Reduced visual acuity impairs place but not cued learning in the Morris water task

The Morris water task is a standard method for testing spatial learning in rodents. In a place version of the task, animals utilize multiple visual cu es to learn the location of a hidden platform. The ability of animals to lo cate a cued platform is often used to qualitatively test for possible non-c ognitive contributions to deficient place learning, including reduced visua l function. We investigated the role of visual acuity in water maze perform ance quantitatively by depriving rats of pattern vision during a critical p eriod for visual plasticity, which reduced their acuity by approximate to 2 7% and then tested them in typical place and cued platform configurations o f the Morris water task. Animals with reduced visual acuity had a significa nt deficit in place learning, but eventually reached the same escape latenc y as non-deprived animals. Deprived and non-deprived animals, however, did not differ in their ability to locale a cued platform following place learn ing. These data indicate that reduced visual acuity in rats can influence m easurement of their place learning and that a typical cued platform version of the task cannot detect a modest, but significant, visual deficit. (C) 2 000 Elsevier Science B.V. All rights reserved.