Scientists studying 12 mice observed that while these animals rely on the primary motor cortex to manipulate a joystick when they initially learn the task, they do not seem to use the cortex once they have mastered it. The findings suggest that the brain (at least in mice) contains multiple movement control systems, with a system separate from the primary motor cortex taking control of movements as learning progresses. While scientists are already aware of the cortex’s involvement in the early stages of motor learning, its role in later stage learning has remained mysterious. To investigate, Eun Jung Hwang et al. trained 12 mice over a period of 60 days to grab a joystick with their left forepaw and press it into a target zone, rewarding them with water. Over time, the mice learned to perform the task with greater speed and accuracy, rapidly improving until they became expert joystick-pullers after about 23 days and then maintaining their skill level through the remainder of the training. The researchers used blue LED lights to inactivate the cortex mice at various points throughout the period, finding that the mice’s performance was severely impaired without use of the cortex during the early stage of learning (four to eight days), somewhat less impaired during the middle stage (20 to 25 days), and completely unaffected by the late learning stage (61 to 69 days). Hwang and colleagues note that these results do not suggest that every movement would become independent from the cortex with long-term training–certain movements may always require it.
This part of information is sourced from https://www.eurekalert.org/pub_releases/2019-10/aaft-ama102819.php