Sarah Petruno, Robert E Clark, and Pamela Reinagel (2013)
Get paper at: PLoS One 8(2):e56543.
The pigmented Long-Evans rat has proven to be an excellent subject for studying visually guided behavior including
quantitative visual psychophysics. This observation, together with its experimental accessibility and its close homology to
the mouse, has made it an attractive model system in which to dissect the thalamic and cortical circuits underlying visual
perception. Given that visually guided behavior in the absence of primary visual cortex has been described in the literature,
however, it is an empirical question whether specific visual behaviors will depend on primary visual cortex in the rat. Here
we tested the effects of cortical lesions on performance of two-alternative forced-choice visual discriminations by Long-
Evans rats. We present data from one highly informative subject that learned several visual tasks and then received a
bilateral lesion ablating .90% of primary visual cortex. After the lesion, this subject had a profound and persistent deficit in
complex image discrimination, orientation discrimination, and full-field optic flow motion discrimination, compared with
both pre-lesion performance and sham-lesion controls. Performance was intact, however, on another visual two-alternative
forced-choice task that required approaching a salient visual target. A second highly informative subject learned several
visual tasks prior to receiving a lesion ablating .90% of medial extrastriate cortex. This subject showed no impairment on
any of the four task categories. Taken together, our data provide evidence that these image, orientation, and motion
discrimination tasks require primary visual cortex in the Long-Evans rat, whereas approaching a salient visual target does
not.
Daily performance on four visually guided tasks during training (above) and after a complete lesion to primary visual cortex (below). Colors indicate tasks as follows: Approach Salient Visual Target, with statue target (red) or with grating target (magenta); Image Discrimination (blue); Random Dot Motion Discrimination (green, cyan); and Orientation Discrimination (black).
For videos of normal rats performing the image and motion tasks, click icons below.
Image credit: the icon of the rollerskating mouse came from www.zebracorn.com