DRD2 and Parkinson disease: Therefore, the relevant compensatory mechanisms that effect AIP severity are probably more specifically related to DRD2 signaling at the striatal level, but may be more general and essentially similar to those mechanisms involved in PD at the extra-striatal level (e.g., alternation of indirect pathway activity by involvement of additional neurotransmission systems, or recruitment of brain region and networks in motor regions in the cortex or in the cerebellum that modulate parkinsonian symptoms and produce compensatory effect – as presented in Table 1).