A cautionary note regarding drug and brain lesion studies that use swimming pool tasks: partial reinforcement impairs acquisition of place learning in a swimming pool but not on dry land
Clr. Gonzalez et al., A cautionary note regarding drug and brain lesion studies that use swimming pool tasks: partial reinforcement impairs acquisition of place learning in a swimming pool but not on dry land, BEH BRA RES, 112(1-2), 2000, pp. 43-52
Spatial tasks are used widely in neurobiological studies because it is thou
ght that they provide an unbiased assessment of the integrity of neural str
uctures that mediate spatial learning. For example, in the Morris swimming
pool place task, animals are required to locate a hidden platform in a swim
ming pool in relation to environmental cues. Treatments that result in an a
nimal's failure to find the platform are assumed to reflect defects in the
function of neural systems involved in spatial learning. The present study
demonstrates, however, that an animal's reinforcement history can contribut
e to its spatial performance. Animals were trained in the Morris place task
with the platform present on 100, 75 or 50% of trials. Relative to the 100
% group, the 75% group was impaired in place acquisition, and the 50% group
failed to learn. Even placing the 50% group animals onto the platform at t
he completion of an unsuccessful trial failed to improve acquisition. Anima
ls trained to search for food on an identical dry maze problem were not aff
ected by similar reinforcement schedules. The present findings demonstrate
that the Morris swimming pool place task does not provide an unbiased asses
sment of spatial learning: A treatment effect may be confounded with reinfo
rcement history. The results are discussed in relation to widespread applic
ations of the Morris place task to neurobiological problems. (C) 2000 Elsev
ier Science B.V. All rights reserved.