The opto-locomotor reflex as a tool to measure sensitivity to moving random dot patterns in mice

Abstract

We designed a method to quantify mice visual function by measuring reflexive opto-locomotor responses. Mice were placed on a Styrofoam ball at the center of a large dome on the inside of which we projected moving random dot patterns. Because we fixed the heads of the mice in space and the ball was floating on pressurized air, locomotion of the mice was translated to rotation of the ball, which we registered. Sudden onsets of rightward or leftward moving patterns caused the mice to reflexively change their running direction. We quantified the opto-locomotor responses to different pattern speeds, luminance contrasts, and dot sizes. We show that the method is fast and reliable and the magnitude of the reflex is stable within sessions. We conclude that this opto-locomotor reflex method is suitable to quantify visual function in mice.

Opto-locomotor reflexes of mice to reverse-phi stimuli

“…The temporal interval here was 67 ms. In our experiment, a positive stimulus speed corresponds to leftward displacement; therefore, Figure 2 a shows that the mouse responded by attempting to turn in the same direction as the dots, as reported previously for unlimited lifetime stimuli ( Kirkels et al, 2018 ). To test for differences between the blue and red OLRs, we averaged each trace over the interval from 1 to 2 seconds after stimulus onset and performed a one-sided, two-sample t -test where ( t (249) = –2.55; p = 0.006).…”

“…Our results show that the responses of mice are variable. First of all, the magnitude of the OLRs to phi and reverse-phi stimuli is considerably smaller than that for the OLRs we observed to unlimited lifetime motion stimuli we used in previous work ( Kirkels et al, 2018 ). In the present study, the mean OLR peaks at about 15°/s with our most optimal parameter settings for perception of motion reversal, whereas our previous work reported a peak amplitude of about 30°/s.…”

“…Here we measured OLRs using our previously described head-fixed paradigm ( Kirkels et al, 2018 ) to investigate whether mice perceive reverse-phi stimuli. Mice respond to changes in direction for phi stimuli and reverse-phi stimuli in opposite ways.…”

“…We placed the mouse on a treadmill consisting of a Styrofoam ball floating on air in a custom-made socket (University College London workshops) at the center of this dome. The display area covered 220° of visual angle horizontally and from 10° below the mouse to 80° above it vertically (for details, see Kirkels et al, 2018 ).…”

“…As a first step, we developed a behavioral experiment to investigate responses of mice to phi and reverse-phi stimuli. We positioned mice head-fixed on a spherical, two-dimensional treadmill and projected randomly positioned black and white dots on a spherical screen surrounding the animal ( Harvey, Collman, Dombeck, & Tank, 2009 ; Hölscher, Schnee, Dahmen, Setia, & Mallot, 2005 ; Kirkels, Zhang, Havenith, Tiesing, Glennon, Wezel, & Duijnhouwer, 2018 ; Schmidt-Hieber & Häusser, 2013 ). We measured the opto-locomotor reflex (OLR) ( Kirkels et al, 2018 ) in response to phi and reverse-phi stimuli to the left and right by recording the rotation of the treadmill along the vertical axis.…”