Of note, the extent of striatal DA

Of note, the extent of striatal DA loss exceeds that of SNpc dopaminergic neurons, suggesting that the process begins and/or is more severe at the terminals73–75. The caudal putamen exhibits a somatotopic organization that mirrors that of the primary motor cortex and supplementary motor areas76,77, whereas the SNpc does not appear to be somatotopically organized78. Accordingly, the initial motor features of PD fit well with the focal dopaminergic putaminal deficit and the somatotopic organization of the motor circuit26,79. Interestingly, the same topographic pattern of putaminal denervation is repeated in the less affected hemisphere some 2–3 years later80.