Abstract
Purpose::
Assess scotopic and photopic vision in mice with behavioral techniques.
Methods::
We tested visual sensitivity of wildtype (C57BL/6J), rod-less (Gnat2cpfl3) and cone-less (rod transducin α KO) mice by observing their optomotor responses to rotating sinusoidal patterns (Optomotry©) with a double-blind procedure. We measured the spatial and temporal contrast functions over a wide range of illumination (5.6x10-7 cd/m2 to 70 cd/m2).
Results::
Mice can see over a 100 million-fold range of illumination using both rods and cones. Rods mediate vision under dim illuminations (< 3x10-4 cd/m2) whereas cones mediate vision with bright level (> 3x10-4 cd/m2). At photopic light levels the contrast sensitivity functions were broadly tuned (0.031 to 0.511 cyc/deg) and band-pass in shape. The contrast sensitivity was nearly invariant over a 30000-fold increase in intensity consistent with Weber’s law. For all spatial frequencies, sensitivity was tuned to the speed of rotation (peak: ~12 deg/sec). Rod-less and wildtype mice had similar sensitivities in the photopic range whereas cone-less mice were completely insensitive. At scotopic light levels, the spatial contrast sensitivity was low-pass in shape, and the spatial frequency range was limited to approximately 0.1-0.2 cyc/deg. Cone-less and wildtype mice had similar sensitivities in the scotopic range, but rod-less mice were insensitive. Remarkably, in the scotopic range visual sensitivity is tuned to the temporal frequency of the rotating pattern rather than to its speed of rotation.
Conclusions::
Mice process visual information differently under photopic and scotopic conditions.NIH Grant EY00667, Lions Club of Central New York and Research to Prevent Blindness
Keywords: photoreceptors • retinal degenerations: cell biology