DRD2 and Parkinson disease: An improved mechanistic understanding of the relationship between striatal D2/3R signalling and cognitive performance is highly relevant for understanding the cognitive deficits seen in normal ageing (associated with reduced striatal D2R availability [Bäckman et al., 2000; Matuskey et al., 2016]), and neuropsychiatric conditions associated with dysregulated striatal dopamine such as Parkinson’s disease and schizophrenia (Millan et al., 2012; Simpson et al., 2010; McCutcheon et al., 2018a; Meder et al., 2019).