For example, current PET studies with the well-known PDE4 radioligand [11C]rolipram indicated that changes in the PDE4 availability might be associated with cognitive impairments and sleep dysfunctions in Parkinson’s disease (PD) [44,46] as well as with dysregulations in the disrupted in schizophrenia protein 1 (DISC1) related to the progression of neuropsychiatric disorders [51]. Here, PDE4A is linked to Parkinson disease.