<p>The basal ganglia make a significant contribution to the generation of motor behavior through their involvement in the descending motor pathways. Gaining insight into how the motor cortex produces motor patterns is also a key to understanding the function of the basal ganglia. The population dynamics approach is convenient for the reevaluation of the behavior of the motor cortex and also the roles of other components in the motor system. Here, it is proposed that the basal ganglia amplify preparatory activity in the motor cortex with the modulatory effect of phasic dopamine release. The influence of the basal ganglia is tested with a computational model on a center-out-reaching task. The results show that the basal ganglia facilitate movement initiation and increase the robustness of the behavior. These results, based on the perspective of population dynamics, may improve our understanding of the role of the basal ganglia in motor control and the symptoms of dopamine-related conditions in neurodegenerative diseases of motor control.</p>