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Christopher L Passaglia, Sarah Davis, Jordan Carbono, Miral Gomaa; Spatial and temporal contrast sensitivity of rats under varying light level. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2766.
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© 2017 Association for Research in Vision and Ophthalmology.
Rats are a commonly used model for vision research and for investigating disorders of the visual system. The purpose of this study is to quantify the spatial and temporal acuity of healthy adult Brown-Norway rats over a range of scotopic and photopic illumination conditions.
Brown-Norway rats (male, 300-400g, 6-8 months old) were placed on a restricted diet to reduce their ad lib body weights to 85%. Animals were tested in a behavior apparatus that contained two platforms behind which a computer screen displayed a drifting sinusoidal grating above either the left or right platform at random in a dark room. Each trial the grating varied either in contrast, spatial frequency (0.01, 0.1, 0.3, 0.7, 0.9, 1.0 cycles/deg), or temporal frequency (0.01, 1.0, 4.0, 6.0, 16.0, 24.0, 36.0, 40.0 cycles/s). The rats were trained to cross onto the platform that displayed the grating pattern in order to receive a food reward. Animals were placed in the dark for at least 3 hours prior to testing. Behavioral data were collected at different light levels with neutral density filters (2, 4, 6, 8 log units attenuation) placed in front of the computer screen (37 cd/m2). Contrast threshold for a given grating pattern was determined via a computer-automated algorithm that applied a staircase method of adjustment and averaged the 5 lowest contrast levels the animal correctly identified.
Spatial contrast sensitivity curves had bandpass characteristic, with peak spatial frequencies ranging from 0.1 to 0.5 cycles/deg under photopic illumination. The highest spatial frequency rats were able to detect was ~1.0 cycle/deg at maximum contrast. The highest temporal frequency rats detected was ~40 Hz. Contrast thresholds increased as mean light level was lowered, along with a modest change in spatial and temporal cutoff frequencies.
A computer-automated vision testing system has been developed for assessing the visual abilities of rats under different illumination conditions. Measured spatial and termporal contrast sensitivity functions of healthy rats provide a database for evaluating visual dysfunction in rat models of ocular disease.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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