MouseVUER: video based open-source system for laboratory mouse home-cage monitoring

Abstract

Video monitoring of mice in the home-cage reveals behavior profiles without the disruptions caused by specialized test setups and makes it possible to quantify changes in behavior patterns continually over long time frames. Several commercial home-cage monitoring systems are available with varying costs and capabilities; however there are currently no open-source systems for home-cage monitoring. We present an open-source system for top-down video monitoring of research mice in a slightly modified home-cage. The system is designed for integration with Allentown NexGen ventilated racks and allows unobstructed view of up to three mice, but can also be operated outside the rack. The system has an easy to duplicate and assemble home-cage design along with a video acquisition solution. The system utilizes a depth video camera, and we demonstrate the robustness of depth video for home-cage mice monitoring. For researchers without access to Allentown NexGen ventilated racks, we provide designs and assembly instructions for a standalone non-ventilated rack solution that holds three systems for more compact and efficient housing. We make all the design files, along with detailed assembly and installation instructions, available on the project webpage ( https://github.com/NIH-CIT-OIR-SPIS/MouseVUER ).

Figure 1

Modified Allentown Lid– Cutouts were made on commercially available Allentown lids to lock the hopper in place and to provide an unobstructed camera view. A cut-to-shape acrylic piece is placed on the lid when the camera mounting enclosure is not used. The image was generated with SolidWorks Visualize 2022 and annotated with Microsoft PowerPoint.

Figure 2

MouseVUER system – Camera mounting enclosure over modified Allentown lid and Cage. The camera is positioned to capture an unobstructed view of the mouse. Due to a crossbar at the front of the rack, the camera mounting enclosure must be placed on top of the cage AFTER it has been inserted/slid into the rack. The image was generated with SolidWorks Visualize 2022 and annotated with Microsoft PowerPoint.

Figure 3

Food and Water Hopper – Custom 2-compartment hopper for food and water. The compartments are protected with metal grates at the front to prevent mice from chewing any edges. The cage support wings rest on the inner edge of the cage while the locking tab fits into a slot made in the modified lid. A commercially available water bottle is supported at an angle by the bottle support bar. The images were generated with SolidWorks Visualize 2022 and annotated with Microsoft PowerPoint.

Figure 4

Camera Mounting Enclosure—Positions depth camera above cage environment for unobstructed video recording. The camera attachment (rack bar latch) latches to a crossbar above the cage during cage changes. A front handle allows for easy handling of the enclosure. The panels are made from clear acrylic to allow view of the mice to observers. The image was generated with SolidWorks Visualize 2022 and annotated with Microsoft PowerPoint.

Figure 5

Mouse Mezzanine—Provides enrichment to the mice (ramps, tunnels, etc.). On the sides, weight anchors have been added to prevent potential dragging or flipping. The image was generated with SolidWorks Visualize 2022 and annotated with Microsoft PowerPoint.

Figure 6

Custom Cage Racks—Modular Rack which houses three MouseVUER systems and associated electronics. The rack includes horizontal bars to hang the camera mounting enclosures during cage changes. Due to its modular properties, the rack can be expanded to fit any number of MouseVUER systems. The image was generated with SolidWorks Visualize 2023 and annotated with Microsoft PowerPoint.

Figure 7

Power and control module which provides electronics for powering and establishing communication with three monitoring units. The power and control unit also has 3 auxiliary lines to power external illumination to cages if needed. The image was generated with SolidWorks Visualize 2023.

Figure 8

Compression Pipeline. A sequence of depth frames (colorized for visualization purposes) is split into 8-bit video frames. Each video frame is then compressed and sent to a central storage unit.

Figure 9

A visual diagram showing the general function of the server computer and client computer as well as the relation between the two. Multiple client computers (indicated by blue boxes) connect to a single server computer (indicated by yellow box).

Figure 10

Example frames of an annotated mouse subject from (a–c) the color stream and (d–f) the depth stream. Body parts include nose, left ear, right ear, and tail base. Compared to the RGB stream, the depth stream provides a significant visual challenge for the annotation of the mouse’s key points for annotation tasks.

Figure 11

The best OKS values for white, black and tan depth frames are shown in (a, b, c). The worst OKS values for white, black, and tan depth frames are shown in (d, e, f). The ground truth annotations are labeled with a blue circle while the model’s annotations are labeled with a red triangle.