Ability to Discriminate Visual Signals in the Morris Water Maze in High- and Low-Impulsivity Rats
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Ability to Discriminate Visual Signals in the Morris Water Maze in High- and Low-Impulsivity Rats M. I. Zaichenko, G. Kh. Merzhanova, and G. A. Grigoryan
UDC 612.821
Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 70, No. 2, pp. 231–242, March–April, 2020. Original article submitted March 18, 2019. Revised version received September 10, 2019. Accepted September 16, 2019. High-impulsivity (HI) rats learned to locate a visible platform bearing a special stimulus object (a bannerette) in the Morris water maze more quickly than low-impulsivity (LI) rats. HI rats also successfully acquired differentiation between a sail (the differential stimulus object) and the bannerette, as assessed in terms of a decrease in the number of incorrect swims to the location of the sail. During differentiation, HI rats reached the platform more quickly than LI rats and thus swam shorter distances. In the case of reverse differentiation (remodeling), between-group differences in platform reaching time and distance covered disappeared. However, the number of swims to the differential object (now the bannerette) by HI rats decreased, which did not occur in LI animals. These data provide evidence that “egocentric” tasks in the Morris water maze with the platform visible and bearing the bannerette are solved more easily by HI rats, while “allocentric” tasks associated with finding a platform hidden beneath the surface of the water are solved better by LI animals. Keywords: impulsivity, learning, remodeling, Morris water maze, cue memory, delay discount.
garded as linked with the simplest, most economical, and least effort-requiring cognitive processes in choice situations [Salamone et al., 1994; Mazur, 1987]. For example, when presented with a choice between a weak immediate reinforcement and a strong delayed reinforcement, an impulsive subject (or animal) selects the first option [Mazur, 1987; Cardinal et al., 2004]. The same occurs on selection of a weak but probable reinforcement or a strong but improbable reinforcement [Zoratto et al., 2016]. When an animal is presented with a choice between receipt of an easily accessed weak reinforcement and a difficult-to-reach strong reinforcement, for example, in conditions of unhindered receipt of the reinforcement on one side of the chamber and hindered receipt (crossing a barrier ladder) of the reinforcement on the other, animals prefer the former [Salamone et al., 1994]. Cost-benefit analysis is applicable to these situations. This can always find an equilibrium point at which the difficulty of carrying out the task balances the magnitude of the benefit received. The more impulsive the subject (or animal), the more the equilibrium point shifts to the left, i.e., towards preference for the weak but easily obtained
Impulsivity is the tendency of a subject to carry out rapid, thoughtless actions. It is seen as a property of the individual-typological characteristics of both humans and animals. Extreme impulsivity can be accompanied by number of serious psychopathol
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