This chapter reviews functional imaging studies, including those with functional magnetic resonance imaging (fMRI), and nuclear tracing studies such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) scanning as they relate to motor signs of Parkinson's disease (PD). fMRI of healthy controls (HC) performing unilateral hand movements typically identifies cerebral correlates in the motor system. To examine the functional changes occurring with learning of automatic finger movements, T. Wu and M. Hallett performed fMRI on a group of individuals with moderate or advanced PD before and after practicing a finger-sequence. To study cerebral correlates of increasing demand by dual-task performance, they also introduced two secondary distractor tests in addition to the sequential finger movements during the same experimental session. A whole brain analysis demonstrated a significant increase of the blood oxygen level dependent (BOLD) signal in the posterior mid-mesencephalon in PD with freezing.