Name: an open-source virtual reality system for the measurement of spatial learning in head-restrained mice
Uploaded: 2023-03-03T13:33:00.000+00:00
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Description: Watch this Scientific Journal Video about An Open-Source Virtual Reality System for the Measurement of Spatial Learning in Head-Restrained Mice at JoVE.com

We would like to thank Noah Pettit from the Harvey lab for the discussion and suggestions while developing the protocol in this manuscript. This work was supported by a BBRF Young Investigator Award and NIMH 1R21MH122965 (G.F.T.), in addition to NINDS R56NS128177 (R.H., C.L.) and NIMH R01MH068542 (R.H.).

<ol>
	<li>Lisman, 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=Viewpoints:+How+the+hippocampus+contributes+to+memory,+navigation+and+cognition.">Viewpoints: How the hippocampus contributes to memory, navigation and cognition.</a> Nature Neuroscience. 20 (11), 1434-1447 (2017).</li><li>Buzsaki, G., Moser, E. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Memory,+navigation+and+theta+rhythm+in+the+hippocampal-entorhinal+system.">Memory, navigation and theta rhythm in the hippocampal-entorhinal system.</a> Nature Neuroscience. 16 (2), 130-138 (2013).</li><li>O'Keefe, J., Dostrovsky, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+hippocampus+as+a+spatial+map.+Preliminary+evidence+from+unit+activity+in+the+freely-moving+rat.">The hippocampus as a spatial map. Preliminary evidence from unit activity in the freely-moving rat.</a> Brain Research. 34 (1), 171-175 (1971).</li><li>O'Keefe, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Place+units+in+the+hippocampus+of+the+freely+moving+rat.">Place units in the hippocampus of the freely moving rat.</a> Experimental Neurology. 51 (1), 78-109 (1976).</li><li>Fyhn, M., Molden, S., Witter, M. P., Moser, E. I., Moser, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatial+representation+in+the+entorhinal+cortex.">Spatial representation in the entorhinal cortex.</a> Science. 305 (5688), 1258-1264 (2004).</li><li>Letzkus, 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=A+disinhibitory+microcircuit+for+associative+fear+learning+in+the+auditory+cortex.">A disinhibitory microcircuit for associative fear learning in the auditory cortex.</a> Nature. 480 (7377), 331-335 (2011).</li><li>Lacefield, C. O., Pnevmatikakis, E. A., Paninski, L., Bruno, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reinforcement+learning+recruits+somata+and+apical+dendrites+across+layers+of+primary+sensory+cortex.">Reinforcement learning recruits somata and apical dendrites across layers of primary sensory cortex.</a> Cell Reports. 26 (8), 2000-2008 (2019).</li><li>Dombeck, D. A., Harvey, C. D., Tian, L., Looger, L. L., 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=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> Nature Neuroscience. 13 (11), 1433-1440 (2010).</li><li>Gauthier, J. L., 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=A+dedicated+population+for+reward+coding+in+the+hippocampus.">A dedicated population for reward coding in the hippocampus.</a> Neuron. 99 (1), 179-193 (2018).</li><li>Rickgauer, J. P., Deisseroth, K., 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=Simultaneous+cellular-resolution+optical+perturbation+and+imaging+of+place+cell+firing+fields.">Simultaneous cellular-resolution optical perturbation and imaging of place cell firing fields.</a> Nature Neuroscience. 17 (12), 1816-1824 (2014).</li><li>Yadav, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prefrontal+feature+representations+drive+memory+recall.">Prefrontal feature representations drive memory recall.</a> Nature. 608 (7921), 153-160 (2022).</li><li>Priestley, J. B., Bowler, J. C., Rolotti, S. V., Fusi, S., Losonczy, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Signatures+of+rapid+plasticity+in+hippocampal+CA1+representations+during+novel+experiences.">Signatures of rapid plasticity in hippocampal CA1 representations during novel experiences.</a> Neuron. 110 (12), 1978-1992 (2022).</li><li>Heys, J. G., Rangarajan, K. V., Dombeck, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+functional+micro-organization+of+grid+cells+revealed+by+cellular-resolution+imaging.">The functional micro-organization of grid cells revealed by cellular-resolution imaging.</a> Neuron. 84 (5), 1079-1090 (2014).</li><li>Harvey, C. D., Collman, F., Dombeck, D. A., 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=Intracellular+dynamics+of+hippocampal+place+cells+during+virtual+navigation.">Intracellular dynamics of hippocampal place cells during virtual navigation.</a> Nature. 461 (7266), 941-946 (2009).</li><li>. Harvey Lab Mouse VR Available from: <a target="_blank" href="https://github.com/Harvey/Lab/mouseVR">https://github.com/Harvey/Lab/mouseVR</a> (2021)</li><li>Pettit, N. L., Yap, E. L., Greenberg, M. E., Harvey, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fos+ensembles+encode+and+shape+stable+spatial+maps+in+the+hippocampus.">Fos ensembles encode and shape stable spatial maps in the hippocampus.</a> Nature. 609 (7926), 327-334 (2022).</li><li>Turi, G. F., 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=Vasoactive+intestinal+polypeptide-expressing+interneurons+in+the+hippocampus+support+goal-oriented+spatial+learning.">Vasoactive intestinal polypeptide-expressing interneurons in the hippocampus support goal-oriented spatial learning.</a> Neuron. 101 (6), 1150-1165 (2019).</li><li>Ulivi, A. F., 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=Longitudinal+two-photon+imaging+of+dorsal+hippocampal+CA1+in+live+mice.">Longitudinal two-photon imaging of dorsal hippocampal CA1 in live mice.</a> Journal of Visual Experiments. (148), e59598 (2019).</li><li>Wang, Y., Zhu, D., Liu, B., Piatkevich, K. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Craniotomy+procedure+for+visualizing+neuronal+activities+in+hippocampus+of+behaving+mice.">Craniotomy procedure for visualizing neuronal activities in hippocampus of behaving mice.</a> Journal of Visual Experiments. (173), e62266 (2021).</li><li>Tuncdemir, S. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Parallel+processing+of+sensory+cue+and+spatial+information+in+the+dentate+gyrus.">Parallel processing of sensory cue and spatial information in the dentate gyrus.</a> Cell Reports. 38 (3), 110257 (2022).</li><li>Dombeck, D. A., Khabbaz, A. N., Collman, F., Adelman, T. L., 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=Imaging+large-scale+neural+activity+with+cellular+resolution+in+awake,+mobile+mice.">Imaging large-scale neural activity with cellular resolution in awake, mobile mice.</a> Neuron. 56 (1), 43-57 (2007).</li><li>Guo, Z. V., 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=Procedures+for+behavioral+experiments+in+head-fixed+mice.">Procedures for behavioral experiments in head-fixed mice.</a> PLoS One. 9 (2), 88678 (2014).</li><li>Jordan, J. T., Gon&#231;alves, J. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silencing+of+hippocampal+synaptic+transmission+impairs+spatial+reward+search+on+a+head-fixed+tactile+treadmill+task.">Silencing of hippocampal synaptic transmission impairs spatial reward search on a head-fixed tactile treadmill task.</a> bioRxiv. , (2021).</li><li>Urai, A. E., 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=Citric+acid+water+as+an+alternative+to+water+restriction+for+high-yield+mouse+behavior.">Citric acid water as an alternative to water restriction for high-yield mouse behavior.</a> eNeuro. 8 (1), (2021).</li><li>Saleem, A. B., Diamanti, E. M., Fournier, J., Harris, K. D., Carandini, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coherent+encoding+of+subjective+spatial+position+in+visual+cortex+and+hippocampus.">Coherent encoding of subjective spatial position in visual cortex and hippocampus.</a> Nature. 562 (7725), 124-127 (2018).</li><li>Ravassard, P., 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=Multisensory+control+of+hippocampal+spatiotemporal+selectivity.">Multisensory control of hippocampal spatiotemporal selectivity.</a> Science. 340 (6138), 1342-1346 (2013).</li><li>Aghajan, Z. M., 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=Impaired+spatial+selectivity+and+intact+phase+precession+in+two-dimensional+virtual+reality.">Impaired spatial selectivity and intact phase precession in two-dimensional virtual reality.</a> Nature Neuroscience. 18 (1), 121-128 (2015).</li></ol>

Clay Lacefield is the founder and maintainer of OpenMaze.org, which provides designs for the OMwSmall PCB used in this protocol free for download.

This open-source VR system for mice will only function if the serial connections are made properly between the rotary and behavior ESP32 microcontrollers and the single-board computer (step 2), which can be confirmed using the IDE serial monitor (step 2.4.5). For successful behavioral results from this protocol (step 4), the mice must be habituated to the apparatus and be comfortable running on the wheel for liquid rewards (steps 4.3-4.5). This requires sufficient (but not excessive) water restriction, as mice given ...

Spatial navigation is an ethologically important behavior by which animals encode the features of new locations into a cognitive map, which is used for finding areas of possible reward and avoiding areas of potential danger. Inextricably linked with memory, the cognitive processes underlying spatial navigation share a neural substrate in the hippocampus1 and cortex, where neural circuits in these areas integrate incoming information and form cognitive maps of environments and events for later recall2. While the discovery of place cells in the hippocampus3,4 and grid cells in the entorhinal cortex5 has shed light on how the cognitive map within the hippocampus is formed, many questions remain about how specific neural subtypes, microcircuits, and individual subregions of the hippocampus (the dentate gyrus, and cornu ammonis areas, CA3-1) interact and participate in spatial memory formation and recall.
In vivo two-photon imaging has been a useful tool in uncovering cellular and population dynamics in sensory neurophysiology6,7; however, the typical necessity for head restraint limits the utility of this method for examining mammalian spatial behavior. The advent of virtual reality (VR)8 has addressed this shortcoming by presenting immersive and realistic visuospatial environments while head-restrained mice run on a ball or treadmill to study spatial and contextual encoding in the hippocampus8,9,10 and cortex11. Furthermore, the use of VR environments with behaving mice has allowed neuroscience researchers to dissect the components of spatial behavior by precisely controlling the elements of the VR environment12 (e.g., visual flow, contextual modulation) in ways not possible in real-world experiments of spatial learning, such as the Morris water maze, Barnes maze, or hole board tasks.
Visual VR environments are typically rendered on the graphical processing unit (GPU) of a computer, which handles the load of rapidly computing the thousands of polygons necessary to model a moving 3D environment on a screen in real time. The large processing requirements generally require the use of a separate PC with a GPU that renders the visual environment to a monitor, multiple screens13, or a projector14 as the movement is recorded from a treadmill, wheel, or foam ball under the animal. The resulting apparatus for controlling, rendering, and projecting the VR environment is, therefore, relatively expensive, bulky, and cumbersome. Furthermore, many such environments in the literature have been implemented using proprietary software that is both costly and can only be run on a dedicated PC.
For these reasons, we have designed an open-source VR system to study spatial learning behaviors in head-restrained mice using a Raspberry Pi single-board computer. This Linux computer is both small and inexpensive yet contains a GPU chip for 3D rendering, allowing the integration of VR environments with the display or behavioral apparatus in varied individual setups. Furthermore, we have developed a graphical software package written in Python, &#34;HallPassVR&#34;, which utilizes the single-board computer to render a simple visuospatial environment, a virtual linear track or hallway, by recombining custom visual features selected using a graphical user interface (GUI). This is combined with microcontroller subsystems (e.g., ESP32 or Arduino) to measure locomotion and coordinate behavior, such as by the delivery of other modalities of sensory stimuli or rewards to facilitate reinforcement learning. This system provides an inexpensive, flexible, and easy-to-use alternative method for delivering visuospatial VR environments to head-restrained mice during two-photon imaging (or other techniques requiring head fixation) for studying the neural circuits underlying spatial learning behavior.

<table><tbody><tr><td>1/4 &quot; diam aluminum rod</td><td>McMaster-Carr</td><td>9062K26</td><td>3&quot; in length for wheel axle</td></tr><tr><td>1/4&quot;-20 cap screws, 3/4&quot; long (x2)</td><td>Amazon.com</td><td>B09ZNMR41V</td><td>for affixing head post holders to optical posts</td></tr><tr><td>2&quot;x7&quot; T-slotted aluminum bar (x2)</td><td>8020.net</td><td>1020</td><td>wheel/animal mounting frame</td></tr><tr><td>6&quot; diam, 3&quot; wide acrylic cylinder (1/8&quot; thick)</td><td>Canal Plastics</td><td>33210090702</td><td>Running wheel (custom width cut at canalplastics.com)</td></tr><tr><td>8-32 x 1/2&quot; socket head screws</td><td>McMaster-Carr</td><td>92196A194</td><td>fastening head post holder to optical post&amp;nbsp;</td></tr><tr><td>Adjustable arm (14&quot;)</td><td>Amazon.com</td><td>B087BZGKSL</td><td>to hold/adjust lick spout</td></tr><tr><td>Analysis code (MATLAB)</td><td></td><td>custom written</td><td>file at github.com/GergelyTuri/HallPassVR/software/Analysis code</td></tr><tr><td>Axle mounting flange, 1/4&quot; ID</td><td>Pololu</td><td>1993</td><td>for mounting wheel to axle</td></tr><tr><td>Ball bearing (5/8&quot; OD, 1/4&quot; ID, x2)</td><td>McMaster-Carr</td><td>57155K324</td><td>for mounting wheel axle to frame</td></tr><tr><td>Behavior ESP32 code</td><td></td><td>custom written</td><td>file at github.com/GergelyTuri/HallPassVR/software/Arduino code/Behavior board</td></tr><tr><td>Black opaque matte acrylic sheets (1/4&quot; thick)</td><td>Canal Plastics</td><td>32918353422</td><td>laser cut file at github.com/GergelyTuri/HallPassVR/hardware/VR screen assembly</td></tr><tr><td>Clear acrylic sheet (1/4&quot; thick)</td><td>Canal Plastics</td><td>32920770574</td><td>laser cut file at github.com/GergelyTuri/HallPassVR/hardware/VR wheel assembly</td></tr><tr><td>ESP32 devKitC v4 (x2)</td><td>Amazon.com</td><td>B086YS4Z3F</td><td>microcontroller for behavior and rotary encoder</td></tr><tr><td>ESP32 shield</td><td>OpenMaze.org</td><td>OMwSmall</td><td>description at www.openmaze.org (https://claylacefield.wixsite.com/openmazehome/copy-of-om2shield). ZIP gerber files at: https://github.com/claylacefield/OpenMaze/tree/master/OM_PCBs</td></tr><tr><td>Fasteners and brackets&amp;nbsp;</td><td>8020.net</td><td>4138, 3382,3280</td><td>for wheel frame mounts</td></tr><tr><td>goniometers</td><td>Edmund Optics</td><td>66-526, 66-527</td><td>optional for behavior. Fine tuning head for imaging</td></tr><tr><td>HallPassVR python code</td><td></td><td>custom written</td><td>file at github.com/GergelyTuri/HallPassVR/software/HallPassVR</td></tr><tr><td>Head post holder</td><td></td><td>custom design</td><td>3D design file at github.com/GergelyTuri/HallPassVR/hardware/VR head mount/Headpost Clamp</td></tr><tr><td>LED projector</td><td>Texas Instruments</td><td>DLPDLCR230NPEVM</td><td>or other small LED projector</td></tr><tr><td>Lick spout</td><td>VWR</td><td>20068-638</td><td>(or ~16 G metal hypodermic tubing)</td></tr><tr><td>M 2.5 x 6 set screws</td><td>McMaster-Carr</td><td>92015A097</td><td>securing head post&amp;nbsp;</td></tr><tr><td>Matte white diffusion paper</td><td>Amazon.com</td><td></td><td>screen material</td></tr><tr><td>Metal headposts</td><td></td><td>custom design</td><td>3D design file at github.com/GergelyTuri/HallPassVR/hardware/VR head mount/head post designs</td></tr><tr><td>Miscellenous tubing and tubing adapters (1/16&quot; ID)</td><td></td><td></td><td>for constructing the water line</td></tr><tr><td>Optical breadboard</td><td>Thorlabs</td><td>as per user&#039;s requirements</td><td></td></tr><tr><td>Optical posts, 1/2&quot; diam (2x)</td><td>Thorlabs</td><td>TR4</td><td>for head fixation setup</td></tr><tr><td>Processing code</td><td></td><td>custom written</td><td>file at github.com/GergelyTuri/HallPassVR/software/Processing code</td></tr><tr><td>Raspberry Pi 4B</td><td>raspberry.com, adafruit.com</td><td></td><td>Single-board computer for rendering of HallPassVR envir.</td></tr><tr><td>Right angle clamp</td><td>Thorlabs</td><td>RA90</td><td>for head fixation setup</td></tr><tr><td>Rotary encoder (quadrature, 256 step)</td><td>DigiKey</td><td>ENS1J-B28-L00256L</td><td>to measure wheel rotation</td></tr><tr><td>Rotary encoder ESP32 code</td><td></td><td>custom written</td><td>file at github.com/GergelyTuri/HallPassVR/software/Arduino code/Rotary encoder</td></tr><tr><td>SCIGRIP 10315 acrylic cement</td><td>Amazon.com</td><td></td><td></td></tr><tr><td>Shaft coupler</td><td>McMaster-Carr</td><td>9861T426</td><td>to couple rotary encoder shaft with axle</td></tr><tr><td>Silver mirror acrylic sheets</td><td>Canal Plastics</td><td>32913817934</td><td>laser cut file at github.com/GergelyTuri/HallPassVR/hardware/VR screen assembly</td></tr><tr><td>Solenoid valve</td><td>Parker</td><td>003-0137-900</td><td>to administer water rewards</td></tr></tbody></table>

an open-source virtual reality system for the measurement of spatial learning in head-restrained mice

Head-restrained behavioral experiments in mice allow neuroscientists to observe neural circuit activity with high-resolution electrophysiological and optical imaging tools while delivering precise sensory stimuli to a behaving animal. Recently, human and rodent studies using virtual reality (VR) environments have shown VR to be an important tool for uncovering the neural mechanisms underlying spatial learning in the hippocampus and cortex, due to the extremely precise control over parameters such as spatial and contextual cues. Setting up virtual environments for rodent spatial behaviors can, however, be costly and require an extensive background in engineering and computer programming. Here, we present a simple yet powerful system based upon inexpensive, modular, open-source hardware and software that enables researchers to study spatial learning in head-restrained mice using a VR environment. This system uses coupled microcontrollers to measure locomotion and deliver behavioral stimuli while head-restrained mice run on a wheel in concert with a virtual linear track environment rendered by a graphical software package running on a single-board computer. The emphasis on distributed processing allows researchers to design flexible, modular systems to elicit and measure complex spatial behaviors in mice in order to determine the connection between neural circuit activity and spatial learning in the mammalian brain.

This open-source virtual reality behavioral setup allowed us to quantify licking behavior as a read-out of spatial learning as head-restrained mice navigated a virtual linear track environment. Seven C57BL/6 mice of both sexes at 4 months of age were placed on a restricted water schedule and first trained to lick continuously at low levels while running on the wheel for random spatial rewards (&#34;random foraging&#34;) without VR. Although their performance was initially affected when moved to the VR projection screen s...

Watch this Scientific Journal Video about An Open-Source Virtual Reality System for the Measurement of Spatial Learning in Head-Restrained Mice at JoVE.com

An Open-Source Virtual Reality System for the Measurement of Spatial Learning in Head-Restrained Mice

Here, we present a simplified open-source hardware and software setup for investigating mouse spatial learning using virtual reality (VR). This system displays a virtual linear track to a head-restrained mouse running on a wheel by utilizing a network of microcontrollers and a single-board computer running an easy-to-use Python graphical software package.

Head-restrained behavioral experiments in mice allow neuroscientists to observe neural circuit activity with high-resolution electrophysiological and ...

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Research

JoVE Journal

Neuroscience

1.9K Views.  New York State Psychiatric Institute. Here, we present a simplified open-source hardware and software setup for investigating mouse spatial learning using virtual reality (VR). This system displays a virtual linear track to a head-restrained mouse running on a wheel by utilizing a network of microcontrollers and a single-board computer running an easy-to-use Python graphical software package.

Video: An Open-Source Virtual Reality System for the Measurement of Spatial Learning in Head-Restrained Mice

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.

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 ...

Behavior

Assessing Spatial Memory Impairment in a Mouse Model of Traumatic Brain Injury Using a Radial Water Tread Maze

Despite the recent increase in use of mouse models in scientific research, researchers continue to use cognitive tasks that were originally designed and validated for rat use. The Radial Water Tread (RWT) maze test of spatial memory (designed specifically for mice and requiring no swimming) has been shown previously to successfully distinguish between controlled cortical impact-induced TBI mice and sham controls. Here, a detailed protocol for this task is presented. The RWT maze capitalizes on the natural tendency of mice to avoid open areas in favor of hugging the sides of an apparatus (thigmotaxis). The walls of the maze are lined with nine escape holes placed above the floor of the apparatus, and mice are trained to use visual cues to locate the escape hole that leads out of the maze. The maze is filled with an inch of cold water, sufficient to motivate escape but not deep enough to require that the mouse swim. The acquisition period takes only four training days, with a test of memory retention on day five and a long-term memory test on day 12. The results reported here suggest that the RWT maze is a feasible alternative to rat-validated, swimming-based cognitive tests in the assessment of spatial memory deficits in mouse models of TBI.

Here we present a protocol for a mouse-specific test of cognition that does not require swimming. This test can be used to successfully distinguish controlled cortical impact-induced traumatic brain injury mice from sham controls.

Despite the recent increase in use of mouse models in scientific research, researchers continue to use cognitive tasks that were originally designed and ...

Video-oculography in Mice

Eye movements are very important in order to track an object or to stabilize an image on the retina during movement. Animals without a fovea, such as the mouse, have a limited capacity to lock their eyes onto a target. In contrast to these target directed eye movements, compensatory ocular eye movements are easily elicited in afoveate animals1,2,3,4. Compensatory ocular movements are generated by processing vestibular and optokinetic information into a command signal that will drive the eye muscles. The processing of the vestibular and optokinetic information can be investigated separately and together, allowing the specification of a deficit in the oculomotor system. The oculomotor system can be tested by evoking an optokinetic reflex (OKR), vestibulo-ocular reflex (VOR) or a visually-enhanced vestibulo-ocular reflex (VVOR). The OKR is a reflex movement that compensates for "full-field" image movements on the retina, whereas the VOR is a reflex eye movement that compensates head movements. The VVOR is a reflex eye movement that uses both vestibular as well as optokinetic information to make the appropriate compensation. The cerebellum monitors and is able to adjust these compensatory eye movements. Therefore, oculography is a very powerful tool to investigate brain-behavior relationship under normal as well as under pathological conditions (f.e. of vestibular, ocular and/or cerebellar origin).
Testing the oculomotor system, as a behavioral paradigm, is interesting for several reasons. First, the oculomotor system is a well understood neural system5. Second, the oculomotor system is relative simple6; the amount of possible eye movement is limited by its ball-in-socket architecture ("single joint") and the three pairs of extra-ocular muscles7. Third, the behavioral output and sensory input can easily be measured, which makes this a highly accessible system for quantitative analysis8. Many behavioral tests lack this high level of quantitative power. And finally, both performance as well as plasticity of the oculomotor system can be tested, allowing research on learning and memory processes9.
Genetically modified mice are nowadays widely available and they form an important source for the exploration of brain functions at various levels10. In addition, they can be used as models to mimic human diseases. Applying oculography on normal, pharmacologically-treated or genetically modified mice is a powerful research tool to explore the underlying physiology of motor behaviors under normal and pathological conditions. Here, we describe how to measure video-oculography in mice8.

Video-oculography is a very quantitative method to investigate ocular motor performance as well as motor learning. Here, we describe how to measure video-oculography in mice. Applying this technique on normal, pharmacologically-treated or genetically modified mice is a powerful research tool to explore the underlying physiology of motor behaviors.

Eye movements are very important in order to track an object or to stabilize an image on the retina during movement. Animals without a fovea, such as the ...

Utilizing a Reconfigurable Maze System to Enhance the Reproducibility of Spatial Navigation Tests in Rodents

Several maze shapes are used to test spatial navigation performance and behavioral phenotypes. Traditionally, each experiment requires a unique maze shape, thus requiring several separate mazes in different configurations. The maze geometry cannot be reconfigured in a single environment to accommodate scalability and reproducibility. The reconfigurable maze is a unique approach to address the limitations, allowing quick and flexible configurations of maze pathways in a repeatable manner. It consists of interlocking pathways and includes feeders, treadmills, movable walls, and shut-off sensors. The current protocol describes how the reconfigurable maze can replicate existing mazes, including the T-shaped, plus-shaped, W-shaped, and figure-eight mazes. Initially, the T-shaped maze was constructed inside a single experimental room, followed by modifications. The rapid and scalable protocol outlined herein demonstrates the flexibility of the reconfigurable maze, achieved through the addition of components and behavioral training phases in a stepwise manner. The reconfigurable maze systematically and precisely assesses the performance of multiple aspects of spatial navigation behavior.

The present protocol describes a reconfigurable maze, a unique system for testing spatial navigation and behavioral phenotypes in rodents. The adaptability of this maze system enables the execution of various experiments in a single physical environment. The ease of structural rearrangement generates reliable and reproducible experimental results.

Several maze shapes are used to test spatial navigation performance and behavioral phenotypes. Traditionally, each experiment requires a unique maze ...

Game-Based Exploration: Unlocking Human Spatial Navigation Abilities

Assessing Human Spatial Navigation in a Virtual Space and its Sensitivity to Exercise

Spatial navigation (SN) is the ability to locomote through the environment, which requires an understanding of where one is located in time and space. This capacity is known to rely on the sequential firing of place cells within the hippocampus. SN is an important behavior to investigate as this process deteriorates with age, especially in neurodegenerative disorders. However, the investigation of SN is limited by the lack of sophisticated behavioral techniques to assess this hippocampal-dependent task. Therefore, the goal of this protocol was to develop a novel, real-world approach to studying SN in humans. Specifically, an active virtual SN task was developed using a cross-platform game engine. During the encoding phase, participants navigated their way through a virtual city to locate landmarks. During the remembering phase, participants remembered where these reward locations were and delivered items to these locations. Time to find each location was captured and episodic memory was assessed by a free recall phase, including aspects of place, order, item, and association. Movement behavior (x, y, and z coordinates) was assessed through an asset available in the game engine. Importantly, results from this task demonstrate that it accurately captures both spatial learning and memory abilities as well as episodic memory. Further, findings indicate that this task is sensitive to exercise, which improves hippocampal functioning. Overall, the findings suggest a novel way to track human hippocampal functioning over the course of time, with this behavior being sensitive to physical activity training paradigms.

Author Spotlight: Investigating the Effects of Mind-Body-Movement Practices on Brain Function

Here, we present a novel, brief, and active spatial navigation task that assesses both spatial navigation and episodic memory ability. Importantly, spatial navigation and episodic memory were associated with one another, and this task demonstrated sensitivity to exercise.

Spatial navigation (SN) is the ability to locomote through the environment, which requires an understanding of where one is located in time and space. ...

Understanding Spatial Learning in Mice Using the Active Place Avoidance Test

The Active Place Avoidance (APA) Test, an Effective, Versatile and Repeatable Spatial Learning Task for Mice

Hippocampus-dependent spatial learning in rodents has been tested using a variety of methods. These include the Morris water maze (MWM), Y-maze, and novel object location (NOL) tasks. More recently, the active place avoidance (APA) task has been developed as an alternative to these more traditional approaches. In the APA task, mice must use spatial cues placed around a rotating arena to avoid a stationary shock zone. Due to the multiple parameters that can be adjusted, the APA task has been demonstrated to be a very versatile approach. It lends itself to being used longitudinally and repeatedly for the same cohort of mice. Here, we provide a detailed protocol to successfully conduct the APA task. We also highlight alternative APA approaches that can be used to examine different components of spatial learning. We describe the data collection and analysis processes. Critical steps during the APA task are discussed to increase the likelihood of successfully conducting the test. The APA task has several advantages over more traditional spatial navigation tests. It is appropriate to use with aged mice or those with disease phenotypes such as Alzheimer's disease. The complexity of the task can be easily altered, allowing a wide range of mouse strains to be tested. Further, the APA task is suitable for testing animals that have undergone surgery or experimental interventions that may have affected motor or neural function, such as stroke or traumatic brain injury.

Author Spotlight: Investigating the Impact of Aging on Hippocampal-Dependent Spatial Learning

Here, we present a protocol for the active place avoidance test, a hippocampus-dependent spatial learning paradigm designed for rodents. Altering key parameters allows for re-testing of animals before and after treatments or over time.

Hippocampus-dependent spatial learning in rodents has been tested using a variety of methods. These include the Morris water maze (MWM), Y-maze, and novel ...

Behavioral Training Procedures for Head-fixed Virtual Reality in Mice

Virtual reality (VR) combined with head-fixation is increasingly being utilized in behavioral neuroscience studies as it allows complex behavioral assays to be performed in head-fixed mice. This enables precise behavioral recordings while incorporating various neurophysiological techniques that require head-fixation to minimize movement-related signal noise during neural recordings. However, despite the growing use of VR, there is little published data on the detailed methodology of how to implement it. In this study, a training protocol is developed whereby male and female C57B16/J mice are trained to run down a virtual linear corridor, the length of which is increased from 1-3 m over multiple training sessions. Building upon this foundation, this study investigated the feasibility of mice performing complex behaviors within VR using a Y-maze paradigm. The task required navigating to the arm with black walls from the choice point in the Y-maze. After reaching a criterion of two consecutive days equal to or greater than 70% correct, the mice progressed to increasingly difficult sensory discrimination. The findings provide important details on the methodologies useful for the successful training of mice in VR and demonstrate that mice exhibit learning capabilities in navigating the Y-maze. The methodology presented not only offers insights into training duration in VR-based assays but also underscores the potential for probing intricate behaviors in mice, opening avenues for more comprehensive neuroscience investigations.

The article describes the experimental procedures for the commonly used linear track virtual reality (VR) paradigm in mice as well as determining the feasibility of running complex VR tasks by testing a Y-shaped signal discrimination task.

Virtual reality (VR) combined with head-fixation is increasingly being utilized in behavioral neuroscience studies as it allows complex behavioral assays ...

Long-term Sensory Conflict in Freely Behaving Mice

Long-term sensory conflict protocols are a valuable means of studying motor learning. The presented protocol produces a persistent sensory conflict for experiments aimed at studying long-term learning in mice. By permanently wearing a device fixed on their heads, mice are continuously exposed to a sensory mismatch between visual and vestibular inputs while freely moving in home cages. Therefore, this protocol readily enables the study of the visual system and multisensory interactions over an extended timeframe that would not be accessible otherwise. In addition to lowering the experimental costs of long-term sensory learning in naturally behaving mice, this approach accommodates the combination of in vivo and in vitro experiments. In the reported example, video-oculography is performed to quantify the vestibulo-ocular reflex (VOR) and optokinetic reflex (OKR) before and after learning. Mice exposed to this long-term sensory conflict between visual and vestibular inputs presented a strong VOR gain decrease but exhibited few OKR changes. Detailed steps of device assembly, animal care, and reflex measurements are hereby reported.

The presented protocol produces a persistent sensory conflict for experiments aimed at studying long-term learning. By permanently wearing a fixed device on their heads, mice are continuously exposed to a sensory mismatch between visual and vestibular inputs while freely moving in home cages.

Long-term sensory conflict protocols are a valuable means of studying motor learning. The presented protocol produces a persistent sensory conflict for ...

A Flexible Platform for Monitoring Cerebellum-Dependent Sensory Associative Learning

Climbing fiber inputs to Purkinje cells provide instructive signals critical for cerebellum-dependent associative learning. Studying these signals in head-fixed mice facilitates the use of imaging, electrophysiological, and optogenetic methods. Here, a low-cost behavioral platform (~$1000) was developed that allows tracking of associative learning in head-fixed mice that locomote freely on a running wheel. The platform incorporates two common associative learning paradigms: eyeblink conditioning and delayed tactile startle conditioning. Behavior is tracked using a camera and the wheel movement by a detector. We describe the components and setup and provide a detailed protocol for training and data analysis. This platform allows the incorporation of optogenetic stimulation and fluorescence imaging. The design allows a single host computer to control multiple platforms for training multiple animals simultaneously.

We have developed a single platform to track animal behavior during two climbing fiber-dependent associative learning tasks. The low-cost design allows integration with optogenetic or imaging experiments directed towards climbing fiber-associated cerebellar activity.

Climbing fiber inputs to Purkinje cells provide instructive signals critical for cerebellum-dependent associative learning. Studying these signals in ...

Virtual Reality Tools for Assessing Unilateral Spatial Neglect: A Novel Opportunity for Data Collection

Unilateral spatial neglect (USN) is a syndrome characterized by inattention to or inaction in one side of space and affects between 23-46% of acute stroke survivors. The diagnosis and characterization of these symptoms in individual patients can be challenging and often requires skilled clinical staff. Virtual reality (VR) presents an opportunity to develop novel assessment tools for patients with USN.
We aimed to design and build a VR tool to detect and characterize subtle USN symptoms, and to test the tool on subjects treated with inhibitory repetitive transcranial magnetic stimulation (TMS) of cortical regions associated with USN.
We created three experimental conditions by applying TMS to two distinct regions of cortex associated with visuospatial processing- the superior temporal gyrus (STG) and the supramarginal gyrus (SMG) - and applied sham TMS as a control. We then placed subjects in a virtual reality environment in which they were asked to identify the flowers with lateral asymmetries of flowers distributed across bushes in both hemispaces, with dynamic difficulty adjustment based on each subject's performance. 
We found significant differences in average head yaw between subjects stimulated at the STG and those stimulated at the SMG and marginally significant effects in the average visual axis.
VR technology is becoming more accessible, affordable, and robust, presenting an exciting opportunity to create useful and novel game-like tools. In conjunction with TMS, these tools could be used to study specific, isolated, artificial neurological deficits in healthy subjects, informing the creation of VR-based diagnostic tools for patients with deficits due to acquired brain injury. This study is the first to our knowledge in which artificially generated USN symptoms have been evaluated with a VR task.

The goal was to design, build, and pilot a novel virtual reality task to detect and characterize unilateral spatial neglect, a syndrome affecting 23-46% of acute stroke survivors, expanding the role of virtual reality in the study and management of neurologic disease.

Unilateral spatial neglect (USN) is a syndrome characterized by inattention to or inaction in one side of space and affects between 23-46% of acute stroke ...