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Arkady Lyubarsky, Muhammad Sheheryar Khan, Meera Sivalingam, Jean Bennett; High Throughput Behavioral Estimates of Visual Thresholds in Mice in a Watermaze with Cued Escape Platform. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3030. doi: https://doi.org/.
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To develop a quantitative, sensitive, cost-effective, non-invasive behavioral technique for evaluation of vision in mice with emphasis on its suitability for the end point characterization in gene therapy of retinal diseases.
The apparatus was a round (1.2 m diameter and 0.7 m high) tub made of a dark blue plastic, and filled with water to a 20 cm depth with a single submerged escape platform (8 cm diameter). A plastic 20 cm high pole covered with a disposable aluminum foil sleeve and standing at the platform center served as a visual cue assisting animals in finding the platform. Four infrared sources provided a uniform, invisible for mice, illumination of the tub, and a video camera with an infrared filter was recording animal’s moves. Four regulated visible light sources provided uniform illumination inside the apparatus in a 1E-5 to 1E+2 scot cd m-2 range. Wild-type (WT) and neural retina leucine zipper (NRL) knock-out (KO) mice lacking rod photoreceptors were trained to escape to the platform at the brightest level of illumination, and then were tested at 0.5 - 0.8 log-unit decrements of the illumination intensity. To determine the threshold, we first evaluated the probability of reaching the platform by chance per second of swimming time; to do this we measured the frequency of platform encounter by mice swimming in dark with only IR illumination on. In test runs an animal was considered as “seeing” the pole if it reached the platform in 3 out of 3 consecutive trials, and the probability of achieving this result by way of 3 random hits was <1%.
The thresholds for seeing the platform were ~1E-5 and ~5 scot cd m-2 for the WT and NRL KO mice, respectively; the value of the threshold for the WT mice was somewhat lower than the one determined by Hayes and Balkema (5E-5 scot cd m-2, Behavior Genetics, VoI. 23, No. 4, 1993) in 6-way water maze experiments. In contrast with their paradigm which required over 10 days of training plus a comparable time for testing, our method needs only 6-8 hours for training , 1-3 days for testing, and it does not require specialized tracking software.
We suggest a quantitative behavioral test for evaluating vision in mice which, as compared to analogous existing techniques, offers 5-10 fold higher throughput at comparable or better sensitivity.
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