This work was supported by grants from Samsung Science and Technology Foundation (Project Number SSTF-BA1801-10).

<ol>
	<li>Gonzalez, W. G., Zhang, H., Harutyunyan, A., Lois, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Persistence+of+neuronal+representations+through+time+and+damage+in+the+hippocampus.">Persistence of neuronal representations through time and damage in the hippocampus.</a> Science. 365 (6455), 821-825 (2019).</li><li>Ghandour, 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=Orchestrated+ensemble+activities+constitute+a+hippocampal+memory+engram.">Orchestrated ensemble activities constitute a hippocampal memory engram.</a> Nature Communications. 10 (1), 2637 (2019).</li><li>Grundemann, 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=Amygdala+ensembles+encode+behavioral+states.">Amygdala ensembles encode behavioral states.</a> Science. 364 (6437), (2019).</li><li>Krabbe, 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=Adaptive+disinhibitory+gating+by+VIP+interneurons+permits+associative+learning.">Adaptive disinhibitory gating by VIP interneurons permits associative learning.</a> Nature Neuroscience. 22 (11), 1834-1843 (2019).</li><li>Betley, J. 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=Neurons+for+hunger+and+thirst+transmit+a+negative-valence+teaching+signal.">Neurons for hunger and thirst transmit a negative-valence teaching signal.</a> Nature. 521 (7551), 180-185 (2015).</li><li>Jennings, J. H., 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=Visualizing+hypothalamic+network+dynamics+for+appetitive+and+consummatory+behaviors.">Visualizing hypothalamic network dynamics for appetitive and consummatory behaviors.</a> Cell. 160 (3), 516-527 (2015).</li><li>LeDoux, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Emotion+circuits+in+the+brain.">Emotion circuits in the brain.</a> Annual Review of Neuroscience. 23, 155-184 (2000).</li><li>Burgoyne, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+calcium+sensor+proteins:+generating+diversity+in+neuronal+Ca2++signalling.">Neuronal calcium sensor proteins: generating diversity in neuronal Ca2+ signalling.</a> Nature Reviews Neuroscience. 8 (3), 182-193 (2007).</li><li>Miyakawa, H., 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=Synaptically+activated+increases+in+Ca2++concentration+in+hippocampal+CA1+pyramidal+cells+are+primarily+due+to+voltage-gated+Ca2++channels.">Synaptically activated increases in Ca2+ concentration in hippocampal CA1 pyramidal cells are primarily due to voltage-gated Ca2+ channels.</a> Neuron. 9 (6), 1163-1173 (1992).</li><li>Denk, W., Yuste, R., Svoboda, 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=Imaging+calcium+dynamics+in+dendritic+spines.">Imaging calcium dynamics in dendritic spines.</a> Current Opinion in Neurobiology. 6 (3), 372-378 (1996).</li><li>Mank, 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=A+genetically+encoded+calcium+indicator+for+chronic+in+vivo+two-photon+imaging.">A genetically encoded calcium indicator for chronic in vivo two-photon imaging.</a> Nature Methods. 5 (9), 805-811 (2008).</li><li>Akerboom, 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=Genetically+encoded+calcium+indicators+for+multi-color+neural+activity+imaging+and+combination+with+optogenetics.">Genetically encoded calcium indicators for multi-color neural activity imaging and combination with optogenetics.</a> Frontiers in Molecular Neuroscience. 6, 2 (2013).</li><li>Nakai, J., Ohkura, M., Imoto, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+high+signal-to-noise+Ca(2+)+probe+composed+of+a+single+green+fluorescent+protein.">A high signal-to-noise Ca(2+) probe composed of a single green fluorescent protein.</a> Nature Biotechnology. 19 (2), 137-141 (2001).</li><li>Akerboom, 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=Optimization+of+a+GCaMP+calcium+indicator+for+neural+activity+imaging.">Optimization of a GCaMP calcium indicator for neural activity imaging.</a> Journal of Neuroscience. 32 (40), 13819-13840 (2012).</li><li>Chen, T. W., 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=Ultrasensitive+fluorescent+proteins+for+imaging+neuronal+activity.">Ultrasensitive fluorescent proteins for imaging neuronal activity.</a> Nature. 499 (7458), 295-300 (2013).</li><li>Dana, H., 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=High-performance+calcium+sensors+for+imaging+activity+in+neuronal+populations+and+microcompartments.">High-performance calcium sensors for imaging activity in neuronal populations and microcompartments.</a> Nature Methods. 16 (7), 649-657 (2019).</li><li>Zariwala, H. 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=A+Cre-dependent+GCaMP3+reporter+mouse+for+neuronal+imaging+in+vivo.">A Cre-dependent GCaMP3 reporter mouse for neuronal imaging in vivo.</a> Journal of Neuroscience. 32 (9), 3131-3141 (2012).</li><li>Mittmann, W., 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=Two-photon+calcium+imaging+of+evoked+activity+from+L5+somatosensory+neurons+in+vivo.">Two-photon calcium imaging of evoked activity from L5 somatosensory neurons in vivo.</a> Nature Neuroscience. 14 (8), 1089-1093 (2011).</li><li>Huber, D., 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=Multiple+dynamic+representations+in+the+motor+cortex+during+sensorimotor+learning.">Multiple dynamic representations in the motor cortex during sensorimotor learning.</a> Nature. 484 (7395), 473-478 (2012).</li><li>Grewe, B. 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=Neural+ensemble+dynamics+underlying+a+long-term+associative+memory.">Neural ensemble dynamics underlying a long-term associative memory.</a> Nature. 543 (7647), 670-675 (2017).</li><li>Cai, D. 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+shared+neural+ensemble+links+distinct+contextual+memories+encoded+close+in+time.">A shared neural ensemble links distinct contextual memories encoded close in time.</a> Nature. 534 (7605), 115-118 (2016).</li><li>Lin, M. Z., Schnitzer, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetically+encoded+indicators+of+neuronal+activity.">Genetically encoded indicators of neuronal activity.</a> Nature Neuroscience. 19 (9), 1142-1153 (2016).</li><li>Zhang, L., 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=Miniscope+GRIN+Lens+System+for+Calcium+Imaging+of+Neuronal+Activity+from+Deep+Brain+Structures+in+Behaving+Animals.">Miniscope GRIN Lens System for Calcium Imaging of Neuronal Activity from Deep Brain Structures in Behaving Animals.</a> Current Protocols in Neuroscience. 86 (1), 56 (2019).</li><li>Jacob, A. D., 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+Compact+Head-Mounted+Endoscope+for+In+vivo+Calcium+Imaging+in+Freely+Behaving+Mice.">A Compact Head-Mounted Endoscope for In vivo Calcium Imaging in Freely Behaving Mice.</a> Current Protocols in Neuroscience. 84 (1), 51 (2018).</li><li>Ghosh, K. 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=Miniaturized+integration+of+a+fluorescence+microscope.">Miniaturized integration of a fluorescence microscope.</a> Nature Methods. 8 (10), 871-878 (2011).</li><li>Xiong, B., 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=Precise+Cerebral+Vascular+Atlas+in+Stereotaxic+Coordinates+of+Whole+Mouse+Brain.">Precise Cerebral Vascular Atlas in Stereotaxic Coordinates of Whole Mouse Brain.</a> Frontiers in Neuroanatomy. 11, 128 (2017).</li><li>Mukamel, E. A., Nimmerjahn, A., Schnitzer, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automated+analysis+of+cellular+signals+from+large-scale+calcium+imaging+data.">Automated analysis of cellular signals from large-scale calcium imaging data.</a> Neuron. 63 (6), 747-760 (2009).</li><li>Millhouse, O. E., DeOlmos, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+configurations+in+lateral+and+basolateral+amygdala.">Neuronal configurations in lateral and basolateral amygdala.</a> Neuroscience. 10 (4), 1269-1300 (1983).</li><li>McDonald, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+organization+of+the+lateral+and+basolateral+amygdaloid+nuclei+in+the+rat.">Neuronal organization of the lateral and basolateral amygdaloid nuclei in the rat.</a> Journal of Comparative Neurology. 222 (4), 589-606 (1984).</li><li>McDonald, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurons+of+the+lateral+and+basolateral+amygdaloid+nuclei:+a+Golgi+study+in+the+rat.">Neurons of the lateral and basolateral amygdaloid nuclei: a Golgi study in the rat.</a> Journal of Comparative Neurology. 212 (3), 293-312 (1982).</li></ol>

The author has nothing to disclose

Skillful surgery techniques are essential for achieving successful in vivo optical calcium imaging with head-mount miniature microscopy in deeper brain regions such as the amygdala as we described here. Therefore, although this protocol provides a guideline for optimized surgical processes of baseplate attachment and GRIN lens implantation, additional optimization processes might be necessary for critical steps. As mentioned in the protocol section, amygdala coordinates in surgery, airflow speed in baseplate attachment s...

Calcium is a ubiquitous second messenger, playing a crucial role in almost every cellular functions8. In neurons, action potential firing and synaptic input cause rapid change of intracellular free [Ca2+]9,10. Therefore, tracking calcium transients provides an opportunity to monitor neuronal activity. GECIs are powerful tools that allow for monitoring [Ca2+] in defined cell populations and intra-cellular compartments11,12. Among many different types of protein based calcium indicator, GCaMP, a Ca2+ probe based on a single GFP molecule13, is the most optimized and thus widely used GECI. Through multiple rounds of engineering, a number of variants of GCaMP has been developed12,14,15,16. We use one of the recently developed GCaMPs, GCaMP7b, in this protocol16. GCaMP sensors have greatly contributed to the study of neural circuit functions in a number of model organisms such as imaging of Ca2+ transients during development17, in vivo imaging in a specific cortical layer18, measurement of circuit dynamics in motor task learning19 and imaging of cell ensemble activity related with associative fear memory in the hippocampus and amygdala20,21.
Optical imaging of GECIs has several advantages22. Genetic encoding enables GECIs to be stably expressed for a long-term period of time in a specific subset of cells that are defined by genetic profile or specific patterns of anatomical connectivity. Optical imaging enables in vivo chronic simultaneous monitoring of hundreds to thousands of neurons in live animals. A few optical imaging systems have been developed for in vivo imaging and analysis of GECIs within the brain of freely behaving mice with head-mount miniaturized fluorescence microscopes21,23,24,25. Despite the in vivo optical imaging technique based on GECIs, GRIN lens, and a head-mount miniature microscope being a powerful tool to study the link between neural circuit activity and behavior, applying this technology to the amygdala has been difficult due to several technical issues related with targeting the GRIN lens to cells expressing GECIs in the amygdala without causing motion artifacts that severely reduce the quality of image acquisition and finding cells expressing GECIs. This protocol aims to provide a helpful guideline for surgical procedures of baseplate attachment and GRIN lens implantation that are critical steps for successful in vivo optical calcium imaging in the amygdala. Although this protocol targets the amygdala, most procedures described here are commonly applicable to other deeper brain regions. Although this protocol is based on a particular system (e.g., Inscopix), the same purpose may be easily achieved with other alternative systems.

<table><tbody><tr><td>26G needle</td><td>BD</td><td>302002</td><td>Surgery</td></tr><tr><td>AAV1-Syn-GCaMP7b-WPRE</td><td>Addgene</td><td>104493-AAV1</td><td>Surgery</td></tr><tr><td>AAV2/1-CaMKii&amp;alpha;-GFP</td><td>custom made</td><td></td><td>Surgery</td></tr><tr><td>Acrylic-Dental cement (Ortho-jet Acrylic Pink)</td><td>Lang</td><td>1334-pink</td><td>Surgery &amp;amp; Baseplate Attachment</td></tr><tr><td>Air flow manipulator</td><td>Neurotar</td><td>NTR000253-04</td><td>Baseplate Attachment</td></tr><tr><td>Amoxicillin</td><td>SIGMA</td><td>A8523-5G</td><td>Surgery</td></tr><tr><td>Baseplate</td><td>INSCOPIX</td><td>1050-002192</td><td>Baseplate Attachment</td></tr><tr><td>Baseplate cover</td><td>INSCOPIX</td><td>1050-002193</td><td>Baseplate Attachment</td></tr><tr><td>Behavioral apparatus (chamber)</td><td>Coulbourn Instrument</td><td>Testcage</td><td>Behavior test</td></tr><tr><td>Behavioral apparatus (software)</td><td>Coulbourn Instrument</td><td>Freeze Frame</td><td>Behavior test</td></tr><tr><td>Carbon cage</td><td>Neurotar</td><td>180mm x 70mm</td><td>Baseplate Attachment</td></tr><tr><td>Carprofen</td><td>SIGMA</td><td>PHR1452-1G</td><td>Surgery</td></tr><tr><td>Data processing software</td><td>INSCOPIX</td><td>INSCOPIX Data Processing Software</td><td>Baseplate Attachment &amp;amp; Behavior test</td></tr><tr><td>Dexamethasone</td><td>SIGMA</td><td>D1756-500MG</td><td>Surgery</td></tr><tr><td>Drill</td><td>Seyang</td><td>marathon-4</td><td>Surgery</td></tr><tr><td>Drill bur</td><td>ELA</td><td>US1/2, Shank104</td><td>Surgery</td></tr><tr><td>Glass needle</td><td>WPI</td><td>PG10165-4</td><td>Surgery</td></tr><tr><td>GRIN lens (INSCOPIX Proview Lens Probe)</td><td>INSCOPIX</td><td>1050-002208</td><td>Surgery</td></tr><tr><td>Hamilton Syringe</td><td>Hamilton</td><td>84875</td><td>Surgery</td></tr><tr><td>Head plate</td><td>Neurotar</td><td>Model 5</td><td>Surgery</td></tr><tr><td>Hex-key</td><td>INSCOPIX</td><td>1050-004195</td><td>Baseplate Attachment</td></tr><tr><td>Laptop computer</td><td>Samsung</td><td>NT950XBV</td><td>Surgery &amp;amp; Baseplate Attachment</td></tr><tr><td>Lens holder, Stereotaxic rod (INSCOPIX proview implant kit)</td><td>INSCOPIX</td><td>1050-004223</td><td>Surgery</td></tr><tr><td>Microscope gripper</td><td>INSCOPIX</td><td>1050-002199</td><td>Baseplate Attachment</td></tr><tr><td>Microscope, DAQ software, hardware</td><td>INSCOPIX</td><td>nVista 3.0</td><td>Baseplate Attachment &amp;amp; Behavior test</td></tr><tr><td>Mobile homecage</td><td>Neurotar</td><td>MHC V5</td><td>Baseplate Attachment</td></tr><tr><td>Moterized arm</td><td>Neurostar</td><td>Customized</td><td>Surgery</td></tr><tr><td>Moterized arm software</td><td>Neurostar</td><td>Customized</td><td>Surgery</td></tr><tr><td>NI board</td><td>National instrument</td><td></td><td>Behavior test</td></tr><tr><td>Removable epoxy bond</td><td>WPI</td><td>Kwik-Cast</td><td>Surgery</td></tr><tr><td>Resin cement (Super-bond)</td><td>Sun medical</td><td>Super bond C&amp;amp;B</td><td>Surgery</td></tr><tr><td>Skull screw</td><td>Stoelting</td><td>51457</td><td>Surgery</td></tr><tr><td>Stereotaxic electrode holder</td><td>ASI</td><td>EH-600</td><td>Surgery</td></tr><tr><td>Stereotaxic frame</td><td>Stoelting</td><td>51600</td><td>Surgery</td></tr><tr><td>Stereotaxic manipulator</td><td>Stoelting</td><td>51600</td><td>Baseplate Attachment</td></tr></tbody></table>

successful in vivo calcium imaging with a head-mount miniaturized microscope in the amygdala of freely behaving mouse

In vivo real-time monitoring of neuronal activities in freely moving animals is one of key approaches to link neuronal activity to behavior. For this purpose, an in vivo imaging technique that detects calcium transients in neurons using genetically encoded calcium indicators (GECIs), a miniaturized fluorescence microscope, and a gradient refractive index (GRIN) lens has been developed and successfully applied to many brain structures1,2,3,4,5,6. This imaging technique is particularly powerful because it enables chronic simultaneous imaging of genetically defined cell populations for a long-term period up to several weeks. Although useful, this imaging technique has not been easily applied to brain structures that locate deep within the brain such as amygdala, an essential brain structure for emotional processing and associative fear memory7. There are several factors that make it difficult to apply the imaging technique to the amygdala. For instance, motion artifacts usually occur more frequently during the imaging conducted in the deeper brain regions because a head-mount microscope implanted deep in the brain is relatively unstable. Another problem is that the lateral ventricle is positioned close to the implanted GRIN lens and its movement during respiration may cause highly irregular motion artifacts that cannot be easily corrected, which makes it difficult to form a stable imaging view. Furthermore, because cells in the amygdala are usually quiet at a resting or anesthetized state, it is hard to find and focus the target cells expressing GECI in the amygdala during baseplating procedure for later imaging. This protocol provides a helpful guideline for how to efficiently target cells expressing GECI in the amygdala with head-mount miniaturized microscope for successful in vivo calcium imaging in such a deeper brain region. It is noted that this protocol is based on a particular system (e.g., Inscopix) but not restricted to it.

Validation of GRIN lens implantation 
Before chronically attaching the baseplate to the brain by cementing, the GRIN lens implantation needs to be validated. In animals with successful lens implantation, both GCaMP expressing cells and blood vessels were clearly observed within a focal plane range determined by the distance between objective lens of microscope and implanted GRIN lens (Figure 2A and B). In contrast, in animals with off-t...

Watch this Scientific Journal Video about Successful In vivo Calcium Imaging with a Head-Mount Miniaturized Microscope in the Amygdala of Freely Behaving Mouse at JoVE.com

Successful In vivo Calcium Imaging with a Head-Mount Miniaturized Microscope in the Amygdala of Freely Behaving Mouse

In vivo microendoscopic calcium imaging is an invaluable tool that enables real-time monitoring of neuronal activities in freely behaving animals. However, applying this technique to the amygdala has been difficult. This protocol aims to provide a useful guideline for successfully targeting amygdala cells with a miniaturized microscope in mice.

In vivo real-time monitoring of neuronal activities in freely moving animals is one of key approaches to link neuronal activity to behavior. For this ...

successful-vivo-calcium-imaging-with-head-mount-miniaturized

Research

JoVE Journal

Neuroscience

12.1K Views.  Korea Advanced Institute of Science and Technology (KAIST). In vivo microendoscopic calcium imaging is an invaluable tool that enables real-time monitoring of neuronal activities in freely behaving animals. However, applying this technique to the amygdala has been difficult. This protocol aims to provide a useful guideline for successfully targeting amygdala cells with a miniaturized microscope in mice.

Video: Successful In vivo Calcium Imaging with a Head-Mount Miniaturized Microscope in the Amygdala of Freely Behaving Mouse

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

In vivo Calcium Imaging in Mouse Inferior Olive

Inferior olive (IO), a nucleus in the ventral medulla, is the only source of climbing fibers that form one of the two input pathways entering the cerebellum. IO has long been proposed to be crucial for motor control and its activity is currently considered to be at the center of many hypotheses of both motor and cognitive functions of the cerebellum. While its physiology and function have been relatively well studied on single-cell level in vitro, presently there are no reports on the organization of the IO network activity in living animals. This is largely due to the extremely challenging anatomical location of the IO, making it difficult to subject to conventional fluorescent imaging methods, where an optic path must be created through the entire brain located dorsally to the region of interest.
Here we describe an alternative method for obtaining state-of-the-art -level calcium imaging data from the IO network. The method takes advantage of the extreme ventral location of the IO and involves a surgical procedure for inserting a gradient-refractive index (GRIN) lens through the neck viscera to come into contact with the ventral surface of the calcium sensor GCaMP6s-expressing IO in anesthetized mice. A representative calcium imaging recording is shown to demonstrate the feasibility to record IO neuron activity after the surgery. While this is a non-survival surgery and the recordings must be conducted under anesthesia, it avoids damage to life-critical brainstem nuclei and allows conducting large variety of experiments investigating spatiotemporal activity patterns and input integration in the IO. This procedure with modifications could be used for recordings in other, adjacent regions of the ventral brainstem.

In vivo Calcium Imaging in Mouse Inferior Olive

We present a protocol to expose the brainstem of adult mouse from the ventral side. By using a gradient-refractive index lens with a miniature microscope, calcium imaging can be used to examine the activity of inferior olive neural somata in vivo.

Inferior olive (IO), a nucleus in the ventral medulla, is the only source of climbing fibers that form one of the two input pathways entering the ...

Craniotomy Procedure for Visualizing Neuronal Activities in Hippocampus of Behaving Mice

Imaging neuronal activities at single-cell resolution in awake behaving animals is a very powerful approach for the investigation of neural circuit functions in systems neuroscience. However, high absorbance and scattering of light in mammalian tissue limit intravital imaging mostly to superficial brain regions, leaving deep-brain areas, such as the hippocampus, out of reach for optical microscopy. In this video, we show the preparation and implantation of the custom-made imaging window to enable chronic in vivo imaging of the dorsal hippocampal CA1 region in head-fixed behaving mice. The custom-made window is supplemented with an infusion cannula that allows targeted delivery of viral vectors and drugs to the imaging area. By combining this preparation with wide-field imaging, we performed a long-term recording of neuronal activity using a fluorescent calcium indicator from large subsets of neurons in behaving mice over several weeks. We also demonstrated the applicability of this preparation for voltage imaging with single-spike resolution. High-performance genetically encoded indicators of neuronal activity and scientific CMOS cameras allowed the recurrent visualization of subcellular morphological details of single neurons at high temporal resolution. We also discuss the advantages and potential limitations of the described method and its compatibility with other imaging techniques.

This article demonstrates the preparation of a custom-made imaging window supplemented with infusion cannula and its implantation onto the CA1 region of the hippocampus in mice.

Imaging neuronal activities at single-cell resolution in awake behaving animals is a very powerful approach for the investigation of neural circuit ...

Implantation of a Cranial Window for Repeated In Vivo Imaging in Awake Mice

To fully understand the cellular physiology of neurons and glia in behaving animals, it is necessary to visualize their morphology and record their activity in vivo in behaving mice. This paper describes a method for the implantation of a chronic cranial window to allow for the longitudinal imaging of brain cells in awake, head-restrained mice. In combination with genetic strategies and viral injections, it is possible to label specific cells and regions of interest with structural or physiological markers. This protocol demonstrates how to combine viral injections to label neurons in the vicinity of GCaMP6-expressing astrocytes in the cortex for simultaneous imaging of both cells through a cranial window. Multiphoton imaging of the same cells can be performed for days, weeks, or months in awake, behaving animals. This approach provides researchers with a method for viewing cellular dynamics in real time and can be applied to answer a number of questions in neuroscience.

Implantation of a Cranial Window for Repeated In Vivo Imaging in Awake Mice

Presented here is a protocol for the implantation of a chronic cranial window for the longitudinal imaging of brain cells in awake, head-restrained mice.

To fully understand the cellular physiology of neurons and glia in behaving animals, it is necessary to visualize their morphology and record their ...

Stereotaxic Viral Injection and Gradient-Index Lens Implantation for Deep Brain In Vivo Calcium Imaging

A miniature fluorescence microscope (miniscope) is a potent tool for in vivo calcium imaging from freely behaving animals. It offers several advantages over conventional multi-photon calcium imaging systems: (1) compact; (2) light-weighted; (3) affordable; and (4) allows recording from freely behaving animals. This protocol describes brain surgeries for deep brain in vivo calcium imaging using a custom-developed miniscope recording system. The preparation procedure consists of three steps, including (1) stereotaxically injecting the virus at the desired brain region of a mouse brain to label a specific subgroup of neurons with genetically encoded calcium sensor; (2) implantation of gradient-index (GRIN) lens that can relay calcium image from deep brain region to the miniscope system; and (3) affixing the miniscope holder over the mouse skull where miniscope can be attached later. To perform in vivo calcium imaging, the miniscope is fastened onto the holder, and neuronal calcium images are collected along with simultaneous behavior recordings. The present surgery protocol is compatible with any commercial or custom-built single-photon and two-photon imaging systems for deep brain in vivo calcium imaging.

Stereotaxic Viral Injection and Gradient-Index Lens Implantation for Deep Brain In Vivo Calcium Imaging

Miniscope in vivo calcium imaging is a powerful technique to study neuronal dynamics and microcircuits in freely behaving mice. This protocol describes performing brain surgeries to achieve good in vivo calcium imaging using a miniscope.

A miniature fluorescence microscope (miniscope) is a potent tool for in vivo calcium imaging from freely behaving animals. It offers several advantages ...

Simultaneous Imaging of Microglial Dynamics and Neuronal Activity in Awake Mice

Since brain functions are under the continuous influence of the signals derived from peripheral tissues, it is critical to elucidate how glial cells in the brain sense various biological conditions in the periphery and transmit the signals to neurons. Microglia, immune cells in the brain, are involved in synaptic development and plasticity. Therefore, the contribution of microglia to neural circuit construction in response to the internal state of the body should be tested critically by intravital imaging of the relationship between microglial dynamics and neuronal activity.
Here, we describe a technique for the simultaneous imaging of microglial dynamics and neuronal activity in awake mice. Adeno-associated virus encoding R-CaMP, a gene-encoded calcium indicator of red fluorescence protein, was injected into layer 2/3 of the primary visual cortex in CX3CR1-EGFP transgenic mice expressing EGFP in microglia. After viral injection, a cranial window was installed onto the brain surface of the injected region. In vivo two-photon imaging in awake mice 4 weeks after the surgery demonstrated that neural activity and microglial dynamics could be recorded simultaneously at the sub-second temporal resolution. This technique can uncover the coordination between microglial dynamics and neuronal activity, with the former responding to peripheral immunological states and the latter encoding the internal brain states.

Here, we describe a protocol combining adeno-associated virus injection with cranial window implantation for simultaneous imaging of microglial dynamics and neuronal activity in awake mice.

Since brain functions are under the continuous influence of the signals derived from peripheral tissues, it is critical to elucidate how glial cells in ...

In Vivo Wide-Field and Two-Photon Calcium Imaging from a Mouse Using a Large Cranial Window

Wide-field calcium imaging from the mouse&#39;s neocortex allows one to observe cortex-wide neural activity related to various brain functions. On the other hand, two-photon imaging can resolve the activity of local neural circuits at the single-cell level. It is critical to make a large cranial window to perform multiple-scale analysis using both imaging techniques in the same mouse. To achieve this, one must remove a large section of the skull and cover the exposed cortical surface with transparent materials. Previously, glass skulls and polymer-based cranial windows have been developed for this purpose, but these materials are not easily fabricated. The present protocol describes a simple method for making a large cranial window consisting of commercially available polyvinylidene chloride (PVDC) wrapping film, a transparent silicone plug, and a cover glass. For imaging the dorsal surface of an entire hemisphere, the window size was approximately 6 x 3 mm2. Severe brain vibrations were not observed regardless of such a large window. Importantly, the condition of the brain surface did not deteriorate for more than one month. Wide-field imaging of a mouse expressing a genetically-encoded calcium indicator (GECI), GCaMP6f, specifically in astrocytes, revealed synchronized responses in a few millimeters. Two-photon imaging of the same mouse showed prominent calcium responses in individual astrocytes over several seconds. Furthermore, a thin layer of an adeno-associated virus was applied to the PVDC film and successfully expressed GECI in cortical neurons over the cranial window. This technique is reliable and cost-effective for making a large cranial window and facilitates the investigation of the neural and glial dynamics and their interactions during behavior at the macroscopic and microscopic levels.

In Vivo Wide-Field and Two-Photon Calcium Imaging from a Mouse Using a Large Cranial Window

The present protocol describes making a large (6 x 3 mm2) cranial window using food wrap, transparent silicone, and cover glass. This cranial window allows in vivo wide-field and two-photon calcium imaging experiments in the same mouse.

Wide-field calcium imaging from the mouse&#39;s neocortex allows one to observe cortex-wide neural activity related to various brain functions. On the ...

Subcellular Imaging of Neuronal Calcium Handling In Vivo

Calcium (Ca2+) imaging has been largely used to examine neuronal activity, but it is becoming increasingly clear that subcellular Ca2+ handling is a crucial component of intracellular signaling. The visualization of subcellular Ca2+ dynamics in vivo,&#160;where neurons can be studied in their native, intact circuitry, has proven technically challenging in complex nervous systems. The transparency and relatively simple nervous system of the nematode Caenorhabditis elegans enable the cell-specific expression and in vivo visualization of fluorescent tags and indicators. Among these are fluorescent indicators that have been modified for use in the cytoplasm as well as various subcellular compartments, such as the mitochondria. This protocol enables non-ratiometric Ca2+ imaging in vivo with a subcellular resolution that permits the analysis of Ca2+ dynamics down to the level of individual dendritic spines and mitochondria. Here, two available genetically encoded indicators with different Ca2+ affinities are used to demonstrate the use of this protocol for measuring relative Ca2+ levels within the cytoplasm or mitochondrial matrix in a single pair of excitatory interneurons (AVA). Together with the genetic manipulations and longitudinal observations possible in C. elegans, this imaging protocol may be useful for answering questions regarding how Ca2+ handling regulates neuronal function and plasticity.

Subcellular Imaging of Neuronal Calcium Handling In Vivo

The current methods describe a non-ratiometric approach for high-resolution, sub-compartmental calcium imaging in vivo in Caenorhabditis elegans using readily available genetically encoded calcium indicators.

Calcium (Ca2+) imaging has been largely used to examine neuronal activity, but it is becoming increasingly clear that subcellular Ca2+ handling is a ...

Two-Photon and Wide-Field Calcium Imaging in the Superior Colliculus

Calcium Imaging in Mouse Superior Colliculus

The superior colliculus (SC), an evolutionarily conserved midbrain structure in all vertebrates, is the most sophisticated visual center before the emergence of the cerebral cortex. It receives direct inputs from ~30 types of retinal ganglion cells (RGCs), with each encoding a specific visual feature. It remains elusive whether the SC simply inherits retinal features or if additional and potentially de novo processing occurs in the SC. To reveal the neural coding of visual information in the SC, we provide here a detailed protocol to optically record visual responses with two complementary methods in awake mice. One method uses two-photon microscopy to image calcium activity at single-cell resolution without ablating the overlaying cortex, while the other uses wide-field microscopy to image the whole SC of a mutant mouse whose cortex is largely undeveloped. This protocol details these two methods, including animal preparation, viral injection, headplate implantation, plug implantation, data acquisition, and data analysis. The representative results show that the two-photon calcium imaging reveals visually evoked neuronal responses at single-cell resolution, and the wide-field calcium imaging reveals&#160;neural activity across the entire SC. By combining these two methods, one can reveal the neural coding in the SC at different scales, and such combination can also be applied to other brain regions.

Author Spotlight: Unveiling Neural Coding and Mechanisms of Visual Processing in the Superior Colliculus 

This protocol details the procedure for imaging calcium responses in the superior colliculus (SC) of awake mice, including imaging single-neuron activity with two-photon microscopy while leaving the cortex intact in wild-type mice, and imaging the entire SC with wide-field microscopy in partial-cortex mutant mice.

The superior colliculus (SC), an evolutionarily conserved midbrain structure in all vertebrates, is the most sophisticated visual center before the ...

Real-Time Imaging for Neuron Activity in the Dentate Gyrus Cells of Mice 

In Vivo Calcium Imaging of Granule Cells in the Dentate Gyrus of Hippocampus in Mice

Real-time approaches are typically needed in studies of learning and memory, and in vivo calcium imaging provides the possibility to investigate neuronal activity in awake animals during behavior tasks. Since the hippocampus is closely associated with episodic and spatial memory, it has become an essential brain region in&#160;this field&#39;s research. In recent research, engram cells and place cells were studied by recording the neural activities in the hippocampal CA1 region using the miniature microscope in mice while performing behavioral tasks including open-field and linear track. Although the dentate gyrus is another important region in the hippocampus, it has rarely been studied with in vivo imaging due to its greater depth and difficulty for imaging. In this protocol, we present in detail a calcium imaging process, including how to inject the virus, implant a GRIN (Gradient-index) lens, and attach a base plate for imaging the dentate gyrus of the hippocampus. We further describe how to preprocess the calcium imaging data using MATLAB. Additionally, studies of other deep brain regions that require imaging may benefit from this method.

Author Spotlight: Investigating Neural Activity of Dentate Gyrus Granule Cells with Miniature Microscope

The dentate gyrus of the hippocampus carries out essential and distinct functions in learning and memory. This protocol describes a set of robust and efficient procedures for in vivo calcium imaging of granule cells in the dentate gyrus in freely moving mice.

Real-time approaches are typically needed in studies of learning and memory, and in vivo calcium imaging provides the possibility to investigate neuronal ...

Successful In vivo Calcium Imaging with a Head-Mount Miniaturized Microscope in the Amygdala of Freely Behaving Mouse

Summary

Explore More Videos

Chapters in this video

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

In vivo Calcium Imaging in Mouse Inferior Olive

Craniotomy Procedure for Visualizing Neuronal Activities in Hippocampus of Behaving Mice

Implantation of a Cranial Window for Repeated In Vivo Imaging in Awake Mice

Stereotaxic Viral Injection and Gradient-Index Lens Implantation for Deep Brain In Vivo Calcium Imaging

Simultaneous Imaging of Microglial Dynamics and Neuronal Activity in Awake Mice

In Vivo Wide-Field and Two-Photon Calcium Imaging from a Mouse Using a Large Cranial Window

Subcellular Imaging of Neuronal Calcium Handling In Vivo

Calcium Imaging in Mouse Superior Colliculus

In Vivo Calcium Imaging of Granule Cells in the Dentate Gyrus of Hippocampus in Mice