Discrimination of computer-graphic stimuli by mice: A method for the behavioral characterization of transgenic and gene-knockout models.

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The touchscreen testing method for rodents is a computer-automated behavioral testing method that allows computer graphic stimuli to be presented to rodents and the rodents to respond to the computer screen via a nose-poke directly to the stimulus. The advantages of this method are numerous; however, a systematic study of the parameters that affect learning has not yet been conducted. We therefore sought to optimize stimuli and task parameters in this method. We found that when parameters were optimized, Lister Hooded rats could learn rapidly using this method, solving a discrimination of two-dimensional stimuli to a level of 80% within five to six sessions lasting ∼30 min each.In a final experiment we tested both male and female rats of the albino Sprague-Dawley strain, which are often assumed to have visual abilities far too poor to be useful for studies of visual cognition. The performance of female Sprague-Dawley rats was indistinguishable from that of their male counterparts. Furthermore, performance of male Sprague-Dawley rats was indistinguishable from that of their Lister Hooded counterparts. Finally, Experiment 5 examined the ability of Lister Hooded rats to learn a discrimination between photographic stimuli. Under conditions in which parameters were optimized, rats were remarkably adept at this discrimination. Taken together, these experiments served to optimize the touchscreen method and have demonstrated its usefulness as a high-throughput method for the cognitive testing of rodents.It is now well understood that the use of animal models is an essential component in our quest to understand the brain mechanisms of cognition. In addition, such models are necessary for researchers to be able to test potential therapeutic agents in a direct and expedient manner that is not possible in human subjects. Moreover, we are experiencing a revolution in the sophistication of transgenic and knock-out animal models that creates opportunities for cognitive testing and therapeutic screening that were until recently, unthinkable (Kobayashi and Chen 2005).To achieve successful translation of findings from animal models to humans, the cognitive tasks we use with our rodents should resemble as closely as possible those used with human subjects. Increasingly, human subjects are tested using computerautomated methods. A particularly powerful approach is the "touchscreen" testing method, in which subjects respond directly to stimuli on a computer screen (e.g., Robbins et al. 1994). The advantages of this method are numerous and include facilitated performance due to contiguity between stimuli and responses and the ability to present a battery of different cognitive tests in which parameters such as stimuli, responses, and feedback are consistent across tasks and conditions.To create a cognitive testing method for rodents that matched, as far as possible, the touchscreen testing method for humans, Bussey et al. (1994Bussey et al. ( , 1997a) (see Fig. 1A) developed the touchscreen testing method for rats, a method which has...

Section: Experiments 2: Optimizing Stimulus Sizementioning

confidence: 99%

Section: Experiments 2: Optimizing Stimulus Sizementioning

confidence: 99%

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confidence: 99%

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The touchscreen cognitive testing method for rodents: How to get the best out of your rat

Bussey¹,

Padain²,

Skillings³

et al. 2008

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222

“…This may reflect either a failure to visually process global shape information or a failure to discover shape as the discriminative stimulus in a simultaneous discrimination. Either way, our results suggest that simultaneous shape discrimination is not a good task for studies of visual perception in rodents.Discrimination tasks have long been used to probe perceptual processes in animals, and visual discrimination tasks, particularly automated ones, are increasingly used in rodents because of the contribution that rodent neurobiological studies (such as newly emerging transgenic models) can make to understanding the brain mechanisms underlying visual perception (Bussey et al 1994(Bussey et al , 2001Cook et al 2004). Visual discrimination tasks often require the animals to choose between simple geometric shapes, and an implicit assumption in these studies is that rats and mice process shape in a holistic manner when making these discriminations.…”

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Do rats use shape to solve “shape discriminations”?

Minini¹,

Jeffery²

2006

Visual discrimination tasks are increasingly used to explore the neurobiology of vision in rodents, but it remains unclear how the animals solve these tasks: Do they process shapes holistically, or by using low-level features such as luminance and angle acuity? In the present study we found that when discriminating triangles from squares, rats did not use shape but instead relied on local luminance differences in the lower hemifield. A second experiment prevented this strategy by using stimuli-squares and rectangles-that varied in size and location, and for which the only constant predictor of reward was aspect ratio (ratio of height to width: a simple descriptor of "shape"). Rats eventually learned to use aspect ratio but only when no other discriminand was available, and performance remained very poor even at asymptote. These results suggest that although rats can process both dimensions simultaneously, they do not naturally solve shape discrimination tasks this way. This may reflect either a failure to visually process global shape information or a failure to discover shape as the discriminative stimulus in a simultaneous discrimination. Either way, our results suggest that simultaneous shape discrimination is not a good task for studies of visual perception in rodents.Discrimination tasks have long been used to probe perceptual processes in animals, and visual discrimination tasks, particularly automated ones, are increasingly used in rodents because of the contribution that rodent neurobiological studies (such as newly emerging transgenic models) can make to understanding the brain mechanisms underlying visual perception (Bussey et al. 1994(Bussey et al. , 2001Cook et al. 2004). Visual discrimination tasks often require the animals to choose between simple geometric shapes, and an implicit assumption in these studies is that rats and mice process shape in a holistic manner when making these discriminations. This assumption, however, has never been properly verified, and rests mainly on a relatively old literature (Fields 1932;Lashley 1938; Sutherland 1961a,b). Discovering the perceptual and cognitive processes underlying these kinds of behavioral tasks is critical if we are to make appropriate links with emerging neurobiological discoveries.The present paper reports a series of investigations that led us to try and determine whether rats really use "shape" when making shape discriminations. Believing at the outset that this was a well-secured fact, we began with a more ambitious experiment to determine whether rats could respond to figures defined by illusory contours (the so-called "Kanizsa figures"), in which illusory form is created by means of "inducing stimuli" (Fig. 1) and is perceived in the absence of real (i.e., luminance-defined) contours. Several authors have proposed that the perception of illusory figures is largely the result of low-level mechanisms that have evolved to extract contours that are present in the environment but absent from the retinal representation: due, for instance, to occlus...

“…Learning was assessed in a touchscreen-based operant system described previously for rats (Bussey et al 2001) and mice (Brigman et al 2006;Izquierdo et al 2006). The operant chamber measuring 21.6 ‫ן‬ 17.8 ‫ן‬ 12.7 cm (model no.…”

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Impaired discrimination learning in mice lacking the NMDA receptor NR2A subunit

Brigman¹,

Feyder²,

Saksida³

et al. 2008

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146

156

N-Methyl-D-aspartate receptors (NMDARs) mediate certain forms of synaptic plasticity and learning. We used a touchscreen system to assess NR2A subunit knockout mice (KO) for (1) pairwise visual discrimination and reversal learning and (2) acquisition and extinction of an instrumental response requiring no pairwise discrimination. NR2A KO mice exhibited significantly retarded discrimination learning. Performance on reversal was impaired in NR2A KO mice during the learning phase of the task; with no evidence of heightened perseverative responses. Acquisition and extinction of an instrumental behavior requiring no pairwise discrimination was normal in NR2A KO mice. The present findings demonstrate a significant and selective deficit in discrimination learning following loss of NR2A.