The performance for both orientations became similar after prolonged training, suggesting that learning permits equally high perceptual tuning towards oblique stimuli. Parallel training revealed a higher task performance for cardinal orientations in an early phase of the training. To study the discrimination of cardinal and oblique stimuli in the same mice, we, therefore, applied, a different training regime where mice learned to discriminate cardinal and oblique gratings in parallel. Surprisingly, the expert discrimination performance was similar for both groups but showed large inter-individual differences in performance and training time. Using this chamber, we applied an iterative convergence towards orientation discrimination thresholds for cardinal or oblique orientations in different cohorts of mice. Here, we describe the design of a novel custom-built touchscreen chamber that allows testing natural scene perception and orientation discrimination performance by applying different task designs. However, it is still unknown if mice also show a perceptual dominance of cardinal orientations. Such biased angular tuning has recently been shown in the mouse primary visual cortex.
A potential reason for this increased performance could be an increased number of neurons in the visual cortex that are tuned to cardinal orientations, which is likely to be an adaptation to the natural scene statistics. Correspondingly, many mammalian species are much better at discriminating these cardinal orientations compared to obliques. Natural scenes are composed of a wide range of edge angles and spatial frequencies, with a strong overrepresentation of vertical and horizontal edges.
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