Emergence of the exploratory motive in rats

Abstract

As infant rats approach weaning, they must overcome their infantile attraction to the home nest and prepare to leave its safety to forage for food. Although nutritive needs may help to motivate pups to make this bold move, a newly emerging exploratory motive also may play a role. Three experiments are reported here which examine age-related changes in the exploratory motive. In the first experiment, preferences for a novel side over a familiar side of a two-sided testing chamber were examined in postnatal Days 15 (P15), 17 (P17), 19 (P19), and 21 (P21) rat pups. Subjects did not prefer to explore the novel side until P19. In the same test, no preference for a novel object was observed at any of the ages tested, suggesting that this preference, which is expressed in adulthood, does not emerge until a later age; however, additional studies are needed to verify this. In the second experiment, P15 subjects demonstrated their ability to discriminate the two sides of the testing chamber in a novelty-induced locomotion test. In the third experiment, the presence of a home-nest-associated object was shown to inhibit exploration of novel context in P15, but not P21, subjects. These data suggest that home nest egression may be more the consequence of the declining attractiveness of the home nest than of a growing exploratory motive.

Behavioral differences between late preweanling and adult female Sprague–Dawley rat exploration of animate and inanimate stimuli and food

“…We and others have suggested that the well-documented phenomena of increased exploration of the environment by the young rat during the peri-weaning period may be based on having a higher level of motivation for environmental exploration than adults (Gerrish and Alberts, 1997, Goodwin and Yacko, 2004; Smith and Morrell, 2007). Based on our current data, we posit that this enhanced motivation for environmental exploration in the preweanling extends to many specific stimuli within the environment.…”

The development of spatial behaviour and the hippocampal neural representation of space

“…Similarly, pups placed on an open platform with their littermates (but without their mother) make only very short forays away from the huddle between P16 and P18, and the distance of these forays increases from P19 onwards [71]. Likewise, pups prefer to explore the novel side of a box only from P19 onwards [72]. Rearing on the hind legs, an important behavioural marker of novelty-induced exploration [73], first emerges at around P17, and increases rapidly from P19 onwards [39].…”

Prenatal stress effects on emotion regulation differ by genotype and sex in prepubertal rats

“…This test followed Goodwin and Yacko (1984), with modifications. It was performed on ''spare'' weanling pups from RPS, PS, and control litters, beyond those examined in the other behavioral tests.…”