Remembrance of places you passed: Social spatial working memory in rats.

Abstract

Pairs of rats were tested in a radial-arm maze to determine whether the spatial choices made by one rat affect the subsequent spatial choices of the other rat. In a free-choice procedure, rats showed an increased tendency to choose the location that had most recently been chosen by a foraging partner but a decreased tendency to visit locations that the foraging partner had visited earlier. Forced-choice procedures were used to better control the social stimulus and the interactions between the rats. Under some conditions, locations were chosen later in the choice sequence of a subject rat if another rat had been observed choosing that location. Odor and other physical traces of the other rat's visits were ruled out as explanations for this effect. The results demonstrate the existence of working memory for locations visited by a familiar conspecific.

Social effects on spatial choice in the radial arm maze

“…Reports from our laboratory have explained the tendency of a rat to choose maze arms in the radial maze that were visited earlier by a foraging partner in terms of an influence of the foraging partner on choices made by the focal rat (Brown et al, 2007;Brown et al, 2008). However, an alternative possibility is that the tendency to visit the most recent location chosen by the other rat is an artifact of common preferences for particular maze arms.…”

“…Recently, work in our laboratory has shown that rats foraging together with their cagemate in a radial-arm maze are also affected by the choices of the other rat and that at least some of these effects are produced by memory for the choices made earlier during the trial by the other rat (Brown, Farley, & Lorek, 2007;Brown et al, 2008). The nature of the effect produced by choices of the other rat is sometimes an increase in the tendency to visit the locations chosen by it and sometimes an opposite tendency to avoid visits to those locations.…”

“…There was a tendency to selectively choose the location that had been most recently d visited by the other rat but an opposite tendency to avoid locations visited earlier during the trial by the other rat. Brown et al (2007) suggested that the physical presence d of the other rat on or near the maze location that it had most recently visited functioned as an attractant stimulus. However, rats avoided locations that they remembered to have been visited earlier during the trial by the other rat.…”

“…(2008) reported a series of experiments using the same free-choice procedure used in some of the experiments reported by Brown et al (2007). Rather than the usual technique of baiting each maze arm with a small amount of food that is depleted when a rat visits the arm, each maze arm was baited with a large number of pellets, so that food remained throughout each trial.…”

“…The nature of the effect produced by choices of the other rat is sometimes an increase in the tendency to visit the locations chosen by it and sometimes an opposite tendency to avoid visits to those locations. Brown et al (2007) used a free-choice procedure in which two rats chose simultaneously from the eight locations in the maze, as well as an observer/model procedure in which a subject rat observed a model rat make choices in the maze and later made choices itself. In the latter procedure, the subject rat avoided locations that had been chosen by the model rat.…”