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A. Lindsey, O. Z. Abdul-Salaam, R. Danilowicz; Behavioral Contrast Sensitivity Functions in the Neotenic Tiger Salamander. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1301.
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© ARVO (1962-2015); The Authors (2016-present)
The tiger salamander (Ambystoma tigrinum) is a commonly used model to study retinal physiology. However, the application of behavioral psychophysical methods is needed to describe and quantify visual behavior in this animal. The purpose of this study was to use psychophysical methods to measure behavioral contrast sensitivity functions (CSFs) in the neotenic tiger salamander.
Stimulus parameters and testing procedures were modified from Bilotta & Powers (1991). The stimulus was a drifting (1.5 Hz) sinusoidal grating of alternating black and white stripes. The sinusoidal grating was produced by a computer program and displayed on a flat-screen color monitor. Animals were placed in a water-filled aquarium and faced the monitor at a viewing distance of 29.0 cm. Contrast luminance thresholds were measured as a function of 10 spatial frequencies that ranged from 0.19 - 2.01 cycles / degree (cpd) visual angle in five neotenic tiger salamanders (22.5 - 28.5 cm body length; 3.0 - 4.0 mm eye diameter) under red light illumination. Threshold was defined as the stimulus value at which the probability of responding (swimming in the direction of the drifting grating) was 0.5. CSFs were created for each animal.
Animals responded to a range of spatial frequencies from 0.26 - 1.15 cpd with average peak sensitivity (1/threshold) at 0.34 cpd. However, the largest animal responded to a narrower range of spatial frequencies (0.47 - 1.15 cpd) with peak sensitivity at 0.8 cpd and had lower contrast sensitivity compared to other animals. The smallest animal examined, in contrast, responded to a broader range of spatial frequencies (0.21 - 2.01 cpd) with a peak sensitivity at 0.34 cpd and had higher contrast sensitivity.
(1) Behavioral psychophysical methods can be used to assess visual behavior in neotenic tiger salamanders. (2) Contrast sensitivity functions for the neotenic tiger salamander are similar in shape to other species. (3) Psychophysical measures of visual behavior may contribute to our understanding of the visual system in these animals.
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