Hi Mohammed - a complex question. LTD and LTP is probably more important in the basal ganglia for the learning of motor skills, in terms of ensuring that an appropriate action is selected in a specific situation to achieve a specific goal. In the motor cortex, LTP and LTD may be involved in the formation of the complex pattern of muscle activation that constitutes a specific action, but this is not entirely clear. Cerebellar plasticity helps to shape the coordinated pattern that forms the appearance of a skilled movement, e.g. helps you get good at a specific skill such as improving your bowling accuracy in cricket. So you can see that all three brain areas are involved in learning of a new skill such as riding a bike.    For motor cortex, you could read the reviews of Grzegorz Hess and John Donoghue as well as Apostolos Georgopoulos,  and for basal ganglia Ann Graybiel and Jim Surmeier. Our lab has contributed some papers regarding LTP and LTD in striatum of basal ganglia and its role in skill acquisition. Cerebellum is not my area so others may comment.

Best of luck!

John Reynolds 

what I know that cerebral cortex, basal ganglia and cerebellum all have a role in learning but with different roles (cerebellum: supervised learning, BG: reinforcement learning, cerebral cortex: unsupervised learning).

See this article by Calabresi et al. It would be helpful for you

http://www.jneurosci.org/content/12/11/4224.full.pdf