Invariant visual object recognition and shape processing in rats.
Bottom Line: Historically, this has limited the invasive investigation of its neuronal underpinnings to monkey studies, in spite of the narrow range of experimental approaches that these animal models allow.Meanwhile, rodents have been largely neglected as models of object vision, because of the widespread belief that they are incapable of advanced visual processing.Here, I review these recent investigations, as well as earlier studies of rat pattern vision, to provide an historical overview and a critical summary of the status of the knowledge about rat object vision.
Affiliation: Visual Neuroscience Lab, International School for Advanced Studies (SISSA), 34136 Trieste, Italy. Electronic address: email@example.com.Show MeSH
Mentions: Simpson's and Gaffan's study  was based on a procedure/apparatus to test rats in visual tasks that Gaffan and colleagues had described in previous reports [158,159], and that they later applied in a series of lesion studies to identify the neuronal substrates of visual object discrimination and memory in rats [160–164]. The apparatus consisted of a Y maze, with the three arms having equal length and the three angles formed by each arm pair having equal amplitude. A pair of computer monitors (jointed by a 117° angle, so as to subtend ∼94° horizontally, when viewed from the maze center) was located at the end of each arm, where reward was also delivered. Visual scenes of various complexity (containing a number of 2-dimensional objects, such as ellipses, ASCII text characters, polygons, rectangles, etc.) were displayed on the monitors, with the scenes shown in the adjacent monitors at the end of an arm being the mirror version of each other along the vertical axis (each pair of mirror scenes on adjacent monitors constituted one stimulus scene; see examples in Fig. 3A). Each rat was trained in a spatial two-alternative forced-choice task, in which two different stimulus scenes were displayed at the end of the two arms not currently occupied by the animal, and the rat had to learn to either approach a target positive-constant or avoid a target negative-constant scene. This constant scene was paired, in every trial, to a trial-unique variable scene, containing visual objects that could differ from those of the constant scene in a variety of properties (examples of a constant scene and some variable scenes that were paired to it in Simpson's and Gaffan's study  are shown in Fig. 3A).
Affiliation: Visual Neuroscience Lab, International School for Advanced Studies (SISSA), 34136 Trieste, Italy. Electronic address: firstname.lastname@example.org.