Using Looming Visual Stimuli to Evaluate Mouse Vision

Summary

To examine mouse vision, we conducted a looming test. Mice were placed in a large square arena with a monitor on its ceiling. The looming visual stimulus consistently evoked freezing or flight reactions in the mice.

Abstract

The visual system in the central nervous system processes diverse visual signals. Although the overall structure has been characterized from the retina through the lateral geniculate nucleus to the visual cortex, the system is complex. Cellular and molecular studies have been conducted to elucidate the mechanisms underpinning visual processing and, by extension, disease mechanisms. These studies may contribute to the development of artificial visual systems. To validate the results of these studies, behavioral vision testing is necessary. Here, we show that the looming stimulation experiment is a reliable mouse vision test that requires a relatively simple setup. The looming experiment was conducted in a large enclosure with a shelter in one corner and a computer monitor located on the ceiling. A CCD camera positioned next to the computer monitor served to observe mouse behavior. A mouse was placed in the enclosure for 10 minutes and allowed to acclimate to and explore the surroundings. Then, the monitor projected a program-derived looming stimulus 10 times. The mouse responded to the stimuli either by freezing or by fleeing to the hiding place. The mouse's behavior before and after the looming stimuli was recorded, and the video was analyzed using motion tracking software. The velocity of the mouse movement significantly changed after the looming stimuli. In contrast, no reaction was observed in blind mice. Our results demonstrate that the simple looming experiment is a reliable test of mouse vision.

Introduction

The visual system starts at the retina, where visual signals are captured by photoreceptors, channeled to bipolar cells (2^nd-order neurons), and finally passed to ganglion cells (3^rd-order neurons). Retinal 2^nd- and 3^rd-order neurons are thought to form multiple neural pathways that convey particular aspects of visual signaling such as color, motion, or shape. These diverse visual features are relayed to the lateral geniculate nucleus and the visual cortex. In contrast, visual signals leading to eye movement are sent to the superior colliculus. Classically, two retino-cortical pathways have been identified: the magnocellular....

Protocol

All experiments and animal care were conducted in accordance with protocol approved by the Institutional Animal Care and Use Committees at Wayne State University (protocol no. 17-11-0399).

1. Preparation for the experiment

1. Build a rectangular open-lid enclosure to house the mouse during looming visual stimuli presentation. We constructed a 40 cm x 50 cm x 33 cm enclosure using aluminum framing and PVC panels (Figure 1A,B). Lay a sheet of paper to cover the entire floor of the enclosure to ensure easy cleanup between trials. Add an opaque shelter in a corner of the enclosure with an ....

Results

A mouse with healthy eyes was placed in the enclosure and allowed to acclimate for 10 min. The arena with the monitor on the ceiling was kept under mesopic light conditions (7 x 10⁵ photons/μm²/s). During the acclimation period, the mouse explored the space and found the opaque dome as a refuge. When the mouse moved away from the refuge, video capturing started, followed by initiation of the visual stimulus. In response to the looming stimulus, most mice ran into the dome (flight response), which wa.......

Discussion

With the looming visual stimuli system, a majority (97%) of healthy eye-mice showed flight response. One of 29 mice did not show an obvious flight response. However, the mouse walked toward the dome and remained near it until looming disappeared, indicating that the mouse was at least cautious when the looming stimuli occurred. Therefore, the looming stimuli consistently elicited innate fear responses in healthy-eyed mice. On the other hand, three blind mice did not show any responses to the looming (preliminary results).......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
10.1" monitor (2° display)	Elecrow	Elecrow 10.1 Inch Raspberry Pi 1920x1080p Resolution Display
14" Business Class Laptop 5490	Dell	84 / rcrc961481-4860836
20" x 50" Absorbant Liners	Fisher Scientific	AL2050	works well to protect floor of arena, could use any type of liner
21.5" monitor (1° display)	Acer	Acer R221Q bid 21.5-inch IPS Full HD Display
CCD Camera	Lumenera Corporation	Infiniyy3S-1UR	excellent for behavioral studies due to high fps rate (60 fps)
Enclosure (alminum frames and PVC panels)	80/20 Inc.	4x cat.#9010, 4x cat.#9005, 1x cat.#9000, 5x cat.#65-2616	excellent, used quick build tab to find PVC, joints, and frame
Ethanol	Fisher Scientific	22-032-601
Excel Spreadsheet Software	Microsoft Office		user friendly and widespread knowledge of Microsoft Office software
Freearm	Amazon		used to mount camera to the table, could use any mountable extendable arm
ImagePro Premiere 3D	Media Cybernetics	version 9.3	good program, could use some updating with the automated tracking feature
Matlab software (Psychotoolbox 3)	MathWorks	Matlab R2018b 64-bit (9.5.0.944444)	excellent software to generate pattern stimuli of any conditions
SteamPix sorftware	Norpix	StreamPix 7 64-bit Single Camera	works well, a few problems with frame dropping but good customer service
WD My Book External Hard Drive	Western Digital	WDBBGB0080HBK hard drive 8 TB USB 3.0	necessary if using .avi files with no compression codec due to large size of files
Wide angle lens	Navitar	NMV-5M23	excellent and necessary to capture entire arena