A system to measure the pupil response to steady lights in freely behaving mice

Abstract

Background Transgenic mice are widely used for the study of basic visual function and retinal disease, including in psychophysical tests. Mice have a robust pupillary light reflex that controls the amount of light that enters the eye, and the attenuating effects of the pupil must be considered during such tests. Measurement of the size of pupils at various luminance levels requires that mice remain stable over prolonged periods of time; however, sedation of mice with anesthesia and/or manual restraint can influence the size of their pupils. New Method We present a system to measure the pupillary light response to steady lights of freely behaving mice using a custom-built, portable device that automatically acquires close-up images of their eyes. The device takes advantage of the intrinsic nature of mice to inspect objects of interest and can be used to measure pupillary responses in optomotor or operant behavior testing chambers. Results The size of the pupils in freely behaving mice decreased gradually with luminance from a maximal area in the dark of 3.8 mm2 down to a minimum 0.14 mm2 at 80 scotopic cd/m2. The data was well fit with a Hill equation with Lo equal to 0.21 cd/m2 and coefficient h=0.48. Comparison with existing methods These values agree with prior measurements of the pupillary response of unrestrained mice that use more laborious and time consuming approaches. Conclusions Our new method facilitates practical, straightforward and accurate measurements of pupillary responses made under the same experimental conditions as those used during psychophysical testing.

High-Throughput Automatic Training System for Odor-Based Learned Behaviors in Head-Fixed Mice

“…Although the head-movement was restrained in the current design, one would like to monitor the muscles controlling head or chewing movement to further eliminate the potential artifacts in electrophysiological recording. To obtain deep understanding of neural circuit underlying these behavior, one would also like to integrate more monitoring systems for behavioral events, such as sniffing (Kepecs et al, 2007 ; Verhagen et al, 2007 ; Wesson et al, 2008 ; Shusterman et al, 2011 ; Deschenes et al, 2012 ; McAfee et al, 2016 ), pupil size (Reimer et al, 2014 , 2016 ; McGinley et al, 2015 ; Vinck et al, 2015 ; Bushnell et al, 2016 ), and whisker movement (Orbach et al, 1985 ; Friedman et al, 2006 ; Birdwell et al, 2007 ; O’Connor et al, 2010 ; Deschenes et al, 2012 ; Petreanu et al, 2012 ; Moore et al, 2013 ).…”

Rod Photoreceptors Signal Fast Changes in Daylight Levels Using a Cx36-Independent Retinal Pathway in Mouse

“…Briefly, values of corneal irradiance were measured with an M370 Optometer (Graseby Optronics) placed in the position of the cornea of the mice and directed toward the side panels of the chamber. The corresponding steady-state pupil areas of freely behaving mice in the operant chamber were determined as described by Bushnell et al (2016) and the values are listed in Table 1. The values of corneal irradiance and pupil areas were used to estimate retinal irradiance using the approach described by Lyubarsky et al (2004) and Umino et al (2019) (Table 1 lists the pupil areas and corresponding retinal irradiance values for each mouse line used in this study).…”

Rod Photoresponse Kinetics Limit Temporal Contrast Sensitivity in Mesopic Vision

“…Briefly, corneal irradiance (in Watts/area) was mea-sured with an M370 Optometer (Graseby Optronics) and converted into scotopic illuminance units (s lux) using established formulas (Wyszecki and Stiles, 2000). Pupil areas of WT, R9OE, G2, and G2::R9OE mice behaving freely in the behavioral chamber were measured as a function of corneal illuminance using a custom-built portable device as described previously (Bushnell et al, 2016). Using pupil area and corneal illuminance information (Fig.…”