The Visual Acuity of Rats in Touchscreen Setups

Abstract

Touchscreen setups are increasingly used in rodents for a wide range of cognitive tasks, including visual discrimination. The greater automation and high throughput of this platform could greatly facilitate future vision research. However, little information is available regarding decision distance and on the limitations of stimulus size. Especially when studying visual functions, the lack of control of basic visual properties is a drawback. Therefore, we determined the maximal number of cycles per screen gratings can have so that Long Evans rats can reliably perform orientation discrimination. To relate our results to literature on visual acuity we tried to make an estimate of the decision distance in the touchscreen platform. The rats can discriminate between orientations with 70% accuracy up to 44 cycles per screen. This could roughly translates to the previously reported visual acuity of 1 c/degree assuming a viewing distance of 12.5 cm. This could be useful when designing new stimuli based on published results in c/degree. One could assume a viewing distance of 12.5 cm and expect similar discrimination performance in the touchscreen setup as in other tasks with a predefined viewing distance.

Prelimbic cortex maintains attention to category-relevant information and flexibly updates category representations

“…The spatial frequency of the gratings ranged from 0.2532 cycles per visual degree (cpd) to 1.2232 cpd, and the orientation of the gratings ranged from 0 rad to 1.75 rad. These values were obtained from pilot experiments and are within the perceptual limits of rats ( Crijns & Op de Beeck, 2019 ). Linear transformations of these dimensions were made so that both dimensions had a common range (i.e., 0 to 100).…”

Category learning in rodents using touchscreen‐based tasks

“…Maximum acuity is determined when the organism cannot distinguish a grating stimulus from a solid gray stimulus. Although humans have visual acuity as high as 30 cycles per degree, the visual acuity of pigmented rat strains (ie, Long Evans, Dark Agouti and wild strains) is much lower (1.0 cycle per degree) 45‐49 . Non‐pigmented rats (ie, Sprague‐Dawley, Wistar and Fischer‐344), as well as mice, have even poorer visual acuity (0.5 cycles per degree), whereas the Fischer‐Norway rat strain is above average (1.5 cycles per degree) 45 .…”

Mice (Mus musculus) do not perceive emergent gestalt.

“…The stimuli used by Talpos et al (2016) were 4 cm 2 ; however, the viewing distance was unknown. Crijns and Op de Beeck (2019) examined the rat’s visual acuity using a similar apparatus to that in Talpos et al (2016) and estimated that the mean viewing distance was 12.5 cm. This allows us to estimate that the rats’ stimulus size was 18 degrees in Talpos et al (2016).…”