Rats’ learning of a new motor skill: Insight into the evolution of motor sequence learning

Abstract

Recent behavioral and neural evidence has suggested that ethologically relevant sub-movements (movement primitives) are used by primates for more complex motor skill learning. These primitives include extending the hand, grasping an object, and holding food while moving it toward the mouth. In prior experiments with rats performing a reach-to-grasp-food task, we observed that especially during early task learning, rats appeared to have movement primitives similar to those seen in primates. Unlike primates, however, during task learning the rats performed these sub-movements in a disordered manner not seen in humans or macaques, e.g. with the rat chewing before placing the food pellet in its mouth. Here, in two experiments, we tested the hypothesis that for rats, learning this ecologically relevant skill involved learning to concatenate the sub-movements in the correct order. The results confirmed our initial observations, and suggested that several aspects of forepaw/ hand use, taken for granted in primate studies, must be learned by rats to perform a logically connected and seemingly ecologically important series of sub-movements. We discuss our results from a comparative and evolutionary perspective.

Motivational state, reward value, and Pavlovian cues differentially affect skilled forelimb grasping in rats

“…Many motor skills in higher mammals are dependent on upper limb control and dexterity (Lemon 2008). Skilled grasping is the most widely used paradigm to study motor skill learning and performance in rodents (Whishaw and Pellis 1990;Buitrago et al 2004;Hermer-Vazquez and Moshtagh 2009;Azim et al 2014;Esposito et al 2014). In this task, animals use their forepaw to reach through a small opening for a sugar pellet positioned on a shelf or pedestal.…”

Pattern of novel object exploration in cynomolgus monkey Macaca fascicularis

“…It should be noted that an orderly motor sequence does not appear to be present in rodents, as rodents often perform motor movements in a seemingly random fashion, without any discernable order . In primates, correct order of motor sequence appears to be the norm .…”

“…In studies of motor skill learning, rodents do not display a strong tendency for a patterned sequence of activities, as they often perform motor movements in a seemingly random fashion, without any discernable order . Non‐human primates, on the other hand, are known to acquire an orderly sequence of discrete motor movements, as shown in hand grasping activities .…”

A system for automated tracking of motor components in neurophysiological research

“…Training entailed habituation of the rat to the apparatus, habituation to the food reward (pellet) and establishment of paw dominance. The training continued until performance no longer improved between sessions, reflecting a fully learned behavior (Hermer-Vazquez and Moshtagh, 2009). See Appendix A for details.…”