Preference of Negative Contrast in Behaving Rats
Date Issued
2016
Date
2016
Author(s)
Wu, Sheng-Hui
Abstract
Humans can detect negative contrast (black on gray) better and more easily than positive contrast (white on gray). The black-over-white preference in visual perception is accordance with the findings that negative-contrast stimuli can evoke larger neuronal responses than positive-contrast stimuli in primary visual cortex (V1). In contrast, strong white-dominant responses were recently found in mouse V1 with the voltage-sensitive dye imaging (VSDI) technique. Based on these findings, it is possible that nocturnal rodents may prefer positive contrast to negative contrast. Here we used a two-alternative forced choice task to test the preference of contrast polarity in behaving rats (Long Evans). We manipulated contrast polarity (positive or negative contrast), contrast intensity and the mean luminance of the screen (high: 50 cd/m2, low: 20 cd/m2) in our experiments. Surprisingly we found that rats could detect the negative-contrast stimuli better than the positive-contrast stimuli, when the contrast intensity became stronger, in the low luminance condition. This asymmetry in detecting contrast polarity also occurred in the learning progress when rats were learning the contrast detection task. Overall, our behavioral results show that nocturnal rodents can detect negative contrast better than positive contrast in photopic vision. The better sensitivity to negative contrast suggests that the visual system of nocturnal rodents also displays black-over-white bias in visual processing. The white-dominant responses in mouse V1 might reflect the stronger inhibitory signals evoked by the positive-contrast stimuli.
Subjects
contrast
rat
vision
V1
visual system
behavior
Type
thesis
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