Do rats use shape to solve "shape discriminations"?

Minini, L. and Jeffery, K. J. (2006) Do rats use shape to solve "shape discriminations"? Learning and Memory, 13(3), pp. 287-297. (doi: 10.1101/lm.84406) (PMID:16705141) (PMCID:PMC1475809)

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Abstract

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.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Jeffery, Professor Kate
Authors: Minini, L., and Jeffery, K. J.
College/School:College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Journal Name:Learning and Memory
Publisher:Cold Spring Harbor Laboratory Press
ISSN:1072-0502
ISSN (Online):1549-5485
Published Online:16 May 2006

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