The role of cortico-basal ganglia systems in the construction of movement: Action selection and sequencing

Abstract: The cortico-basal ganglia system is instrumental in the construction of movement, through its involvement in aspects such as action selection, initiation/termination and sequencing, though the precise role of the different structures and how they collaborate on a network level to allow us to fluidly change from one behavior to another has long proven to be elusive.We have here recorded neuronal activity throughout the cortico-basal ganglia circuit in rats, in a series of projects in order to understand more about how some of these functions are controlled.We first set out to study the sequencing of actions through the rat grooming behavior, whose phases were shown to be concatenated in a stepwise manner where the selection of an upcoming phase depended primarily on the current one. Our data also suggested an involvement of both cortex and striatum in the initiation and termination of the behavior as a whole, while mainly primary motor cortex was modulated during the transitions between phases. In the primary motor cortex activity we also found correlation to the transition probability in the moment of transition, as well as the momentaneous probability of transitioning away from the current phase throughout its execution.Next, we showed that out of the neuronal changes in activity that occur after administration of D1 or D2 type receptor antagonists, the only one that reliably precede the onset of catalepsy in any of the structures throughout the loop is a balanced change in firing rate. Finally, we show that tactile input to the cortico-basal ganglia system in rats changes as an effect of acquiring a novel reaching skill, indicating that reshaping the representation of tactile input to motor circuits could be an important part of the learning process in skill acquisition in reaching and grasping.