title: A system to measure the pupil response to steady lights in freely behaving mice.
abstract: 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.
  
  
  
  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.
  
  
  
  The size of the pupils in freely behaving mice decreased gradually with luminance from a maximal area in the dark of 3.8mm2down to a minimum 0.14mm2at 80 scotopic cd/m2. The data was well fit with a Hill equation with Lo equal to 0.21cd/m2and coefficient h=0.48.
  
  
  
  These values agree with prior measurements of the pupillary response of unrestrained mice that use more laborious and time consuming approaches.
  
  
  
  Our new method facilitates practical, straightforward and accurate measurements of pupillary responses made under the same experimental conditions as those used during psychophysical testing.
authors: Center for Vision Research and SUNY Eye Institute, Department of Ophthalmology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, New York 13210, USA.
authors: Mark
authors: M
authors: Bushnell
authors: Center for Vision Research and SUNY Eye Institute, Department of Ophthalmology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, New York 13210, USA.
authors: Yumiko
authors: Y
authors: Umino
authors: Center for Vision Research and SUNY Eye Institute, Department of Ophthalmology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, New York 13210, USA. Electronic address: solessie@upstate.edu.
authors: Eduardo
authors: E
authors: Solessio
mesh_terms: D000818:Animals; D005260:Female; D008027:Light; D008029:Lighting / Q000379:methods; D051379:Mice; D017711:Nonlinear Dynamics; D061848:Optical Imaging; D010775:Photic Stimulation; D011680:Pupil / Q000502:physiology* / Q000528:radiation effects*; D014851:Wakefulness
keywords: Freely behaving mice; Habituation; Mouse; Operant behavior; Optomotor response; Pupillary reflex; Visual behavior