Parkinson’s disease (PD) as a progressive neurodegenerative disorder is believed to start with a deficiency of dopamine (DA) followed by the degeneration of dopaminergic (DAergic) neurons of SNc (substantia nigra pars compacta) in the basal ganglia (BG). The lack of DA in the SNc causes dynamical changes within the BG. However, these changes are not restricted to BG; it is also shown that cortico-thalamo-cerebellar loops play a critical role in the generation of PD manifestations. This chapter aims to introduce these cortical and subcortical loops, which are taking part in the appearance of PD symptoms.