title: Grating acuity at different luminances in wild-type mice and in mice lacking rod or cone function.
abstract: OBJECTIVE
  The mouse eye has become an important model in vision research. However, it is not known how visual acuity changes with luminance. Therefore, grating acuity of mice was measured at different luminances in an automated optomotor paradigm. Furthermore, mutant mice lacking either rods (RHO-/- and CNGB1-/-) or cones (CNGA3-/-), or both, were studied to determine the rod and cone contribution to visual acuity.
  
  
  METHODS
  Freely ranging individual mice were automatically tracked at a 25-Hz sampling rate with a self-programmed video system in a large rotating optomotor drum. The drum had a square-wave grating inside with adjustable spatial frequency. The angular speed of the mice with respect to the center of the drum and the angular orientation of the snout-tail body axis were analyzed. In addition, the motor activity of the wild-type mice was recorded at different luminances.
  
  
  RESULTS
  The optomotor drum provided reliable data on visual input to the mouse's behavior and was convenient to use, since the experimenter's had only to place the mice individually in a Perspex cylinder. Optomotor grating acuity of the wild-type mice was limited to 0.3 to 0.4 cyc/deg. Maximum optomotor responses were obtained at 0.1 to 0.2 cyc/deg. The importance of visual input declined monotonically with decreasing luminance (30 cd/m2, 100%; 0.1 cd/m2, 76.4%; 0.005 cd/m2, 45.9%; and darkness, -9%). Mice lacking functional rods were able to resolve gratings up to 0.1 cyc/deg at 30 cd/m2. Surprisingly, mice lacking functional cones had an optomotor acuity that was similar to the wild-type. Double-knockout mice without rods and cones had no detectable grating acuity.
  
  
  CONCLUSIONS
  Because the visual system of the mouse is more responsive at bright luminances, experiments in which visual input is important should be performed in photopic conditions (30 cd/m2 or even more). Apparently, spatial vision is governed by the rod system, which is not saturated in the mesopic or low photopic range. Mice lacking both rods and cones have no detectable grating acuity, indicating that the retinal melanopsin system does not contribute to spatial vision.
authors.affiliation: Section of Neurobiology of the Eye, University Eye Hospital, Tübingen, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Schmucker
authors.forename: Mathias
authors.initials: M
authors.lastname: Seeliger
authors.forename: Pete
authors.initials: P
authors.lastname: Humphries
authors.forename: Martin
authors.initials: M
authors.lastname: Biel
authors.forename: Frank
authors.initials: F
authors.lastname: Schaeffel
mesh_terms: D000818:Animals; D054815:Cyclic Nucleotide-Gated Cation Channels; D005260:Female; D017353:Gene Deletion; D007473:Ion Channels / Q000235:genetics; D008029:Lighting; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009043:Motor Activity / Q000502:physiology; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology*; D012243:Rhodopsin / Q000235:genetics; D017299:Rod Opsins / Q000235:genetics; D013028:Space Perception / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology*; D000099210:Melanopsin
chemical_list: D054815:Cyclic Nucleotide-Gated Cation Channels; D007473:Ion Channels; D012243:Rhodopsin; D017299:Rod Opsins; D000099210:Melanopsin