Behavioral Evaluation of the Visual Function of Rats Using a Pattern Detection Apparatus

Abstract

Purpose: : To evaluate the visual capacity of normal and retinal degenerate (RD) rats using a pattern detection apparatus.

Methods: : A pattern detection apparatus was used to train normal pigmented rats and S334ter–line–3 pigmented rats to distinguish between 2 different visual patterns – a dark background versus a striped (black & white) pattern. The apparatus is a modified Y maze that consists of two chambers leading to an exit door allowing the rats to escape into their home cage as a reward. The rats were trained to find the unlocked exit door based on the stimulus pattern displayed on the back of each chamber beside the exit door. Training consisted of multiple trials within the testing chamber on alternate days (with no more than three trials/animal every two days). Additional motivation was achieved by overnight food deprivation. To measure the luminance threshold level, the luminance level of the white stripes was reduced by steps of 0.5 log using changeable filters.

Results: : After two weeks of training, both normal pigmented rats and RD rats were able to distinguish between a dark background versus a striped (black & white) pattern. Normal pigmented rats could detect the striped pattern at a threshold luminance level of –5.42 ± 0.05 log cd/m2. RD rats at 100 day of age were able to distinguish between the above two patterns only at a higher luminance level (–1.18 ± 0.14 log cd/m2). When tested at a later age (150 days), the threshold luminance level in RD rats was further increased to –0.72 ± 0.098 log cd/m2. There was considerable variability in the performance of RD rats.

Conclusions: : A pattern detection apparatus allowed rats to be trained to distinguish between different visual patterns. The apparatus may be a useful tool for evaluation of visual function in rats following therapeutic interventions for retinal degeneration.

Keywords: retinal degenerations: hereditary • visual acuity • perception