of the fiber with a wet lint-free wipe prior to drying. In this step, prepare a tower microdrive prior to each testing session.Then affix a 25-gauge guide tube with a beveled tip to the lower clamp on the drive. Secure the large volume illuminator in the upper clamp on the same drive. This clamp is attached to the drive motor.Afterward, thread the large volume illuminator through the guide tube fully, and confirm that the tip of the illuminator extends past the tip of the guide tube. Alternately, lab tape may be applied to the fiber so that the tape, rather than the fiber itself, is clamped, to protect the fiber. Next, soak the guide tube and illuminator in an antiseptic solution for sterilization.Place a custom sterilized grid with one millimeter hole spacing inside the clean chamber, and secure it at a prespecified orientation with the screw on the side of the chamber. Retract the sterilized illuminator from the guide tube by pulling the illuminator up using sterile blunt forceps. The tip of the illuminator should be five to 10 millimeters above the tip of the guide tube.Affix the microdrive to the holder and place the guide tube into the target grid hole. Then, lower the microdrive stage until the guide tube is just through the level of the dura. At the same time, lower the illuminator manually with sterile forceps.If there is any resistance, retract the illuminator five to 10 millimeters, wait 10 minutes, and try again. If there is still resistance on the second attempt, retract the illuminator tip into the guide tube, lower the guide tube 0.25 millimeters, and try again. Connect the ferrule on the other end of the illuminator to the larger optic setup or laser.This figure shows that the error rates increased significantly with illumination. And the raster plots here show the inhibition of neurons spanning the 2.5 millimeter thickness of cortex. And the local field potential showing the light artifact spanning 4.5 millimeters.Once mastered, a large volume illuminator can be constructed using this technique in 10 to 15 minutes, plus epoxy drying time. Calibration adds another half hour or so, so to maximize efficiency, we usually make several illuminators at once. While attending this procedure, it's important to remember that many of the illuminators won't meet quality control standards.That's okay. If they fail tip inspection, we discard them. But if they fail calibration, we usually repolish them and repeat the calibration.After its development, this technique helped pave the way for researchers in the field of neuroscience to use optogenetics to suppress neuronal firing and modulate behavior in non-human primates. After watching this video, you should have a good understanding of how to construct a large volume tissue illuminator.

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Research

JoVE Journal

Behavior

8.0K vistas.  Massachusetts Institute of Technology. The overall goal of this protocol is to create a large volume tissue illuminator that is well suited to optogenetic manipulations in non human primates. This method can help answer key questions in the field of neuroscience, such as how do populations of neurons in the different brain regions contribute to behavior, and how can temporally specific neuronal firing patterns in one region impact another region? The main advantage of this technique is that it uses light, and thus allows optogenet...