The reach-to-grasp-food task for rats: A rare case of modularity in animal behavior?

Abstract

Humans and nonhuman animals make use of sensory hierarchies in "selecting" strategies for solving many cognitive and behavioral tasks. Often, if a preferred type of sensory information is unavailable or is not useful for solving a given task, the animal can switch to a lower-priority strategy, making use of a different class of sensory information. In the case of rats performing a classic reach-to-graspfood task, however, prior studies indicate that the reaching maneuver may be a fixed action pattern that is guided exclusively by the food's odor plume until the point of contact with the food morsel [1][2][3]. We sought to confirm and extend these findings in several ways. In Experiment 1, using a GO/NO-GO variant of the classic task, we demonstrated that rats used the GO target's odor both to trigger and guide their reaches. In Experiment 2, we showed that rats deprived of (a) vision, (b) object-recognizing rostral whiskers and forearm sinus hairs, or (c) both, displayed no deficits in triggering and guiding their reaches. Finally, in a third experiment in which the GO target's location varied randomly across trials and only olfactory cues were available, we demonstrated that rats could determine the spatial endpoint of their reach without any loss of accuracy. Combined with results from a prior study in which bulbectomized rats never developed a new, successful reaching strategy despite extensive post-operative training [1], these results indicate that rats do not have a sensory hierarchy for solving the reach-to-grasp-food task, but rather, are guided by olfaction alone until their paw contacts the food morsel.

Food Prehension and Manipulation in Microcebus murinus (Prosimii, Cheirogaleidae)

“…Indeed, before leaving the nest, the lemur turned its head in the direction of the food. This visual detection of food in this species sets it apart from many rodents which invariably locate and reach their food by sniffing [Whishaw and Tomie, 1989;Whishaw et al, 1998;Hermer-Vazquez et al, 2007].…”

Female CGG knock-in mice modeling the fragile X premutation are impaired on a skilled forelimb reaching task

“…To further characterize the nature of the motor performance deficits in CGG KI mice, female CGG KI mice heterozygous for the fragile X premutation were trained on a skilled reaching task based on work by Whishaw and colleagues (Farr & Whishaw, 2002), among others (Buitrago et al, 2004; Hermer-Vazquez et al, 2007; Kolb & Gibb, 2010; Tennant & Jones, 2009). Female mice heterozygous for the fragile X premutation were chosen for this study over male mice because the frequency of fragile X premutation is higher in females than males (1:113 females vs 1:250 in males; cf.…”

Pattern in Behavior

“…For example, when dodging, rats can use a combination of visual and tactile cues , but when reaching for a food item, both the orientation towards and the reach itself is limited to only one sensory modality, olfaction (Hermer-Vazquez, Hermer-Vasquez, & Chapin, 2007). Consequently, blocking vision does not prevent dodging , but blocking olfaction abolishes reaching (Whishaw & Tomie, 1989).…”