This work was supported by the Friedrich Miescher Institute for Biomedical Research, the Max Planck Society, and the Human Frontiers Science Program.

All animal procedures were approved and carried out in accordance with guidelines of the Veterinary Department of the Canton Basel-Stadt.
1. Hardware and Software Setup
<ol>
	<li>Two-photon scanning microscope setup:
	<ol>
		<li>Use a pulsed infrared laser as an illumination source (pulse width &#60;120 fsec).</li>
		<li>Use a scan head composed of an 8 or 12 kHz resonant scanner and a standard galvanometer. Note: This enables frame rates of 40 or 60 Hz at 750 x 400 pixels. ...

<ol>
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W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+imaging+of+hippocampal+place+cells+at+cellular+resolution+during+virtual+navigation.">Functional imaging of hippocampal place cells at cellular resolution during virtual navigation.</a> Nat. Neurosci. 13 (11), 1433-1440 (2010).</li><li>Harvey, C. D., Coen, P., Tank, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Choice-specific+sequences+in+parietal+cortex+during+a+virtual-navigation+decision+task.">Choice-specific sequences in parietal cortex during a virtual-navigation decision task.</a> Nature. 484 (7395), 62-68 (2012).</li><li>Huber, D., Gutnisky, D. 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The key to the success of behavioral two-photon imaging is the stability of the preparation in two ways:
<ol>
	<li>Over the course of days post window implantation, inflammatory responses of the tissue can lead to enhancement of the formation of granulation tissue and cartilage that will hinder or even prevent imaging.</li>
	<li>During the experiment the brain has to be stable enough to prevent motion artifacts from corrupting neural activity related fluorescence signal.</li>
</ol>
To keep the...

Two-photon imaging of calcium indicators (genetically encoded like GCaMP57 or R-GECO8, or synthetic dyes like OGB or Fluo4) has emerged as a powerful method of measuring neuronal activity in behaving mice1-6. It enables the simultaneous measurement of the activity of hundreds of cells at near-single action potential resolution, up to approximately 800 &#181;m below the brain surface9,10. Moreover, using genetically encoded calcium indicators (GECIs) neuronal activity can be measured chronically5,11,12, and in genetically defined cell types13. Together, these methods provide a degree of temporal and spatial resolution that open up a multitude of new possibilities in the study of neuronal computation in vivo.
Surgical intervention is necessary to expose and label the mouse brain for imaging. Cells are typically transfected using a recombinant adeno-associated virus (AAV) system for GECI delivery and a cranial window is implanted over the injection site to gain optical access to the brain. A head bar is then attached to the skull for head fixation under the two-photon microscope. The design and implementation of these steps is critical as most of the problems with awake imaging arise from instabilities in the preparation. Ideally the procedure described here should allow for chronic imaging of up to several months following the surgery.
To enable visually guided behavior during two-photon imaging, the head fixed mouse sits on an air supported spherical treadmill, which it can use to navigate a virtual reality environment. Locomotion of the mouse on the treadmill is coupled to movement in the virtual environment that is displayed on a toroidal screen surrounding the mouse14,15. Behavioral variables such as locomotion, visual stimulus, and pupil position can be recorded6.
We describe the procedures involved in chronic two-photon imaging in mice exploring a virtual reality environment. The key points addressed are: reduction of movement artifacts, reduction of light leak, maximization of the number of simultaneously recorded cells, and minimization of photo damage. We also provide details on setting up the air-supported treadmill, pupil tracking, and the virtual reality environment. The procedures described here can be used for imaging fluorescently labeled cell populations in head fixed mice&#160;in a potentially wide variety of behavioral paradigms.

<table border="0" cellpadding="0" cellspacing="0" width="653">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">cover slips (d = 3-5 mm)</td>
			<td style="width:151px;">Menzel</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">window implant</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">InSight DeepSee laser</td>
			<td>Spectra-Physics</td>
			<td></td>
			<td>microscope</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">12kHz resonance scanner</td>
			<td>Cambridge Technology</td>
			<td>G1-003-30026</td>
			<td>microscope</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Galvometer</td>
			<td>Cambridge Technology</td>
			<td>G6215H</td>
			<td>microscope</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Digitizer</td>
			<td>National Instruments</td>
			<td>NI 5772</td>
			<td>microscope</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">FPGA</td>
			<td>National Instruments</td>
			<td>PXIe 7965R</td>
			<td>microscope</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Acquisition card</td>
			<td>National Instruments</td>
			<td>PCIe 6363</td>
			<td>microscope</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Emission filter 525/50</td>
			<td>Semrock</td>
			<td>FF03-525/50-25</td>
			<td>microscope</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Piezo-electric z-drive</td>
			<td>Physikinstrumente</td>
			<td>P-726.1CD</td>
			<td>microscope</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Controller for piezo-electric drive</td>
			<td>Physikinstrumente</td>
			<td>E665 LVPZT</td>
			<td>microscope</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Objective 16x, 0.8NA</td>
			<td>Nikon</td>
			<td>CFI75</td>
			<td>microscope</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Current amplifier</td>
			<td style="width:151px;">Femto</td>
			<td style="width:119px;">DHPCA-100</td>
			<td>microscope</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Photomultiplier tube</td>
			<td style="width:151px;">Hamamatsu</td>
			<td style="width:119px;"></td>
			<td>microscope</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">USB Camera without IR filter</td>
			<td>ImagingSource</td>
			<td>DMK22BUC03&#160;</td>
			<td>pupil tracking</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Objective 50 mm</td>
			<td>ImagingSource</td>
			<td>M5018-MP&#160;</td>
			<td>pupil tracking</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Macro adapter rings</td>
			<td>ImagingSource</td>
			<td>LAexSet</td>
			<td>pupil tracking</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Optical computer mouse</td>
			<td>Logitech</td>
			<td>G500</td>
			<td>motion tracking</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Styrofoam ball 20 cm</td>
			<td>e.g. idee-shop.de</td>
			<td>08797.00.15</td>
			<td>virtual environment</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">LED projector</td>
			<td>Samsung</td>
			<td>SP-F10M&#160;</td>
			<td>virtual environment</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Acquisition card</td>
			<td>National Instruments</td>
			<td style="width:119px;">NI 6009</td>
			<td>virtual environment</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Panda3D game engine</td>
			<td></td>
			<td><a href="http://www.panda3d.org/">www.panda3d.org</a></td>
			<td>virtual environment</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Numpy library for Python</td>
			<td style="width:151px;"></td>
			<td style="width:119px;"><a href="http://www.scipy.org/">www.scipy.org</a></td>
			<td>virtual environment</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Scipy library for Python</td>
			<td style="width:151px;"></td>
			<td style="width:119px;"><a href="http://www.scipy.org/">www.scipy.org</a></td>
			<td>virtual environment</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">NI-DAQmx driver</td>
			<td style="width:151px;">National Instruments</td>
			<td style="width:119px;"><a href="http://www.ni.com/">www.ni.com</a></td>
			<td>virtual environment</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Ultrasound gel</td>
			<td style="width:151px;">Dahlhausen</td>
			<td style="width:119px;">5701.0342.10</td>
			<td>imaging</td>
		</tr>
	</tbody>
</table>

two-photon calcium imaging in mice navigating a virtual reality environment

In recent years, two-photon imaging has become an invaluable tool in neuroscience, as it allows for chronic measurement of the activity of genetically identified cells during behavior1-6. Here we describe methods to perform two-photon imaging in mouse cortex while the animal navigates a virtual reality environment. We focus on the aspects of the experimental procedures that are key to imaging in a behaving animal in a brightly lit virtual environment. The key problems that arise in this experimental setup that we here address are: minimizing brain motion related artifacts, minimizing light leak from the virtual reality projection system, and minimizing laser induced tissue damage. We also provide sample software to control the virtual reality environment and to do pupil tracking. With these procedures and resources it should be possible to convert a conventional two-photon microscope for use in behaving mice.

The image quality in two-photon calcium imaging of cell populations labeled with a GECI largely depends on the quality of the cranial window implant. Two weeks following virus injection the cranial window should be inspected for clarity. There should be no granulation tissue or bone regrowth visible (Figure 1A). Moreover, the pattern of superficial blood vessels should remain unchanged and boundaries of the vasculature should be sharply defined. At the same time, GECI expression can also be checked. Boli...

Watch this Scientific Journal Video about Two-photon Calcium Imaging in Mice Navigating a Virtual Reality Environment at JoVE.com

Two-photon Calcium Imaging in Mice Navigating a Virtual Reality Environment

Here we describe the experimental procedures involved in two-photon imaging of mouse cortex during behavior in a virtual reality environment.

In recent years, two-photon imaging has become an invaluable tool in neuroscience, as it allows for chronic measurement of the activity of genetically ...

two-photon-calcium-imaging-mice-navigating-virtual-reality

Research

JoVE Journal

Behavior

30.7K vistas.  Friedrich Miescher Institute for Biomedical Research.  Aquí se describen los procedimientos experimentales que participan en dos fotones de imágenes de la corteza del ratón durante comportamiento en un entorno de realidad virtual. 